Operational and public health entomology 

July – September 2009 

Perspective 1 

MG Russell J. Czerw 

Outbreak of Dermatitis Linearis Caused by Paederus ilsae and 6 

Paederus iliensis (Coleoptera: Staphylinidae) at a Military Base in Iraq 

CPT Silas Davidson, COL (Ret) Scott Norton; LTC Mark Carder; COL Mustapha Debboun 

Operational Vector-borne Disease Surveillance and Control: 16 

Closing the Capabilities Gap through Research at Overseas Military Laboratories

MAJ Brian Evans; CPT Jeffrey Clark; LT Kathryn Barbara (USN); LT Kirk Mundal (USN); et al 

Applications of Ecological Niche Modeling to Enhance Medical Threat 28 

Assessment and Disease Control and Prevention Strategies

MAJ Michelle Colacicco-Mayhugh 

Addressing Feral and Wild Animal Threats During Deployment: 33 

The Distinction Between Animal Control and Rabies Control 

LTC Raymond Dunton; MAJ Gerald Sargent 

Perspectives on Scrub Typhus, Tick-Borne Pathogens, 40 

and Hantavirus in the Republic of Korea

LTC William Sames; Heung-Chul Kim, PhD; COL (Ret) Terry Klein 

Remote Teaching of Arthropod Species Identification 50

Through Interactive Multimedia

CDR (Ret) George Schultz (USN); Richard Robbins, PhD

Behavioral Resistance of House Flies, 54 

Musca domestica (Diptera: Muscidae) to Imidacloprid

MAJ Alec Gerry; Diane Zhang, MD 

Field Trial of Five Repellent Formulations Against Mosquitoes in Ahero, Kenya 60

LTC Van Sherwood; Elizabeth Kioko; Sichangi Kasili; Philip Ngumbi; Michael Hollingdale, PhD 

Characterization of a New Ultra-Low Volume Fuselage Spray Configuration 66

on Air Force C‐130H Airplane Used For Adult Mosquito Control 

Maj Mark Breidenbaugh (USAFR); Maj Karl Haagsma (USAFR); Mark Latham; Ferenc de Szalay, PhD 

The Armed Forces Pest Management Board: Force Multiplier Through Policy, 77 

Guidance, Research, and Information 

Col William Rogers (USAF); Richard Robbins, PhD; CAPT Stanton E. Cope (USN) 

Evaluation of Efficacy and Duration of the Stick Camouflage Face Paint 84 

with 30% Deet Against Mosquitoes in Belize

MAJ Kendra Lawrence; John Paul Benante; Nicole Close, PhD; Nicole Achee, PhD 

Comparison of the Attractiveness of Organic Infusions 91 

to the Standard CDC Gravid Mosquito Trap

CPT Lee McPhatter; Cara Olsen, DrPH; COL Mustapha Debboun 
LTG Eric B. Schoomaker 

The Surgeon General 

Commander, US Army Medical Command 

MG Russell J. Czerw 

Commanding General 

US Army Medical Department Center and School 

July – September 2009 The Army Medical Department Center & School PB 8-09-7/8/9 

0926004 

GEORGE W. CASEY, JR 

General, United States Army 

Chief of Staff

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Views expressed are those of the author(s) and do not necessarily reflect official US 

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 July – September 2009 1

Among the more well-known of the ancient Chinese 

maxims of military principles attributed to Sun Tzu is 

“Know your enemy as you know yourself,” a common 

sense requirement for anyone planning strategy and 

tactics for an impending conflict. Of course, one 

immediately thinks of intelligence operatives gathering 

information about the character of the enemy’s forces, 

locations, capabilities, and support structure, among 

other things, and analysts examining that data to 

identify ways to counter and eliminate the threat. The 

same approach applies not only to opposing military 

forces, but also to any adversary with the potential to 

inflict harm on your force and reduce its combat 

capability. As we have learned from hard experience 

over the last 110 years, some of the most pernicious 

threats to our Soldiers are posed by the smallest of 

adversaries—mosquitoes, ticks, sand flies, fleas, mites, 

and other arthropods—which cause problems directly 

through bites and irritation, and, more importantly, 

vector some of the most virulent disease pathogens 

that afflict humans and other mammals. 

Ever since MAJ Walter Reed confirmed and extended 

Dr Carlos Finlay’s previously ridiculed theories about 

the role of an arthropod, the mosquito, as intermediary 

host in the spread of yellow fever, the need to know 

this constant, pervasive enemy has been recognized by 

the military. Further, as understanding of the extent 

and significance of the threat has grown, the military’s 

organization and application of resources has become 

increasingly sophisticated, with military entomologists 

on the point. The US Army first commissioned 

entomologists into the Sanitary Corps during World 

War I, and significantly increased those numbers 

during World War II. Today, there are some 64 active 

duty and 35 reservist Army entomologists serving in a 

variety of roles in operational commands, on staffs, in 

research laboratories, and in training organizations, 

often jointly with entomologists from our sister 

services. The senior medical and veterinary 

entomologist at the Army Medical Department 

(AMEDD) Center and School, COL Mustapha 

Debboun, has organized this special focus issue of the 

AMEDD Journal to feature the work of those military 

entomology professionals, including contributions by 

Air Force, Navy, and civilian authors. The result is an 

outstanding issue that is not only a wealth of 

important, timely medical information, but also 

provides insight as to the broad scope of roles and 

responsibilities of medical entomologists in today’s 

military. 

Although the role of arthropods as vectors of disease 

pathogens is, understandably, the best known of the 

threats they pose, there are other hazards. In the first 

article, CPT Silas Davidson and his coauthors present 

an excellent description of the problems caused by 

beetles that do not sting or bite, but secrete vesicating 

chemicals which cause blistering in human skin. These 

blisters are often misdiagnosed, and have sometimes 

even been attributed to suspected chemical warfare 

agents. In certain parts of the world, the beetles 

periodically swarm in numbers large enough to pose a 

considerable health threat, and have in fact adversely 

affected military operations. The biology of the 

production of the irritant, and the physiology of its 

harmful effects are clearly explained as the authors use 

an outbreak of dermatitis among US Soldiers in Iraq in 

Perspective 

Major General Russell J. Czerw
2 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

Perspective 

2007 as a case study to illustrate the reality of the 

threat to readiness. It was discovered that the 

possibility of vesicating beetles had not been 

considered as Soldiers and Airmen at Joint Base Balad 

were being treated for blisters, assumed to be burns 

from maintenance activities. Sampling at the locations 

where the affected personnel worked revealed the 

presence of such beetles, and further collections 

determined the types of beetles, potential sources, the 

attraction factors (lights), and the times of activity. 

Based on the data collected, preventive measures were 

instituted to reduce human contact with the beetles, 

and the incidence of dermatitis was significantly 

reduced. This very informative article is a textbook 

example of how the teamwork of the healthcare provider and the entomologist effectively identified and 

resolved a potentially serious public health concern. 

By the end of World War II, US military planners 

understood that learning, or relearning, the particulars 

of regional disease threats each time US forces 

deployed was counterproductive, and often proved 

deadly to military personnel. Overseas medical 

research laboratories were established in Thailand, 

Indonesia, Peru, Egypt, and Kenya to minimize such 

knowledge gaps by developing and using surveillance 

tools to discover and understand the spread of disease 

and the vectors involved. MAJ Brian Evans has 

assembled a team of authors representing all five of 

those laboratories to present an examination of the 

most serious disease threats targeted by their research, 

and describe the ongoing work to address the gaps in 

our knowledge and capabilities to counter them. In a 

well-developed, very informative article, they 

carefully lay out the core questions that pertain to the 

particular vector of concern, and how the answers 

drive the approach to developing preventive measures 

to mitigate the respective threat. This article is detailed 

and complete in its approach that defines the task 

necessary, identifies the deficiencies encountered in 

accomplishing the task, and describes the solutions 

under development to address those deficiencies. 

However, even though the information presented is 

extensive, it is only a snapshot of the fascinating and 

extremely important work under way in those 

laboratories by our military and civilian entomology 

professionals. 

One advantage of dealing with a vector-borne disease 

is that the potential occurrence of the disease in a 

given area is predictable, as long as the absence or 

presence of the vector can be determined. 

Unfortunately, that is often the most difficult aspect of 

the medical threat assessment, in that surveillance of 

vectors in the area may be impossible prior to 

deployment, and even after arrival in a combat 

environment. MAJ Michelle Colacicco-Mayhugh has 

contributed a very interesting article which looks at 

one way technology is providing assistance to planners 

for this problem. The adaptation of remotely sensed 

data into a number of modeling techniques is 

providing basic information about distribution, 

ecology, and the potential range of species without the 

collection of actual sampling data. By combining what 

is known about the vector species’ biological and 

environmental requirements with the environmental 

and geographic data obtained from remote sensors, 

ecological niche modeling allows planners to 

determine if conditions in a geographic area are 

favorable for a given vector, and to assign probabilities 

to their occurrence. Obviously, this information is of 

great value to preventive medicine planners in that it 

allows them to sharpen their focus in their 

assessments, reducing the unknowns by a considerable 

amount. MAJ Colacicco-Mayhugh’s article is a concise, clearly presented description of niche modeling 

as a potentially invaluable tool for those planning not 

only combat deployments, but also humanitarian 

assistance missions in remote parts of the world. 

Although military entomologists are usually focused 

on management of the smallest of pests, they often 

share responsibilities with military veterinarians in 

dealing with feral and wild animals in deployment 

areas. LTC Raymond Dunton and MAJ Gerald Sargent 

have contributed an important article that addresses 

their experiences in this area while deployed to Iraq. 

Their article provides detailed insight into an often 

controversial area of public health, the significant 

differences in purpose and capabilities between 

contingency animal control efforts and rabies control 

programs. Ideally, a military deployment is temporary 

and localized, contending with environmental and 

public health concerns which directly affect the 

readiness of the force. Invariably, there is contact 

between deployed personnel and feral dogs and cats, 

as well as wild animals drawn to the deployment area 

by the increased availability of food, either as 

predators or foragers. Resulting animal bites take 

military personnel away from their duties until the 
 July – September 2009 3

THE ARMY MEDICAL DEPARTMENT JOURNAL

status of potential rabies infection has been 

determined, and resources are dedicated to locating, 

capturing, and examining the animal involved. In their 

explanation of why the military must use capture and 

euthanasia as animal control measures, LTC Dunton 

and MAJ Sargent clearly and completely explain the 

various rabies control measures that are used as part of 

long-term, national programs designed to first reduce 

zoonotic disease, but often with reduction in the 

numbers of animals as only a secondary effect. They 

explain why such measures are neither practical nor 

effective in protecting personnel in a localized, 

temporary situation, and how the military works very 

hard to minimize animal movement into the bases, 

thus reducing the requirement for euthanasia as much 

as possible. The information in this article should be 

used in predeployment training to expose personnel to 

the “whys” of the Army’s animal control policy, 

which, to the uninformed, may seem harsh. Such 

concerns are distracting and counterproductive to 

accomplishing the military mission of the deployment. 

Identification of arthropod species is one of the most 

important skills that a military medical entomologist 

must have. Recognition of disease vectors during 

surveillance is the vital first step in planning and 

implementing countermeasures to the disease threat 

they represent. As with every other extensive field of 

science, entomology has many areas of expertise 

among its specialists, but those entering the military 

must be proficient in species recognition and 

identification—our Soldiers’ health depends on their 

ability. Such training has been expensive and time 

consuming, involving contracting classes and experts. 

In their informative article, Navy CDR (Ret) George 

Schultz and Dr Richard Robbins introduce a project by 

the Armed Forces Pest Management Board to provide 

training in species identification using interactive 

programs available on computer CDs and DVDs. They 

describe in detail the 3 initial remote teaching 

programs focusing on ticks and mosquitoes, and 

include illustrations of their functionality and 

interactive capabilities. The advantages in 

accommodation of student schedules, flexibility of use, 

and cost effectiveness are clearly explained. This is an 

exciting first step in training in a specific skill set that 

is undoubtedly adaptable into many other areas that 

require specialized medical training of smaller student 

populations. 

For most people, perhaps the most common of 

arthropod pests are the various species of house flies. 

These ubiquitous insects are not only annoying, but 

have been recognized for many years as threats to 

human health as transporters of a considerable array of 

human pathogens. The presence of house flies is especially problematic in deployed environments, where 

public health infrastructure to support sanitation and 

hygiene may not exist, or, in many cases, has never 

existed. Their large numbers pose significant challenges for our military preventive medicine professionals in reducing both their existing numbers and 

their reproduction rates. Unfortunately, we have 

learned that house flies are extremely adaptable, 

rapidly developing resistance in their breeding cycles 

to our attempts to control them with insecticides. Two 

University of California at Riverside scientists, MAJ 

Alec Gerry (USAR) and Dr Diane Zhang, investigated 

the rapidly spreading resistance to a common fly bait 

that house flies in southern California have demonstrated since 2003. They describe their well researched, carefully designed study in a fascinating article that 

reveals the complexity of attempting to identify whether the generational change is increased physiological 

resistance to the bait’s toxic component, a change in 

behavior by which the flies increasingly avoid the bait, 

or a combination of both. Their study is an illustration 

of the scientific rigor that must be applied when examining a phenomenon that has multiple, perhaps 

interacting causes which may also be changing over 

time. Further, this study is a classic example of an area 

of public health research that clearly has significant 

value for both military and civilian applications. 

The problems of obtaining data and understanding the 

situation with regard to vector-borne diseases is not 

limited to remote areas with no advanced medical 

surveillance and laboratory resources. The US military 

has had a continuous, significant presence in the 

Republic of Korea (ROK) for over 50 years, and a 

tremendous amount of work has been done in 

improving public health and dealing with vector-borne 

diseases. However, as LTC William Sames and his 

coauthors point out in their detailed, very informative 

article, much is still unknown about the presence and 

distribution of a number of tick- and rodent-borne 

pathogens that cause serious illnesses in humans. This 

is due to a number of factors over the years, and, as 

pointed out in the article, the ROK government and US 

military are both placing increased emphasis and 
4 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

Perspective 

resources into surveillance, tracking, and analysis of 

disease data, and research into the vectors and pathogens throughout the country. Because the presence of 

these diseases may not be well known, the potential for 

misdiagnosis is significant. This well-researched, 

carefully developed article contains important 

information for healthcare providers who provide 

services to military personnel stationed in the ROK, or 

to those who rotate there on training deployments. 

The first line of the individual Soldier’s defense 

against arthropod-borne pathogens is the proper use of 

personal protective measures, particularly the 

application of an effective repellent. The most widely 

produced and used repellent, N,N-diethyl-3-

methylbenzamide (deet), was developed in 1954, but 

over the last decade has come under increasing critical 

scrutiny for associated adverse effects and other 

troubling chemical properties. LTC Van Sherwood and 

his team have contributed an excellent article reporting 

a formal study they performed in Kenya evaluating 

deet in comparison with 4 other commercially 

produced repellent formulations against mosquitoes. 

This was a detailed, scientifically rigorous field study 

involving volunteers and careful data collection and 

analysis. LTC Sherwood et al point out that although 

the work performed and data analysis of this study 

were extensive and did produce solid results, the study 

should be contributory to additional studies exploring 

other aspects of repellent effectiveness, under other 

conditions. This article is another excellent example of 

the high caliber of work being performed every day by 

the US military’s dedicated scientific professionals in 

our overseas laboratories. 

One method for rapid application of pesticides over 

large areas is aerial spraying. Although on the surface 

it may appear to be a straightforward process involving 

special equipment and skillful flying, in reality it is a 

much more complex undertaking. USAFR Maj Mark 

Breidenbaugh and his coauthors have contributed a 

fascinating article which reports on the test and evaluation trials that the USAF Aerial Spray Unit performed to determine the character and dispersal of the 

spray patterns generated by a new fuselage-mounted 

spray boom configuration installed on their C-130H 

airplanes. Generation of predictable droplet size and 

prediction of drift are key parameters in planning 

effective aerial pesticide spray applications, especially 

for mosquito control. Therefore, the new configuration 

had to be carefully tested to evaluate the effect of the 

airplane’s turbulence on droplet size and drift, under 

various atmospheric conditions. This article is an 

illuminating presentation of the myriad of details, 

calculations, considerations, and allowances which 

must be included in planning spray missions, not only 

considering the weather and coverage areas, but the 

species of the target pest as well. Different species 

may require different droplet sizes and dispersals to be 

effective, and may also have different optimal times of 

application, which could then affect the configuration 

of the delivery system. This article gives insight into 

the high level of expertise and professionalism that is 

required for this very specialized capability, which is 

extremely important to both the military and civilian 

emergency management agencies. 

The extent of the serious impact of diseases on combat 

effectiveness, especially in large-scale, extended 

hostilities, was fully understood after World War II 

and the Korean War, and military leadership realized 

that addressing that threat was a full-time effort, in 

periods of both peace and war. In addition to 

establishing the overseas laboratories, a centralized 

activity was envisioned to coordinate efforts and 

resources, and ensure the timely availability and 

exchange of current pest management information 

across the services. The predecessor of the Armed 

Forces Pest Management Board (AFPMB) was created 

in 1956 and chartered to be the US military’s 

clearinghouse in support of US forces worldwide in 

the prevention of arthropod-borne diseases, as well as 

losses from other forms of pest attacks. USAF Col 

William Rogers, Dr Richard Robbins, and Navy CAPT 

Stanton Cope of the AFPMB have contributed an 

excellent article describing the history, responsibilities, 

organization, and functioning of the AFPMB. Among 

other important resources provided by the AFPMB, the 

article details the Literature Retrieval System which 

accesses the AFPMB’s extensive reference library, one 

of the world’s most highly respected sources of 

information in vector-borne diseases and medically 

related zoological topics, especially entomology. In 

addition, the authors highlight the important role 

AFPMB plays in careful management of pest control 

products, ensuring that military pest control efforts are 

environmentally sound, and, above all, safe for all 

concerned. 
 July – September 2009 5

THE ARMY MEDICAL DEPARTMENT JOURNAL

Soldiers in many tactical environments must use 

camouflage face paints to improve their concealment, 

especially in jungles or other areas of foliage and trees. 

Operations in such areas also make Soldiers vulnerable 

to arthropods, and to the disease pathogens they may 

carry. As mentioned earlier, the first defense in such 

situations is proper use of personal protective 

measures, especially repellents. Application of the 

separate face paint and repellent is a 2 step process, 

repellent first, then paint. The Army has developed a 

formulation of face paint combined with 30% deet 

repellent to eliminate that second step, and reduce the 

number of items involved. The development process 

had to ensure that the efficacy of neither the paint nor 

the deet was compromised in the blend, and the 

product had to be field tested before it could be 

accepted and put into production and distribution. In 

their article, MAJ Kendra Lawrence and her coauthors 

present a detailed, well-developed report on the field 

trials of the combined product. The tests were 

conducted in rural Belize, using local volunteers, and 

were designed to be scientifically rigorous and 

thorough, examining every aspect of product 

effectiveness and safety. The data was analyzed 

producing extensive statistical profiles of effectiveness 

against a number of mosquito species. The article by 

MAJ Lawrence et al is yet another example of the 

professional skills and technical expertise of AMEDD 

professionals that directly benefit our Warriors in 

every tactical environment and situation. 

As the science of identification and analysis of vectors 

and their pathogens has become increasingly more 

sophisticated, our ability to plan and counter the 

threats they impose have markedly improved. 

However, no matter the capabilities of laboratory 

science, the first requirement of the process remains 

basic—specimens of the potential vectors must be 

collected in the field. In their article, CPT Lee 

McPhatter, Cara Olsen, and COL Mustapha Debboun 

describe their study into ways to refine the 

methodology of collecting specific mosquito species, 

especially gravid female mosquitoes which provide the 

best estimate of an infected population. We are all 

familiar with the commercial types of mosquito 

control traps, especially the light and CO2 attractant 

versions, but research has show that any trap must use 

a lure to be truly effective. In order to attract and 

ultimately trap gravid female mosquitoes, research 

such as that described in this article must determine 

the type of aquatic site that a mosquito species prefers 

for depositing eggs. CPT McPhatter et al infused a 

variety of organic substances in water to examine their 

respective effectiveness in traps placed in a variety of 

locations across Fort Sam Houston. Their detailed, 

clearly written article presents the methodology, 

results and analysis of a well-researched, carefully 

planned and executed study project. Their work is 

another important contribution to the ever-growing 

body of vital scientific knowledge with which we 

better know and combat these dangerous and evolving 

scourges to human health. 

A new book by an international collaboration of 3 military 

medical entomologists is another clear example of the 

significant contributions to worldwide public health made by 

the research and experience of military medical professionals 

worldwide. COL (Ret) Dan Strickman of the US Dept of 

Agriculture Research Service, Dr Stephen Frances of the 

Australian Army Malaria Institute, and COL Mustapha 

Debboun of the AMEDD Center & School designed their book 

as a practical, easy to read resource for those with an interest 

in the subject, or, more importantly, anyone involved in 

activities presenting the potential for contact with harmful 

arthropods. The Editor

OF INTEREST
6 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

INTRODUCTION

Several families of beetles have the ability to secrete 

vesicating chemicals. The presumed significance of 

these chemicals is that they deter predators, and, when 

passed along to the eggs, improve the likelihood of 

successful reproduction.1,2 From a medical standpoint, 

the vesicating chemicals can injure human skin. From 

a public health standpoint, some of the beetles swarm 

during certain seasons and the large numbers of beetles 

pose a considerable public health threat. 

The beetle families with the greatest impact on humans 

are Meloidae (blister beetles), Oedemeridae (false 

blister beetles), and Staphylinidae (rove beetles). 

Although many people use the term “blister beetle” to 

describe any beetle with vesicating properties, in this 

article that term will be applied strictly to Meloid 

beetles. Blister beetles and false blister beetles are 

medically important because they produce the 

chemical cantharidin that causes skin blistering. There 

are approximately 2,500 species within the family 

Meloidae worldwide, and all produce cantharidin.3

There are approximately 1,000 species within the 

family Oedemeridae, but only a few species in the 

Pacific basin and Caribbean are known to produce 

cantharidin.4,5 Cantharidin is synthesized by male 

beetles and passed to females during mating.2

 It is 

contained in the hemolymph and is exuded by 

reflexive bleeding from leg joints of adult beetles as a 

defensive mechanism or in response to external 

pressure, such as a person rubbing a beetle against the 

skin. It is a potent vesicant and causes blisters within 

24 hours of skin contact. If a blister beetle is ingested, 

the consumed cantharidin causes severe irritation of 

the gastrointestinal tract and inflammation of the 

kidneys.6

 Cantharidin poses a special hazard for horses 

which can die after eating Meloid contaminated hay.7,8

Soldiers may encounter these beetles when working 

outdoors. Indeed, there are numerous examples of 

cantharidin affecting military operations. A large 

number of French Legionnaires were hospitalized in 

Algeria for cantharidin poisoning after eating frogs 

that had ingested Meloids,9

 and Oedemerids have 

caused blistering among troops in New Zealand.10

The genus Paederus (Staphylinidae) contains more 

than 600 members with species occurring in all 

Outbreak of Dermatitis Linearis Caused by 

Paederus ilsae and Paederus iliensis 

(Coleoptera: Staphylinidae) at a 

Military Base in Iraq 

CPT Silas A. Davidson, MS, USA 

COL (Ret) Scott A. Norton, MC, USA 

LTC Mark C. Carder, MS, USA 

COL Mustapha Debboun, MS, USA

ABSTRACT

An outbreak of dermatitis linearis caused by Paederus iliensis (Coiffait) and Paederus ilsae (Bernhauer) occurred at 

Joint Base Balad in north central Iraq during 2007. It was the first reported incident of P iliensis in Iraq. Some Paederus 

species contain the vesicating chemical, pederin, which causes painful lesions when crushed on the skin. At this 

location, 20 Soldiers and Airmen sought medical treatment for skin blistering, most commonly affecting the neck and 

hands. All cases presented during May and June. Sampling for Paederus began in June after beetles were collected in an 

area where Soldiers had developed dermatitis and continued until October when no further beetles were collected. 

Paederus beetles were most likely flying in from areas surrounding the base, and were most common near the base’s 

perimeter in close proximity to bright lights. Nighttime sampling showed that Paederus beetles were most active from 

one hour after sunset until midnight. Most of the military personnel affected were Soldiers who worked night shifts near 

bright lights. The occurrence of dermatitis linearis can largely be prevented by modifying the light sources that attract 

Paederus beetles. 
 July – September 2009 7

temperate and tropical continents, north and south of 

the equator.11 Most species are slender, about 7 mm to 

13 mm long, and are distinctly colored with black 

heads, orange bodies, black abdominal tips, and 

metallic blue or green elytra (Figure 1). One or a 

combination of the vesicating chemicals pederin, 

pseudopederin, and pederone have been found in 20 

species of Paederus.12 Pederin is the most common 

chemical of the three and is one of the most complex 

nonproteinaceous insect secretions known.12 It acts at 

the cellular level by blocking mitosis and is produced 

by endosymbiotic bacteria within beetles.13 Females 

that are “infected” with these symbiotic bacteria 

produce eggs that contain the bacteria in the outer shell 

walls. Subsequent generations of beetles acquire the 

symbiotes necessary to produce pederin by ingesting 

eggs shells “infected” by the symbiotic bacteria or by 

cannibalizing larvae containing the bacteria.14 Not all 

Paederus contain endosymbiotic bacteria and 

uninfected beetles do not produce pederin. Outbreaks 

often contain mixed populations of infected and 

noninfected Paederus.

15

Paederus beetles do not release pederin as a defensive 

secretion and people are exposed to the chemical only 

when a beetle is accidentally crushed on the skin.12

Therefore, skin blistering most often occurs on 

exposed skin of body parts such as the neck, head, 

arms, and legs where a beetle is felt crawling on the 

skin and subsequently crushed (Figure 2). Mirrorimage lesions, commonly called “kissing” lesions, may 

form when uncontaminated skin is pressed against an 

opposite area of pederin contaminated skin. Pederin is 

sometimes transferred to other sensitive areas of the 

body such as the eyes or genitals by pederincontaminated hands. Ocular and periocular lesions 

caused by accidentally rubbing pederin into the 

conjunctivae and eyelids are commonly known as 

“Nairobi eye” in east Africa.16

The skin condition in humans that is caused by 

vesicating chemicals from Paederus is called 

dermatitis linearis.17 This eruption usually begins 24 to 

72 hours after pederin contacts exposed human skin. 

Initially, affected areas turn red and then vesicles form 

a few days later. These vesicles typically coalesce into 

bullae that last for one or 2 weeks and eventually crust 

over, dry, and peel off, leaving red marks that can last 

for months.6

 The lesions are often very uncomfortable 

and may itch or burn severely.18 In rare cases, contact 

with pederin can cause fever, headache, joint pain, and 

vomiting.17

Dermatitis caused by cantharidin is generally less 

symptomatic than that caused by pederin because 

cantharidin blisters do not cause as intense burning or 

itching. Cantharidin signs and symptoms usually begin 

within 12 to 24 hours, which is sooner than pederin’s 

effects.18 Another difference is that victims usually 

remember coming into contact with 

Meloid or Oedemerid beetles because 

of their large size (Figure 3). Many 

victims are not aware that Paederus

were ever crushed on their skin 

because of their small size and the 

delayed onset of blistering. 

An additional militarily-relevant 

concern with Paederus is that blisters 

can easily be mistaken for the effects 

of chemical weapons. Some authors 

Figure 1. Adults of Paederus ilsae (top) and Paederus iliensis

(bottom). The bright coloration may function to warn potential 

predators that these beetles are toxic. 

(Photo courtesy of Mr Lyle Buss, University of Florida) 

Figure 2. Blisters caused by Paederus on the neck and hand of Soldiers at Joint 

Base Balad in 2007. 
8 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

regard pederin as a natural mimic of vesicating warfare 

agents such as mustard and Lewisite.19 When adult 

beetles are active, a large number of individuals may 

be affected, which could lead to the false assumption 

that a chemical agent was used. In 1997, during a 

training exercise in Arizona, several Marines 

developed blisters, probably caused by Paederus, but 

believed they had been exposed to chemical 

weapons.20

In the tropics, outbreaks of dermatitis linearis are more 

common among western expatriates than among 

indigenous populations because the westerners 

typically use more lights at night, which then attract 

Paederus.

18 Similarly, outbreaks of dermatitis linearis 

that have affected military operations often involve the 

creation of well-illuminated camps in Paederus

endemic areas. Outbreaks have occurred among 

British troops conducting operations in northern 

Kenya,16 Canadian forces serving in the Central 

African Republic and in Sierra Leone,21 and the Indian 

military during a training exercise in northern India.22 

Dermatitis linearis was recently 

observed among US military 

members serving in central and 

southwest Asia. From December 

2001 to March 2002, 191 cases 

of dermatitis linearis were 

observed among military 

personnel serving at a remote 

military base in Pakistan.23 Most 

of the affected individuals 

worked near artificial lights at 

night. In May 2002, more than 

30 cases of dermatitis linearis 

were observed among Special 

Operations Forces serving in 

Afghanistan.24 The majority of 

affected Soldiers were night shift 

maintenance personnel. 

There are few reports of Paederus species collected in 

Iraq. Paederus mesopotamicus (Eppelsheim) was 

described near Baghdad in 1889.25 Paederus fuscipes

(Curtis) and Paederus ilsae (Bernhauer) were included 

among a list of Iraqi insects published in 1965.26 P 

ilsae has been found in cotton and clover fields near 

the city of Mosul in northern Iraq.27 The first report of 

dermatitis linearis occurring in Iraq was recently 

published by an Iraqi doctor.28 His report described 87 

cases among Iraqi civilians that were treated at a 

hospital in the Najaf province of southern Iraq from 

April 2006 to April 2007, with the majority of cases 

occurring in May and June. The Iraqi doctor noted that 

dermatitis linearis has been a well known skin disease 

in the area for several years. 

This article describes Paederus activity that occurred 

in 2007 at Joint Base Balad in Iraq. Although 

dermatitis linearis in Iraq is not limited to Joint Base 

Balad, it is the only location where the species of 

Paederus causing dermatitis linearis was identified. 

Information presented here can be used to help prevent 

and identify future outbreaks at other locations. 

MATERIALS AND METHODS

Joint Base Balad is approximately 110 km north of 

Baghdad in north central Iraq (Figure 4). The base is 

surrounded by agricultural areas that are supplied with 

water from the Tigris River through an extensive 

system of canals. There are no large urban areas in 

close proximity to the base. 

In early May 2007, information 

was presented at a Multi-National 

Corps-Iraq Surgeon’s Conference 

held in Baghdad about the 

possibility of vesicating beetles 

causing dermatitis in Iraq. 

Several military dermatologists 

had observed cases over the 

previous 4 years that they 

suspected might have been 

caused by beetles. At that time, 

no Meloid blister beetles or 

Paederus beetles had been 

collected and linked to cases of 

dermatitis occurring among 

Soldiers in Iraq. Based on the 

information presented at the 

Surgeon’s Conference in 

Baghdad, a short presentation about vesicating beetles 

was made at a monthly Preventive Medicine Forum 

hosted at Joint Base Balad by the 133rd Medical 

Detachment on May 31, 2007. Within 24 hours, the 

133rd Medical Detachment was contacted by medical 

personnel from 2 separate medical treatment facilities 

on base stating that they had recently treated Soldiers 

and Airmen with blisters that matched the clinical 

Outbreak of Dermatitis Linearis Caused by Paederus ilsae and 

Paederus iliensis (Coleoptera: Staphylinidae) at a Military Base in Iraq 

Figure 3. Size comparison between Epicauta 

vittata (left) at 18 mm, a common cantharindproducing Meloid blister beetle from North 

America, and Paederus iliensis (right) at 7 mm, 

from Iraq. 
 July – September 2009 9

THE ARMY MEDICAL DEPARTMENT JOURNAL

signs and locations on the body associated with 

vesicating beetles. One medical provider noted that he 

assumed he was treating classical burns since his 

patients were mechanics and may have accidentally 

came into contact with hot vehicle parts or had hot 

fluids drip on their skin while working. 

A survey was conducted on June 2, 2007, at a site 

where 5 Airmen worked and who had sought treatment 

for blisters on their necks the previous week. Sampling 

during the day at this site did not identify any beetles, 

however, 2 Paederus beetles were found the next 

morning on cockroach sticky traps that were placed 

overnight in the area. These beetles were sent for 

identification to Dr Howard Frank, an entomologist at 

the University of Florida who is a leading authority on 

Paederus, along with other specimens collected later 

during the summer. 

During the following week, sampling for Paederus

was conducted throughout the base and was focused 

around bodies of water because many species of 

Paederus are known to live in wet places, such as the 

edges of lakes, marshes, and floodplains.12 Visual 

searches for beetles were conducted among plants and 

rocks surrounding retention ponds and other areas with 

standing water on base. Also dozens of cockroach 

sticky traps were placed around the edges of bodies of 

water. 

Starting on June 6, 2007, sampling was conducted near 

portable light towers because many of the Soldiers and 

Airmen who developed blisters worked near bright 

lights at night. More than 100 generator-powered 

portable light towers were located throughout the base. 

Portable light towers were set at heights from 6 m to 9 

m and had 1,000 watt metal halide lamps. White 

plastic dinner plates 26 cm in diameter were placed on 

the ground under the towers. The plates were filled 

with water and 3 to 4 drops of commercial 

dishwashing soap were added to each plate to break 

the surface tension. The plates were collected the 

following morning and the beetles counted. 

Sampling was conducted each night from June 6 

through June 9, 2007, at 20 light towers located 

throughout the base. After June 10 only light towers 

near the perimeter were used and sampling was 

conducted 3 times a week until the end of October 

2007. An index for nightly beetle activity was 

determined by dividing the total number of beetles 

caught per night by the number of plates set out. 

Sampling was conducted for 3 nights during the week 

of June 10 to June 16, 2007, to determine how 

proximity to the light source affected the number of 

beetles captured. On each night, 5 light towers were 

selected and 3 plates were placed at each light tower at 

fixed distances. One plate was placed directly 

underneath the light source, another at 2 meters, and a 

third 6 meters away. 

Sampling was conducted on June 5 and June 20, 2007, 

to determine what times of the night beetles were 

actively flying. A particular light tower near the base’s 

perimeter was selected based on high beetle collection 

counts during previous sampling periods. A white bed 

sheet was spread on the ground and visually observed 

from dusk and throughout the night. The observers 

counted beetles that actually landed on the sheet and 

recorded these tallies in one hour increments. 

There were many questions asked by Soldiers and 

medical personnel as to whether permethrin treated 

uniforms would function to repel Paederus. To answer 

their questions, 10 live beetles were collected on the 

Figure 4. Location of Joint Base Balad in Iraq. (Map courtesy of 

US State Department, 2008, annotated separately.) 
10 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

night of June 20, 2007, and placed in clean Petri dishes 

that were kept inside an air conditioned building until 

the following day. Three of the beetles were 

individually placed on an Army Combat Uniform field 

jacket that was treated with permethrin 2 weeks earlier 

with an Individual Dynamic Application Absorption 

Kit. The beetles were left on the jacket for 15 minutes, 

their activity was recorded, and then they were placed 

back into Petri dishes and monitored until they died. 

RESULTS AND DISCUSSION

Twenty Soldiers and Airmen sought treatment at Joint 

Base Balad in 2007 for symptoms related to dermatitis 

linearis. It is possible that more individuals were 

affected but did not seek medical 

treatment. All cases occurred 

between late April and early June 

2007. The most commonly affected 

body region was the neck followed 

by the hands and forearms (Table 1). 

The neck was the most affected 

region because it is one of the few 

exposed areas of skin when a Soldier 

is wearing a uniform. The hands 

were less commonly affected 

although they were probably 

involved with crushing beetles on 

the neck. The thick epidermis of the 

palms often prevents lesions from 

forming even when a beetle is 

crushed.12 There were no reports of 

conjunctivitis caused by pederin contacting the eye. 

There was one case where a “kissing” lesion formed 

on a Soldier’s neck and another Soldier developed a 

blister near the waistline which most likely occurred 

when a beetle fell down into his shirt and was crushed 

against his body. 

The beetles collected at Joint Base Balad were 

identified by Dr Frank as Paederus (Heteropaederus) 

iliensis (Coiffait) and Paederus (Dioncopaederus) 

ilsae (Bernhauer). Paederus ilsae has been identified 

in 2 previous collections from Iraq.26,27 This is the first 

known report of P iliensis occurring in Iraq. However, 

it is possible that this species was misidentified as 

another species in earlier studies. A report from 1965 

listed P fuscipes in Iraq.26 P fuscipes is closely related 

to P iliensis, and since P iliensis was not described 

until 1970,29 it is possible that the earlier described P 

fuscipes was actually P iliensis. Both of the identified 

species are known in other countries to cause blister 

dermatitis. P ilsae has been identified as causing 

dermatitis in Israel30 and P ilsae and P iliensis in 

southern Iran.31,32

The severity of dermatitis and amount of pederin 

contained by each species was not determined in this 

study. In Iran, P ilsae is known to cause more severe 

and longer lasting dermatitis than P iliensis.

31 In 

southern Iran, P ilsae was also more abundant than P 

iliensis.

32 In 2007, P iliensis was the most common 

species collected at Joint Base Balad. On the nights of 

24 July and 25 July, 269 P iliensis and 9 P ilsae were 

collected, for a ratio of 30:1. 

The period when beetles initially 

became active was not determined 

because surveillance did not begin 

until early June when cases of 

dermatitis were being noticed. 

Sampling showed that beetles 

became less active in mid-July and 

the last beetle was collected on 

October 8, 2007 (Figure 5). Since all 

cases of dermatitis occurred between 

late April and early June, beetle 

activity might have been greater 

during those months. Paederus

activity at Joint Base Balad was 

consistent with previous reports 

showing that P ilsae and P iliensis

were most active in the spring and 

early summer. P ilsae adults have been collected in 

northern Iraq in early June27 and in Israel from May to 

July.30 P ilsae and P iliensis were found in southern 

Iran from late April to early September.31 Even though 

the species of Paederus were not identified, dermatitis 

linearis occurred in the Najaf province of Iraq from 

April to August with a peak incidence in May.28

There were no obvious peaks during sampling that 

indicated distinct generations of beetle emergence. 

Paederus beetles have one to 3 generations per year 

with more generations occurring in the tropics.12 P 

ilsae is thought to have 2 generations per year in 

Iran.32 A late start of sampling and overlap of 

generations may have masked generation peaks. 

Flight activity by Paederus is often considered to 

follow rain showers or the rainy season.12 Beetles most 

likely fly after rain showers because the higher 

Outbreak of Dermatitis Linearis Caused by Paederus ilsae and 

Paederus iliensis (Coleoptera: Staphylinidae) at a Military Base in Iraq 

Affected Body 

Region Number % 

Face 1 5 

Neck 14 67 

Torso 1 5 

Arm and 

forearm 2 10 

Hand 6 28 

Total 24 115 

Table 1. Most commonly affected 

body regions among 20 individuals 

at Joint Base Balad in 2007. Note: 

total percentage is greater than 

100 because some patients had 

more than one region affected. 
 July – September 2009 11

THE ARMY MEDICAL DEPARTMENT JOURNAL

humidity helps the beetle avoid becoming desiccated 

during dispersal flights.12 Cases of dermatitis in 

southern Iraq have been attributed to beetles beginning 

to fly after the rainy season ends in late March or early 

April.28 At Joint Base Balad in 2007, there was no 

significant rainfall that immediately preceded beetle 

activity. However, it is possible that extensive 

irrigation in the area could have created conditions 

favorable for beetle flight. 

During the night time sampling, observers first noticed 

beetles flying one hour after sunset 

(Figure 6). Beetle activity peaked 

before midnight and did not continue 

throughout the night. Reports from 

Israel indicated that P ilsae actively 

flies after sunset when the sky is 

completely dark.30

Beetles were most commonly 

collected directly beneath light 

sources. Placing plastic plates filled 

with water at fixed distances from 

light towers showed that significantly 

more beetles were found directly 

under lights than at distances only a 

few meters away (Table 2). Beetles 

were observed to have a positive 

phototaxis whether flying or running. 

Flying beetles fell to the ground as 

they approached a light source. 

Once beetles were on the 

ground, they moved rapidly to 

the spot of greatest illumination 

directly below the light source. 

This strong attraction to light 

greatly influences which 

individuals come into contact 

with the beetles. Many of the 

Soldiers who developed 

dermatitis were mechanics who 

worked at night on vehicles and 

other equipment that were 

directly illuminated by overhead 

light sources. Security guards 

were also commonly affected, 

especially those who had placed 

ultraviolet electrocution devices 

(Bug Zappers®) near their guard 

posts. In contrast, other Soldiers 

who worked at the same time, 

but not directly under a light source, were not affected. 

The following 3 conditions are most often associated 

with outbreaks of dermatitis linearis18: 

People working in agricultural areas where beetles 

are active 

Beetles entering a building where people are 

working or sleeping 

People working at night in illuminated areas. 

0

5

10

15

20

25

30

35

40

6-Jun

20-Jun

4-Jul

18-Jul

1-Aug

15-Aug29-Aug

12-Sep

26-Sep

10-Oct24-Oct

Date

Paederus Beetles Per Trap

Figure 5. Average number of Paederus spp collected in water filled plastic plates under 

light towers per night at Joint Base Balad in 2007. 

0

2

4

6

8

10

12

14

2000 2100 2200 2300 2400 0100 0200 0300 0400 0500

Hours 

Beetles Observed per Hour

10 June

14 June

Time (24 hour clock) 

Figure 6. Number of Paederus spp observed at hourly intervals at Joint Base Balad 

in 2007. Nautical sunset was at 2011 hours June 10, 2007 and at 2013 hours on 

June 14, 2007. 
12 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

It appeared that all cases in 2007 at Joint Base Balad 

resulted from Soldiers working under lights at night. 

Mass aggregations of beetles were never observed 

inside buildings as sometimes happens during 

outbreaks. Sometimes Paederus can be so numerous 

inside buildings that white walls appear black.33

Observed Paederus spp were most likely flying in 

from fields surrounding the base and were not found 

breeding around bodies of water on the base. On base, 

live beetles were found only near light sources at 

night. Dead beetles were found during the day under 

rocks or concrete barriers close to light towers. 

Another indication that beetles were flying onto the 

base was that they were more common near the 

perimeter of the base compared to the interior. The 

majority of Soldiers who developed dermatitis worked 

or lived near the base perimeter. 

Joint Base Balad is an ideal environment for attracting 

Paederus because it has a large quantity of bright 

lights in a rural area with few competing light sources. 

It is unclear how common dermatitis linearis is among 

the communities surrounding the base. In southern 

Iraq, dermatitis linearis is commonly called 

phosphorous insect rash due to the beetles’ attraction 

to fluorescent lights.28

To answer Soldiers’ questions as to whether 

permethrin-treated uniforms repelled Paederus, 3 P 

iliensis were placed on a permethrin treated field 

jacket (Figure 7). The beetles showed no obvious 

aversion to being on the jacket and moved to 

concealed places, such as under the collar, where they 

remained until removed. We do not know if 

permethrin-treated uniforms will effectively cause 

beetles to quickly fly or drop off after they have landed 

on a Soldier. Nevertheless, we noticed that when a 

small sample of 3 beetles were placed on the treated 

uniform, they died sooner than the other beetles, ie, 2 

to 3 days sooner, while the other beetles lived from 5 

to 12 days in their Petri dishes. It is possible that the 

exposure to permethrin caused them to die sooner after 

being placed on the uniform. The efficacy of N,Ndiethyl-3-methylbenzamide (deet) was not evaluated, 

although it might be useful, since it repels other types 

of beetles.34 More studies are needed to determine if 

permethrin and deet repel Paederus. 

Paederus beetles are highly susceptible to insecticides 

and there are many reports of controlling outbreaks 

with insecticides.12 Most reports describe situations 

where Paederus enter buildings or form large 

aggregations and are clearly visible crawling on the 

walls. Permethrin was applied with an ultralow volume 

sprayer to control Paederus in a US military fitness 

center in Pakistan.23 However, it does not seem 

practical to use insecticides to control Paederus in 

situations where they are attracted to lights and fly in 

from unknown distances away. The area that would 

need to be treated is too large and the sites where the 

beetles are breeding are often unknown. 

The best strategy to prevent outbreaks of dermatitis 

linearis when Paederus are flying into an area based 

on their attraction to light is to modify the attracting 

light sources. Staphylinid beetles are attracted to 

ultraviolet and white light, but are relatively 

insensitive to orange and yellow light.35 An 

outbreak of dermatitis linearis at a game reserve in 

Tanzania was quickly halted after all mercury tube 

lights, which emit ultraviolet light, were replaced by 

incandescent light bulbs, which emit mainly yellow 

and orange light.36 If possible, switch to sodium 

vapor and halogen lights because they emit only 

orange and yellow light and are therefore the least 

attractive to flying insects.37 Another method of 

prevention would be to remove unnecessary lights 

Outbreak of Dermatitis Linearis Caused by Paederus ilsae and 

Paederus iliensis (Coleoptera: Staphylinidae) at a Military Base in Iraq 

Distance from 

Light Source 10 June 12 June 16 June Average 

0 meters 35.8 ± 15.6 27.8 ± 15.4 44 ± 21.7 35.9 ± 17.6 

2 meters 1.8 ± 1.5 2.2 ± 1.9 3 ± 2.3 2.3 ± 1.9 

6 meters 0.2 ± 0.4 0.4 ± 0.9 0.2 ± 0.4 0.3 ± 0.6 

 Date 

Table 2. Paederus spp collections at different distances from 

a light source at Joint Base Balad in 2007. 

Figure 7. Paederus iliensis crawling on permethrin treated 

uniform. 
 July – September 2009 13

THE ARMY MEDICAL DEPARTMENT JOURNAL

from an area to reduce the number of beetles attracted. 

At Joint Base Balad in 2007, Paederus were a problem 

at guard posts where ultraviolet insect electrocution 

devices were used but ceased to be a problem when 

those devices were removed. Rest and work areas can 

be relocated farther away from bright lights. There 

were several cases of dermatitis linearis among a 

group of night-shift mechanics who took smoke breaks 

at a table located directly under a light tower, but new 

cases of dermatitis ceased once the table was moved. 

Sampling for Paederus was performed by placing 

water-filled plastic plates under light towers near the 

perimeter of base. This sampling method was efficient 

because it collected a large number of beetles, did not 

require special equipment, and was easily 

implemented by preventive medicine personnel during 

their routine mosquito and sand fly surveillance. Using 

light towers or other bright lights to determine if 

Paederus are present would be worthwhile at other 

locations because outbreaks are often unpredictable. 

When large outbreaks do occur, they can have a major 

impact on public health. In 1966, more than 2,000 

patients sought treatment for dermatitis linearis at a US 

Army hospital in Okinawa,38 and outbreaks among 

Australian aboriginal communities have forced the 

evacuation of entire villages.39 Early detection of 

Paederus through sampling will allow implementation 

of preventive measures to lessen the effects of an 

outbreak. Notification of medical personnel of the 

presence of Paederus enables prompt education on 

diagnosis and management of cases of dermatitis and 

averts or dispels needless concern that chemical 

weapons have been released.19 Information from 

entomologic surveillance can help educate Soldiers 

about the time periods when beetles are active and 

what to do if they work in an area infested with 

Paederus. Soldiers should be instructed to try to avoid 

crushing any insects crawling on their skin, and if a 

Paederus beetle is crushed, to immediately wash the 

area with soap and water to prevent skin blistering.12

ACKNOWLEDGEMENT

We thank Dr Howard Frank at the University of 

Florida’s Department of Entomology and Nematology 

for identifying Paederus specimens and his suggestions 

of methods for beetle collection. 

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Paederus iliensis (Coleoptera: Staphylinidae) at a Military Base in Iraq 
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AUTHORS

CPT Davidson is an instructor and course writer at the Medical Zoology Branch in the Department of Preventive 

Health Services, Academy of Health Sciences, US Army Medical Department Center and School, Fort Sam Houston, 

Texas. 

COL (Ret) Norton, is an Associate Professor, Department of Dermatology, Uniformed Services University of the 

Health Sciences, Bethesda, Maryland. 

LTC Carder is an instructor and course writer at the Medical Zoology Branch in the Department of Preventive Health 

Services, Academy of Health Sciences, US Army Medical Department Center and School, Fort Sam Houston, Texas. 

COL Debboun is Director, Center for Health Education and Training, Academy of Health Sciences, US Army Medical 

Department Center & School, Fort Sam Houston, Texas. 

UNIFORMED SERVICES UNIVERSITY

of the Health Sciences 

The US Army Medical Department 

Center & School 
16 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

INTRODUCTION

Since its inception, the US military has consistently 

been called upon to wage battles and to conduct 

peacekeeping and humanitarian relief operations in 

locations of the world where the most formidable 

enemy is often a tiny, 6- or 8-legged creature. Indeed, 

in every war fought by the United States up through 

the Vietnam conflict, the number of casualties caused 

by arthropod-borne diseases has significantly exceeded 

the number of battlefield casualties.1

 It was the 

pioneering efforts of Walter Reed, William Gorgas, 

and others that helped to decipher the link between 

microbes, human disease, and mosquito vectors.2

 Their 

discoveries led the way in the fight against typhoid 

fever, yellow fever, malaria, and other diseases that 

had plagued military and civilian populations for 

millennia. 

In spite of these discoveries, malaria continued to take 

its toll on US forces. During World War I, almost 

17,000 troops acquired malaria.1

 Over 24,000,000 

person days were lost during World War II to malaria 

and other arthropod-borne diseases such as scrub 

typhus and dengue fever.1

 In 1943, Allied forces 

averaged 208 new cases of malaria per 1,000 Soldiers 

stationed in the south Pacific.3

 In the Vietnam conflict, 

annual case rates of malaria reached as high as 600 per 

1,000 troops.1 In the 1940s, entomologists from the US 

Department of Agriculture developed methods and 

equipment to use DDT* to control mosquitoes, lice, 

and other vectors. In collaboration with military 

entomologists, they developed insecticide dispersal 

equipment and implemented malaria eradication 

programs which together reduced the number of 

malaria cases in the south Pacific to 5 per 1000 

Soldiers by 1945.3

Despite these early successes, there has been a 

dramatic resurgence of mosquito-borne diseases 

Operational Vector-borne Disease 

Surveillance and Control: Closing the 

Capabilities Gap through Research at 

Overseas Military Laboratories 

MAJ Brian P. Evans, MS, USA 

CPT Jeffrey W. Clark, MS, USA 

LT Kathryn A. Barbara, MSC, USN 

LT Kirk D. Mundal, MSC, USN 

LT Barry D. Furman, MSC, USN 

James C. McAvin 

MAJ Jason H. Richardson, MS, USA 

ABSTRACT

Malaria, dengue fever, chikungunya virus, leishmaniasis, and a myriad of other vector-borne diseases pose 

significant threats to the warfighter and to the overall combat effectiveness of units. Military preventive 

medicine (PM) assets must accurately evaluate the vector-borne disease threat and then implement and/or 

advise the commander on countermeasures to reduce a particular threat. The success of these measures is 

contingent upon the biology of the disease vector and on the tools or methods used to conduct vector/pathogen 

surveillance and vector control. There is a significant gap between the tools available and those required for 

operational PM assets to provide real-time, effective surveillance and control. A network of US Army and US 

Navy overseas laboratories is focused on closing the current capabilities gap. Their mission is to develop and 

field test tools and methods to enhance the combatant commander’s ability to identify and mitigate the threat 

posed by these vector-borne diseases. 

*Dichlorodiphenyltrichloroethane
 July – September 2009 17

during the post-DDT era, and today’s military 

continues to face a significant threat from arthropod 

vectors. While significant strides have been made in 

the implementation of personal protective measures, 

including malaria chemoprophylaxis, bed nets, 

repellents, and permethrin-treated uniforms, the battle 

against arthropod-borne disease is far from won. 

Compliance with such measures remains a problem, as 

evidenced from a survey of Soldiers returning from 

Afghanistan.4

 In general, though, the advances in 

science and medicine have been outpaced by the 

adaptability of vectors and the evolution of pathogens. 

Novel more efficient strategies to reduce transmission 

of vector-borne diseases are required if the military is 

to effectively combat this threat. 

The required tools would allow deployed PM 

personnel to accurately evaluate the risk of disease 

transmission through vector/pathogen surveillance, 

and subsequently implement control measures to break 

the cycle of transmission. However, there currently 

exists a gap between what preventive medicine assets 

have at their disposal for surveillance and control and 

what they require to more effectively minimize the 

potential for arthropod-borne disease transmission. 

Effective control measures are only achievable through 

the use of real-time, accurate surveillance tools along 

with a sufficient understanding of the biology and 

behavior of problem vectors. 

US Army, Navy, and Air Force entomologists 

stationed in 5 overseas laboratories are focused on 

developing and evaluating tools and methods that 

would fill this capabilities gap: 

 Thailand – the Armed Forces Research Institute 

of Medical Sciences (AFRIMS) 

 Kenya – the US Army Medical Research Unit - 

Kenya (USAMRU-K) 

 Indonesia – the US Naval Medical Research Unit 

No. 2 (NAMRU-2) 

 Egypt – the US Naval Medical Research Unit 

No. 3 (NAMRU-3) 

 Peru – the US Naval Medical Research Center 

Detachment (NMRCD) 

This group of researchers is on the front lines working 

to address the military’s vector/pathogen surveillance 

and control shortfalls. What follows is a summary of 

the team’s efforts associated with 5 priority arthropodborne disease threats (malaria, dengue fever, 

chikungunya virus, visceral leishmaniasis, and 

cutaneous leishmaniasis).5

DISEASE OVERVIEW 

Malaria 

Annually, 300 to 500 million people are infected with 

malaria, with 1.5 to 2.7 million fatalities (mostly 

children).6

 Several hundred cases of malaria, 

transmitted by night-feeding Anopheles mosquitoes, 

continue to infect military personnel deployed in 

locations throughout southwest Asia, sub-Saharan 

Africa, and the Korean peninsula. A total of 425 cases 

of malaria were diagnosed in US military personnel 

between the years 2000 and 2005.7

 Most notable was 

the occurrence of 38 cases of vivax malaria in a 725-

man US Army Ranger task force that deployed to 

Afghanistan between June and September 2002.4

Another significant malaria outbreak occurred during 

the deployment of 225 Marines to Liberia in which 80 

Marines contracted falciparum malaria.8

 Since the 

early 1990s, US troops deployed in South Korea have 

consistently been at risk of exposure to vivax malaria.9

Although there are significant efforts underway from 

Department of Defense (DoD) researchers, the Gates 

Foundation, and private industry to develop 

antimalarial drugs and malaria vaccines, a licensed 

vaccine is likely a decade or more away, and drug 

resistant parasites are continually appearing.10 In the 

interim, improved methods to reduce the risk of 

infection through mosquito control or personal 

protection are critical. 

Dengue Fever 

We are currently witnessing a worldwide resurgence 

(and in some cases emergence) of arthropod-borne 

viral (arboviral) diseases, and dengue fever leads the 

list as a public health threat.11 The 4 dengue virus 

(DENV) strains are maintained in cycles involving 

humans and the container-breeding Aedes aegypti

mosquito, a vector that typically feeds on humans 

during the daylight hours. The lack of treatment, the 

explosive nature of this disease, and the potential for 

acquiring dengue hemorrhagic fever (a deadly form of 

the disease) are causes for concern among DoD 

planners. While DoD researchers are working towards 

a vaccine that is protective against all 4 DENV 

serotypes, mosquito surveillance and control remain 

central to prevention and control of dengue fever 

outbreaks. 
18 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

Chikungunya 

Chikungunya virus (CHIKV) is an alphavirus 

transmitted to humans by container-breeding Aedes 

mosquitoes. The virus is endemic to Africa and 

various parts of Asia, including Indonesia and the 

Philippines.12 This disease is currently showing a 

pattern of reemergence. In the last 5 years, explosive 

outbreaks have occurred in Kenya, the Seychelles, 

Comoros, Mayotte, Mauritius, Madagascar, India, and 

Italy.13 A specific example of the alarming attack rates 

occurred on the island of La Reunion where almost 

40% of the island’s total population of 785,000 fell ill 

in 2005-2006.14 Recent outbreaks have also been 

reported in Singapore, Malaysia, and Thailand. 

Symptoms include fever, incapacitating joint pain, and 

rash which generally disappear after a few days. While 

CHIKV is rarely fatal, joint pain can persist for months 

or even years. Given the lack of a vaccine or treatment 

and the history of large epidemics, prevention of 

infection through vector control is paramount. 

Leishmaniasis 

Leishmaniasis presents itself in 2 main forms: 

cutaneous leishmaniasis, which often results in skin 

lesions or attacks mucous membranes; and visceral 

leishmaniasis, which can lead to liver and other organ 

damage, and sometimes even death. Leishmaniasis is a 

parasitic infection caused by a variety of Leishmania

species. Phlebotomine sand flies are involved in the 

transmission of Leishmania, from rodents and canids 

to humans. Sand flies are elusive, pinhead-sized 

insects of which little is understood about their biology 

and behavior. Consequently, control of these disease 

vectors continues to be a significant challenge for 

military entomologists.15 No prophylactic drugs or 

vaccines are currently available, and emphasis is 

placed on preventive measures to break the cycle of 

transmission.16

DEFINING THE GAP

Effective vector-borne disease prevention relies on 

answering a core set of questions. Once these 

questions are answered, decision makers can design 

strategies based on evidence and tailored to the unique 

dynamics of their specific situation (in space and 

time). The fewer questions we can answer, and the 

more assumptions we make, the more likely we are to 

implement ineffective, one-size-fits-all solutions. At a 

minimum, the following questions must be answered.16

1. Is there disease transmission in the area? 

2. Which arthropod species are present and which 

ones are vectors of disease? 

3. Which ones feed on humans? 

4. Where does human-vector contact occur? 

5. Where do the vector species breed and rest? 

6. When and where should a vector control strategy 

be implemented? 

7. What proportion of the vector population is 

susceptible or resistant to insecticides? 

8. What vector control options will likely reduce 

disease transmission? 

Malaria can be used as an example to highlight the 

importance of addressing the previous questions. 

Approximately 430 Anopheles species are found 

worldwide of which only 30 to 40 species transmit 

malaria in nature.17 Of these, some feed indoors and 

others feed outdoors. If mosquito control programs are 

designed without determining when and where 

personnel are being exposed, they will likely fail to 

reduce the threat. However, with answers to the 

questions above, preventive medicine personnel may 

advise the use of insecticides inside sleeping areas to 

control a mosquito species which prefers to feed 

indoors at night. Although it is paramount that most, if 

not all, of the questions above be addressed prior to the 

implementation of a program, the current reality is that 

we do not yet have the capability to answer all of 

them. Seven of the major gaps are presented below, 

along with the measures that are being undertaken by 

military entomologists working overseas to overcome 

the recognized deficiencies. 

DEFINING AND CLOSING THE CAPABILITIES GAPS 

Task: Conduct Vector Surveillance 

Gap: Adult mosquito and sand fly collection devices 

are minimally effective 

Problem. Numerous devices have been developed 

over the years to survey for Aedes (dengue/

chikungunya vectors) and Anopheles mosquitoes (malaria vectors).18 Sticky traps, visual traps, light traps 

and backpack aspirators are the most widely used tools 

for conducting mosquito surveillance,19-21 with Centers 

for Disease Control and Prevention (CDC) light traps 

(Figure 1) often considered the industry standard for 

mosquito surveillance. However, all of these trap types 

Operational Vector-borne Disease Surveillance and Control: 

Closing the Capabilities Gap through Research at Overseas Laboratories 
 July – September 2009 19

THE ARMY MEDICAL DEPARTMENT JOURNAL

have drawbacks.18 For example: sticky traps can 

damage sampled mosquitoes, the degree of success 

with backpack aspirators is highly dependent on the 

collector/inspector, visual traps are generally of lower 

efficiency, and CDC light traps lack an olfactory-based 

attractant and contain a light source that has the 

unintended effect of repelling some mosquito species. 

Ideally, human landing counts (HLCs) can be used to 

evaluate the efficacy of vector control. This technique 

involves collecting host-seeking arthropod females 

that land on an individual human’s exposed legs. Data 

collected using this technique generally correlates well 

with local vector population densities. The HLCs can 

also be used to help determine entomological 

inoculation rates, which are true estimates of the 

disease risk posed to humans. While surveillance using 

HLCs is the most effective approach for determining 

mosquito densities, the ethical issue of placing humans 

at risk for contracting disease from pathogens 

originating from mosquito vectors makes this approach 

less appealing in today’s environment. Currently, PM 

assets depend on the CDC light trap (or a related 

version) to conduct most adult mosquito surveillance. 

The main attractant is a 4- to 6-watt incandescent light 

bulb. As the mosquito approaches the light source, it is 

drawn downward into a collection bag by a fan 

mounted just below the light bulb. This surveillance 

tool has significant limitations with regard to 

collecting disease vectors: 

The trap is only effective for some mosquito 

species that feed at night (ie, Anopheles). The 

CDC light trap is an inadequate surveillance tool 

for mosquitoes which feed during the day, such as 

DENV and CHIKV vectors. 

Not all night-feeding adult mosquitoes are 

attracted to the light source of a CDC trap. 

Mosquitoes only see in the visible light spectra of 

blue, green, and red. Incandescent light sources 

emit light most strongly in the infrared spectra and 

weakly in the visible light spectra of blue, green, 

and red.22 Therefore, even though Anopheles feed 

during the night, potentially important vectors are 

often “repelled” by the light source. 

The trap should be augmented with a carbon 

dioxide source to enhance trap effectiveness. The 

carbon dioxide source might come in the form of 

dry ice, granular CO2-sachets, or a canister of CO2. 

Blood-feeding mosquitoes use a combination of 

olfactory cues in addition to visual cues to find a 

suitable host. Carbon dioxide is considered to be a 

principal olfactory attractant. 

The efficiency of converting electrical current to 

light using incandescent light bulbs is 

exceptionally low (approximately 6%). The 

remainder (94%) is often dispersed as heat or 

infrared radiation.22 As a consequence, this device 

consumes a great deal of energy. 

The effectiveness of these traps for collecting sand 

flies has not been systematically evaluated. 

Solutions

BG-Sentinel Trap (BGS) (Biogents AG, Regensburg, 

Germany). The BGS (Figure 2) has shown significant 

promise as a tool for collecting Ae aegypti,

23-26 and Ae 

albopictus.

27 To our knowledge, this device has not 

been evaluated for malaria vectors in Asia. The BGS 

uses a blend of mosquito attractants consisting of lactic 

acid, ammonia, and caproic acid, substances all found 

on human skin. The blend is released in a fixed ratio 

from a dispenser known as the BG Lure.23 The 

efficacy of the BGS (with and without carbon dioxide) 

relative to other surveillance devices for collecting 

DENV and malaria vectors is being evaluated in 

Thailand. 

Bed Net Traps. An alternative to HLCs is needed, 

particularly in areas of high disease transmission. The 

performance of a self-supporting bed net trap is 

undergoing evaluation by Navy entomologists at 

NAMRU-2. Preliminary results show that a 

lightweight (2 kg), easy-to-assemble bed net trap 

Figure 1. A CDC light trap. 
20 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

collected significantly greater numbers of Anopheles

spp and Culex spp (vectors of Japanese encephalitis 

virus and filariasis) than a CDC trap. The trap, shown 

in Figure 3, is designed to protect the person (the 

attractant) in the bed net while simultaneously trapping 

(in an outer tent structure) vectors that can be 

identified and tested for human pathogens. In areas 

where disease transmission is very high or drug 

resistant pathogens occur, collections of mosquitoes 

could be made while minimizing the risk to the 

collector.28,29

Mass Trapping Techniques for Surveillance/Control.

Traps that generate CO2 by catalyzing propane have 

demonstrated a reduction in nuisance mosquito or 

biting midge populations.30-33 Little is known 

regarding the effectiveness of these traps on reducing 

disease vector species in isolated, tropical environments.33 Manufacturers of commercially available 

traps claim the ability to control mosquito populations 

over an area as large as one acre.* Future evaluations 

of this technology at overseas field sites will determine the efficacy of a commercial mosquito trap in 

reducing prevalence of mosquito populations in a 

specific area. 

Sand Fly Attractants. Modified CDC light traps were 

recently tested in southern Egypt by NAMRU-3 

researchers. The light traps were modified to accommodate light emitting diodes, and proved to be very 

effective for sand fly surveillance.34 At present, field 

studies are being conducted to determine the efficacy 

of a wide range of semiochemicals, either repellents or 

attractants, on the activity of sand flies. Pheromones 

from Lutzomyia longipalpis (leishmaniasis vector) 

males have shown significant promise.35 Like many 

sand flies, L longipalpis is a lekking species, one in 

which males gather for the purposes of a competitive 

mating display. Females are attracted to displays of 

male wing-fanning behavior and pheromones released 

by the male. It is therefore likely that traps baited with 

male pheromones will attract female sand flies in the 

field (their potential has already been shown in the 

laboratory). Efforts are underway in Colombia where 

scientists from the NMRCD, in collaboration with Rothamsted Research (Harpenden, Hertfordshire, UK)20

are evaluating the efficacy of these pheromones as 

baits in a variety of commercial traps placed in jungle 

encampments in the Colombian Amazon. 

Task: Identify Vector Species 

Gap: Limited availability of country-specific 

taxonomic keys and limited knowledge of 

species’ bionomics, relative vector status, and 

distribution 

Problem. The Walter Reed Biosystematics Unit has 

made significant strides in designing user-friendly, 

regional keys for the identification of mosquitoes and 

sand flies worldwide. These keys have proven their 

utility, most especially in southwest Asia. However, 

regionally relevant identification keys along with 

descriptions related to the feeding, breeding, and 

resting behavior, relative vector status, and distribution 

of species are still lacking for much of the tropics. 

Without these references, PM planners are not able to 

answer the relevant questions which drive 

implementation of sound control programs. 

Operational Vector-borne Disease Surveillance and Control: 

Closing the Capabilities Gap through Research at Overseas Laboratories 

Figure 2. The BG-Sentinel trap. 

Figure 3. The bed net trap. 

*Example: Mosquito Magnet®, Woodstream Corp, Lititz, PA 

Information available at http://www.mosquitomagnet.com
 July – September 2009 21

THE ARMY MEDICAL DEPARTMENT JOURNAL

Solutions

Sand Fly Biology and Taxonomic Research. The 

NAMRU-3 has been conducting extensive sand fly 

research and surveillance in countries throughout 

Africa and the Middle East for over 50 years. During 

that time, the NAMRU-3 Vector Biology Research 

Program (VBRP) has determined the vector status of 

numerous Phlebotomus species found throughout the 

Middle East and African region,36-38 and has developed 

a better understanding of sand fly ecology in various 

countries within the aforementioned region, including 

extensive bionomics studies of sand flies in the 

Sinai36,39 and in southern Egypt, where sand fly 

daytime resting sites were recently discovered for the 

first time.40 Sand fly species distributions have been 

determined in Djibouti,41 and NAMRU-3 is 

completing compilations for Egypt and parts of Ghana. 

Further, wide-scale species distribution projects are 

currently underway in Afghanistan and Libya. 

Collectively, NAMRU-3 has produced taxonomic keys 

for the sand flies of Afghanistan, Egypt, Ghana, Sudan 

(B.D.F., unpublished data, 2009), and Djibouti.41 To 

supplement the morphological identification of sand 

flies, VBRP has a rapidly expanding polymerase chain 

reaction component which allows for the molecular 

identification of sand flies. 

Mosquito Keys. World-renowned mosquito taxonomist 

Dr Rampa Rattanarithikul has spent decades at 

AFRIMS dissecting, classifying, and analyzing 

mosquitoes.42 With the assistance of illustrator 

Prachong Panthusiri, they are on the verge of 

completing the last volume of a 6-volume publication 

entitled Illustrated Keys to the Mosquitoes of 

Thailand.

43-47 This tool will be exceptionally valuable 

for preventive medicine assets deploying to southeast 

Asia, especially for those associated with the annual 

Cobra Gold exercises in Thailand and current 

operations in the Republic of the Philippines. 

Task: Conduct Pathogen Surveillance 

Gap: Rapid pathogen surveillance devices are 

lacking 

Problem. While a disease vector may be present in a 

particular area, the broad application of control 

measures may not necessarily be warranted. Pathogen 

surveillance tools allow for the effective local targeting of control measures, thereby enhancing the possibility of managing the disease, while reaping the benefits of reduced costs and avoidance of the potential 

environmental and human health risks often associated 

with insecticide application. For example, the malaria 

dipstick assay is a rapid, one-step procedure that uses a 

test strip capable of detecting and then differentiating 

between infections of P falciparum and P vivax in 

adult mosquito collections within minutes.48 This 

particular hand-held device is of lower cost and is very 

user-friendly relative to polymerase chain reaction 

methods, and can potentially identify areas where the 

risk of contracting malaria is high. Such a tool can 

help to prioritize control efforts and has significant 

impact when requesting support or the assistance of 

the command. This type of rapid screening tool is not 

available for most vector-borne pathogens. 

Solutions. The overseas laboratories are actively 

involved in the field evaluation of hand-held dipstick 

assays for the detection of leishmaniasis, DENV, 

Japanese encephalitis virus, and Rift Valley fever 

virus. In addition, in collaboration with both the US 

Army Research Institute for Infectious Diseases and 

the US Air Force 59th Clinical Research Division, 

entomologists at AFRIMS, NAMRU-3, and USAMRU

-K are conducting field evaluations of real-time 

polymerase chain reaction assays to detect vectorborne pathogens. Many of these assays are designed 

for the Joint Biological Agent Identification and Diagnostic System using the Ruggedized Advanced Pathogen Identification Device (Idaho Technology Incorporated, Salt Lake City, Utah) as the platform.49,50

Task: Provide Personal Protective Measures 

Gap: The military has yet to field bed nets, tents, or 

other materials which have been treated with 

long lasting insecticides 

Problem. The use of insecticide-treated nets (ITNs) 

and insecticide-treated tents is regarded as one of the 

most promising measures available to reduce vectorborne disease transmission.51 However, treatment of 

ITNs with insecticide is performed in the field (not at 

the factory) which presents an added burden for PM 

assets. Application of insecticide to bed nets and tents 

is labor-intensive and not often a command priority. 

Solutions

Long-lasting Insecticidal Net (LLIN) Evaluations. Manufacturers have developed LLINs such as Perma-Net®

(Vestergaard Frandsen, Lausanne, Switzerland) which 

are ready-to-use, factory pretreated nets. Many of 

these nets are designed to release insecticide slowly so 

that the nets retain their efficacy after repeated 
22 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

washings. Some LLINs are said to require no further 

treatment during their physical lifespan of 4 to 5 

years.51 Currently, AFRIMS is evaluating the longterm efficacy of LLINs on vector densities in villages 

located in western Thailand. If shown to be effective, 

LLINs may be a valuable alternative to the fieldapplication of insecticide to bed nets. 

Insecticide-impregnated Tent Evaluations. US Army 

Deployable Rapid Assembly Shelter (DRASH) tents 

are woven from a noncanvas XYTEX® (DHS 

Technologies LLC, Orangeburg, New York) fabric, 

which is polyester-coated with polyvinyl chloride. 

Studies are underway in southeastern Thailand to 

determine whether insecticide-impregnated tents are 

indeed a viable approach for protecting Soldiers from 

vector-borne disease over the long-term. If this is 

found to be the case, further studies will then evaluate 

the utility of insecticide-impregnated DRASH tents 

(assuming that the technology is developed) in 

affording protection for Soldiers. 

Task: Conduct Vector Control 

Gap: Lack of effective and sustainable control 

methods for Aedes mosquitoes (CHIKV and DENV 

vectors) 

Problem. Given adequate personnel, community 

involvement, money, and time, Ae aegypti population 

control can be achieved through sanitation and the 

elimination of mosquito breeding sites. This option is 

often not viable for military pest controllers during 

deployments. Effective source reduction is difficult 

when the military has no control of areas surrounding 

encampments occupied by US personnel. Chemical 

control using DoD-registered larvicides (larval stage 

insecticides) such as methoprene, temephos, and 

Bacillus thuringiensis israelensis (Bti) and various 

adulticides (adult stage insecticides) has proven 

effective in managing both larval and adult 

populations respectively of Ae aegypti.

52 However, 

these options have obvious limitations when it comes 

to deployments and protecting the Warfighter. Indoor 

adulticide application can effectively reduce Ae 

aegypti populations but must be applied inside 

occupied structures on a regular basis. This can be 

difficult to justify as a preventive measure and is often 

unachievable. In general, the military is more likely to 

practice indoor adulticide application in response to 

disease transmission rather than as a preventive 

measure. Traditional larval control is logistically 

daunting and is minimally effective if surrounding 

areas are left untreated, or if coverage in the target area 

is low. What is lacking is an expedient, low risk, 

efficient, and sustainable approach to achieving 

epidemiologically-relevant levels of Ae aegypti

population suppression. 

Solutions

Resting/oviposition Lures Treated with Pyriproxyfen.

Pyriproxyfen is classified as an insect growth regulator 

and a potent inhibitor of embryogenesis, 

metamorphosis, and adult formation in insects.53 In 

addition, it has been shown to decrease the fertility and 

fecundity of Ae aegypti adults that develop from 

sublethally exposed larvae.54 Evidence also suggests 

that adult mosquitoes not killed by contact with 

pyriproxyfen that is applied to breeding containers can 

actually carry the chemical to uncontaminated 

environments. The tiny doses of pyriproxyfen that are 

moved can then negatively affect the development of 

susceptible larvae.55 Pyriproxyfen has long residual 

efficacy yet has an excellent mammalian toxicity 

profile. The most promising scenario involves females 

resting on surfaces treated with pyriproxyfen, picking 

up tiny doses of chemical that sterilize the females 

which then transports the pesticide to other breeding 

sites. Work conducted by the NMRCD, Rothamsted 

Research, and the Peruvian health authorities suggests 

that this approach has considerable potential. The 

NMRCD is designing a variety of simple resting and 

oviposition lures which will attract Ae aegypti and 

which can be treated with pyriproxyfen. The efficacies 

of these treated lures on fecundity and on the 

horizontal transfer of pyriproxyfen will be evaluated 

under seminatural conditions with future plans for 

field evaluations to establish the optimal distribution 

of such treated lures. 

Pyriproxyfen-treated Ovitrap/resting Station Device 

Design/evaluation. Researchers at AFRIMS are 

designing and evaluating a visually attractive, 

pyriproxyfen-treated ovitrap (egg trap)/resting station 

device. It is clear that Ae aegypti females tend to 

spread their eggs among many sites. This behavior 

should improve the natural transfer of pyriproxyfen. 

Ae aegypti tend to remain relatively close to their 

larval habitat, with maximum dispersal distances 

around 100 to 200 m,56 therefore significant control (or 

local eradication) via this approach is within reason. 

This is particularly relevant in the context of a military 

Operational Vector-borne Disease Surveillance and Control: 

Closing the Capabilities Gap through Research at Overseas Laboratories 
 July – September 2009 23

THE ARMY MEDICAL DEPARTMENT JOURNAL

camp where sanitation is high and larval habitat can be 

minimized. Initial lab evaluation of prototypes is 

underway using field cages/tunnels. Field trials are 

scheduled to assess the impact of the final product, 

spatially arranged as a barrier-like treatment, on Ae 

aegypti densities in a simulated military camp within a 

dengue-endemic village. 

ProVectorTM Trap Evaluations. A possible tool for the 

control of adult Ae aegypti populations currently being 

evaluated at USAMRU-K is the ProVectorTM trap 

(MIT Holding Inc, Savannah, Georgia). This low cost 

trap mimics visual and chemical cues used by 

mosquitoes in search of a sugar meal. The trap is 

designed in such a way that only mosquitoes can feed 

on it, thus reducing the possibility of exposure to 

nontarget organisms and accidental environmental 

contamination. These traps, designed at the Biodefense 

and Infectious Disease Laboratory at Georgia Southern 

University, use a formulation of Bacillus thuringiensis 

israeliensis bioinsecticide as the active ingredient. 

This trap will be evaluated not only for its efficacy as a 

method for DENV and malaria vector control tool, but 

also as a tool for increasing the efficacy of Ae aegypti

surveillance. 

Push-pull System. Research is underway at NMRCD 

to develop a novel insecticide treated material (ITM) 

push-pull system to reduce Ae aegypti inside homes 

where they are most likely to feed on humans and 

transmit DENV. The system is comprised of ITMs 

designed to repel Ae aegypti from inside homes and an 

attractive, lethal trap positioned outside the home to 

pull the mosquitoes from the peridomestic 

environment. Following proof-of-concept, long-term 

goals include defining the public health impact of the 

system through epidemiological studies for operational 

refinement. 

Gap: No effective replacement for the insecticide 

DDT 

Problem. The successful eradication of malaria from 

the developed world and large portions of tropical Asia 

and Latin America was due largely to the widespread 

use of DDT.57 The effectiveness of DDT is primarily a 

result of its long lasting persistence. Ironically, this 

quality also led to the cancellation of its registration by 

the Environmental Protection Agency.58 Modern 

alternatives to DDT are relatively unstable in the 

environment and therefore have shorter windows of 

efficacy. Effective vector control operations thus 

require more frequent spraying with obvious 

repercussions on sustainability. A DDT alternative 

with similar durability and effectiveness is desperately 

needed. 

Solution. Pyrethroids have replaced many older 

insecticides because of their effectiveness and relative 

safety for the applicator.58 The chemical structure of 

pyrethroids resembles a component of the natural 

botanical insecticide known as pyrethrum. Pyrethroids 

are highly toxic to most insects at very low rates of 

application. While pyrethroids do not measure up to 

DDT in terms of stability, there is evidence that the 

pyrethroid bifenthrin may be efficacious against 

mosquitoes for a considerable length of time 

postapplication (6 weeks) when applied to vegetation 

relative to other insecticides.59 TalStarOneTM (FMC 

Corp, Philadelphia, Pennsylvania) (bifenthrin 7.9%) is 

EPA-registered and endorsed by the Armed Forces 

Pest Management Board for use on military 

installations and during deployments. Recent work at 

USAMRU-K, in partnership with the US Department 

of Agriculture Center for Medical and Veterinary 

Entomology, have shown that bifenthrin-treated 

camouflage nets provide an effective protective barrier 

against mosquitoes and sand flies, significantly 

reducing total trap numbers for over 6 weeks. 

Additionally, mortality rates were significantly higher 

for those vectors that made it through the nets, 

suggesting that treated nets provide protection beyond 

the initial barrier effect for which they were tested. 

Evaluations are also being performed in Thailand to 

determine the extent to which this insecticide is 

effective for the long-term control of malaria vectors 

when applied to vegetation along the perimeter of a 

village (Figure 4). 

Gap: No effective sand fly control strategies 

Problem. Unlike mosquito control, sand flies pose 

numerous problems that prevent the coherent 

development of an effective control strategy. Sand fly 

breeding habitats are much more cryptic and often 

impossible to identify, thus preventing the 

development of any effective larviciding strategy. 

Sand fly populations are extremely focal, with 

significant geographical and seasonal variations. Sand 

fly surveillance is a challenge and without the 

surveillance data, it is difficult to make sound 

decisions for targeted sand fly control operations. In 
24 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

the absence of better alternatives, deployed personnel 

currently revert to mosquito control methods. 

Sustainable and evidence-based strategies for targeting 

sand flies are clearly needed. 

Solution. Rodent Pass-through System. The effectiveness of a rodent pass-through system to control sand 

fly populations is being evaluated at USAMRU-K. 

Laboratory studies have shown that diflubenzuron can 

prevent synthesis of chitin (the material composing the 

outer skeleton of arthropods). Diflubenzuron is 

nontoxic to rodents and remains active after passage 

through the rodent digestive tract.60 Since the larvae of 

many sand fly species feed on rodent feces,61 this may 

provide the first truly effective technique for targeting 

larval sand flies. Once baits are formulated for the 

targeted rodent fauna, diflubenzuron will be 

incorporated and the baits offered on a monthly basis. 

It is important to note that this would target native 

rodent populations in areas where troops are deployed, 

not pest rodent populations that are normally targeted 

with anticoagulant baits. Also, preliminary work is 

underway to evaluate the efficacy of using a sugar 

solution spray as bait for targeting adult male and 

female sand flies in search of sugar meals. 

CONCLUSION

There is a well recognized gap between the resources 

required and those available to manage the risks to the 

Warfighter posed by malaria, dengue fever, 

chikungunya virus, leishmaniasis, and myriad other 

vector-borne disease threats. Vector control experts are 

expected to accurately evaluate the vector-borne 

disease threat and then make sound decisions to reduce 

that threat. Following the models of the pioneering 

work of Reed, Gorgas, and others, US Army, Navy, 

and Air Force researchers working overseas are 

helping to close this gap. Their efforts are enhancing 

the combatant commander's ability to identify and 

mitigate the threat posed by these vector-borne 

diseases. 

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Operational Vector-borne Disease Surveillance and Control: 

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 July – September 2009 25

THE ARMY MEDICAL DEPARTMENT JOURNAL

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Operational Vector-borne Disease Surveillance and Control: 

Closing the Capabilities Gap through Research at Overseas Laboratories 
 July – September 2009 27

THE ARMY MEDICAL DEPARTMENT JOURNAL

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AUTHORS

MAJ Evans is Deputy Chief, Department of 

Entomology, Armed Forces Research Institute of 

Medical Sciences, Bangkok, Thailand. 

CPT Clark is Chief, Department of Entomology & 

Vector Borne Diseases, US Army Medical Research 

Unit-Kenya. 

LT Barbara is Head, Medical Entomology Department, 

US Naval Medical Research Unit No. 2, Jakarta, 

Indonesia. 

LT Mundal is Director, Entomology Research Program, 

US Naval Medical Research Center Detachment, Lima 

Peru. 

LT Furman is Head, Vector Biology Research Program, 

US Naval Medical Research No. 3, Cairo, Egypt. 

James McAvin is a visiting scientist at the Armed 

Forces Research Institute of Medical Sciences, 

Bangkok, Thailand. 

MAJ Richardson is Chief, Department of Entomology, 

Armed Forces Research Institute of Medical Sciences, 

Bangkok, Thailand. 

Sand Fly 

Asian Tiger Mosquito 
28 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

One of the major challenges for military preventive 

medicine is in developing medical threat assessments 

both prior to and during deployment. When it comes to 

vector-borne diseases, this can be especially 

problematic. In many areas, it is either impractical or 

impossible to conduct a thorough predeployment 

surveillance program. This leads to reliance on 

products, such as the Disease Vector Ecology Profiles, 

that may be out of date or too general in nature. 

In recent years, the use of remotely sensed data (ie, 

satellite imagery) has gained popularity in many areas 

of biology, including epidemiology.1

 Along with this, 

a number of modeling approaches have been 

developed to answer basic questions about the 

distribution, ecology, and potential range of a species 

in the absence of comprehensive sampling data. These 

techniques are commonly referred to as ecological 

niche modeling or species distribution modeling. 

Niche modeling holds the potential to be a powerful 

tool for the military preventive medicine community in 

developing more robust risk assessments for vectorborne disease and better targeting surveillance, control, 

and education efforts. 

BACKGROUND

Joseph Grinell originally presented the idea that 

species inhabit specific areas (the niche), defined by 

the species’ biological requirements for survival.2

 The 

ecological niche is determined by 4 interacting 

factors.3-5 These are: 

Biotic factors: Interactions with other species 

including: predators, pathogens, prey, parasites, 

and vegetation. 

Abiotic factors: The environmental factors that 

determine whether or not a species can survive in a 

given location (climate, soil, etc.). 

The ability of a species to disperse to new areas. 

This includes any physical barriers to dispersion 

(such as mountain ranges, bodies of water, and 

deserts) as well as the biological capacity or 

propensity of a species to disperse. 

The ability of the species to adapt to new 

environments. 

Together, these factors determine the actual and 

potential geographic distribution of a species.3

 Niche 

modeling techniques aim to answer a variety of 

questions based on the knowledge of these factors for 

a given species. 

Figure 1 presents a diagrammatic representation of the 

factors that determine the niche for a given organism. 

The area in which all 3 circles overlap is the actual 

niche of a species. The areas where only 2 circles 

overlap are the potential niche. For instance, the area 

labeled “D” in this example is currently uninhabitable 

by a species due to abiotic factors (such as temperature 

or precipitation). If the abiotic factors limiting the 

range of the species are changed (such as through an 

El Niño or La Niña event, or some other form of 

climate change) so that they are conducive to that 

species, the niche could shift to include that area. 

Niche modeling has been increasingly applied to 

disease ecology.5

 Models of monthly predictions of 

Dengue fever in Mexico have been created based on 

mosquito activity.6

 Niche modeling has been used to 

help prevent anthrax in wildlife and livestock, by 

predicting the expected distribution of the pathogen, 

Bacillus anthracis (Cohn) in the environment.7

 Niche 

models of malaria vectors in the Anopheles gambiae

complex have been developed for undersampled 

regions of Africa.8

 The distributions of Triatoma spp 

vectors of Chagas’ disease in the Americas have been 

examined in an effort to better refine vector control 

programs.4,9 A number of studies have focused on both 

present and potential distributions of Lutzomyia spp 

vectors of cutaneous and visceral leishmaniasis in 

Applications of Ecological Niche Modeling to 

Enhance Medical Threat Assessment and 

Disease Control and Prevention Strategies 

MAJ Michelle Colacicco-Mayhugh, MS, USA 
 July – September 2009 29

Central and South America.10-13 Niche modeling 

allows the user to develop maps showing predicted 

distribution of an organism based on current and 

projected data. 

One of the reasons that niche modeling has grown in 

use is the ability to use records from a variety of 

sources, including museum records, literature reports, 

and direct sampling. Many of the computer algorithms 

that have been developed for this modeling can create 

distribution models without actual absence records. 

This ability to use only presence records is what 

enables the creation of models for areas with poor or 

incomplete sampling. A number of methods have been 

developed to perform niche modeling. However, the 

most prevalent are GARP (genetic algorithm rule-set 

predictor) and MAXENT (maximum entropy) 

techniques.14 Software for both applications is 

available freely on the internet and is simple to install 

and use. However, knowledge of geographic 

information system software is helpful in developing 

and refining the risk maps created by these techniques. 

USING NICHE MODELING TO DETERMINE SAND FLY

DISTRIBUTION

Niche modeling has been used to develop a map of the 

predicted distribution of Phlebotomus papatasi

(Scopoli) which is a vector of sand fly fever virus and 

Leishmania major, a protozoan that causes cutaneous 

leishmaniasis (M.C-M., unpublished data, 2009). Both 

sand fly fever and cutaneous leishmaniasis are 

important disease threats to military operations in the 

middle east and Mediterranean regions.15-17 The abiotic 

factors affecting this species include temperature, 

precipitation, and elevation. The biotic factors relevant 

to this species include availability of acceptable blood 

meal sources, level of predation, and the availability of 

the appropriate vegetation to provide a sugar source. 

The limits to dispersal include mountain ranges, bodies 

of water, and the distance the insect can fly. Using 

Figure 1 as a reference, the area labeled “A” represents 

the actual distribution of this species. If military forces 

were entering an area that did not meet the 

requirements of area A, the diseases vectored by this 

species would not be a concern. However, if military 

forces were operating in this area, preventive medicine 

personnel could plan appropriately for prevention and 

control of the vectors, and Soldier training could be 

adjusted to address the actual threat. 

Figure 2 shows the predicted distribution of P papatasi

across a portion of the Middle East. This map was 

developed using the niche modeling software Maxent, 

version 3.2.1. It incorporates sand fly collection 

records (both from direct collections and records in the 

Figure 1. Venn diagram illustrating the factors that determine a species’ niche. 

A indicates the actual niche area of a species. 

B indicates the area where the conditions are right for 

a species, but barriers to dispersion keep it from 

reaching. 

C indicates areas where the biotic factors are not 

conducive to the species’ survival. 

D indicates areas where the abiotic factors are not 

conducive to survival.3

ABIOTIC FACTORS

LIMITATIONS ON

DISPERSAL

Figure 2. Map developed using niche modeling showing the 

relative risk that the cutaneous leishmaniasis and sand fly 

fever vector (Phlebotomus papatasi) is present in an area. 

The light areas have lowest risk and the darkest areas have 

the highest risk of P papatasi presence. 

   Predators

BIOTIC

FACTORS

        Prey          Parasites

           Disease

        Vegetation

     Climate                       Geography

               Soil                                  Slope

           Altitude

        Bodies of Water

           Deserts

   Mountain Ranges
30 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

literature), temperature, precipitation, and land use 

data (M.C-M., unpublished data, 2009). While the map 

is similar to the one in the Disease and Vector Ecology 

Profile for cutaneous leishmaniasis in the same area 

(Figure 3), it provides more refined information about 

the distribution of a specific vector of concern and is 

easily updated. Such models could be developed 

rapidly, targeting specific areas of interest to provide 

the most realistic picture of the disease risk to 

deployed or deploying military personnel. 

USING NICHE MODELING TO DETERMINE MOSQUITO

DISTRIBUTION

Researchers at the Walter Reed Biosystematics Unit 

are developing a novel online tool called 

MosquitoMap19 that provides a clearinghouse of 

information on mosquito distribution and risk of 

mosquito-borne diseases worldwide. The application 

incorporates niche models developed by individuals 

across the modeling community. Users may use the 

tool to determine what mosquito species are present, 

overlay distributional models of specific mosquito 

species, and/or overlay models of mosquito-borne 

diseases. Disease models currently incorporated in 

MosquitoMap are Plasmodium vivax and Plasmodium 

falciparum malaria, yellow fever, dengue fever, 

Japanese encephalitis, and Rift Valley fever. A useful 

component of this effort is the development of the 

“Mal-area calculator” which determines the areas 

where the distribution of human populations, 

Plasmodium spp parasites, and disease vectors overlap 

in order to better gauge the real malaria risk in a given 

area.19 Figure 4 is a representation of the 

MosquitoMap model for the Republic of Korea, 

displaying the distribution of Anopheles sinensis

(Wiedemann), a vector of P vivax malaria. 

Once complete, this tool will allow public health 

personnel to better determine the threat of mosquitoborne disease in an area of interest. This sort of global 

or regional plan could be applied to other vectors and 

vector-borne diseases. Such a resource could provide 

preventive medicine personnel targeted maps to use in 

planning disease control and prevention strategies. 

Ultimately, this sort of comprehensive effort could 

help to target use of prophylaxis, allow military 

entomologists to refine surveillance and control 

measures, and help emphasize the risk and importance 

of disease threats to an operation. 

MILITARY APPLICATIONS

Niche modeling tools have potential to help preventive 

medicine personnel better understand the medical 

threat to our forces in areas to which they are deployed 

or may be deploying. Some of the potential 

applications have already been highlighted. 

These tools may be used to assist in the development 

of the predeployment medical threat assessment. For 

some operations (such as the movement of combat 

forces), it may be impossible or impractical to conduct 

a thorough, on the ground, predeployment site survey 

of areas in which US military units will be engaged. In 

addition, many areas in which we operate have 

incomplete or inaccurate data regarding the threat of 

disease. In these instances, niche modeling could help 

fill in the information gaps by modeling the relative 

risk of key vector species or vector-borne diseases 

across an area of interest. 

Niche modeling can be used to help identify the effects 

of habitat or climate change on a species or disease. 

This application would be beneficial in projecting 

disease threat in areas where the environment is 

changing (ie, as a result of a hurricane or tsunami). 

Modeling with the goal of predicting future 

populations of vector species could assist public health 

planners in addressing ongoing preventive medicine 

Applications of Ecological Niche Modeling to Enhance Medical Threat Assessment 

and Disease Control and Prevention Strategies 

Figure 3. Map from the Disease Vector Ecology Profile of 

the Middle East18 showing areas in the Middle East where 

cutaneous leishmaniasis is endemic. 
 July – September 2009 31

THE ARMY MEDICAL DEPARTMENT JOURNAL

concerns over weeks or months after such a habitat 

alteration scenario. 

At a finer scale, these techniques could help target 

vector surveillance efforts, determine the best layout of 

a base in order to minimize contact with a vector, or 

identify appropriate engineering controls for a target 

species. If these tools are available to the military 

entomologists on the ground, vector control strategies 

could be enhanced through the use of remote imagery 

and predictive models to increase the overall efficacy 

of surveillance and control strategies. 

RECOMMENDATION

A great deal of work remains for the military to 

employ these tools to their full potential. There should 

be some effort to coordinate public health research 

utilizing remote sensing and predictive modeling 

across the military in order to most effectively and 

efficiently exploit these technologies. Work should be 

targeted and focused on priority vectors, diseases, and 

regions in order to create a comprehensive and useful 

tool for the military public health community. With 

some forethought and deliberate planning, these tools 

hold tremendous potential to improve our ability to 

identify the risk to our forces and develop better 

disease prevention and control strategies during all 

phases of deployment. 

REFERENCES

1. Peterson AT. Ecological niche modeling and spatial 

patterns of disease transmission. Emerg Infect Dis. 

2006;12(12):1822-1826. 

2. Grinnell J. Field tests of theories concerning 

distributional control. Am Nat. 1917;51:115-128. 

Figure 4. The MosquitoMap19 niche model for the mosquito, Anopheles sinensis (Wiedeman). Map generated Feb 27, 2009. 
32 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

3. Soberon J, Peterson AT. Interpretation of models of 

fundamental ecological niches and species' 

distributional areas. Biodiversity Informatics. 

2005;2:1-10. 

4. Costa J, Peterson AT, Beard CB. Ecological niche 

modeling and differentiation of populations of 

Triatoma brasiliensis Neiva, 1911, the most 

important Chagas' disease vector in northeastern 

Brazil (Hemiptera, Reduviidae, Triatominae). Am J 

Trop Med Hyg. 2002;67(5):516-520. 

5. Peterson A. Biogeography of diseases: a framework 

for analysis. Naturwissenschaften. 2008;95:483-491. 

6. Peterson AT, Martinez-Campos C, Nakazawa Y, 

Martinez-Meyer E. Time-specific ecological niche 

modeling predicts spatial dynamics of vector insects 

and human dengue cases. Trans R Soc Trop Med 

Hyg. 2005;99:647-655. 

7. Blackburn J, McNyset K, Curtis A, Hugh-Jones M. 

Modeling the geographic distribution of Bacillus 

anthracis, the causative agent of anthrax disease, for 

the contiguous United States using predictive 

ecological niche modeling. Am J Trop Med Hyg. 

2007;77(6):1103-1110. 

8. Levine RS, Peterson AT, Benedict MQ. Geographic 

and ecological distributions of the Anopheles 

gambiae complex predicted using a genetic 

algorithm. Am J Trop Med Hyg. 2004;70(2):105-109. 

9. Peterson AT, Sanchez-Cordero V, Beard CB, Ramsey 

JM. Eclogical niche modeling and potential reservoirs 

for chagas disease, Mexico. Emerg Infect Dis. 2002;8

(7):662-667. 

10. Peterson AT, Shaw J. Lutzomyia vectors for 

cutaneous leishmaniasis in Southern Brazil: 

ecological niche models, predicted geographic 

distributions, and climate change effects. Int J 

Parasitol. 2003;33:919-931. 

11. Peterson AT, Pereira RS, Neves V. Using 

epidemiological survey data to infer geographic 

distributions of leishmaniasis vector species. Rev Soc 

Bras Med Trop. 2004;37:10-14. 

12. da Costa SM, Cechinel M, Bandiera V, Zannuncio 

JC, Lainson R, Rangel EF. Lutzomyia (Nyssomyia) 

whitmani s.l. (antunes & Coutinho, 1939) (Diptera: 

Psychodidae: Phlebotominae): geographical 

distribution and the epidemiology of American 

cutaneous leishmaniasis in Brazil - mini review. Mem 

Inst Oswaldo Cruz. 2007;102(2):149-153. 

13. Nieto P, Malone JB, Bavia ME. Ecological niche 

modeling for visceral leishmaniasis in the state of 

Bahia, Brazil, using genetic algorithm for rule-set 

prediction and growing degree day-water budget 

analysis. Geospat Health. 2006;1:115-126. 

14. Elith J, Graham C, Anderson R, et al. Novel methods 

improve prediction of species' distributions from 

occurrence data. Ecography. 2006;29:129-151. 

15. Coleman RE, Burkett DA, Putnam JL, et al. Impact 

of Phlebotomine sand flies on US military operations 

at Tallil Air Base, Iraq: 1. Background, Military 

Situation, and Development of a "Leishmaniasis Control Prorgam". J Med Entomol. 2006;43(4):647-662. 

16. Aronson N, Sanders J, Moran K. In harm's way: 

infections in deployed American military forces. Clin 

Infect Dis. 2006;43:1045-1051. 

17. Ellis SB, Appenzeller G, Lee H, et al. Outbreak of 

sandfly fever in Central Iraq, September 2007. Mil 

Med. 2008;173(10):949-953. 

18. Defense Pest Management Information Analysis 

Center. Regional Disease Vector Ecology Profile: 

The Middle East. Silver Spring, MD: Armed Forces 

Pest Management Board; 1999. Available at: http://

www.afpmb.org/pubs/dveps/mid_east.pdf. Accessed 

August 6, 2009. 

19. Foley D, Wilkerson R. MosquitoMap Website. 

Available at: http://www.mosquitomap.org/

index.htm. Accessed February 27, 2009. 

AUTHOR

MAJ Colacicco-Mayhugh is Chief, Department of Sand 

Fly Biology, Division of Entomology, Walter Reed 

Army Institute of Research, Silver Spring, Maryland. 

Applications of Ecological Niche Modeling to Enhance Medical Threat Assessment 

and Disease Control and Prevention Strategies 

US Army Medical Research and Materiel Command 
 July – September 2009 33

BACKGROUND

Preventive medicine and veterinary personnel should 

be prepared to conduct feral and wild animal control 

on every deployment—it is critical in the Iraq theater 

of operations. Animal bites take both service members 

and military working dogs out of the fight and place a 

preventable burden on medical care and logistics 

systems. Feral, as used in this article, refers to 

ownerless dogs and cats that have reverted to the wild 

state and lack characteristics associated with 

domestication. 

Iraqi cultural and religious beliefs (dogs and cats are 

considered dirty; they are seldom kept as pets), the 

absence of a government-backed animal/zoonotic 

disease control program, and the new food and water 

sources on US bases in Iraq led to the establishment of 

unacceptable animal populations soon after the bases 

were occupied. This, in turn, led to the development of 

the Theater Animal Control Program early in 

Operation Iraqi Freedom. 

Military animal control during deployments has 

neither the same goals nor the same options as a 

government-sponsored, long-term zoonotic disease 

control program. The focus of a military preventive 

medicine contingency animal control program is to 

reduce animal contact and human injury. A national 

rabies control program is designed to reduce zoonotic 

disease. 

A successful rabies control program requires a longterm government commitment, either at the regional or 

national level. In its guidelines for canine rabies 

control, the World Health Organization (WHO) 

recommends mandatory vaccination of owned animals, 

movement restriction, and reducing the number of 

ownerless animals by euthanasia.1

 The WHO also 

recommends that nontraditional canine rabies control 

programs such as the oral rabies vaccine not be started 

without first collecting at least 5 years of data on dog 

population parameters and infection rates.2

 As an 

example of the level of commitment required, it took 

almost 60 years of national effort to rid the United 

States of dog-to-dog rabies transmission.3

 While a 

properly run program of this type will reduce the 

incidence of rabies over time, it cannot be expected to 

have any impact on US contingency bases in the 

absence of a national program. 

CANINE RABIES CONTROL

Rabies is an acute viral encephalomyelitis that 

principally affects carnivores and insectivorous bats, 

although it can affect any mammal. It is almost 

Addressing Feral and Wild Animal Threats 

During Deployment: The Distinction Between 

Animal Control and Rabies Control 

LTC Raymond F. Dunton, MS, USA 

MAJ Gerald R. Sargent, VC, USA 

ABSTRACT

Feral and wild animal control is a critical component of force health protection during troop deployments. The primary 

goal of animal control during a military deployment is to limit human injury or disease by reducing the likelihood of 

human-animal contact on US bases. For deployed US military forces, animal control will often be necessary, and 

trapping and euthanasia will remain the standard. In contrast, a rabies control program focuses on reducing disease 

incidence in an animal population with a subsequent reduction in rabies risk to military personnel. A successful rabies 

control program requires several components that typically are not possible in areas where the US Army deploys. The 

responsibility for animal control during an Army deployment has historically fallen to Army Preventive Medicine 

Sciences officers (Area of Concentration 67C). Understanding that the deployed US Army conducts animal control to 

limit human-animal contact, and also that it is generally not possible to mount a successful rabies control program on 

US contingency bases in the absence of an established, mature national plan will ensure that we are doing all we can to 

protect Soldiers from animal injury and disease transmission. 
34 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

invariably fatal once clinical signs appear; there are 

only 6 documented cases of humans recovering from 

rabies following appearance of clinical signs.4

Reservoirs of rabies vary throughout the world. Canine 

rabies predominates in Africa, Asia, Latin America, 

and the middle east.5

 According to the World Health 

Organization, there are about 55,000 deaths from 

rabies annually, mostly in Asia and Africa.6

The WHO lists 3 basic elements of a successful rabies 

control program: epidemiological surveillance, mass 

vaccination, and dog population control.1

 In areas that 

have large populations of ownerless dogs such as Iraq, 

the WHO recognizes that mass parenteral vaccination 

may not be possible1,2 Control or elimination of canine 

rabies is possible as demonstrated by successes in the 

US, Japan, and other countries.1

 These control efforts 

required long-term commitment, wide-area coverage, 

local population buy-in, significant managerial 

investment, and legislation. 

The Centers for Disease Control and Prevention’s 

(CDC) program in the US is viewed as a model of 

success by the WHO.1

 The CDC’s 2008 program7

advocates mandatory vaccination of owned animals 

and removal of unwanted animals/animal control as 

cornerstones. In support of the national rabies control 

program in the US, city and county programs 

collectively euthanize almost 10 million animals every 

year.8

 This underscores the fact that there are far more 

stray animals in the US than can be adopted. The 

problem is magnified in a country like Iraq where 

there is no organized rabies control program and 

people do not keep pets. Most medium-sized cities and 

counties in the US kill more animals annually than the 

US does theater-wide in Iraq. Table 1 provides a 

comparison between animal euthanasia in Iraq and 

representative US districts. 

The CDC plan also emphasizes supporting activities 

including public education, ongoing surveillance, and 

identification of vaccinated animals. As a result of 

many years of national commitment, the US has gone 

from almost 7,000 rabies-positive dogs per year in the 

late 1940s to declaring the country free of dog-to-dog 

rabies transmission less than 60 years later.3

 Sporadic 

canine infections continue to be reported in the US (71 

in 2006).3

 these infections are attributed to spillover 

from virus types that circulate in wild animal 

populations.3

 Mass vaccination campaigns combined 

with euthanization of ownerless dogs has also been 

used in Malaysia, another country that has succeeded 

in eliminating canine rabies.1

ALTERNATIVE APPROACHES TO RABIES CONTROL

In addition to mass parenteral vaccination of owned 

animals and elimination of strays, the WHO has 

suggested 2 supplementary approaches for consideration in some situations.1,2

Oral Rabies Vaccine (ORV). Successful wild animal 

rabies control programs that incorporate the ORV have 

been run in several countries.1

 The ORV is a 

potentially useful tool for canine rabies control in 

countries where a large percentage of the dogs are 

ownerless or where the target reservoir is a wild 

animal species. A successful ORV canine rabies 

control program would still have to be region- or 

country-wide and require long-term national 

commitment. The WHO recommends considering the 

following criteria before deciding to use ORV for 

control of rabies in dogs2

: 

Dog rabies is endemic. 

A monitored dog rabies vaccination program by 

parenteral vaccination is in place for the last 5 

years and is permanently evaluated. 

Commitment of the authorities is demonstrated by 

allocation of sufficient annual budget for the 

operation of the rabies surveillance and control 

program. 

There is a network of biomedical services and 

diagnostic laboratory capacity established in the 

Addressing Feral and Wild Animal Threats During Deployment: 

The Distinction Between Animal Control and Rabies Control 

Iraq* San Antonio, 

TX†

Albuquerque, 

NM†

Ft. Hood, 

TX†

2005 14,000 37,927 16,306 500 

2006 6,500‡ 33,785 14,839 981 

2007 7,092 32,210 12,003 900 

*Numbers for Iraq are from contract vector control records and 

do not include animals euthanized on bases that did not have 

permanent contract presence. 

†Three United States representative districts are provided for 

comparison: a large city (San Antonio), a medium-sized city 

(Albuquerque), and a primarily rural Army installation (Fort 

Hood). Data supplied by local humane societies. 

‡Iraq 2006 data was incomplete. 

Table 1. Numbers of dogs and cats euthanized by year 

in the Iraq theater of operations and in 3 representative US locations. 
 July – September 2009 35

THE ARMY MEDICAL DEPARTMENT JOURNAL

country and historical data on human and animal 

rabies cases for at least the 5 previous years are 

available. 

Dog demography information (population size 

estimates, density, distribution, age structure, 

turnover, etc) is available. 

A properly managed ORV campaign could eventually 

reduce the prevalence of rabies in the target 

population, but it is not appropriate for military 

contingency purposes. It does not address the numbers 

of animals on bases, it will not change how we treat 

bite victims, and it will foster a false sense of security 

that could lead to increased violation of General Order 

Number 1, which prohibits the adoption of pets and 

mascots. The suggestion that we should use ORV to 

vaccinate animals inside our bases, and that this would 

allow us to stop euthanizing animals, ignores the 

primary goal of Army contingency animal control: 

reducing the number of human-animal encounters. In 

the absence of an ongoing national program, spreading 

ORV bait throughout the installations of deployed US 

forces protects neither military personnel nor the local 

population. 

Trap-Neuter-Return (TNR) or Animal Birth Control. In 

1990 the WHO published guidelines for rabies control 

programs built around the sterilization, vaccination, 

and release of dogs.9

 It was thought that this would 

reduce the size of the dog population, the number of 

animals susceptible to rabies infection, and ultimately 

the number of human infections. While it may have 

potential in some situations, a military deployment is 

not one of them. TNR will not reduce human-animal 

encounters, does not protect military personnel, is 

impractical in terms of work load for deployed 

veterinarians, and therefore should not be considered 

in a contingency situation. 

There is an ongoing debate in the United States on the 

utility of TNR programs designed to control the size of 

animal populations,10-12 (not rabies control programs), 

with more evidence against than for TNR. Discussions 

regarding the best way to address feral animal 

population control in the US typically have an 

emotional component, with people averse to 

euthanasia advocating TNR.13,14 In many instances, 

this has been the primary impediment to solving a feral 

animal problem.15,16

Focusing strictly on rabies control, there is very little 

hard evidence that TNR programs are effective. The 

WHO itself states that, almost 20 years after they 

issued guidance on conducting this type of program, 

“...the results are promising, but data are limited and 

independent evaluation of projects has not yet been 

undertaken”.1

Vaccination of owned animals and elimination of 

strays are the mainstays of WHO rabies control 

recommendations. An ORV program may be of value 

for controlling rabies in wild populations or in large 

populations of ownerless dogs, but ORV and TNR are 

not good options for the US military on deployment. 

None of the rabies control approaches address the 

basic goal of military contingency animal control. 

ANIMAL CONTROL IN A CONTINGENCY ENVIRONMENT

The primary goal of military animal control in a 

contingency environment is to reduce the feral animal 

population inside US bases. This has at least 5 distinct 

benefits: 

 Reduces human-animal contact and thus the 

likelihood of human injury by an animal. 

 Reduces the disease reservoir population. 

 Reduces damage to personal and government 

property. 

 Reduces interference between military or contract 

working dogs and feral animals. 

 Allows us to produce data on zoonotic disease 

prevalence in the animal populations. 

The Army’s approach for contingency deployments, 

euthanization of ownerless animals inside the base 

perimeter, addresses all of the threats posed to US and 

coalition forces by animals. Rabies control methods do 

not. Historically, the chain of command has authorized 

and advocated very basic means of animal control, 

such as kinetic force, early in a deployment and on 

more remote bases, acknowledging the importance of 

limiting human-animal contact. As the theater matures, 

animal trapping and chemical euthanasia become the 

norm, at least on the larger bases. 

It is essential that preventive medicine and veterinary 

services personnel, installation commanders, and 

contractors in theater work closely together in the 
36 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

initial development of a comprehensive animal 

control program. Army Preventive Medicine 

Sciences officers, and enlisted Preventive 

Medicine Specialists (MOS* 68S), have 

primary responsibility for contingency animal 

control in their pest management role. They 

build a team to assess the problem, develop a 

plan to address the problem, and make 

recommendations to commanders regarding 

animal control. 

Veterinary Officers (Area of Concentration 

64A/64B) and enlisted Animal Care Specialists 

(MOS 68T), consult on the initial development 

of the animal control plan, provide euthanasia 

support, collect disease surveillance data using 

the trapped animals, and provide quality control 

oversight to the program. This support will vary 

depending on mission priorities and number of 

veterinary personnel available. Veterinary 

services are responsible for euthanasia 

whenever personnel are available. They should 

also provide oversight and guidance when 

others must euthanize trapped animals to ensure 

that humane methods are being used in 

accordance with current American Veterinary 

Medical Association Guidelines.17

While preventive medicine has overall responsibility for animal control, installation commanders assume responsibility for implementing trapping programs on their bases. Base 

programs are developed based on theater guidance and support the theater plan. Both preventive medicine and veterinary service personnel 

should monitor these programs to ensure the use 

of proper trapping methods and humane 

treatment of animals. 

Deployment animal control has been conducted 

during most of Operation Iraqi Freedom (OIF) 

in much the same way as in other US deployments. 

Although it is not a viable option as a long-term 

disease control program, animal trapping combined 

with humane euthanasia of trapped animals is effective 

at reducing the threat and frequency of Soldier injury 

by animals on US bases. The program used by the US 

Army and other military services deployed in support 

of OIF is designed to reduce the number of animals 

“inside the wire.” 

Preventive medicine’s focus with regard to animal 

control has been and must continue to be very 

limited—protect our military personnel, DoD civilians, 

contractors, and coalition partners from animal 

injuries. Euthanizing trapped animals accomplishes 

this, and in addition reduces the available disease 

reservoir population. Military and contract working 

dogs have a proven record of protecting US forces. 

However, in situations where unrestrained feral dogs 

exist, these working dogs may be harassed, attacked, 

and distracted from their duties. Euthanizing animals 

Addressing Feral and Wild Animal Threats During Deployment: 

The Distinction Between Animal Control and Rabies Control 

*Military occupational specialty

Table 2. Comparison of the ability of deployment animal control 

(trapping and euthanasia) and 2 rabies control programs to reduce 

human-animal encounters. The comparison uses selected parameters of importance in a general deployment setting and specifically in the Iraq theater of operations.* 

* The assessment of the rabies control programs assumes no established 

national program, as is the case in Iraq. 

† For the US DoD in a contingency environment, trapping and euthanizing 

animals on US bases provides the most protection for deployed personnel. 

‡ The primary rabies reservoirs in Iraq according to the WHO and NCMI. 

§ Some infected animals are removed from the population, but this is not 

measurable because tests are not available that identify infected animals 

prior to the time that they become infective. Reducing the number of animals 

on US installations makes human-animal encounters less likely and thus 

contributes to reducing rabies risk and damage of personal and government 

property. 

¶ If captured animals are euthanized. 

# If captured animals are tested. 

**Rabies risk reduced from those animals that consume the bait. 

††No Affect is the desirable result for this parameter. 

§ 

# 

Control Measures 

Animal Trapping 

& Euthanasia†

Oral Rabies 

Vaccine 

Sterilize, Vaccinate, 

& Release 

Protection from animal 

bites  No 

Affect 

No 

Affect

Immediate reduction of 

rabies risk to Soldiers  No 

Affect

No 

Affect

Protection from other 

diseases (leishmaniasis, 

cryptococcosis, Q fever) 

 No 

Affect

No 

Affect

Keeps animal 

populations at 

acceptable levels 

 No 

Affect

No 

Affect

Reduces rabies risk from 

jackal & fox‡   No 

Affect

Provides rabies 

prevalence data for risk 

assessments 

 No 

Affect

No 

Affect

Reduces threatened 

animal population††

No 

Affect

No 

Affect

No 

Affect

Makes people 

uncomfortable or 

increases stress††  No 

Affect

No 

Affect

Parameters of 

Importance 

** 
 July – September 2009 37

THE ARMY MEDICAL DEPARTMENT JOURNAL

trapped on coalition bases also provides the 

opportunity to generate data on zoonotic disease 

prevalence in the theater of operations which currently 

does not exist.1,18,19

While some have suggested that we should not 

euthanize animals and even that some animals should 

be released, it is critical that all animals known to be 

zoonotic disease reservoirs trapped in a contingency 

environment be euthanized. In Iraq, contract vector 

control personnel have not trapped an endangered or 

threatened animal during more than 5 years of animal 

control operations on US bases. Moreover, the 

National Center for Medical Intelligence (NCMI, 

formerly the Armed Forces Medical Intelligence 

Center) lists fox and jackal as the primary reservoirs of 

rabies in Iraq.19 The International Union for the 

Conservation of Nature (IUCN), referenced in the 

2007 Iraq Animal Control Plan, lists no endangered or 

threatened mammals that are likely to be caught 

incidentally during the animal control trapping 

program. The IUCN is currently tracking 5 endangered 

and 9 vulnerable mammals in Iraq,20 listed in Table 3. 

Iraqi cultural and religious beliefs explain in part why 

there are so many feral dogs and cats in Iraq. Iraqis do 

not keep pets such as dogs and cats, because they are 

considered unclean and are not allowed in the house. 

The other major factor that has resulted in a large feral 

animal population is that there was no regional or 

national program to address this health threat before 

September 2008. 

Animal trapping and euthanizing trapped animals 

works on deployment in general and on US bases in 

Iraq in particular because we concurrently do 2 other 

things: movement restriction and habitat modification.1

The walls and fences around our bases, while not completely impassable, serve to limit animal movement 

onto the bases. Refuse on bases is managed in much 

the same way that it is in the US, which limits food 

sources for animals. While animal-proof compounds 

are not a realistic expectation, both waste management 

and exclusion are continually improved throughout the 

theater. Holes under walls and in fences were 

identified and repaired, more incinerators were put into 

operation, and burn pit management was improved. 

The US feral and wild animal control program in Iraq 

was effective in reducing the number of animals to 

which coalition forces are exposed. Organized animal 

control has been conducted continuously on major US 

bases in Iraq since the beginning of Operation Iraqi 

Freedom in 2003. Contract vector control personnel 

trapped approximately 14,000 feral and wild animals, 

such as those shown on page 39, in 2005; 6,500 in 

2006; and 7,092 animals in 2007 (Table 1). This is a 

good indication that the program is working—reducing 

the number of feral animals on our bases. 

CONCLUSION

For the deployed US military, some type of animal 

control will often be necessary, and animal trapping 

and euthanasia will remain the standard. In countries 

with large feral animal populations such as Iraq, 

animal control is a critical component of force health 

protection. In the absence of a functioning national 

disease control program, it is the only tool we have 

that addresses injury by animals and effectively 

reduces the zoonotic disease reservoir population. 

If US forces are tasked to assist the Iraq government in 

the establishment of a sustainable national animal or 

zoonotic disease control program, it will be critical to 

understand both the Iraqi culture and the programs that 

have worked in other countries. Since Iraqis do not 

keep pets and consider dogs and cats to be unclean, a 

program that includes euthanasia would probably 

receive more support than one that advocates 

sterilization and release of animals. An ORV program 

is ill-advised for the same reason. 

Common Name Scientific Name 

Blue Whale Balaenoptera musculus

Persian Fallow Deer Dama mesopotamica

Asiatic Wild Ass Equus hemionus

Bunn's Short-tailed Bandicoot Rat Nesokia bunnii

Arabian Oryx Oryx leucoryx

Cheetah Acinonyx jubatus

Long-fingered Bat Myotis capaccinii

Mehely's Horseshoe Bat Rhinolophus mehelyi

Indian Smooth-Coated Otter Lutrogale perspicillata

African Lion Panthera leo

Goitered gazelle Gazella subgutturosa

European Marbled Polecat Vormela peregusna

Finless Porpoise Neophocaena phocaenoides

Brown Bear Ursus arctos 

Table 3. Iraq mammals currently listed as Endangered 

(blue rows) and Vulnerable by the World Conservation 

Union (http://www.iucnredlist.org). 
38 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

Until about 25 years ago, the Iraq government paid a 

bounty for dogs and cats, dead or alive. Apparently, 

this program worked very well and reduced the feral 

animal populations significantly in Iraq. Resurrecting 

the program could be the solution to the country’s feral 

animal problem. In November 2008, the government 

of Iraq initiated kinetic dog control in Baghdad to 

prevent rabies transmission and stop feral dog packs 

from killing people. Expanding this initiative to other 

population concentrations will benefit all Iraqis. 

The US must continue to make improvements to 

installations that will limit the number of animals 

gaining entrance to our bases. This includes 

maintenance of barriers such as fences and walls, and 

also taking steps to exclude animals from dump sites 

as much as possible. We must continue to improve 

burn pit management where necessary, and continue 

efforts to increase the number of incinerators in use in 

the theater. Finally, our expectations for animal 

exclusion efforts must be tempered with a clear understanding of the costs versus benefits—neither bases 

nor burn pits can be made completely animal-proof. 

Whenever and wherever our Army deploys, we must 

be prepared to conduct animal control operations as 

necessary. In Iraq, the US military must stay the 

course with its animal trapping and euthanasia 

program until the Iraqi government is able to establish 

a program that addresses the feral animal problem 

throughout the country, and that program begins to 

show positive results. To do anything else increases 

health risks to Soldiers. 

REFERENCES

1. Who Technical Report Series No. 931. WHO Expert 

Consultation on Rabies, First Report. Geneva: WHO 

Press; 2005. 

2. Oral Vaccination of Dogs Against Rabies. Geneva: 

World Health Organization: 2007. Available at: 

http://www.who.int/rabies/resources/guidelines%

20for%20oral%20vaccination%20of%20dogs%

20against%20rabies_with%20cover.pdf. Accessed 

June 24, 2009. 

3. Blanton JD, Hanlon CA, Rupprecht CE. Rabies 

surveillance in the United States during 2006. J Am 

Vet Med Assoc. 2007;231:540-556. 

4. Willoughby RE, Rotar MM, Dhonau HL, et al. 

Recovery of a Patient from Clinical Rabies–

Wisconsin, 2004. MMWR Morb Mortal Wkly Rep. 

2004;53:1171-1173. 

5. Aiello SE, ed. The Merck Veterinary Manual. 8th ed. 

Whitehouse Station, NJ: Merck & Co, Inc; 1998:966-

967. 

6. World Health Organization. Human and animal 

rabies. Available at: http://www.who.int/rabies/en/. 

Accessed May 15, 2009. 

7. Compendium of Animal Rabies Prevention and 

Control, 2008. MMWR Morb Mortal Wkly Rep. 

2008;57(No.RR-2). 

8. Animal Shelter Euthanasia. American Humane 

Association web site. Available at: http://

www.americanhumane.org/about-us/newsroom/factsheets/animal-shelter-euthanasia.html. Accessed June 

25, 2009. 

9. Bögel K. Guidelines for Dog Population 

Management. Geneva: World Health Organization & 

World Society for the Protection of Animals; 1990. 

Available at: http://whqlibdoc.who.int/hq/1990/

WHO_ZOON_90.166.pdf. Accessed June 25, 2009. 

10. Andersen MC, Martin BJ, Roemer GW. Use of 

matrix population models to estimate the efficacy of 

euthanasia versus trap-neuter-return for management 

of free-roaming cats. J Am Vet Med Assoc. 2004;225

(12):1871-1876. 

11. Levy JK, Gale DW, Gale LA. Evaluation of the effect 

of a long-term trap-neuter-return and adoption 

program on a free-roaming cat population. J Am Vet 

Med Assoc. 2003;222(1):42-46. 

12. Castillo D, Clarke AL. Trap/neuter/release methods 

ineffective in controlling domestic cat "colonies" on 

public lands. Nat Area J. 2003;23(3):247-253. 

13. Sleeman JM. Additional input on feral cat debate. J 

Am Vet Med Assoc. 2003;223(12):1729-1730. 

14. Tim RM. Trends in wildlife management in North 

America. Outlooks Pest Manag. 2005;16(5):215-219. 

15. Hawkins CC. Feral cats, colonies, and wildlife. 

Outlooks Pest Manag. 2005;16(4):177-178. 

16. Wolff EF. Final letters for now on feral cats. J Am 

Vet Med Assoc. 2002;221(11):1548. 

17. AVMA Guidelines on Euthanasia. Schaumburg, 

Illinois: American Veterinary Medical Association; 

2007. Available at: http://www.avma.org/issues/

animal_welfare/euthanasia.pdf. Accessed June 25, 

2009. 

18. Communicable Disease Profile Iraq. Geneva: World 

Health Organization; 2003. Available at: http://

www.who.int/infectious-disease-news/IDdocs/

whocds200317/1profile.pdf. Accessed June 25, 

2009. 

Addressing Feral and Wild Animal Threats During Deployment: 

The Distinction Between Animal Control and Rabies Control 
 July – September 2009 39

THE ARMY MEDICAL DEPARTMENT JOURNAL

19. Baseline Infectious Disease Risk Assessment, Animal 

Contact Diseases page. National Center for Medical 

Intelligence web site. Available at: https://

www.intelink.gov/ncmi/product/idra.php?

id=64706#Rabies. Accessed July 1, 2009. 

20. International Union for Conservation of Nature and 

Natural Resources. IUCN Red List of Threatened 

Species. Available at: http://www.iucnredlist.org/

static/introduction. 

AUTHORS

LTC Dunton is Director, Proponency Office for 

Preventive Medicine – San Antonio, and a Medical 

Entomology Staff Officer at the US Army Medical 

Command, Fort Sam Houston, Texas. 

MAJ Sargent is Chief, Animal Medicine Division, US 

Army Veterinary Command, Fort Sam Houston, Texas. 

Wild animals captured by contract vector control personnel during animal control operations in Iraq. Although 

trap locations are selected to maximize capture of feral dogs and cats, wild animals are occasionally trapped. 

Decisions regarding whether to euthanize or release these animals must take into account command guidance, 

disease threat, and the additional risk to which personnel are exposed in attempting to release wild animals. 

Species: hyena (A), badger (B), reed cat (C), hedgehog (D), jackal (E), fox (F) 

(Photos of hyena, badger, jackal, and fox courtesy of Scott Brown, KBR Vector Control Supervisor, Camp 

Victory, Iraq. Other photos provided by the authors.) 

A B 

C D 

E F 
40 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

INTRODUCTION

In a previous article,1 we reviewed the status of 

malaria and Japanese encephalitis in the Republic of 

Korea (ROK) with the intent of providing the reader 

useful information on understanding and dealing with 

these diseases in the ROK. This article is a 

continuation of that discussion with a focus on one 

disease (scrub typhus) and 2 disease groups (tickborne pathogens and hantaviruses). 

SCRUB TYPHUS

Scrub typhus, caused by the rickettsial bacterium 

Orientia tsutsugamushi (Hyashi) that is transmitted by 

several species of larval mites belonging to the family 

Trombiculidae, is a disease of major military 

importance. During World War II (WWII), its 

presence made such a dramatic impact on US military 

personnel deployed to southeast Asia and the Pacific 

islands that the military initiated a research project 

performed by the US Department of Agriculture on the 

concept of treating clothing with a repellent to reduce 

chigger (larval mites) bites.2-4 This research was 

conducted in Florida, with field trials in New Guinea, 

after which it was 

e x p o r t e d f o r 

immediate use on 

military uniforms of 

Soldiers deployed to 

the frontlines. Later, 

this method was 

adopted for use 

against malaria and 

other diseases caused 

by vector-borne 

pathogens, but it was the effects of scrub typhus that 

eventually led to the development of permethrin 

uniform treatments used by US military forces and 

similarly treated clothing made available to nonmilitary consumers. 

Scrub typhus was first reported in Korea when 8 

United Nations Soldiers were diagnosed with it during 

the Korean War and shortly after the signing of the 

armistice (1951-1954).5

 Prior to the Korean War, scrub 

typhus was not known to occur among the Korean 

population, although unconfirmed reports based on 

symptoms of scrub typhus, fever, chills, headache, and 

rash had been observed during the late autumn to early 

winter for many years.6,7 After the Korean War, scrub 

typhus cases were reported in relatively low numbers 

in the ROK population. However, reported cases 

increased dramatically from 1,415 cases in 2003 to 

4,698 cases in 2004, and peaking with 6,780 cases in 

2005, as shown in Table 1. While mortality rates vary 

in different areas, the usual fatality rates among 

untreated patients range from 10% to 20% in the 

tropics.8

 During WWII, 6,861 cases were reported in 

Burma, India, and the Philippines, and in some areas 

more than one of every 4 Soldiers died of the disease 

during this preantibiotic period. Of those that survived, 

the disease was often prolonged with an average time 

loss of 60 to70 days per Soldier.8-10

The Koreans use indirect fluorescent antibody tests for 

definitive diagnosis of scrub typhus, whereas some US 

medical laboratories frequently use only enzymePerspectives on Scrub Typhus, Tick-Borne 

Pathogens, and Hantavirus in the Republic 

of Korea 

LTC William J. Sames, MS, USA 

Heung-Chul Kim, PhD 

COL (Ret) Terry A. Klein, MS, USA 

Disease 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 

Scrub Typhus - ROK 277 1,140 1,342 1,758 2,637 1,919 1,415 4,698 6,780 6,480 6,022 6,035 

Leptospirosis - ROK 4 90 130 106 133 122 119 141 83 119 208 100 

Hantavirus - ROK 104 215 196 203 323 336 392 427 421 422 450 376 

Hantavirus – US 2 4 1 2 2 0 3 0 4 0 0 0 

Table 1. Number of scrub typhus, leptospirosis, and hantavirus (hemorrhagic fever with renal 

syndrome) cases reported by year, 1997-2008.*

*Data from the Korea Center for Disease Control and Prevention (http://dis.cdc.go.kr/english/index.htm).
 July – September 2009 41

linked immunosorbent assay (ELISA) tests. Recent 

studies suggest the ELISA serological tests are often 

negative for scrub typhus for up to 30 days following 

symptoms, as patients may be anergic and not produce 

antibodies during the early stages of scrub typhus. 

Further, after 30 days or more, the patients have selfresolved infections, been successfully treated, or 

died.11 For example, in Japan, 17 of 1,700 Marines 

operating in a “scrub typhus endemic” area (Fuji 

Maneuver Area), demonstrated scrub typhus 

symptoms, and all were treated with loading doses of 

doxycycline and recovered uneventfully.11 All 17 

patients tested serologically negative for scrub typhus 

by ELISA, therefore, either the diagnostic test 

demonstrated low sensitivity, or another pathogen (eg, 

spotted fever group (SFG) Rickettsia) was the cause 

for the illness. Either way, the cause of the illness was 

not definitively determined. Similarly in the ROK, 2 

patients with typical scrub typhus symptoms 

(including eschars), who were also serologically 

negative, were treated with doxycycline, fully 

recovered, and returned to duty with no follow-up 

serology to identify the cause of illness. Eschars, 

however, may be observed in patients with SFG 

Rickettsia which is present in the ROK, thus SFG 

Rickettsia infections could not be ruled out as the 

source of illness.12 Complications with diagnostic tests 

suggest scrub typhus rates in US military personnel 

may be underreported and suggests a need to evaluate 

current and possibly find better, more definitive 

diagnostic tests.11

Investigations to identify transmission rates of scrub 

typhus in US Soldiers deployed to the ROK were 

initiated as a result of a comprehensive rodent 

surveillance program at field training sites supported 

by funding through the Global Emerging Infections 

Surveillance and Response System and the National 

Center for Medical Intelligence. These investigations 

identified scrub typhus infection rates in rodent 

populations ranging from 11.1% to 100%.13 In another 

study, data indicate approximately 0.2% of US 

Soldiers seroconverted for scrub typhus while 

deployed to the ROK.14 In addition, bites by chiggers 

in Korea, unlike the Americas, usually do not elicit an 

“itchy” response, thus, Soldiers do not realize they 

have been bitten.10 These data demonstrate the value of 

conducting vector and reservoir surveillance that 

determines the threat of known diseases, but also 

identifies the presence of reemerging and unknown 

infectious disease threats. Furthermore, these 

surveillance data provide for the development, 

implementation, and evaluation of scrub typhus 

mitigation strategies. 

Assessment of the risk of scrub typhus to the US 

Forces Korea (USFK) population is difficult, as few 

cases are diagnosed in the USFK population compared 

to the disease presence in the Korean population 

(Table 1). The reasons for the number of postdeployment positive sera for scrub typhus and few suspected 

cases is not understood, but may be related to using 

diagnostic assays with low sensitivity, lack of provider 

awareness and education of emerging diseases in the 

ROK, and perhaps presumptive treatment with doxycycline with no serology follow-up to determine the 

cause of illness. Even though scrub typhus appears to 

be having a low impact on current USFK populations, 

a change to hostilities or a natural disaster requiring 

humanitarian interventions could quickly change this 

status, especially in light of the relatively high number 

of cases observed in the Korean population. 

Additional studies of scrub typhus should focus on 

surveillance of small rodents and serological studies of 

Soldiers with suspected scrub typhus and other 

rickettsial diseases, eg, SFG rickettsial pathogens. 

Surveillance of small mammals is needed to provide 

baseline disease risk threats for selected habitats and 

sites where Soldiers train. Serological studies of 

Soldiers with vector-borne pathogen-like illnesses 

where presumptive treatment with antibiotics resolves 

disease symptoms should be thoroughly evaluated to 

determine the pathogen, so appropriate diagnostic 

tools and preventive measures can be applied. Since 

they are similar, preventive measures for scrub typhus 

will be discussed in the tick-borne pathogen section. 

DISEASES CAUSED BY TICK-BORNE PATHOGENS

Identified in the ROK are 31 species of ticks, listed in 

Table 2, and 16 tick-borne pathogens, some of which 

are zoonotic (animal-arthropod-animal/human), as 

shown in Table 3. Early tick-borne pathogen studies in 

the ROK focused on agricultural economic damage. 

However, with advancements in ectoparasite control, 

tick infestations in agricultural and pet animals can be 

severely limited. Studies of tick-borne pathogens as 

they relate to human health came later, but have 

primarily been related to identifying the pathogen’s 

presence in the ROK or documenting new or novel 

cases. The prevalence and incidence rate of human 
42 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

diseases caused by tick-borne pathogens in Korea is 

confounded and not clearly understood for a variety of 

reasons. These include: 

Koreans self-treated with antibiotics prior to a 

medical prescription requirement implemented in 

the year 2000. 

Diseases from tick-borne pathogens are not 

reportable diseases within the ROK. 

Massive urbanization has significantly reduced 

human-tick interaction. 

Changes in the ecosystem (eg, reforestation) since 

the Korean War. 

Operational conditions (hence exposure) may be 

different for military personnel during armistice 

than during wartime. 

Prior to August 2000, a prescription was not required 

to buy antibiotics in the ROK, allowing the populace 

to purchase antibiotics at-will from local pharmacies.13

Since many diseases from tick-borne pathogens range 

from mild to severe, are treatable with antibiotics (eg, 

doxycycline), and may be self-limiting, Koreans may 

have self-treated their symptoms rather than seek 

professional medical care. Another reason for potential 

undocumented cases is that Korean medical authorities 

do not require medical care providers to report 

diseases from tick-borne pathogens, hence, these 

diseases are not tracked within the human population. 

Thus, the health threat of tick-borne pathogens is not 

fully realized, even though several early retrospective 

studies of Korean patients with unidentified diseases 

were serologically positive for spotted fever group 

Rickettsia parasites.31,32 Surprisingly, recent studies of 

pre- and postdeployment sera from US Soldiers 

deployed to the ROK demonstrated a 1.3% 

seroconversion rate to SFG Rickettsia. Thus, some of 

the eschars observed in US Soldiers that were 

suspected to be the result of scrub typhus infections 

may have actually been SFG Rickettsia infections.14

Additionally, studies of associated infections of 

ehrlichiosis and bartonellosis in rodents and ticks 

resulted in the identification of tick-borne encephalitis 

(TBE) virus in the ROK.16,29 The impact of these 

findings are not known as no human TBE cases have 

been reported in Korea. 

Since the Korean War, the ROK has shifted from an 

agricultural society to an industrial and technology 

dominant society, which has led to massive 

urbanization of metropolitan areas such as Seoul, 

Busan, Pyeongtaek, and Daegu. Even though many 

Koreans spend weekends hiking in mountainous areas, 

the trails and paths are generally well worn and free of 

tick harborage like vegetation and leaf litter. However, 

when hikers go off the beaten path into forested areas 

covered with leaf litter and patches of grasses, the 

potential for human-tick interaction greatly increases. 

Still, urbanization appears to have reduced the overall 

exposure potential of the Korean population to ticks. 

Interestingly, very few ticks were found during the 

Korean War,33 when Korea was primarily rural. 

However, in the late 1960s and early 1970s, the ROK 

government directed the replanting of trees on hills 

and mountains, which had been deforested during the 

Japanese occupation of 1910 to 1945. The 

environmental changes may have increased tick populations in those areas by increasing tick survival due to 

increased numbers and density of suitable hosts. 

Presently, large numbers of ticks (not necessarily all 

species) can be collected from selected sites, including 

short-grass and leafy-forest habitats throughout the 

ROK. For example, 2 US Army medical tick surveys 

Perspectives on Scrub Typhus, Tick-Borne Pathogens, and Hantavirus in the Republic of Korea 

Table 2. Tick species reported from Korea.* 

Amblyomma testudinarium†

Argas boueti 

Argas japonicus 

Argas vespertilionis 

Dermacentor marginatus 

Dermacentor reticulates 

Dermacentor silvarum 

Haemaphysalis campanulata 

Haemaphysalis concinna 

Haemaphysalis cornigera 

Haemaphysalis flava†

Haemaphysalis japonensis 

Haemaphysalis japonica‡

Haemaphysalis kutchensis 

Haemaphysalis longicornis†

Haemaphysalis ornithophila§

Haemaphysalis phasiana†

Ixodes acuminatus 

Ixodes cavipalpus 

Ixodes granulatus 

Ixodes nipponensis†

Ixodes ovatus 

Ixodes persulcatus‡

Ixodes pomeranzevi‡

Ixodes ricinus 

Ixodes signatus 

Ixodes turdus†

Ixodes vespertilionis 

Rhipicephalus annulatus¶

Rhipicephalus microplus¶

Rhipicephalus sanguineus

*Sources: Yamaguti et al,15 Ree,16 and as individually annotated. 

†US Army tick surveys, 2007 

‡US Army tick surveys, 2002-2008 

§Captured in 2008 on migratory birds on Hong Island, southwestern 

Korea. 

¶ Formerly Boophilus spp
 July – September 2009 43

THE ARMY MEDICAL DEPARTMENT JOURNAL

in 2007 resulted in the collection of 

approximately 6,800 ticks (total 6 species, shown 

in Table 2) from Jeju Province and along the 

southern coast in Jeollanam and 

Gyeongsangnam Provinces, all shown in the 

Figure. US Army tick surveillance data from this 

area had been lacking, and the surveys resulted in 

substantial collections and information about an 

obscure and uncommonly collected and reported 

tick species, Haemaphysalis phasiana Saito, 

Hoogstraal, and Wassef.34

Additional surveys in 2008 led to the collection 

of another rarely collected species, Ixodes 

pomeranzevi Serdyukova, which was collected in 

low numbers (4 nymphs, 2 adults) on the striped 

field mouse, Apodemus agrarius Pallas. 

However, more than 24 larvae, 9 nymphs, and 17 

adults were removed from an Asiatic chipmunk, 

Tamias sibiricus (Laxmann), which suggested 

the need for extensive small mammal surveys to 

identify the host range, prevalence, and 

associated tick species.35 In 2008, collaboration 

with a Korean Migratory Bird Survey on Hong 

Island (Jeollanam Province) resulted in the 

discovery of another tick, Haemaphysalis 

ornithophila Hoogstraal and Kohls, which is at 

least passing through Korea along the birds’ 

migratory route.36 Why all the new discoveries? 

Perhaps, global warming is creating 

environmental conditions favorable to these species 

and affecting their distribution in Korea,37 or perhaps 

our surveillance activities are just finding what has 

been present, but not detected earlier due to lack of 

funding and personnel to conduct vector-borne 

pathogen surveillance. At any rate, these discoveries 

demonstrate the need for comprehensive and periodic 

surveillance of vector populations and reservoir hosts 

to identify changes in vector populations and disease 

prevalence that may impact Soldier activities. 

Ticks are present in the ROK and researchers are 

finding a high prevalence of tick-borne pathogens 

within tick (Table 2) and rodent populations, but 

where is the corresponding disease? One possibility is 

that humans are not the preferred host of the primary 

vectors while other possibilities include human avoidance of tick habitats, unfamiliarity with disease from 

tick-borne pathogens among the medical community, 

issues with ordering the correct diagnostic test, and 

lack of reporting requirements, as discussed earlier. 

Operational field conditions for military forces are 

typically different during a prolonged armistice than 

intensive combat operations such as during the Korean 

War. Generally speaking, military personnel operating 

during noncombat periods can expect to have a clean 

uniform and perhaps a warm, soapy shower every one 

to 3 days, and many live or operate out of established 

base camps, which provide additional opportunities for 

personal hygiene. These situations allow for frequent 

body inspections for ticks, plus, the soapy water may 

injure or kill attached ticks and interfere with or reduce 

the potential for disease transmission, hence reducing 

the incidence of tick-borne disease. 

In contrast, during major combat operations such as 

those of World War I, World War II, or the Korean 

War, military personnel in forward areas were 

generally not able to sustain the same level of hygiene 

(even with periodic rotations), due to the extended and 

austere battlefield conditions, as they would during 

noncombat operations. Consequently, their exposure to 

Table 3. Human and other animal pathogen associations with 

tentative tick vectors in the Republic of Korea. 

Pathogen Vector(s) 

Anaplasma bovis Haemaphysalis longicornis17

Anaplasma phagocytophilum* Haemaphysalis longicornis, 

Ixodes persulcatus17

Anaplasma platys Haemaphysalis longicornis18

Babesia spp* Haemaphysalis longicornis19

Bartonella elizabethae* Haemaphysalis longicornis20

Bartonella spp* Haemaphysalis longicornis20

Borrelia afzelii* Ixodes persulcatus21

Borrelia burgdorferi sensu lato* Ixodes granulatus, I nipponensis, 

I persulcatus22-24

Borrelia garinii* Ixodes persulcatus21

Borrelia valaisiana* Ixodes nipponensis25

Coxiella spp* Haemaphysalis longicornis26

Ehrlichia canis Haemaphysalis longicornis18

Ehrlichia chaffeensis* Haemaphysalis longicornis, 

Ixodes persulcatus17,18,27

Ehrlichia ewingii* Haemaphysalis longicornis18

Theileria sergenti Haemaphysalis longicornis28

Tick-borne encephalitis virus, 

Western subtype*

Haemaphysalis longicornis, 

H flava29,30

*Causes disease in humans. 
44 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

zoonotic tick-borne and other vector-borne pathogens 

was increased. In addition, they may occupy areas that 

have higher tick populations, eg, forested areas during 

hostility operations, and therefore have increased 

contact with the ground and vegetation harboring 

questing ticks. Similarly, the civilian population may 

experience displacement, homelessness, reduced 

sanitation, increased exposure to vectors and disease, 

elevated disease levels, and thus increase the risk of 

spreading the disease through vectors to military 

forces operating in that region. 

These aspects of Korean society and the current 

hygiene standards of US military personnel make it 

difficult to estimate the impact of tick-borne pathogens 

on a military force operating in substandard field 

conditions during major combat operations in Korea. 

Hence, the tick-borne pathogen threat to military 

forces in the ROK is currently an estimate derived 

from limited reports of the diseases present, the tick 

population densities and distributions, vector 

bionomics, potential human exposure rates, disease 

mitigation actions, season, etc. Increased vector and 

human disease surveillance would lead to a better 

understanding of the tick-borne pathogen risks and 

mitigation strategies required to reduce these risks. 

Fortunately, the Department of Defense (DoD) Insect 

and Arthropod Repellent System, which includes the 

proper wear of the uniform, wearing permethrin 

treated uniforms, and applying military formulations 

of extended duration topical insect and arthropod 

repellent N,N-diethy-3-methylbenzamide (deet) to 

exposed human skin, is estimated to reduce virtually 

all tick exposures in the ROK, significantly mitigating 

the risk of disease from tick-borne pathogens among 

US Soldiers. This repellent system also provides 

protection against other vector-borne pathogens in the 

ROK, so its implementation to prevent disease from 

tick-borne pathogens also provides added protection 

against malaria, Japanese encephalitis, scrub typhus, 

body lice (epidemic typhus), fleas (murine typhus), 

and other biting arthropods. 

However, the fielding of the flame-retardant Army 

Combat Uniforms (FRACU) necessitates a 

reevaluation of the permethrin-fabric properties as 

they relate to protection against ticks, chiggers, and 

other blood-feeding arthropods. These evaluations 

need to determine the protection level of the FRACU 

compared to the standard (>90% protection after 50 

Perspectives on Scrub Typhus, Tick-Borne Pathogens, and Hantavirus in the Republic of Korea 

Provinces and major city areas in the Republic of Korea. 

Two US Army tick surveys in 2007 identified 6 species 

among 6,800 ticks collected in Jeju (18*), Jeollanam (16*), 

and Gyeongsangnam (13*) provinces. 

1 Incheon 

2 Seoul 

3 Gyeonggi 

4 Gangwon 

5 Pyongtaek City 

6 Chungnam 

 7 Chungbuk 

 8 Daejeon City 

 9 Gyeongbuk 

10 Jeollabuk 

11 Daegu City 

12 Ulsan 

13 Gyeongsangnam 

14 Busan 

15 Gwangju 

16 Jeollanam 

17 Haenam City 

18 Jeju 

Identification Key 

* 

* 

* 
 July – September 2009 45

THE ARMY MEDICAL DEPARTMENT JOURNAL

washings) and then determine its effectiveness against 

blood-feeding arthropods. Currently, permethrin 

treatment is not approved for use on FRACUs by the 

military. Permethrin treatments do not meet the 

Environmental Protection Agency label required 

permethrin concentration in the uniforms nor provide 

the required amount of protection against biting 

arthropods. 

General observations during the 2007 surveys in Jeju 

Province and along the southern coast showed that 

survey personnel who wore permethrin treated 

uniforms rarely found a tick on their uniform (in some 

cases the “found” tick was dead), while those who did 

not wear permethrin treated uniforms commonly found 

ticks on their uniform. Of course, personal protective 

measures have to be implemented and used properly, 

eg, tucking the trouser leg into the boot and not using 

blousing garters, for these countermeasures to be most 

effective. 

From an entomological perspective, very little was 

known about Korean ticks during the Korean War. 

Ticks were reported as being uncommon, and very few 

Soldiers complained of tick bites.33 In 1971, US Army 

personnel assigned to the 406th Medical Laboratory, 

Camp Zama, Japan published a comprehensive 

systematic and bionomical work on ticks in Japan and 

the ROK, even though limited Korean tick data were 

available for inclusion.15 This document, however, 

remains useful as many of the ticks found in Japan are 

also found in the ROK, and it is still the primary 

document for identifying Korean ticks. Since 1971, 

few US military or ROK tick surveillance field studies 

have been reported in professional literature, so 

knowledge about the current status of tick populations 

and disease prevalence is lacking. 

Articles have been published on diseases specifically 

caused by Korean tick-borne pathogens, but no tickborne pathogen list or comprehensive discussion of the 

importance of tick-borne pathogens in the ROK could 

be found. To prevent surprises during a time of stress 

(major combat operations) and to develop a better 

understanding of tick-borne pathogens in the ROK, 

there is a need for surveillance which targets host and 

vector species to determine relationships between 

vectors, pathogens, reservoirs, and hosts. This 

surveillance should include a peninsula-wide tick 

collection to better understand tick distributions, 

habitat, population densities, and the potential for 

disease transmission by each species, (eg, human 

attraction, infection rates, and relative abundance, 

seasonal distribution, environmental factors limiting its 

distribution, and host-parasite life cycles), and an 

entire season’s collection to show each species’ 

seasonal activity and disease cycle. 

Ten US Army studies since 2003, such as Chae et al,38

Lee et al,39 and Kim et al,40 have addressed these 

deficiencies. A bibliography on the ticks of the ROK is 

being created based upon an extensive literature search 

and review for all tick-related information for the ROK 

and surrounding countries, ie, North Korea, Japan, 

northeastern China, and southeastern Russia. The 

bibliography and the accompanying PDF files 

(currently about 284 citations with about 69% as PDF 

files) of the articles are being incorporated into the 

Defense Pest Management Information Analysis 

Center for access by DoD personnel. Tick collections 

described within these articles and from recent US 

Army tick surveys are being compiled as a record of 

known tick locations and will be used to create 

graphical tick distribution maps and a list of diseases 

caused by tick-borne pathogens with vector 

associations for the ROK. Table 2 represents our initial 

attempt at extracting vector and disease associations 

from published literature. 

HANTAVIRUS

There are 4 known rodent-borne hantaviruses in the 

ROK: Hantaan virus (Korean Hemorrhagic Fever 

(KHF)), Seoul virus, Soochong virus, and Muju virus. 

Reservoirs of each have primary reservoir hosts with 

the striped field mouse, Apodemus agrarius coreae, 

vectoring KHF; the common roof rat, Rattus rattus 

Linnaeus, and the Norway rat, Rattus norvegicus 

Berkenhout, vectoring Seoul virus; the Korean field 

mouse, Apodemus peninsulae Thomas, vectoring 

Soochong virus; and the royal vole, Myodes regulus 

Thomas, vectoring Muju virus.41,42 A fifth hantavirus 

(Imjin virus) in an insectivore, Crocidura lasiura 

Dobson, has recently been identified.43

Transmission is associated with inhalation of 

aerosolized particles, such as dusts, that have been 

contaminated with rodent excreta and/or secreta (feces, 

urine, and saliva). It also can be contracted through a 

rat or mouse bite, so precautions should be made when 

handling them and they should never be kept as 

mascots or pets. 
46 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

Hantaan virus, commonly referred to as KHF, is the 

most common and virulent of the group and fits into 

the hemorrhagic fever with renal syndrome (HFRS) 

disease group. These diseases are characterized by 

leakage of blood from the circulatory system and 

abnormal kidney function. Conditions during the Korean War led to 2,158 hantavirus cases in US forces.44

Most of these cases occurred north of Seoul and with a 

large majority occurring north of the 38th parallel.45

While the risk for HFRS is always present in the ROK, 

cases in the Korean population show a very small 

transmission peak in May and June, and a much larger 

transmission peak from September through December. 

These transmission periods appear to be associated 

with agricultural practices (planting for May and June, 

draining/drying and harvesting rice fields for 

September and October), which results in significant 

human-rodent interaction and hence exposure. 

However, more recent evidence suggests that the 

primary peak is associated with the rodent’s 

reproductive behavior (primary brood production in 

the early fall preceding the peak transmission) that 

produces large numbers of naïve rodents.46 When 

associated with high local infection rates, movement, 

and competition for overwintering habitat, the results 

are acute infections with high viremias and shedding 

of virus. Consequently, when farmers are actively 

harvesting their fields or military personnel are 

training in the field during these periods, there is an 

increased risk of acquiring hantavirus.47 Generally, the 

risk of HFRS in the ROK can be characterized as 

having a low frequency of occurrence, but a severe 

outcome if acquired, and field training activities that 

lead to human-rodent interactions at any time of the 

year can result in Soldiers contracting HFRS. The 

incubation period may be as long as 50 days before 

symptoms occur, so Soldiers should be informed of 

HFRS symptoms (early symptoms are often flu-like), 

and if they become ill, they should alert their medicalcare providers with information as to their travel or 

field training history. 

Surveillance studies have shown that the reservoir of 

HFRS is very common throughout the country and 

seasonal Hantaan virus rodent infection rates were as 

high as 60% during some trapping periods at some of 

the field training sites.48,49 These studies have also 

shown that a portion of the Hantaan virus genome was 

descriptive for selected sites and made it possible to 

identify transmission sites for HFRS case studies for 4 

Soldiers that demonstrated incubation periods from a 

minimum of 6 to 22 days to a maximum of 15 to 35 

days.50

Studies also have shown that high populations of 

rodents are present in tall grassy and scrub habitats.51

In training sites, areas of tall, unmanaged vegetation 

bordering fighting positions (artillery firing points, 

trenches, and foxholes) increase human-rodent 

interactions along the border vegetation, as well as the 

often barren training area interface that may become 

potentially contaminated with virus laden rodent excreta. Also, dust produced when firing large weapons 

such as field artillery may increase the risk of infection 

as rodent urine and fecal particles become airborne 

from the muzzle blast of these weapons. Similarly, the 

dust from vehicles going through dry vegetated areas, 

trails, or dirt roads bordered by grassy/scrub vegetation 

may increase hantavirus infection risks as rodents 

traversing these grassy borders produce virus laden 

excreta on these trails and roads. These risks can be 

reduced by discouraging rodents from being attracted 

to fighting positions through vegetation control 

(maintaining vegetation cut short to reduce ground 

cover) and sanitary measures, such as frequent 

removal of trash and debris. Fighting positions should 

be located away from heavily traveled roads to prevent 

exposure to potentially infected dusts. Artillery 

personnel should use sanitary measures to discourage 

rodent infestations where they fire their weapons, and 

should take personal preventive measures to reduce 

inhalation of dust from the muzzle blast. 

Exposures in closed spaces have the greatest risk, thus 

military personnel should not bring potentially infested 

materials, such as rice straw for flooring or bedding, 

into closed areas such as tents, barns, houses, or other 

buildings. Additionally, military personnel in the field 

should avoid sleeping on the ground or placing vegetation that was lying on the ground into their helmets. 

CONCLUSION

Scrub typhus, tick-borne pathogens, and hantaviruses 

present challenges to the protection of military forces 

in the ROK, and surveillance studies focused on the 

improvement of our knowledge of these diseases and 

how to prevent them need continual support. While the 

distribution of scrub typhus has been well described, 

the distribution and prevalence of tick-, flea-, and 

Perspectives on Scrub Typhus, Tick-Borne Pathogens, and Hantavirus in the Republic of Korea 
 July – September 2009 47

THE ARMY MEDICAL DEPARTMENT JOURNAL

rodent-borne pathogens affecting man are largely 

unknown. The rickettsial agents are currently under 

investigation and are just now being identified to 

species, which will provide future endeavors to 

determine their distribution and prevalence in rodent 

and human populations. As these parasites are 

identified, appropriate laboratory assays can be 

developed to identify the incidence of disease among 

military and civilian populations in the ROK. 

Similarly, assays to identify Imjin virus, which does 

not serologically cross react with the other rodentborne hantaviruses, can be developed to determine if it 

causes human disease. As an awareness of the 

presence of tick-, mite-, flea-, and rodent-borne 

pathogens are developed, the Korea Center for Disease 

Control and Prevention may place new zoonotic 

pathogens on the reportable disease list, which, in 

conjunction with an understanding of the transmission 

cycle, will enhance our ability to determine health 

risks among US military and civilian populations in 

the ROK. 

Information gathered as a result of surveillance studies 

must be prepared and disseminated through channels 

where actions can be taken by commanders at all 

levels to reduce risks to Soldiers from often 

preventable diseases and nonbattle injuries during 

hostilities, while training, or off-duty. 

Indeed, the real value of such surveillance work is 

reflected in the sentiments of His Royal Highness, 

Prince Mahidol of Songkla (Thailand, 1892-1929): 

True success is not in the learning, but its 

application to the benefit of mankind.52

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malaria and Japanese encephalitis in the Republic of 

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diagnosis of two scrub typhus outbreaks at Camp 

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immunosorbent assay, rapid flow assay, and western 

blot assay using outer membrane 56-KD recombinant 

proteins. Am J Trop Med Hyg. 2003;69:60-66. 

12. Yi KS, Chong Y, Covington SC, Donahue BJ, 

Rothen RL, Rodriguez J, Arthur JD. Scrub typhus in 

Korea: importance of early clinical diagnosis in this 

newly recognized endemic area. Mil Med. 

1993;158:269-273. 

13. O’Guinn ML, Klein TA, Lee JS, et al. Rodent-borne 

disease surveillance. Serological surveillance of scrub 

typhus, murine typhus, and leptospirosis in small 

mammals captured at firing points 10 and 60, 

Gyeonggi Province, Republic of Korea, 2001-2005. 

Vector Borne Zoonotic Dis. In press. 

14. Richards AL. Infections with typhus, spotted fever 

group and scrub typhus group Rickettsiae in the 

Republic of Korea. Paper presented at the AsiaPacific Military Medical Conference; April 7, 2009; 

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15. Yamaguti N, Tipton VJ, Keegan HL, Toshioka S. 

Ticks of Japan, Korea and Ryukyu Islands. Provo, 

UT: Brigham Young University Publications; 1971. 

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1:226. 

16. Ree HI. Medical Entomology (Medical 

Anthropology). 4th ed. Seoul, Republic of Korea: 

Komunsa Publishing; 2005:376-377. 

17. Kim CM, Kim MS, Park MS, Park JH, Chae JS. 

Identification of Ehrlichia chaffensis, Anaplasma 

phagocytophilum, and A. bovis in Haemaphysalis 

longicornis and Ixodes persulcatus ticks from Korea. 

Vector Borne Zoonotic Dis. 2003;3:17-26. 

18. Kim CM, Yi YH, Lee MJ, et al. Tick-borne rickettsial 

pathogens in ticks and small mammals in Korea. Appl 

Environ Microbiol. 2006;72:5766-5776. 

19. Cho SH, Kim TS, Lee HW, et al. Identification of 

newly isolated Babesia parasites from cattle in Korea 

by using the Bo-RBC-SCID mice. Korean J 

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20. Kim CM, Kim JY, Yi YH, et al. Detection of 

Bartonella species from ticks, mites, and small 

mammals in Korea. J Vet Sci. 2005;6:327-334. 

21. Takada N. Vectorial competences and distribution 

patterns of parasitic acari, especially for emerging 

diseases in Japan and east Asia. Med Entomol Zool.

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22. Shim JC, Yoon YH, Kim CL, et al. Studies on vector 

potential of ticks (Ixodidae) in transmitting of lyme 

disease (Borrelia burgdorferi) (II). Rep Natl Inst 

Health. 1993;30:131-136. 

23. Shim JC, Yoon YH, Cho YB, et al. Studies on the 

potential vector of ticks (Ixodidae) in transmitting of 

Lyme disease (Borrelia burgdorferi) (III). Rep Natl 

Inst Health. 1994;31:149-155. 

24. Kee S, Hwang KJ, Oh HB, Park KS. Identification of 

Borrelia burgdorferi isolated in Korea using outer 

surface protein A (OspA) serotyping system. 

Microbiol Immunol. 1994;38:989-993. 

25. Masuzawa T, Fukui T, Miyake M, et al. 

Determination of members of a Borrelia afzeliirelated group isolated from Ixodes nipponensis in 

Korea as Borrelia valaisiana. Int J Sys Bacteriol.

1999;49:1409-1415. 

26. Lee JH, Park HS, Jang WJ, et al. Identification of the 

Coxiella sp. detected from Haemaphysalis 

longicornis ticks in Korea. Microbiol Immunol.

2004;48:125-130. 

27. Lee SO, Na DK, Kim CM, et al. Identification and 

prevalence of Ehrlichia chaffeensis infection in 

Haemaphysalis longicornis ticks from Korea by 

PCR, sequencing and phylogenetic analysis based on 

16S rRNA gene. J Vet Sci. 2005;6:151-155. 

28. Kang YB, Jang H. Induction of Theileria sergenti

infection in splenectomized calf by Haemaphysalis 

longicornis. Res Rep Rural Dev Admin. 1989;31:48-

53. 

29. Ko SJ, Kang JG, Kim SY, et al. Prevalence of tickborne encephalitis virus from ticks in southern 

Republic of Korea. Am J Trop Med Hyg. In press. 

30. Jang WJ, Kim JH, Choi YJ, et al. First serologic 

evidence of human spotted fever group rickettsiosis 

in Korea. J Clin Microbiol. 2004;42:2310-2313. 

31. Kim SY, Yoon SM, Han MG, et al. Isolation of tickborne encephalitis viruses from wild rodents, South 

Korea. Vector Borne Zoonotic Dis. 2008;8:7-13. 

32. Jang WJ, Choi YJ, Kim JH, et al. Seroepidemiology 

of spotted fever group and typhus group rickettsioses 

in humans, South Korea. Microbiol Immunol. 

2005;49:17-24. 

33. Traub R, Hertig M, Lawrence WH, Harriss TT. 

Potential vectors and reservoirs of hemorrhagic fever 

in Korea (preliminary report). Am J Hyg.

1954;59:295-301. 

34. Sames WJ, Kim HC, Chong ST, et al. Haemaphysalis

(Ornithophysalis) phasiana (Acari: Ixodidae) in the 

Republic of Korea: two province records and habitat 

descriptions. Syst Appl Acarol. 2008;13:43-50. 

35. Kim HC, Kim JH, Jo YS, Chong ST, Sames WJ, 

Klein TA, Robbins RG. Ixodes pomeranzevi

Serdyukova, 1941 (Acari: Ixodidae) in the Republic 

of Korea. Syst Appl Acarol. In press. 

36. Kim HC, Ko SJ, Choi CY, et al. Migratory bird tick 

surveillance, including a new record of 

Haemaphysalis ornithophila Hoogstraal and Kohls 

1959, (Acari: Ixodidae) at Hong Island, Republic of 

Korea. Sys Applied Acarol. 2009;14:3-10. 

37. Chae JS, Adjemian JZ, Kim HC, Ko S, Klein TA, 

Foley J. Predicting the emergence of tick-borne 

infections based on climatic changes in Korea. Vector 

Borne Zoonotic Dis. 2008;8:265-275. 

38. Chae JS, Kim CH, Kim EH, et al. Molecular 

epidemiological study for tick-borne disease 

(Ehrlichia and Anaplasma spp.) surveillance at 

selected US military training sites/installations in 

Korea. Ann N Y Acad Sci. 2003;990:118-125. 

Perspectives on Scrub Typhus, Tick-Borne Pathogens, and Hantavirus in the Republic of Korea 
 July – September 2009 49

THE ARMY MEDICAL DEPARTMENT JOURNAL

39. Lee SO, Na DK, Kim CM, et al. Identification and 

prevalence of Ehrlichia chaffeensis infection in 

Haemaphysalis longicornis ticks from Korea by 

PCR, sequencing and phylogenetic analysis based on 

16S rRNA gene. J Vet Sci. 2005;6:151-155. 

40. Kim CH, Yi YH, Yu DH, et al. Tick-borne rickettsial 

pathogens in ticks and small mammals in Korea. Appl 

Environ Microbiol. 2006;72:5766-5776. 

41. Baek LJ, Kariwa H, Lokugamage K, et al. Soochong 

virus: an antigenically and genetically distinct 

hantavirus isolated from Apodemus peninsulae in 

Korea. J Med Virol. 2006;78:290-297. 

42. Song KJ, Baek LJ, Moon S, et al. Muju virus, a novel 

hantavirus harboured by the arvicolid rodent Myodes 

regulus in Korea. J Gen Virol. 2007;88:3121-3129. 

43. Song JW, Kang HJ, Gu SH, et al. Characterization of 

Imjin virus, a newly isolated hantavirus from the 

Ussuri white-toothed shrew (Crocidura lasiura). J 

Virol. 2009;83:6184-6191. 

44. Pruitt FW. General aspects of medicine in Korea and 

Japan, 1951-1953. In: Recent Advances in Medicine 

and Surgery Based on Professional Medical 

Experiences in Japan and Korea, 1950-1953

[seminar 19-30 April 1954]. Vol II. Washington, DC: 

US Army Medical Service Graduate School, Walter 

Reed Army Medical Center; 1954. Medical Science 

Publication No. 4. Available at: http://

history.amedd.army.mil/booksdocs/korea/recad2/

default.htm. Accessed July 22, 2009. 

45. Gauld RL, Craig JP. Epidemiological pattern of 

localized outbreaks of epidemic hemorrhagic fever. J 

Hyg. 1954;59:32-38. 

46. Klein TA, Kim HC, Baek LJ, et al. Hantavirus 

surveillance in the US military in the Republic of 

Korea. Paper presented at: XVII International 

Congress for Tropical Medicine and Malaria; October 

1, 2008; Jeju, Republic of Korea. 

47. Lee HW, Baek LJ, Doo CD. The study of breeding 

season of Apodemus agrarius, the natural host of Korean hemorrhagic fever. Korean J Virol. 1981;11:1-5. 

48. Lee HW, Lee PW, Baek LJ, Song CK, Seong IW. 

Intraspecific transmission of Hantaan virus, etiologic 

agent of Korean hemorrhagic fever, in the rodent 

Apodemus agrarius. Korean J Virol. 1981;30:1106-

1112. 

49. Hong HK, Lee UY. Studies on the biology of 

Apodemus agrarius in Korea. Thesis Collect Incheon 

Univ. 1984;6:417-439. 

50. Song JW, Moon SS, Gu SH, et al. Hemorrhagic fever 

with renal syndrome among four US soldiers while 

training near the demilitarized zone, Republic of 

Korea, 2005. Emerg Inf Dis. In press. 

51. O’Guinn ML, Klein TA, Lee JS, et al. Rodent-borne 

disease surveillance. Ecological surveillance of small 

mammals at firing points 10 and 60, Gyeonggi 

Province, Republic of Korea, 2001-2005. J Vector 

Ecol. 2008;33:370-384. 

52. Important speeches and works page. Prince Mahidol 

Award Foundation Website. Available at: http://

www.princemahidolaward.org/importantspeeches.en.php. Accessed August 5, 2009. 

AUTHORS

LTC Sames is currently deployed in Iraq as the Chief, 

Multinational Corps-Iraq Force Health Protection, and 

the Iraq Theater Entomologist and Pest Management 

Consultant. 

Dr Kim is the senior civilian Research Entomologist 

with the 5th Medical Detachment, Yongsan Army 

Garrison, Republic of Korea. 

COL (Ret) Klein is a consultant to the 65th Medical 

Brigade, Yongsan Army Garrison, Republic of Korea. 
50 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

INTRODUCTION

Remote teaching is most appropriate when the subject 

matter does not change frequently and is of importance 

to a large audience, or where cost-effectiveness is a 

concern. The Armed Forces Pest Management Board 

has recently released 3 diskettes that teach the morphology of ticks, larval mosquitoes, and adult mosquitoes. The lessons emphasize anatomical structures that 

are most commonly used in arthropod identification 

keys. The goal is for students to be able to confidently 

identify unknown arthropod specimens using any 

arthropod identification key written for that group. 

PRODUCTS

The 3 instructional diskettes are: 

Interactive Program for Teaching Tick 

Morphology 

Interactive Program for Teaching Larval Mosquito 

Morphology 

Interactive Program for Teaching Adult Mosquito 

Morphology 

They are available free of charge by contacting the 

Armed Forces Pest Management Board (afpmbwebmaster@osd.mil) and providing a mailing address 

and the titles of the requested disks. The tick program 

is distributed on a CD, the mosquito programs are 

distributed on DVDs.

Each program contains 4 major sections. The first is a 

tutorial that discusses each morphological 

characteristic and how its appearance can vary 

between species and genera (Figure 1). A clear 

instance and a clear non-instance of the characteristic 

are usually presented on the same page. In some cases, 

an unclear instance or an unclear non-instance will 

follow on the next page to let students know where 

mistakes commonly occur and how to avoid them. 

Following the tutorial, students are able to practice 

what they have learned by identifying unknown 

arthropod specimens. It is important for them to use 

their new knowledge to solve problems within the 

same context that they will encounter later in their 

work.1

 A specimen is selected, along with an 

identification key that is commonly used for that 

geographic area, and the student begins working 

through the key’s couplets (Figure 2). After reading 

the descriptions in each couplet and examining the 

image(s), the student selects an identification key path. 

If the choice is incorrect, an explanation is provided. A 

button with a plus symbol is included on some of the 

images (Figure 3). It presents a magnified image of the 

area within the box, similar to the action of the zoom 

feature on a microscope. 

The third section of the program is the glossary, which 

serves as a quick reference. The terms and structures in 

the identification keys are concisely explained using 

words and images (Figure 4). 

Remote Teaching of Arthropod Species 

Identification Through Interactive 

Multimedia 

CDR (Ret) George W. Schultz, MSC, USN 

Richard G. Robbins, PhD 

ABSTRACT

Remote teaching programs are effective means for providing entomologists with the knowledge they need to confidently 

identify medically important arthropods. Using interactive multimedia, these programs teach the morphology of ticks 

and larval and adult mosquitoes through tutorials, followed by practice identifications of collected arthropod specimens. 

Interactive multimedia programs are created in 3 phases: planning, design, and development. Species identification is 

one of the most important skills that entomologists must have, because recognition of disease vectors during field 

surveillance is an important component of overall troop protection. 
 July – September 2009 51

In the mosquito programs, the fourth section contains 

diagrams of hundreds of species (Figure 5). These 

diagrams are taken from the literature. The tick 

program has a unique feature: a collection of identification keys that can be searched by author, tick 

genus, or geographic area (Figure 6). 

METHODS

The creation of an interactive multimedia program 

usually follows 3 phases: planning, design, and 

development.2

 In the planning phase, the scope of the 

project is defined. The tutorial teaches the characteristics that are used in identification keys, as well as 

their variations. Next, the project style and standards 

are determined. The colors, fonts, size of text, and how 

the student navigates and interacts with the program 

are established to maintain consistency.3

The design phase involves the creation of flowcharts 

and storyboards that describe the path that the program 

follows and the lesson to be taught on each page. 

These programs were developed using Authorware 

(Adobe Systems Inc, San Jose, California), an iconbased authoring system. The program is designed 

around a page/chapter metaphor. During this stage, 

each page describes in words what the images will 

show and the audio narrative. 

The development phase begins with photographing the 

specimens and then editing the images before placing 

them into the program. Next, the audio script is 

Figure 1. Extract from the adult mosquito tutorial showing 

variation in wing cell length. 

Figure 2. Couplet and images from the student identification 

practice section of the tick morphology program. 

Figure 3. Some images can be enlarged by clicking the plus 

symbol within the rectangle. 

Figure 4. Extract from the glossary of the adult mosquito 

program. 
52 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

Remote Teaching of Arthropod Species Identification Through Interactive Multimedia 

Figure 5. The menu of diagrams for the larval mosquito program and an example of a chaetotaxy drawing of one species which 

is presented when a link is selected. 

recorded, brought into a sound editor, and added 

to the program. Using audio rather than text to 

describe the images has the advantage of freeing 

the screen for larger images, resulting in higher 

resolution. It also permits more images to be 

placed on the screen simultaneously for 

comparison. Another advantage of audio rather 

than text is that information can be presented to 

the student at a calculated speed.4

 The timing of 

the program requires careful attention so that the 

information is presented at an optimal speed for 

the average user. The program is then tested by a 

variety of users, including subject matter 

experts, before it is released. 

DISCUSSION

Traditional methods of achieving proficiency in 

arthropod identification, such as with ticks or 

mosquitoes, require students to attend classes, 

often at a university. Sometimes they spend a 

week at a museum, studying under a taxonomic expert. 

The disadvantages of these methods are numerous, 

including cost, course availability, and willingness of 

experts to provide training. Even if the students are 

able to attend courses and become proficient in a 

particular group, there are many other orders and 

families of medically important arthropods. Remote 

teaching is the ideal means for presenting an expanded 

knowledge base to large numbers of students over 

broad geo-graphic areas. 

The major disadvantage of a technology-based 

learning program is the initial cost of development, 

which is high compared to preparing a traditional 

Figure 6. The tick program provides identification keys that can be used 

to search by genus, author, or geographic area. The above extract illustrates identification keys for the ticks of Europe. 
 July – September 2009 53

THE ARMY MEDICAL DEPARTMENT JOURNAL

lecture or laboratory identification course. It is 

important to do a cost-benefit analysis before 

beginning such a project.5

 Quantifying benefits can be 

difficult. These programs may also be unsuitable for 

presenting information that changes frequently or 

regularly. Continuous changes in a program would be 

economically unfeasible. 

The advantages of using a technology-based learning 

program to teach arthropod identification are 

numerous. Students can choose the time and location 

for training that is convenient for them. They can work 

at their own pace. Those unfamiliar with the subject 

can spend as much time as needed on the lessons. 

Even inexperienced students usually complete the 

instruction in less time than with traditional, instructorled methods. All the specimens used in technologybased learning programs are of high quality and come 

from major museums. As a result, students receive a 

more comprehensive introduction to taxonomy than 

might otherwise be possible using locally available 

arthropod specimens. 

Another major advantage of these programs is that 

their target audience is broad. The lessons described 

here, although primarily designed for entomologists, 

can be used by anyone in public health, preventive 

medicine, pest control, or other related fields. Also, in 

this particular application, teaching arthropod 

identification, the life cycle of the product is quite long 

because, from a human perspective, insect morphology 

is unchanging. And this teaching tool is inexpensive. 

At an estimated program production cost of $100,000, 

if only 2,000 students were to use the program (a very 

conservative figure), the cost per student would be just 

$50 over the life of the product. 

Medical entomologists entering the military usually 

have broad knowledge of their subject, but few are 

experts in more than one or two areas, such as 

toxicology, ecology, behavior, systematics, or other 

specialties. Even those who are systematists usually 

specialize in no more than a few families within an 

order. After a year or two of training, these entomologists will be deployed, and they will need to make 

health-related decisions that could impact the success 

of their mission. Species identification is one of the 

most important skills that military medical 

entomologists can possess because recognition of 

disease vectors during field surveillance is an 

important component of overall troop protection. 

Remote teaching of arthropod morphology is a 

comprehensive, efficient, cost-effective tool that is 

well suited to the military environment. 

ACKNOWLEDGEMENTS

Funding for these teaching programs was provided by 

the Armed Forces Pest Management Board and the 

Uniformed Services University of the Health Sciences. 

The authors thank Dr Richard C. Wilkerson and the 

staff of the Walter Reed Army Institute of Research 

Biosystematics Unit for providing the specimens used 

to develop the larval and adult mosquito programs. 

REFERENCES

1. Fleming M, Bednar A. Concept-learning principles. 

In: Fleming M, Levie W, eds. Instructional Message 

Design: Principles from the Behavioral and 

Cognitive Sciences. Englewood Cliffs, NJ: 

Educational Technology; 1993. 

2. Alessi SM, Trollip SR. Multimedia for Learning: 

Methods and Development. Needham Heights, MA: 

Pearson Education Company; 2001. 

3. Rieber LP. Computers, Graphics, & Learning. 

Madison, WI: Brown & Benchmark; 1994. 

4. Winn W. Perception principles. In: Fleming M, Levie 

W, eds. Instructional Message Design: Principles 

from the Behavioral and Cognitive Sciences.

Englewood Cliffs, NJ: Educational Technology; 

1993. 

5. Reynolds A, Iwinski T. Multimedia Training: 

Developing Technology-Based Systems. New York, 

NY: McGraw-Hill; 1996. 

AUTHORS

CDR (Ret) Schultz is a senior consultant with Kadix 

Systems, Arlington, Virginia, and is based in Elkhart 

Lake, Wisconsin. 

Dr Robbins is an Entomologist with the Armed Forces 

Pest Management Board, located at the Fort DetrickForest Glen Annex, Silver Spring, Maryland. 
54 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

INTRODUCTION

House flies (Musca domestica L) are a significant pest 

associated with military operations where proper 

sanitation of manure and refuse is often limited.1,2

Developmental sites for house flies include human and 

animal waste and food waste, all of which may be 

common at temporary military encampments or in the 

communities surrounding military encampments. In 

addition to the considerable nuisance caused by large 

populations of these flies, they have also been 

implicated in the transmission of a phylogenetically 

diverse group of human pathogens including 

Escherichia coli O157:H7, Salmonella enteritidis, 

Yersinia pseudotuberculosis, Helicobactor pylori, 

Vibrio cholerae, and rotavirus,3-11 as shown in Table 1.

The extent to which house flies may be involved in 

pathogen persistence and dispersal among troops or 

neighboring communities remains unclear; however, it 

is well known that flies may disperse a considerable 

distance (5 km or more) from breeding sites.32,33 Flies 

dispersing from their developmental sites are commonly attracted to human habitations and food preparation sites where they can transmit pathogens.34-36

Annual increases in human infections with enteric 

pathogens can demonstrate a distinct seasonality that 

coincides with increasing abundance of house flies.13,37

Further, area-wide control of house fly has been 

associated with a concurrent reduction in human 

sickness due to enteric pathogens,16,38-40 providing 

strong evidence that house flies can be important in the 

spread of these enteric diseases. 

With the advent of DDT (dichlorodiphenyltrichloroethane) for control of insects, house fly control has 

been largely through use of chemical insecticides. 

Behavioral Resistance of House Flies, Musca 

domestica (Diptera: Muscidae) to 

Imidacloprid

MAJ Alec C. Gerry, MS, USAR 

Diane Zhang, MD 

ABSTRACT

House flies captured at a field site in southern California were examined for physiological and behavioral resistance to 

the insecticidal toxicant imidacloprid using a no-choice and a choice feeding assay, respectively. Relative to a 

susceptible laboratory colony of house flies, field-captured house flies demonstrated moderate physiological resistance 

to imidacloprid using a no-choice feeding assay. In contrast, behavioral resistance of field-captured flies was very high 

with 72% survival of flies at even the highest imidacloprid concentrations tested using a choice feeding assay. Since the 

introduction of imidacloprid baits in California during 2003, the overuse of imidacloprid baits in southern California has 

resulted in the rapid selection, over only 5 years, of a house fly population that is highly resistant to imidacloprid. While 

house fly resistance is shown to be both physiological and behavioral, observed field failures of imidacloprid fly baits 

are primarily due to behavioral resistance. Field-deployable kits to assess behavioral resistance of house flies and other 

important insect pests are needed. 

Bacteria Viruses 

Acinetobacter spp3 Coxsackievirus3

Campylobacter spp12,13 enteroviruses24

Chlamydia trachomatis14,15 poliovirus3

Enterobacter spp3 rotavirus11

Enterococcus spp3 Parasites 

Escherichia coli O157:H7 6,16-19 Cryptosporidium parvum25

Helicobactor pylori9 Endolimax nana26

Klebsiella spp3 Entamoeba coli26

Proteus spp3 Entamoeba histolytica26

Psuedomonas spp3 Giardia lamblia5,27-29

Salmonella enteritidis7,20 Isospora spp26

Shigella sonnei16,21,22 Sarcocystis spp30

Staphylococcus aureus22,23 Toxoplsma gondii31

Streptococcus22

Vibrio cholerae10

Yersinia pseudotuberculosis8

Table 1. House fly-transmitted pathogens known to 

have the most serious affect on human health. 

Note: The list is not exhaustive for all pathogens carried 

by house flies. 
 July – September 2009 55

However, house flies have shown a great adaptability 

to these insecticides, developing resistance first to 

DDT,41 and then to most of the chemicals that have 

later become available for their control.42,43 The extent 

of house fly resistance to any particular chemical 

appears to be principally determined by the historical 

use of that chemical regionally.44-48 However, crossresistance where selection with one chemical may 

result in resistance to another has also been shown.42

In the military environment, rapid assessment of house 

fly resistance to chemicals approved for management 

of house flies by the Armed Forces Pest Management 

Board is needed whenever military units are deployed 

to a location where sanitation is lacking and house fly 

populations exceed acceptable numbers. 

A rapid assessment of the physiological resistance of 

an insect population to chemicals is typically 

accomplished using some form of contact assay, such 

as the World Health Organization bottle assay,49 or 

topical application of the material to the insect dorsum. 

A standard assay for determining house fly resistance 

to chemicals has been developed using 230 ml glass 

jars.50 For chemicals formulated into fly baits, a 

standard feeding assay has also been developed.43 In 

each of these assays, tested house flies are ensured 

substantial contact with the chemical. However, under 

natural field conditions, fly contact with a chemical 

may be limited due to detection and avoidance of the 

chemical, or due to irritation following contact with 

the chemical resulting in movement away from the 

chemical. Such behavioral resistance to chemicals has 

been shown in some house fly populations using 

“choice assays” even where physiological resistance 

was limited.44,51

In this study, we examined both physiological 

and behavioral resistance of a wild house fly 

population from southern California to 

imidacloprid, the active ingredient found in one 

of the most commonly used fly baits in the 

United States during the last 5 years. 

MATERIALS AND METHODS

House flies from a southern California dairy (BS 

Strain) were collected by sweep net in October 

2008 and colonized at the University of 

California at Riverside (UCR) using standard 

methods.52 Field collected flies were maintained 

in colony through 7 generations for use in this 

study. Susceptibility of this fly population to 

imidacloprid was evaluated relative to a UCR 

susceptible strain population of house flies that have 

been in colony since their collection in 1982 from a 

dairy in Mira Loma, California. 

Feeding Assay 

Because imidacloprid is typically formulated into a fly 

bait material, house fly susceptibility to this chemical 

was assessed using either a no-choice feeding 

bioassay43 or a modification of this bioassay (choice 

feeding assay), providing flies the opportunity to feed 

on a food source with or without imidacloprid. Colony

-reared house flies were chilled in a freezer for 

approximately 4 minutes, and then 25 female house 

flies, 3 to 6 days old, were placed into 230 ml glass 

jars (VWR International (West Chester, PA) catalog 

No. 16195-008) containing either one 4 cm cotton 

dental wick (Richmond Dental Co., Charlotte, NC) 

soaked in 20% sugar water containing technical grade 

imidacloprid (Chem Service Inc., West Chester, PA) 

(no-choice feeding assay), or two 4 cm dental wicks, 

one with sugar water and imidacloprid and the second 

with sugar water only (choice feeding assay). Bioassay 

jars were then covered with mesh netting and kept at 

25°C with a 12:12 L:D photoperiod. Dental wicks 

were hydrated at 24 and 48 hours, and mortality was 

assessed at 72 hours with house flies considered dead 

if they were unable to right themselves. 

For both the no-choice and the choice feeding assays, a 

minimum of 5 jars were used for each imidacloprid 

concentration, with an additional 5 jars provided dental 

wicks with 20% sugar water only as a negative control. 

For both the BS strain and the UCR strain flies, a 

minimum of 5 different concentrations of imidacloprid 

Fly Strain (Assay) N Slope (SE) LD50 (95% CI) 

(μg/ml) 

RR 

UCR (no-choice) 1,250 4.27 (0.29) 15.1 (13.1-17.5) – 

BS (no-choice)* 750 2.12 (0.22) 155.9 (110-194) 10.3 

UCR (choice) 725 2.36 (0.13) 68.2 (38.4-117.3) – 

BS (choice)† 725 0.78 (0.12) NA NA 

Table 2. Physiological and behavioral resistance to imidacloprid 

demonstrated by wild-type house flies captured from a dairy in 

southern California relative to a susceptible laboratory strain. 

*Significantly different from UCR Susceptible strain based on nonoverlap of 95% 

confidence intervals in no-choice assay. 

†Significantly different from UCR Susceptible strain based on failure to achieve 50% 

mortality at maximum dose (2,500 μg/ml) of imidacloprid tested.
56 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

resulting in >0% and <100% 

mortality were used. Bioassay data 

was pooled and analyzed by standard 

probit analysis53 with Abbot’s 

correction to adjust for control 

mortality using POLO-PC (LeOra 

Software, Petaluma, CA). 5 4

Resistance ratios (RR) were 

calculated by dividing the lethal dose 

(LD) values of the wild house fly 

population by the corresponding LD 

value of the UCR susceptible colony 

for each assay type. A significant 

difference (P<0.05 ) in the 

susceptibility of house fly strains to 

imidacloprid was determined by 

nonoverlap of the 95% confidence 

interval of the LD value of each fly 

strain. 

RESULTS AND DISCUSSION

The field-collected BS house fly strain was 

significantly less susceptible (P<0.05) to imidacloprid 

as compared to the UCR susceptible strain using both 

the no-choice and the choice feeding assays, as shown 

in Table 2. House fly resistance to imidacloprid when 

measured by the no-choice assay was moderate 

(RR=10), but was very high when measured by the 

choice assay. Low field fly mortality at even the 

highest concentration of imidacloprid tested in the 

choice assay (50 LD99 of the susceptible UCR strain) 

resulted in the lack of a significant regression line to 

estimate a 50% mortality value (data presented in the 

Figure). From these data, it is reasonable to infer that 

the BS strain of house flies would be minimally 

affected by the use of toxic fly baits containing 

imidacloprid as part of a fly management program 

under natural field conditions. 

The LD50 values for the UCR and BS strain of house 

flies tested for susceptibility to imidacloprid using the 

no-choice feeding assay were similar to previously 

published LD50 values for susceptible and resistant fly 

strains, respectively.48 The UCR susceptible flies will 

readily feed on commercial fly bait containing 0.5% 

imidacloprid (A.C.G., unpublished data, 2006). The 10

 higher LD50 value for UCR susceptible strain flies 

when tested with the choice assay is a result of altered 

test conditions providing both a treated and an 

untreated dental wick on which the flies may feed over 

the 72 hour assay period. Small changes in the test 

conditions can result in significant changes in 

calculated LD values,44 thus a direct comparison 

between the LD50 value for the no-choice and the 

choice feeding assays should be avoided. 

Fly baits containing imidacloprid were first introduced 

in California in 2003. Studies conducted in 2003 

showed imidacloprid baits to be quite effective at 

attracting and killing field fly populations in southern 

California.47 From 2003 to 2008, fly baits containing 

imidacloprid dominated the fly management market 

due to serious house fly resistance to the older baits 

containing the toxicant methomyl44,47 and the lack of 

alternative granular fly baits with quick fly kill 

characteristics. With nearly year-round use of this 

single imidacloprid bait product by most facilities or 

agencies engaged in fly management, it should be no 

surprise that house fly populations quickly became 

resistant to imidacloprid. At a diagnostic imidacloprid 

concentration of 2 LD99 for a susceptible laboratory 

colony, survival of house flies from field sites in 

southern California exposed to dental wicks containing 

imidacloprid in no-choice assays has increased from 

<40% in 2005 to 45% - 51% in 2006,48 and finally to 

73% for BS strain flies in this study. While this 

physiological resistance is significant, substantial 

mortality of the BS strain flies could still be achieved 

Behavioral Resistance of House Flies, Musca domestica (Diptera: Muscidae) to Imidacloprid 

Dose-Mortality of UCR Susceptible and BS Wild-type House 

Flies to Imidacloprid 

0

20

40

60

80

100

1 10 100 1000 10000

Imidacloprid Concentration (ug/ml)

% Mortality

UCR No-Choice

UCR Choice

BS No-Choice

BS Choice

Dose-mortality response of UCR susceptible and field-collected strains of 

house fly to imidacloprid following choice and no-choice feeding assays. 
 July – September 2009 57

THE ARMY MEDICAL DEPARTMENT JOURNAL

using high concentrations of imidacloprid, as indicated 

in the Figure. 

In contrast to the no-choice assay, the choice feeding 

assay indicated that 72% of the BS strain flies could 

not be killed by even the highest concentration of 

imidacloprid used (50  LD99 for a susceptible 

laboratory colony). The choice feeding assay is 

certainly more indicative of field conditions where 

flies have many available food options and are not 

forced to contact or consume toxic bait. Under field 

conditions, flies may be selected for behavioral 

responses to avoid or limit contact with toxic bait. The 

results of the choice feeding assay support field 

observations during 2008, indicating substantial field 

failures of imidacloprid baits in southern California 

(A.C.G., unpublished data, 2008). 

The failure to achieve complete control of the BS 

strain flies at higher imidacloprid concentrations in the 

no-choice assay may also be indicative of behavioral 

resistance. In these assays, flies were not evaluated for 

sugar consumption, and behaviorally resistant flies 

may have limited sugar contact or consumption over 

the 72 hour assay period, even in the no-choice assay. 

This study showed that house flies can develop 

resistance to toxic baits through altered behavioral 

response to a toxicant. These findings are in agreement 

with earlier studies44,47,51,55 showing that avoidance 

behaviors against a chemical toxicant may be selected 

for in house flies. Most volatile compounds in 

commercial fly baits are selected for attractiveness to 

house flies, indicating a priori value to house flies in 

persisting to express appetitive response to these 

compounds. It seems unlikely that behaviors would be 

selected to avoid these attractive volatiles. More 

reasonable would be the selection for flies exhibiting 

either an avoidance response to nonattractive toxicant 

volatiles, or an irritancy response to the toxicant that 

limits fly contact with the toxicant. If true, then a 

change of toxicant in the fly bait product may be all 

that is needed to rescue a failing fly bait. 

Further studies are needed to examine whether house 

fly resistance to toxicants is a result of altered house 

fly perception and response to volatiles associated with 

toxicants, or due to irritation and subsequent 

movement of flies following contact with toxicants. 

Also needed are studies to develop field deployable 

kits for rapidly evaluating behavioral resistance of 

flies, mosquitoes, and other pest arthropods to 

pesticides formulated into baits or applied as space or 

surface sprays. 

ACKNOWLEDGEMENT

Funding for this research was provided by the West 

Valley Mosquito and Vector Control District and by 

federal Hatch funds. 

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Behavioral Resistance of House Flies, Musca domestica (Diptera: Muscidae) to Imidacloprid 
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AUTHORS

MAJ Gerry is an Associate Medical/Veterinary 

Entomologist on the faculty of the University of 

California at Riverside, California. He is an Army 

Reserve Entomologist assigned to the US Army Center 

for Health Promotion and Preventive Medicine–South 

at Fort Sam Houston, Texas. 

Dr Zhang is a Research Associate at the University of 

California at Riverside. Her interests include 

management of disease-transmitting insects and human 

parasitism by arthropods (real or delusional). 
60 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

OVERVIEW

Arthropod repellents represent a first line of defense 

against biting arthropods.1

 The Department of Defense 

and other agencies are interested in repellent 

formulations to replace N,N-diethyl-3-

methylbenzamide (deet) because of deet’s chemical 

properties and safety concerns. Although deet is 

regarded as safe, registered with the Environmental 

Protection Agency, and has been in use over 5 

decades, there have been incidences of serious adverse 

effects associated with the use of deet products, 

especially in infants and young children,2

 its chemical 

properties are damaging to some synthetic material 

and plastics,3

 and deet experienced a major public 

relations hit in the mid 1990s as it was suspected to 

have contributed to the so-called "Gulf War 

Syndrome."4

 Effective candidates, then, must be less 

caustic to the user, a nonplasticizer, and be at least as 

effective as deet. SS220 (1S, 2'S) 2-methylpiperidinyl3-cyclohexene-1-carboxamide) and Bayrepel 

(picardin, 1-methyl-propyl 2-(2-hydroxyethryl)-1-piperidinecarboxylate) are considered such candidates. 

The purpose of this study was to evaluate 2 

formulations each of SS20 and Bayrepel against deet 

using volunteers acting as both treatment and their 

own control against Anopheles, Aedes, Coquillettidia, 

and especially Culex and Mansonia, the 2 most 

prevalent mosquito species in Kisumu, western Kenya. 

In order to confirm that the test leg repellent did not 

have a spatial affect on the other leg (the control leg), 

we included as one of the repellents a “null repellent”, 

which was an application of no repellent at all. 

Volunteers treated with the null repellent, then, had an 

“application” of the “null repellent” on their treatment 

leg, while their other leg served as the control. In other 

words, there was no repellent on either leg. 

MATERIALS AND METHODS

Study Site 

This study was conducted at the homestead of a local 

inhabitant in the midst of a rice growing region near 

Kisumu, in the Kamagaga Village, Ahero Irrigation 

Scheme Sub-Location, Ombeyi Location, Miwani 

Field Trial of Five Repellent Formulations 

Against Mosquitoes in Ahero, Kenya 

LTC Van Sherwood, MS, USA 

Elizabeth Kioko, BS 

Sichangi Kasili, MS 

Philip Ngumbi, MS 

Michael R. Hollingdale, PhD 

ABSTRACT

Twelve volunteers, using one leg for repellent application and the other leg as a control, field-tested 5 

insect repellent formulations—Avon’s (New York, NY) SS220 Spray, SS220 Lotion, and Bayrepel Lotion, 

and SC Johnson’s (Racine, Wisconsin) Autan© Bayrepel Lotion—against the standard N,N-diethyl-3-

methyl-benzamide (deet) in a rice-growing district near Kisumu, western Kenya, in 2 trials in May and 

June 2004. In addition to a control leg for each volunteer, an additional control was introduced into the 

study by the use of a sixth repellent, a “null repellent,” which was literally a treatment application of no 

repellent at all. The 5 active repellent formulations were uniformly applied at the maximum Environmental 

Protection Agency recommended dose of 1.5 g per 600 cm2

 in the first trial and half that dose in the second 

trial, and none of them failed during the nightly 12-hour test period over 6 consecutive days, May 19 

through May 24, 2004, and June 14 through June 19, 2004. However, the repellent control legs 

demonstrated a statistically significant increased landing rate compared to both the null repellent and the 

null repellent control leg. This suggests that, in this approach, active repellents increased the capture rate on 

an adjacent control leg compared to null controls. A single human volunteer can act as his/her own control 

provided null treatment controls are included. 
 July – September 2009 61

Division, Nyando District, Nyanza Province, Kenya, 

Africa (Lat -0.152098°, Long 34.925649°) (Figures 1 

and 2). There were ample species of mosquitoes due to 

the abundant breeding sites and recent seasonal rains 

in April and May 2004. Two field trials were 

conducted during May and July 2004. 

Test Repellents 

The following 5 repellent 

formulations were used: (1 

and 2) SS220 ((1S, 2'S) 2-

methylpiperidinyl-3-

cyclohexene-1-carboxamide) 

formulated as a spray (20%) 

or a lotion (20%) by Avon 

(New York, NY); (3 and 4) 

20% Bayrepel, (1-methylpropyl 2-(2-hydroxyethryl)-1-

p i - p e r i d i n e c a r b o x y l a t e ) 

formulated as a lotion by 

Avon or SC Johnson (Racine, 

Wisconsin); (5) 33% N,Ndiethyl-3-methylbenzamide 

(deet) formulated as a cream 

by 3M (St Paul, MN). For 

statistical design, a “null 

repellent” was introduced as 

t h e s i x t h r e p e l l e n t 

formulation, and consisted of 

no application at all. Note, the null repellent must not 

be confused with the control leg. 

Procedures 

Male volunteers* from the local population were 

selected and screened for acceptance by a brief 

medical questionnaire, and blood pressure and pulse 

check. Each volunteer completed and was given a 

copy of a Kiswahili and English language human use 

protocol approved by the Kenya Medical Research 

Institute and the Walter Reed Army Institute of 

Research. 

Twelve adult male volunteers participated in this 

study. Prior to repellent application, they washed both 

legs with clean water and allowed them to air dry. 

Clothing varied, as long as it prevented mosquito bites 

anywhere except the intentionally exposed skin area 

between the calf and ankle of each leg. The clothing 

usually included a light jacket, pants rolled to the 

knees, and locally purchased cotton work gloves and 

sport head nets which covered the entire head and 

neck. Since many volunteers wore open, slipper style 

shoes (“flip flops”), each foot was protected in a 

loosely fitting enclosure of mosquito bed net material 

which was gathered and taped 

around the volunteer’s leg at 

the treatment line. As shown 

in Figure 3, the loose fitting 

ensured an air space around 

the foot (except for the sole), 

allowing olfactory cues to 

attract mosquitoes but not 

allowing them to feed. An 

area of 600 cm2 was 

calculated and marked on 

each leg of each volunteer by 

averaging 3 equally-spaced 

circumference measurements 

between the lower knee and 

upper calf and dividing into 

600 cm2

 in order to get the 

length. The resulting area was 

taped off to the pants at the 

top, and to the feet netting at 

the bottom. Each repellent 

was weighed for dose and applied evenly with a 

gloved-finger over the exposed skin on the treatment 

leg (Figure 4). To standardize procedure in the study 

design, the control leg was rubbed with a clean, dry, 

*No female volunteers were used, as it was culturally 

unacceptable. The village chiefs and elders, whose 

endorsements were required for the trial to be 

performed at this site, deemed it unwise to have men 

and women together throughout the night. 

Figure 1. Location of The study site was near 

Kisumu, a town on Lake Victoria in western Kenya. 

Lake Victoria 

Approximate location 

of the field trials 

Figure 2. The field trials were held in the rice-growing 

region of western Kenya, near Lake Victoria. 
62 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

gloved finger. Similarly, the null repellent was also 

“applied,” once again using a clean, dry, gloved finger. 

The first volunteer’s repellent was applied at 4 PM, 

followed by the other volunteers at 5 minute intervals. 

Evaluation was conducted on each of 6 nights every 2 

hours starting at 6 PM (then 8 PM, 12 midnight, 2 AM, 

and 4 AM), each volunteer 

staggered at successive 5 

minute intervals based on their 

application time. At the 

assigned time, the volunteer 

left the screened tent and 

walked the short distance (50 to 

60 m) to the assigned test site. 

The test sites were separated 

from each other by at least 15 

m. Each volunteer sat in an 

assigned location that was 

randomly determined, and a 

“collector/helper” sat opposite 

the volunteer. The collector/

helper was fully clothed and 

helped monitor the legs of the 

v o l u n t e e r f o r l a n d i n g 

mosquitoes in order to aspirate 

them before biting could occur 

(Figure 3). Volunteers 

remained in the test area for 20 

minutes. Aspirated mosquitoes 

were expelled into lidded, pint-sized paper collection 

cartons. Each collection carton had a screen mesh in 

the lid for visibility, and a double dental dam portal on 

the side for the aspirating tube. The collected 

mosquitoes were immobilized by ether, counted, 

recorded, and transferred into vials in the field to be 

identified to species at a later date.

Totals at each time point were calculated for each 

repellent group and control. Percentage protection was 

defined as the number of bites received by a treatment 

group relative to that of the control ((control -

treatment)/ control  100). 

Statistical Analysis 

Because there were no failures of 100% protection in 

the treatment group, we did not apply a statistical 

analysis, although had the protection been less than 

100%, we would have performed an arcsine 

transformation before statistical analysis. We used a 

Student 2 tailed T test with groups having equal 

variance to compare the 3 control groups. 

RESULTS AND DISCUSSION

The goal of this study was to compare repellent 

activity of deet with potential candidate replacements 

SS220 and Bayrepel against 

mosquito species commonly 

found in Kisumu, Kenya. 

Mosquito Populations 

Collected 

In the first trial, a total of 3,137 

mosquitoes were collected 

during these exposures. The 

main species were Mansonia 

uniformis (Theobald) (59.9%), 

Culex pipiens Linnaeus 

(18.1%), and Culex poicilipes

(Theobald) (4.3%). Overall, 4 

species of Aedes, 2 species of 

Anopheles, 3 species of 

Coquillettidia, 4 species of 

Culex, and 2 species of 

Mansonia were collected, as 

shown in Table 1. Figure 5 

shows that Mansonia

represented 76.6% of the total 

collected, and Culex

Field Trial of Five Repellent Formulations Against Mosquitoes in Ahero, Kenya 

Figure 3. A volunteer and a collector at a collection site 

with collection cartons. Note the envelopes of net material 

enclosing the feet below the exposed skin test areas. 

Figure 4. Repellent is applied evenly over the 

designated 600 cm2 of skin on a volunteer’s leg 

which will be exposed during the test period. 
 July – September 2009 63

THE ARMY MEDICAL DEPARTMENT JOURNAL

represented 22.9%. It was surprising that few 

Anopheles were collected, as malaria transmission is a 

major problem in Kisumu. It is possible that the time 

of our study, 6 PM to 4 AM, did not coincide with either 

the main biting time of Anopheles, or the study site 

was not an optimal location where Anopheles may be 

found. 

In the second trial, we focused only on the main 

species identified in the first trial. A total of 4,495 

mosquitoes were collected, and of these, the most 

frequent were Culex pipiens (45.3%), Mansonia 

uniformis (42.2%) Culex poicilipes (10.7%) and 

Mansonia africana (Theobald) (1.6%). In this study, 

Culex represented 56.2% of the total collected, and 

Mansonia represented 43.8%. Therefore, the rates of 

collection varied from season to season, but the main 

species that predominated were similar, as were the 

collection rates. 

Effect of Each Repellent on Mosquito Biting Rates 

In the second trial, 10 of the 12 volunteers were used 

to test the 5 repellents, with one leg as the repellent, 

and the other leg as the repellent control. Two of the 

12 volunteers were treated with null repellent on one 

leg and the other leg was the null repellent control. 

We found that each repellent tested at the dose 

specified protected each treated leg 100% from 

mosquito bites, and there were no failures. Therefore, 

this trial did not distinguish whether 

SS220 and Bayrepel were less or more 

effective than deet. However, total 

protection lasted at least 8 hours after 

repellent application. It is clear that 

SS220 and Bayrepel were equally 

effective against the main mosquito 

species collected in Kisumu, Culex and 

Mansonia. A previous study indicated 

that piperidine compounds were less 

effective than deet in controlling Culex 

pipiens,5

 but the dose may have affected 

this outcome. Whether these repellents 

are as active against Anopheles, Aedes, or 

other genera would need confirmation in 

tests in areas where they are more 

prevalent than in Kisumu. 

In a trial in Australia,6

 deet and Bayrepel 

were relatively much less active against 

Anopheles spp, where both protected volunteers for 

only up to one hour after application. However, deet 

and Bayrepel protected volunteers for up to 5 hours 

after application against Culex species,6

 comparable to 

our results in Kisumu. In another study in Burkina 

Mosquito Species First Trial Second Trial 

 Total % Total % 

Aedes (Albopictus) kennethi 1 < 0.1 NT* NT 

Aedes (Neomelanion) 

luteolateralis 1 < 0.1 NT NT 

Aedes (Neomelanion) 

circumluteolus 1 < 0.1 NT NT 

Aedes (Aedimorphus) cumminsii 1 < 0.1 NT NT 

Anopheles coustani 1 < 0.1 NT NT 

Anopheles funestus 1 < 0.1 NT NT 

Coquillettidia aurites 3 < 0.1 NT NT 

Coquillettidia fraseri 2 < 0.1 NT NT 

Coquillettidia fuscopennata 4 0.1 NT NT 

Culex annulioris 4 0.1 NT NT 

Culex pipiens 567 18.1 2,035 45.3 

Culex poicilipes 136 4.3 483 10.7 

Culex theileri 12 0.4 10 0.2 

Mansonia africana 524 16.7 72 1.6 

Mansonia uniformis 1,879 59.9 1,895 42.2 

Grand Total 3,137 100.0 4,495 100.0 

Table 1. Distribution of mosquito species collected at 

the Kisumu area, Western Kenya, May 2004. 

*Not tested 

Figure 5. Distribution of species mosquitoes collected during the first 

trial of the study in the Kisumu area, Western Kenya, May 2004. 
64 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

Faso, Bayrepel performed better than deet 

against Anopheles gambiae Giles, but did not 

repel Aedes.

7

 However, Bayrepel and deet 

were effective against Aedes taeniorhynchus 

(Wiedemann). 

A major problem with all such studies is the 

small sample size. Larger studies may be 

warranted to more effectively determine the 

activity of these repellents. 

The method used in this study was to use each 

volunteer as his/her control, by treating one leg 

and leaving the other leg untreated. At each 

time, 10 volunteers were treated this way, and 2 

volunteers were similarly treated using a null repellent 

(literally, no repellent at all). Surprisingly, the number 

of mosquitoes collected from the legs serving as the 

control for active repellents were statistically higher 

than either the null repellent (P = 0.007) or the null 

repellent controls (P = 0.003) (Table 2). However, 

there was no significant difference between the null 

treatment legs and the null treatment controls (P=0.4) 

(Table 2). 

There is little known about how exactly these 

repellents influence insect behavior. However, a recent 

study has suggested that they cause insects to move 

away from treated skin and bite only skin without the 

chemical.8,9 This suggests that insects use a sense of 

smell to detect the chemicals and avoid biting where 

the repellent is coated. Our data suggests that insects 

were repelled from biting the treated skin and moved 

towards the untreated skin (controls), increasing the 

biting rates compared to the null repellents. We had no 

failures with the repellents in our study. However, this 

behavior effect would increase collections from 

controls and therefore underestimate the effectiveness 

of the repellent on the other leg if it is less than 100%. 

It seems, therefore, if a single volunteer is used as a 

repellent treatment and a no treatment control, it is 

essential that null treatment volunteers are also 

included to detect and correct such underestimation. 

Finally, the wide spectrum of arthropods reacting to 

SS220 and Bayrepel against ticks,10 biting midges 

(Leptoconops),11 and the mosquitoes tested in this and 

similar studies,12-16 suggest that these compounds may 

be valuable in controlling vector-borne diseases, in 

both military and civilian populations. 

CONCLUSION

Studies such as reported here are valuable to better 

define appropriate evaluations of repellents under field 

conditions and to determine the mean protection 

periods.12 Further investigation of the toxicity of 

repellents to mosquitoes may reveal more effective 

compounds or ones that may act synergistically,13 as 

well as compounds that lack potential adverse effects 

of deet such as BioUD.14 Recently, research measuring 

the toxicity of 8 repellents to female mosquitoes 

suggested that another piperidine compound, A13-

37220,15 may be more toxic at lower concentrations 

than deet.16 Therefore, these single volunteer studies in 

Kenya and other regions may aid in the practical 

identification and acceptance of other, more effective 

repellent regimes. 

ACKNOWLEDGEMENTS

The authors thank the following people, among many 

others, whose expertise, energy, and collegial support were 

absolutely integral to this project: 

The Entomology staff at the US Army Medical Research 

Unit – Kenya, most notably, Maurice Agawo, Daniel 

Ngonga, and Francis Ngere from the Kisumu Field 

Station, and Christopher Oyaro, Entomology Department 

Senior Technician, Walter Reed Project and KEMRI. 

MAJ Jason Richardson, USA, Armed Forces Research 

Institute of Medical Sciences, Bangkok, Thailand. 

Pamela Hillis, Defense Logistics Agency. 

Dr Desmond Foley, Walter Reed Biosystematics Unit. 

Dr Gabriela Zollner and MAJ Jittawadee Murphy, USA, 

Walter Reed Army Institute of Research. 

Also, we extend special appreciation to the Chief, 

Elders, villagers, and volunteers of Kamagaga and 

surrounding area. Asante sana! 

Field Trial of Five Repellent Formulations Against Mosquitoes in Ahero, Kenya 

Table 2: Total numbers of each mosquito collected on the repellent 

treated leg and its control untreated legs compared to null repellent controls at the Kisumu area, Western Kenya, May 2004. 

Leg Mean SD SE P Compared with 

Repellent Control 

P Compared 

with Null Control 

Repellent control 48.1 20.00 2.65 — — 

Null repellent 

treatment 29.9 12.10 3.82 0.007 — 

Null repellent 

treatment control 34.4 12.67 3.65 0.003 0.4 

NOTE: The Student 2 tailed-T test where groups have equal variance was used to calculate 

whether more mosquitoes were collected on repellent control legs compared to null 

treatment and null treatment controls, or between null treatment and its null treatment 

control. 
 July – September 2009 65

THE ARMY MEDICAL DEPARTMENT JOURNAL

REFERENCES

1. Debboun M, Strickman DA, Klun JA. Repellents and 

the military: our first line of defense. J Am Mosq 

Control Assoc. 2005;21:4-6. 

2. Osimitz TG, Grothaus RH. The present safety 

assessment of deet. J Am Mosq Control Assoc. 

1995;11:274-278. 

3. Katz TM, Miller JH, Hebert AA. Insect repellents: 

historical perspectives and new developments. J Am 

Acad Dermatol. 2008;58:865-871. 

4. Qiu H, Won Jun H, McCall W. Pharmacokinetics, 

formulation, and safety of insect repellent N,Ndiethyl-3-methylbenzamide (DEET): a review. J Am 

Mosq Control Assoc. 1998;14:12-27. 

5. Coleman RE, Richards AL, Magnon GJ, Maxwell 

CS, Debboun M, Klein TA, Wirtz RA. Laboratory 

and field trials of four repellents with Culex pipiens

(Diptera: Culicidae). J Med Entomol. 1994;31:17-22. 

6. Frances SP, Waterson DG, Beebe NW, Cooper RD. 

Field evaluation of repellent formulations containing 

deet and picaridin against mosquitoes in Northern 

Territory, Australia. J Med Entomol. 2004;41:414-

417. 

7. Costantini C, Badolo A, Ilboudo-Sanogo E. Field 

evaluation of the efficacy and persistence of insect 

repellents deet, IR3535, and KBR 3023 against 

Anopheles gambiae complex and other Afrotropical 

vector mosquitoes. Trans R Soc Trop Med Hyg. 

2004;98:644-652. 

8. Klun JA, Khrimian A, Debboun M. Repellent and 

deterrent effects of SS220, picaridin, and deet 

suppress human blood feeding by Aedes aegypti, 

Anopheles stephensi, and Phlebotomus papatasi. J 

Med Entomol. 2006;43:34-39. 

9. Klun JA, Khrimian A, Rowton E, Kramer M, 

Debboun M. Biting deterrent activity of a deet 

analog, two DEPA analogs, and SS220 applied 

topically to human volunteers compared with deet 

against three species of blood-feeding flies. J Med 

Entomol. 2006;43:1248-1251. 

10. Carrol J, Benenate J, Klun J, White C, Debboun M, 

Pound J, Dheranetra W. Twelve-hour duration of 

cream formulations of three repellents against 

Amblyomma americanum. Med Vet Entomol. 

2008;22:144-151. 

11. Perich MJ, Strickman D, Wirtz A, Stockwell SA, 

Glick JI, Burge R, Hunt G, Lawyer PG. Field 

evaluation of four repellents against Leptoconops 

americanus (Diptera: Ceratopogonidae) biting 

midges. J Med Entomol. 1995;32:306-309. 

12. Rutledge LC, Gupta RK. Variation in the protection 

periods of repellents on individual human subjects: an 

analytical review. J Am Mosq Control Assoc. 1999;15

(3):348-355. 

13. Debboun M, Strickman D, Klein TA, et al. 

Laboratory evaluation of AI3-37220, AI3-35765, CIC

-4, and deet repellents against three species of 

mosquitoes. J Am Mosq Control Assoc. 1999;15

(3):342-347. 

14. Witting-Bissinger BE, Stumpf CF, Donohue KV, 

Apperson CS, Roe RM. Novel arthropod repellent, 

BioUD, is an efficacious alternative to deet. J Med 

Entomol. 2008;45(5),891-898. 

15. Xue RD, Arshad A, Crainich V, Barnard D. 

Oviposition deterrence and larvicidal activity of three 

formulations of piperidine repellent (AI3-37220) 

against field populations of Stegomyia albopicta. J 

Am Mosq Control Assoc. 2007;23(3),283-287. 

16. Pridgeon JW, Bernier UR, Becnel JJ. Toxicity 

comparison of eight repellents against four species of 

female mosquitoes. J Am Mosq Control Assoc. 

2009;25(2),168-173. 

AUTHORS

LTC Sherwood is the Command Entomologist, Defense 

Logistics Agency, Fort Belvoir, Virginia. At the time 

this field study was conducted, he was Chief, 

Entomology Department, US Army Medical Research 

Unit – Kenya.

Elizabeth Kioko is a senior researcher with the 

Entomology Department, Walter Reed Project and 

Kenya Medical Research Institute, Kisumu, Kenya. 

Sichangi Kasili is a senior researcher with the 

Entomology Section and Leishmaniasis Laboratory at 

the Centre for Biotechnology Research and 

Development, Kenya Medical Research Institute, 

Nairobi, Kenya. 

Philip Ngumbi is Chief, Entomology Section and 

Leishmaniasis Laboratory at the Centre for 

Biotechnology Research and Development, Kenya 

Medical Research Institute, Nairobi, Kenya. 

Dr Hollingdale is a biostatistical and research 

consultant at the Walter Reed Army Institute of 

Research, Silver Spring, Maryland. 
66 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

INTRODUCTION

Ultra-low volume (ULV) mosquito spraying has 

become increasingly technologically advanced since it 

was first introduced in the 1960s as a replacement to 

thermal fogging.1

 Examples of technological 

advancements are new nozzles designs to produce 

optimal sized droplets and computer modeling of 

droplet fate under a variety of metrological conditions. 

These technologies help reduce spray volume and are 

important tools to minimize the use of pesticide. 

Aerial ULV sprays are the primary method used to 

interrupt insect-borne epidemics.2-4 For example, the 

US Air Force (USAF) used airplanes to control 

mosquito outbreaks after major hurricanes, and other 

public agencies have used aerial ULV sprays to decrease disease transmission and control nuisance mosquitoes.5-7 ULV applications have been used outside 

the United States to interrupt malaria transmission.8

A crucial element of ULV technology is the creation 

of an effective aerosol cloud that will optimize target 

pest mortality while reducing pesticide use and 

nontarget species mortality.9,10 Maximum efficacy is 

achieved by dispersing uniform droplets of the correct 

size. For mosquitoes, the optimum droplet size is 7 to 

25 μm in diameter as demonstrated by laboratory and 

small scale ground ULV studies. Aerial sprays 

probably need to produce larger droplets in order to 

reach the target.11-13 However, many aircraft spray 

systems create a spectrum of droplet sizes between 1 

μm and 150 μm.14 Extremely small droplets may not 

be lethal and large droplets (>50 μm) can settle out too 

quickly and are less likely to contact flying 

mosquitoes. Larger droplets are also wasteful because 

they contain more toxin than needed to kill the pest.15

Because of their potentially high deposit peaks close to 

the aircraft flight line, large droplets also represent a 

potential hazard to nontarget organisms and thus create 

unfavorable environmental effects.16 

The USAF typically uses a modular aerial spray 

system (MASS) on the C-130H airplane with ULV flat 

fan nozzles installed under the airplane wing.17 The 

wing boom configuration requires pressurized tubing 

installed along the length of the wing, which results in 

Characterization of a New Ultra-Low Volume 

Fuselage Spray Configuration on Air Force 

C‐130H Airplane Used For Adult Mosquito 

Control 

Maj Mark Breidenbaugh, BSC, USAFR 

Maj Karl Haagsma, BSC, USAFR 

Mark Latham 

Ferenc de Szalay, PhD 

ABSTRACT

The US Air Force (USAF) tested a new fuselage boom configuration on the C-130H airplane. We used into-the-wind 

and crosswind field trials to characterize a BVA oil (BVA Inc, Wixom, MI) droplet spectra produced by fuselage 

booms with flat-fan nozzles (8001, 8005) at the Air Force Range at Avon Park, FL. Across all trials, median droplet 

diameter (DV50) for 8001 and 8005 nozzles were 11.4 μm and 54.3 μm, respectively. For 8005 nozzles 22% of droplets 

collected were 7 μm to 25 μm size range while 75% of droplets from 8001 nozzles were < 7 μm. Fuselage 

configuration parameters and field data were also used as input variables into the Agricultural Dispersal (AGDISP) 

computer model to predict aerosol deposition and droplet fate. AGDISP predictions were compared with field data 

from crosswind tests and the model was found to fit reasonably well to empirical data. However, AGDISP predictions 

were better correlated with empirical findings for larger droplets than smaller droplets and for locations closer to the 

release point than further downwind. 
 July – September 2009 67

residual pesticide waste when the equipment is cleaned 

after spray operations. Furthermore, the tubing is 

located in the interior of the wing, which makes 

installation and repairs more difficult. The USAF has 

recently modified the MASS on the C-130H airplane 

to use fuselage-mounted spray booms, as shown in 

Figure 1. The fuselage booms do not require auxiliary 

equipment for installation and reduce pesticide waste 

because the pressurized tubing is shorter. 

The fate of droplets released from airplanes is strongly 

affected by airplane generated turbulence.18 However, 

it is not known how airplane vortices affect droplet 

size and drift when a fuselage boom configuration is 

used with the C-130H. Effective aerial mosquito 

control operations also need to predict the drift of the 

aerosol swath. Although keeping pesticide droplets 

aloft for a longer time is advantageous to increase the 

chance that droplets contact the target pest, it also 

makes it more difficult to predict swath drift patterns. 

The US Forest Service has developed computer 

models to predict pesticide drift for agricultural 

applications (ie, crop dusting).19 An earlier version, the 

Forest Service Cramer Barry Grimm model, has been 

integrated into the Agricultural Dispersal (AGDISP) 

model which can model the lower volumes and smaller 

droplets used in ULV mosquito adulticide sprays.20

Standard parameters for over 173 spray aircraft are 

available in the AGDISP model’s library, including the 

C-130H airplane with wing booms and flat-fan 

nozzles. However, parameters for the new fuselage 

spray boom configuration are not available. Computer 

model predictions validated by field testing are helpful 

to estimate the effects of changing parameters (eg, 

altitude, nozzle type, etc) on droplet dispersal. While 

the model has been well-validated for large droplet/

low altitude agricultural applications,21 few field trials 

have been conducted to confirm its predictive ability 

for the small droplet/high altitude applications used in 

ULV mosquito sprays. 

This study reports on the characterization of droplet 

size and drift generated by USAF C-130H aircraft with 

the newly developed ULV fuselage boom 

configuration. Droplet size and downwind dispersion 

were measured using into-the-wind and crosswind 

field trials, respectively. The resulting droplet size and 

application parameter data was then input into the 

AGDISP computer model to compare the model’s 

predictions with the empirical field results. 

METHODS

Study Site Description 

The fuselage boom tests were performed from 

December 2004 to February 2005 on the Avon Park 

Air Force Range (APAFR), an approximately 42,000 

ha facility in Highland and Polk counties, Florida. The 

field site was chosen to minimize disruption of drifting 

droplets by vegetation.22 As shown in Figure 2, site 

vegetation was dominated by shrubs or open 

woodlands. Primary roads on the APAFR are aligned 

along cardinal directions, which facilitated realignment 

of sampling stations when wind direction changed 

between test dates. 

Field Characterization of Droplet Size 

Applications were made by USAF C-130H airplane 

with fuselage mounted booms containing nozzles that 

were directed towards the ground. The airplane was 

equipped with a Satloc GPS [global positioning 

system] Agricultural Navigation System (Hemisphere 

GPS, Calgary, Canada) to record airplane position and 

time when the spray system was turned on. Fuselage 

boom configurations were tested with flat-fan TeeJet®

nozzles (Spraying Systems Co, Wheaton, IL) sizes 

8001 and 8005, which were rated by the manufacturer 

to deliver 0.4 liters/min and 1.9 liters/min per nozzle at 

276 kPa, respectively. 

The airplane flew at 370.4 km/hr and the spray system 

activated 30 seconds prior to reaching the sampling 

transect (Figure 2) and was left on until 30 seconds 

after passing the transect (60 seconds total). Wind 

speed, direction, air temperature, and humidity were 

recorded 2.5 m above ground surface using a Swath 

Kit Weather Station (Droplet Technologies, College 

Figure 1. The fuselage-mounted spray boom installed on the 

C-130H airplane.
68 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

Station, PA) and at spray altitude using the airplane’s 

self-contained navigation system. 

The MASS delivered an application rate of 45.3 ml/ha 

that was based on standard operational practices of 

public health agencies using a common mosquito control pesticide, Anvil® 10+10 (Clarke Mosquito 

Control Products, Inc, Roselle, IL; hereafter Anvil). 

We conducted multiple trials in the same location, 

which would have caused excessive pesticide 

accumulation. Therefore, our sprays used only the 

pesticide carrier, BVA spray oil 13 (BVA Inc., 

Wixom, MI), without the pesticide. 

On December 4, 6, and 8, 2004, and February 15, 

2005, the airplane flew directly into the prevailing 

wind (into-the-wind trials) at 46 m above ground. To 

quantify the droplet spectra, 9 sampling stations were 

positioned every 61 m along a 488 m transect 

perpendicular to the prevailing wind (Figure 2). The 

airplane flew directly over the center station. Slide 

rotator devices (John Hock Company, Gainesville, 

FL) held spinning Teflon® coated glass microscope 

slides (25 mm by 75 mm, approximately 420 rpm, 

effective slide speed of 3.6 m/second) that collected 

Characterization of a New Ultra-Low Volume Fuselage Spray Configuration on 

Air Force C‐130H Airplane Used For Adult Mosquito Control 

100 meters 

Aircraft path (into the wind) 

Transect line 

Wind direction (into the wind) 

Wind direction (crosswind)

Aircraft path (crosswind) 

Figure 2. Aerial photograph of the field test area at the Avon Park Air Force Range, Florida. Directions of flight paths 

and wind for the test flights are shown. 

Aircraft Lockheed C-130H airplane, weight 

63,047 kg; speed = 371 km/h

Release height 46 m, 91 m; flight lines = 1

Nozzles 8, 8005 flat-fan, positioned at 3.61, 

3.71, 3.81, 3.91 m from aircraft 

centerline, both sides

Drop size 

distribution

DV10 = 22.3 μm; DV50 = 54.3 μm; 

DV90 = 104.7 μm

Material BVA oil (specific gravity = 0.85; 

nonvolatile fractions = 1; active = 1; 

rate = 45.3 ml/ha

Swath width 152 m (maximum allowed), 

Swath displacement = -76

Wind speed 6.4, 7.5 km/hr at 46 m or 91 m 

above ground level

Temperature and 

relative humidity

18.3°C and 70% for 46 m and 17.1°C 

and 92% for 91 m

Stability day - weak (sunset to 1 hour after 

sunrise, weak)

Canopy none

Surface roughness 0.0075 m

Table 1. Parameters entered into the AGDISP model to predict droplet fate from fuselage boom spray applications. 

Drop size distribution used field collected data. 
 July – September 2009 69

THE ARMY MEDICAL DEPARTMENT JOURNAL

the droplet cloud as it passed over the station. 

Microscope slides were collected 30 minutes after the 

airplane passed to allow enough time for airborne 

droplets to drift through the transect. Droplet data from 

all stations were pooled to determine the 

characteristics of the droplet spectra. 

In addition to characterizing the droplet size spectra 

with “into-the-wind” tests, crosswind trials were used 

to compare actual drift in field trials with predictions 

by the AGDISP model. On February 16, 2005, we 

conducted a crosswind trial at a release height of 46 m 

above ground, which is standard for the USAF 

mosquito control operations. Although we ran 2 trials, 

a wind shift during the second trial disrupted the 

application and the data was lost. Also, we only used 

the 8005 nozzles for the crosswind trials because 8001 

nozzles clogged repeatedly during the into-the-wind 

trials. On February 17, 2005, 2 trials measured spray 

drift released at 91 m, which is an altitude proposed 

for potential nighttime mosquito control operations 

with the C-130H airplane. In all crosswind trials, 

droplets were collected with rotating microscope slides 

at 8 stations arranged along the prevailing wind 

direction. On February 16, 2005, stations were set 154 

m apart (154-1,219 m) on a transect downwind from 

the release point (Figure 2). On February 17, 2005, we 

spread the stations 457 m apart (457-3,658 m) along 

the transect in anticipation of greater drift from the 

higher release altitude. 

All slides were processed within 6 hours after the trial 

was conducted. Droplets on slides were measured 

under a compound microscope equipped with a 

reticule. A total of 100 droplets were measured or the 

entire slide was scanned, whichever came first. 

Measured drop diameter was converted to airborne 

drop diameter with a 0.59 correction factor (Anvil 

10+10 Resource guide) that accounted for the spread 

of droplets when they impacted the glass slide.23 These 

data were used to determine volume median diameter 

(DV50) and droplet density at each sampling station.24

The DV50 represents the droplet size which divides the 

droplet spectrum in half by volume, or in other words, 

where 50% of the spray volume is contained in 

droplets smaller than the DV50. Also of interest are the 

DV10 and DV90 values which are the points in the 

droplet distribution where 10% and 90% respectively 

of the spray volume is in drops smaller than this size.10

AGDISP Computer Model 

Droplet size data obtained from the into-the-wind field 

trials with 8005 nozzles were input into the AGDISP 

computer model (version 8.08, USDA Forest Service) 

to predict crosswind droplet trajectories and 

deposition. Operational parameters and meteorological 

conditions recorded during the trials at Avon Park 

were used as input values for the AGDISP model 

(Table 1). To allow placement of the spray boom 

relative to the trailing edge of the wing, the AGDISP 

model has a library of aircraft (including C-130H with 

wing booms) and droplet spectra produced by different 

nozzle types under varying application scenarios. 

However, the specific parameters of the C-130H 

fuselage spray system are not included as a standard. 

Consequently, where possible we used values 

measured in our field trials (eg, boom placement, 

nozzle position, application parameters, meteorology, 

and DV10, DV50, and DV90 droplet sizes) to test the 

model’s accuracy. Predictions for downwind 

deposition of BVA oil released from spray altitudes of 

46 m and 91 m were modeled. Output values regarding 

droplet deposition and trajectories for droplets sized 

22.3, 54.3, and 104.7 μm were 

plotted. Predictions of droplet 

trajectories made by AGDISP 

were then compared to 

empirical data derived from 

crosswind field trials. 

RESULTS

Flight parameters and 

meteorological conditions 

during the trials are given in 

Table 2. Meteorological 

conditions were acceptable 

during the into-the wind and 

4 Dec 04* 45.3 8.5 634 3.2/13.7 8005 (8) 16.1°C 51% 

6 Dec 04* 45.3 8.5 641 3.2/17.7 8005 (8) 25.6°C 59% 

8 Dec 04* 45.3 8.5 621 6.4/12.9 8001 (40) 24.4°C 79% 

15 Feb 05* 45.3 8.5 483 1.6/6.4 8001 (40) 20.6°C 70% 

16 Feb 05† 45.3 8.5 486 6.4/13.0 8005 (8) 18.3°C 70% 

17 Feb 05† 45.3 8.5 472 7.5/12.1 8005 (8) 17.1°C 92% 

4 Dec 04* 45.3 8.5 634 3.2/13.7 8005 (8) 16.1°C 51% 

Date of Trial 

Application 

Rate 

(ml/ha)

Flow 

Rate 

(L/min)

Boom 

Pressure 

(kPa)

Average Wind 

Speed (km/hr), 

ground/altitude

Nozzle 

Configuration 

Size (number) 

Temperature Relative 

Humidity 

Table 2. Parameters of the BVA-13 spray-oil field characterization trials of the C-130H 

airplane ULV fuselage boom configurations. 

*Into-the-wind flight trials 

†Crosswind flight trials 
70 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

crosswind trials. Humidity 

and temperature were typical 

for ULV mosquito control 

operations. Boom pressure 

was relatively constant 

during the into-the-wind 

trials (621 – 641 kPa) in 

December, but was slightly 

lower during the February 

trials (472-486 kPa). Wind 

speeds measured at the 

g r o u n d w e r e w i t h i n 

acceptable ranges (1.6 to 6.4 

km/hr) during the into-thewind trials. 

Over 7,000 droplets were 

measured in samples 

collected during the into-thewind and crosswind field 

trials. The 2 nozzle types 

p r o d u c e d d i f f e r e n t 

cumulative volume curves 

during into-the-wind trials (Figure 3). Average volume 

median diameter (DV50) was 11.4 μm (SE ± 1.0) for 

8001 flat-fan nozzles and 54.3 μm (SE ± 2.2) for 8005 

nozzles. Droplets from 8001 nozzles produced a 

narrow range of relatively small droplets: DV10 was 

1.7 (SE ± 0.6) μm and DV90 was 30.8 μm (SE ± 1.6). 

The larger orifices of the 8005 nozzles delivered a 

wider range of droplet sizes: DV10 was 22.3 μm (SE ± 

2.1), and DV90 was 104.7 μm (SE ± 0.6). Thus, the 

cumulative volume curve of 8005 nozzles generated a 

lower slope than the 8001 nozzles. 

The distribution of drop sizes in spray clouds produced 

during the into-the-wind trials was also different 

between the 8001 and 8005 nozzles. The 8001 nozzles 

produced smaller droplets, with 40% of drops in the 

smallest class size and 75% were <7 μm (Figure 4). In 

contrast, 8005 nozzles generated a wide range of size 

classes with 1.2% of drops <7 μm and 22% of droplets 

in the 7 to 25 μm size range (Figure 4). 

On February 16, 2005, the crosswind trials 

with a spray release height of 46 m had 

droplet sizes ranging from 42.5 μm to 10.1 

μm (Table 3). The swath drifted much 

further when the spray was released at 91 

m above ground on February 17 (Figure 5). 

In both crosswind trials the largest droplets were 

deposited at the first collection station and the mean 

droplet size decreased downwind. 

AGDISP COMPUTER MODEL PREDICTIONS AND

FIELD-TRIAL RESULTS

Droplet spectra data for 8005 nozzles and 

meteorological data from into-the-wind field trials 

were input into the AGDISP model to predict droplet 

fate (Table 1). The model predicted heavy deposition 

near the airplane when spraying at 46 m above ground 

with the fuselage booms (Figure 6). Deposition was 

predicted to reach a maximum of 13.8 ml/ha at 92 m 

from the release point and then rapidly dropped to 4.7 

ml/ha by 300 m downwind. From this point, deposition 

gradually decreased to <0.5 ml/ha at the maximum 

predicted range (1,582 m). Average deposition over 

1,582 m was predicted to be 3.5 ml/ha. Between the 

release point and the standard operational swath width 

Characterization of a New Ultra-Low Volume Fuselage Spray Configuration on 

Air Force C‐130H Airplane Used For Adult Mosquito Control 

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 16 31 46 60 75 90 105 119 134 149

Droplet diameter (μm)

8005 trial 1

8005 trial 2

8001 trial 1

8001 trial 2

DV50

Cumulative volume fraction .

Figure 3. Drop size distribution for droplet spectra produced by 8001 and 8005 flat-fan 

nozzles used with Air Force C-130H fuselage boom characterization trials. 

154 m 305 m 457 m 610 m 762 m 914 m 1,066 m 1,219 m 

Mean±SE 42.5±2.5 24.9±2.6 13.9±2.8 7.8±0.5 8.4±1.2 5.7±0.8 6.0±0.3 6.2±0.4 

Distance Downwind 

Table 3. Average BVA oil droplet size (μm) collected at stations downwind of release point, February 16, 2005. C-130H fuselage boom configuration; 8005 nozzles; crosswind - 6.4 km/hr; release height - 46 m. 
 July – September 2009 71

THE ARMY MEDICAL DEPARTMENT JOURNAL

of the C-130H (610 m) the 

model predicted an average 

deposition of 6.0 ml/ha. 

When release height was 

increased to 91 m, the 

predicted deposition was 

more spread out (Figure 6). 

Deposition was first 

predicted at approximately 

200 m downwind of the 

r e l e a s e p o i n t , w h e n 

d e p o s i t i o n g r a d u a l l y 

increased to peak at 3.5 ml/

ha at 770 m. Deposition was 

predicted to remain within 

half of the maximum over 

the remaining model’s 

predictive range. 

When we modeled droplets 

sprayed from the four 8005 

nozzles on C-130H fuselage 

booms, the AGDISP model 

p r e d i c t e d d i f f e r e n t 

trajectories for small (set at 

22.3 μm, which is our DV10) 

medium (54.3 μm, our DV50) 

and large (104.7 μm, our 

DV90) droplets and for sprays 

released at 46 m or 91 m 

above ground. Overall, 

AGDISP predictions followed standard 

ballistics such that smaller droplets released at 

greater altitudes drifted further than larger 

droplets released at lower heights. However, 

the model also predicted droplet trajectories 

would be affected by airplane vortices. For 

example, all droplets released on the 

windward side at 46 m were affected by 

airplane induced vortices, which first lifted 

them and then allowed them to drift 

downwards (Figure 7). In contrast, droplets 

released on the leeward side of the airplane 

were entrained in down-ward vortices that 

pushed them toward the ground until the 

vortices broke apart or droplets deposited. The 

model predicted that small droplets (eg, 22.3 

μm) remain airborne approximately 450 m 

downwind of the release point, and most 

medium droplets (eg, 54.3 μm) reached the 

Figure 4. Distribution of drop sizes in spray cloud from (A) 8001 and (B) 8005 nozzles. 

A 

B 

Figure 5. Average droplet size recovered from USAF C-130H fuselage 

mounted boom sprays using 8005 flat-fan nozzles at 91 m release 

height, February 17, 2005. (Bars are ±1 standard error.) 
72 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

ground by 250 m. The large droplets (eg, 104.7 μm) 

also fit the previous pattern but reached the ground 

faster (approximately 130 m downwind) than the other 

size classes (Figure 7). 

When the droplet trajectories were modeled from a 

release height of 91 m, trajectories were different than 

when released at 46 m (Figure 8). Overall, an increase 

in spiraling caused by vortices was predicted in all 

drop sizes; this was more pronounced in droplets from 

the windward side of the airplane. Most notable was 

that small and medium droplets from the leeward side 

of the airplane were not pushed to the ground, but 

were brought back in contact with droplets from the 

windward side and crossed paths with these droplets’ 

trajectories (Figure 8). 

DISCUSSION

These trials characterized droplet spectra and dispersal 

to evaluate if the USAF C-130H fuselage boom 

configuration is effective for adult mosquito control 

operations. Under optimal conditions, aerial spray 

operations produce droplets that adhere to mosquitoes 

but do not drift beyond the intended spray area.25 We 

found that both flat-fan nozzles (8001, 8005) produced 

droplets within the optimal range for mosquito control 

(7 to 25 μm), but they had very different droplet size 

distributions. 

In general, droplet distributions from flat-fan nozzles 

show that the largest numbers of drops are found in the 

smallest size classes while the greatest volume is 

found in the relatively scarce but larger size classes.26

In this study, the 8001 nozzles produced a narrow 

spectrum of smaller droplets, and consequently, the ma

-jority of the volume sprayed was comprised of small 

droplets (ie, DV90 = 30.8 μm). Although most droplets 

were within the most effective size range (7 to 25 μm), 

droplets < 7 μm comprised 35% of spray volume. In 

contrast, 8005 nozzles produced larger drops but a 

more even size class distribution (Figure 4). 

We tested the fuselage boom configuration for its 

potential usefulness for ULV adult mosquito control 

with the C-130H airplane. The narrow droplet spectra 

and ideal DV50 of the 8001 nozzles would appear to 

make these a better choice for mosquito adulticiding. 

However, these nozzles produce many droplets 

considered too small for effective mosquito control. In 

addition, the small orifice size required 5 times more 

nozzles than 8005s to produce the desired flow-rate, 

and they often became clogged during field trials. The 

8005 nozzles produced relatively large drops which 

equates to additional chemical waste if they deposit 

without contacting the target pest. Characterization 

tests with intermediate nozzle sizes (eg, 8002, 8003) 

would be useful to further examine the efficacy of 

fuselage booms for mosquito control. 

We used rotating microscope slides to measure droplet 

sizes for 2 flat-fan nozzles, which is a widely used 

method to characterize droplet size.9,27-29 A more 

precise method to determine droplet size is a wind 

tunnel equipped with laser-diffraction equipment. 

Recent wind tunnel studies with 8001 nozzles at wind 

speeds of 225 km/hr produced a DV50 of 55.2 μm, 

which is nearly 5 times larger than in our study.30

Volume median diameter for 8005 nozzles at wind 

speeds of 225 km/hr were 87.7 μm, which were also 

larger than in our results. However, the Hornby et al30

data suggests that increased wind shear at faster speeds 

can create smaller droplets. Since the C-130H airplane 

flew at 370 km/hr, this might have caused the smaller 

droplet size we measured with the 8005 nozzles. 

However, wind shear alone probably cannot account 

Characterization of a New Ultra-Low Volume Fuselage Spray Configuration on 

Air Force C‐130H Airplane Used For Adult Mosquito Control 

Figure 6. Predicted deposition from AGDISP model of droplets sprayed with C-130H fuselage mounted booms released 

at (A) 46 m and (B) 91 m above ground. 

B 

A 
 July – September 2009 73

THE ARMY MEDICAL DEPARTMENT JOURNAL

for the very small DV50 that we measured with the 

8001 nozzles. A possible explanation is that minute 

oil droplets from other sources (eg, engine exhaust) 

were trapped on the microscope slides and were 

counted as sprayed material. This would be more 

likely to affect the data from the 8001 nozzles 

because they made smaller droplets than the 8005 

nozzles. Adding florescent dye to the spray material 

(eg, Barber et al22) might help to distinguish 

between sprayed material and environmental 

contaminants in future studies. Also, we may have 

undercounted the largest possible droplets because 

these would be rare and might have dropped out of 

the air column before they impacted our sampling 

stations. 

Making accurate predictions of pesticide droplet 

dispersal is desirable19 and, therefore, we compared 

AGDISP model predictions to our downwind field 

data. The overall AGDISP predictions and 

empirical data followed a similar and expected 

pattern of larger drops falling first and smaller 

drops drifting further. For example, in crosswind 

field trials from a 46 m release height, the average 

droplet size measured at the second collection 

station (305 m) was ~25 μm (Table 3). In 

comparison, at 305 m downwind, AGDISP 

predicted that 22.3 μm droplets would still be 

airborne but that 54.3 μm droplets would have 

already reached the ground around 225 m 

downwind. Taking into consideration the influence 

that wind speed and direction can have on these 

small to medium-sized drops, the disparity between 

the model and the empirical data may be considered 

reasonably similar at this level of resolution. 

AGDISP predictions regarding trajectories of large 

droplets were also fairly closely confirmed by field 

trials. AGDISP predicted 104.7 μm droplets to 

reach ground level 130 m downwind (Figure 7), 

and many droplets of this size were collected at the 

150 m collection station, although 104.7 μm 

droplets from the leeward side are not predicted to 

reach the ground until 430 m. 

However, we found that some AGDISP predictions 

were different than observed in our field data. For 

instance, a greater disparity existed between AGDISP 

predicted trajectories and field data for droplets 

released from 90 m. The AGDISP model could not 

predict droplet fate past 400 m, but many droplets 

were still airborne at this distance. The AGDISP 

model also predicted further drift than we observed in 

the crosswind trials. For example, the trajectory path 

of all modeled droplet sizes from 91 m predicts 

droplets will still be aloft at approximately 500 m 

downwind from release. In contrast, we collected 

many droplets sizes at the 500 m sampling station 

during the field trials (Figure 5). 

Figure 7. AGDISP model predicted trajectory of an (A) 22.3 

μm droplet (DV10 ), (B) 54.3 μm droplet (DV50), and (C) 104.7 

μm droplet (DV90) from the C-130H airplane at 46 m release 

height. Windward and leeward annotations indicate the side 

of the airplane from which the droplets were released. 

Windward 

Altitude (m) 

Distance from airplane (m) 

A 

Leeward 

Distance from airplane (m) 

Altitude (m) 

C 

Windward 

Leeward 

Altitude (m) 

Distance from airplane (m) 

B 

Windward 

Leeward 
74 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

Our comparisons between predicted and empirical 

data indicate that the AGDISP model is more 

accurate at assessing the environmental fate of larger 

droplets and their movement closer to their release 

points. In general, AGDISP made the most accurate 

predictions of droplet fate at 46 m release height, but 

was less accurate for sprays released at 91 m above 

ground. 

Fuselage sprays from 8005 nozzles produced wide 

pesticide swaths that suggest they would be 

appropriate for military aerial ULV operations where 

a minimum 600 m swath width is required.31

Additional operational evaluations will be necessary 

to determine effective swath width for C-130H 

fuselage booms using sentinel mosquito mortality 

and various pesticides. 

A potential reason for inaccuracies in AGDISP 

models is that the model is unable to use continuous 

weather data. Obviously, even modest changes in 

meteorological conditions (eg, wind direction) could 

have significant effects on droplet fate. Modeling 

ULV sprays at high altitudes is also difficult because 

the model does not calculate downwind drift past 

3,600 seconds. This is an artifact from the model’s 

origins in depositional spraying19 and, subsequently, 

the development of better algorithms that accurately 

incorporate field conditions would improve the 

AGDISP model. 

In conclusion, the fuselage boom configuration we 

tested would be desirable for use in military 

operations because setup and maintenance is simple 

and it produces less pesticide waste than the wing 

boom configuration. Our trials suggest that 8001 and 

8005 flat-fan nozzles produce a droplet spectra and 

swath dispersal that would be effective for ULV 

mosquito control operations. However, we also 

found that small changes in wind speed and direction 

substantially affect droplet dispersion and deposition 

behavior. Therefore, continual monitoring of current 

meteorological conditions should be an ongoing 

consideration during ULV mosquito control 

operations. Increased wind speed and directional 

variability also make it difficult to predict insecticide 

dispersal characteristics with the currently available 

AGDISP modeling software. 

ACKNOWLEDGMENTS

We thank the staff at the Avon Park Range, especially 

Paul Ebersbach and John Bridges, for their help in the 

coordination of these activities. Additionally, we extend 

our thanks to the men and women of the Air Force Spray 

Flight from the 910 Airlift Wing who participated in this 

project. 

Characterization of a New Ultra-Low Volume Fuselage Spray Configuration on 

Air Force C‐130H Airplane Used For Adult Mosquito Control 

Figure 8. AGDISP model predicted trajectory of an (A) 22.3 

μm droplet (DV10 ), (B) 54.3 μm droplet (DV50), and (C) 104.7 

μm droplet (DV90) from the C-130H airplane at 91 m release 

height. Windward and leeward annotations indicate the side 

of the airplane from which the droplets were released. Altitude (m) 

A 

Windward 

Leeward 

Distance from airplane (m) 

Altitude (m) 

B 

Windward 

Leeward 

Distance from airplane (m) 

Altitude (m) 

C 

Windward 

Leeward 

Distance from airplane (m) 
 July – September 2009 75

THE ARMY MEDICAL DEPARTMENT JOURNAL

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Characterization of a New Ultra-Low Volume Fuselage Spray Configuration on 

Air Force C‐130H Airplane Used For Adult Mosquito Control 

AUTHORS

Maj Breidenbaugh is the Chief Entomologist, Air Force Aerial Spray Unit, 757 Airlift Squadron, 910th Airlift Wing, 

USAFR, at the Youngstown Air Reserve Station, Vienna, Ohio. 

Maj Haagsma is a Research Entomologist, Air Force Aerial Spray Unit, 757 Airlift Squadron, 910th Airlift Wing, 

USAFR, at the Youngstown Air Reserve Station, Vienna, Ohio. 

Mr Latham is the Director, Manatee County Mosquito Control District, Palmetto, Florida.

Dr de Szalay is an Associate Professor, Department of Biological Studies, Kent State University, Kent, Ohio. 

The fuselage-mounted spray booms (circled) on a USAF C130H airplane are 

shown in operation during evaluation flights at the Air Force Range, Avon 

Park, Florida. 
 July – September 2009 77

INTRODUCTION

The Armed Forces Pest Management Board 

(AFPMB), located at the Fort Detrick-Silver Spring 

(Maryland) Forest Glen Annex, is the Department of 

Defense’s (DoD) lead agency in the prevention and 

control of arthropod-borne diseases, arthropod pests, 

and invasive species. Whether the issue is contingency 

operations, invasive species, or pest management 

research, the AFPMB is prepared to meet challenges 

head-on through the establishment of pest management 

policies, the encouragement and financial support of 

original research, and the exchange of up-to-theminute scientific and technical information. No similar 

entity exists anywhere within DoD. 

HISTORY

The AFPMB, originally chartered as the Armed Forces 

Pest Control Board, was established by DoD Directive 

5154.12* in 1956. Members have met on a regular 

basis since 1957. The Board currently meets twice a 

year at its Forest Glen location, and once a year at a 

US Department of Agriculture (USDA) laboratory 

where research of interest to DoD is reviewed with 

USDA investigators. The Board was redesignated as 

the Armed Forces Pest Management Board in 1979, 

and the AFPMB secretariat became a directorate of the 

Deputy Assistant Secretary of Defense (Environment) 

after DoD Directive 6050.10* was implemented in 

1985. Reestablished by DoD Directive 4715.1E 1 in 

2005, the AFPMB operates under DoD Instruction 

4150.07 2 and is now a directorate in the Office of the 

Deputy Under Secretary of Defense for Installations 

and Environment (DUSD (I&E)). 

MISSION

The mission of the AFPMB is to recommend, 

coordinate, and develop policy, guidance, and the 

exchange of information on all matters and activities 

related to pest management and arthropod-borne 

disease control throughout DoD. The AFPMB ensures 

that environmentally sound and effective programs are 

implemented to support operating forces worldwide in 

the prevention of arthropod-borne diseases, and to 

prevent losses from pest attack on subsistence, 

supplies, and facilities. The AFPMB functions as 

DoD’s scientific/research advisory body and 

coordination/liaison activity for pest management. In 

support of its mission, the AFPMB: 

Develops and recommends policy to the DUSD 

(I&E). 

Coordinates DoD pest management activities. 

Develops, issues, and maintains manuals and other 

guidance necessary to implement the technical 

requirements of the Federal Insecticide, Fungicide, 

and Rodenticide Act.3

Implements DoD’s plan for certification of 

pesticide applicators, and develops comprehensive 

training guidance for DoD pest management 

personnel. 

Coordinates DoD contingency disease vector and 

pest management with the Joint Staff,†

 the 

combatant commands, and other contingency 

planning organizations. 

Serves as an advisory body to the DoD 

components, and provides timely scientific and 

professional pest management advice. 

Develops and distributes technical information and 

guidance on pest management to the components 

by means of technical guides, disease vector 

ecology profiles, etc. 

The Armed Forces Pest Management Board: 

Force Multiplier Through Policy, Guidance, 

Research, and Information 

Col William M. Rogers, USAF, BSC 

Richard G. Robbins, PhD 

CAPT Stanton E. Cope, USN, MSC 

* Canceled, no longer in effect. 

† US Joint Chiefs of Staff 
78 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

Reviews and approves any introduction, stockage, 

and deletion of pest management materiel 

(excluding disinfectants and biocides) by the 

Defense Logistics Agency in the DoD supply 

system. 

Coordinates and develops DoD’s requirements for 

pest management research, development, testing, 

and evaluations. 

Carries out its mission with 3 new divisions: 

Operations, Research, and Information Services. 

It is the AFPMB’s vision that the DoD will be the 

federal leader for innovative prevention and 

management of disease vectors and pests. The strategy 

of the AFPMB is to support military readiness and 

preventive defense, and to demonstrate environmental 

leadership and avert future pollution problems by 

maximizing the use of nonchemical or least toxic 

chemical techniques to manage pests and disease 

vectors. In furtherance of this strategy, the AFPMB 

promotes integrated pest management, biopesticides, 

and the use of least toxic pesticides for installations 

and deployments, and advocates personal protection 

measures against arthropod bites and stings. The 

AFPMB has received numerous awards and citations 

for such efforts, including frequent recognition by the 

US Environmental Protection Agency’s Pesticide 

Environmental Stewardship Program, which aims to 

“reduce pesticide use, protect human health, and 

preserve the environment.”4

STRUCTURE

The AFPMB includes a directorate, council, and several 

committees: 

Directorate – The full-time 

administrative body of the 

AFPMB currently consists of 7 

active duty medical entomologists representing the US 

Army, Navy, and Air Force, 3 

federal employees, and 3 

contractors. Reorganized in 

January 2009, the permanent 

staff includes a director, 

deputy director, directorate 

support staff, contingency 

liaison officer, research liaison 

officer, information liaison officer, environmental 

biologist, and support personnel, as shown in Figure 1. 

 Director – Supervises the directorate, and plans and 

conducts AFPMB operations. 

 Deputy Director –Responsible for the day-to-day 

operations of the Directorate, the directorate 

support staff, facility maintenance, and personnel. 

 Directorate Support Staff – Includes the financial 

resource manager, information technology 

manager, and administrative assistant. 

 Contingency Liaison Officer (CLO) – In charge of 

the Operations Division and oversees the activities 

of the assistant CLO and the environmental 

biologist. The CLO interfaces with the Joint Staff, 

the unified commands, and component 

headquarters, playing a coordination role in DoD 

readiness planning for prevention and management 

of vector-borne diseases and invasive species. 

 Research Liaison Officer – In charge of the 

Research Division and coordinates and assists in 

research activities pertinent to military pest 

management programs. 

 Information Liaison Officer – In charge of the 

Information Services Division and responsible for 

the acquisition, analysis, and dissemination of 

information on arthropod-borne disease control, 

pest management, and natural resources for the 

AFPMB. 

Council – The Council (voting Board members) is a 

part-time advisory body of senior pest management 

The Armed Forces Pest Management Board: 

Force Multiplier Through Policy, Guidance, Research, and Information 

Figure 1. The components and organization of 

the AFPMB Directorate. 

Operations Division 

Contingency Liaison Officer 

Assistant Contingency 

Liaison Officer 

Environmental 

Biologist 

Research Division 

Research Liaison Officer 

Technical Consultant 

Deputy Director Support Staff 

(IT, Budget, Admin)

THE ARMED FORCES PEST MANAGEMENT BOARD

DIRECTORATE

Director 

Information Services Division 

Information Liaison Officer 

Navy Representative 

Army Representative 

Air Force Representative 

Senior Scientific Associate 

Technical Information Specialist 
 July – September 2009 79

THE ARMY MEDICAL DEPARTMENT JOURNAL

and natural resource professionals appointed from each 

of the military departments and the Defense Logistics 

Agency. It currently meets twice each year. Other 

federal agencies provide nonvoting representation. 

Committees – The major business of the AFPMB is 

accomplished by committees consisting of members 

and agency representatives. Twice each year over 80 

technical professionals representing a broad range of 

federal organizations and allied countries voluntarily 

meet at the AFPMB to contribute their expertise 

toward the resolution of vector-borne disease and pest 

management issues that are of concern to the 

Department of Defense. 

The Executive Committee consists of 7 council 

representatives or alternates and comprises the senior 

pest management consultant from each military 

department, the entomology consultant to each 

military service’s Surgeon, and the single Defense 

Logistics Agency representative. The Director, as ex 

officio, is a nonvoting member of the Committee. 

There are 12 standing committees: 

Contingency Advisory 

Diagnostics 

Education and Training 

Equipment 

Information Management 

Medical Entomology 

Natural Resources 

Pesticides 

Quarantine and Commodities Protection 

Real Property Protection 

Repellents 

Research 

The Contingency Advisory Committee comprises the 

senior medical entomologists from each service and 

functions to ensure delivery of vector-borne disease 

control support for the operating forces. Ad hoc 

subcommittees provide a task force effort on urgent 

issues. 

Operations Division 

The newly formed Operations Division (OD) 

combines the contingency and environmental biology/

invasive species areas into a single, cohesive group. 

The Division’s primary mission is to provide 

consultation, guidance, and liaison with other DoD and 

non-DoD agencies and governments on a variety of 

operational pest management issues. The OD consists 

of the Contingency Liaison Officer, a senior military 

entomologist with substantial deployment experience 

who supervises the division; another military 

entomologist who serves as the Assistant CLO; and the 

Environmental Biologist, who is the liaison with the 

DoD natural resources program managers. The 

Operations Division is ready to assist customers in 

accomplishing their mission of protecting the health 

and safety of service members, civilians, and the 

environment. 

The primary focus is to provide consultation and 

guidance to personnel and units, either deploying or 

already deployed, on any type of contingency, 

stabilization, or humanitarian and civic assistance 

mission. This guidance includes establishing contact 

between a customer and personnel already in the area 

of operation, referral to organizations that can provide 

the most recent entomological risk assessments, 

making recommendations on pesticides and 

application equipment, consulting on the 

implementation of personal protective measures, and 

advising on the handling of contract pest control 

operations. The OD is involved in vegetation control 

during contingency operations, control of agricultural 

pests impacting humanitarian and civic assistance 

efforts, assisting in the acquisition of bed nets for 

distribution, and treatment of uniforms with 

permethrin. These are a few of the many issues that 

may be addressed on a daily basis. The OD seeks 

feedback from deployed personnel to identify 

problems and implement appropriate steps toward their 

resolution through training, education, or the provision 

of equipment. 

The Operations Division acts as a conduit to the 

AFPMB on contingency issues and is able to consult 

and coordinate with offices throughout the DoD and 

among our allies. Thus, the OD is able to assist 

customers in the rapid receipt of information needed to 

address their current situation. If a customer requires a 

piece of equipment or pesticide that is not included in 

the field set, they should contact the OD (email, letter, 

etc) and explain the specifics and purpose of the 

requirement. The Operations Division will then work 

with the requestor to determine if another item can be 

used, or if the request represents a new requirement 

which must be addressed. The OD also needs to know 

what obstacles a customer encountered during 
80 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

deployment (ie, what prevented completion of the job). 

While the OD cannot help with command and control 

issues, it can provide guidance on how to approach 

these matters in order to gain command support. If the 

issue is significant, the OD has points of contact within 

each service’s senior entomological leadership and the 

combatant commands, and potentially can work the 

issue through those avenues. 

In addition to direct customer support, the OD 

addresses contingency issues at the DoD level by 

reviewing new policies and guidance to ensure that 

there are no unrealistic restrictions placed upon 

deployed personnel. Contingency operations 

encompass situations outside day-to-day, installationlevel activities, such as armed conflict, disaster relief, 

and humanitarian support. Such unforeseen events are 

increasingly common, and each operation brings with 

it new pest management issues. 

Environmental Biology, Invasive Species 

The primary focus of the Environmental Biologist is as 

the liaison with DoD natural resource program 

managers and coordinator with federal natural resource 

working groups and the National Invasive Species 

Council. This working relationship fosters better 

partnership development among federal, state, and 

nongovernmental agencies in the management of 

invasive and nuisance animal and plant species. 

Through this relationship, the pest management and 

natural resources program experts are able to discuss 

areas of mutual interest and share their respective 

expertise. 

The Operations Division works with both the DoD 

Legacy Program and the Strategic Environmental Research and Development Program to assist in the selection of proposed projects to aid DoD in the better management of invasive species problems that impact its 

mission and readiness. These issues can range from the 

control of the brown tree snake on Guam, to management of endangered species habitats on installations, 

and guidance on the problems of invasive species with 

regard to retrograde cargo preparation and shipment. 

Research Division 

The Research Division is managed by the Research 

Liaison Officer (RLO). The RLO is the principal 

AFPMB contact with the USDA’s Agricultural 

Research Service and other pest management research 

programs, and helps to coordinate DoD research 

requirements for military pest management and vector 

control. Also, the RLO serves as the Directorate ex 

officio to the AFPMB Council and committees on all 

research matters. 

The principal activity of the RLO is to administer the 

Deployed Warfighter Protection (DWFP) research 

program, a $5 million per year effort to develop new 

pesticides, new application equipment, and new 

methods of personal protection. The DWFP was 

recently profiled in this journal.5

Information Services Division 

The Information Services Division (ISD) provides 

DoD customers with timely information on such topics 

as arthropod-borne disease, pest management, and 

invasive species. Managed by the Information Liaison 

Officer, the division also supports DoD through expert 

consultations and electronic publications retrieval via 

its online Literature Retrieval System. 

The ISD evolved from the Defense Pest Management 

Information Analysis Center (originally the Military 

Entomology Information Service) which was 

established in 1962 as the information and 

communications branch of the Armed Forces Pest 

Control Board, the forerunner of today’s AFPMB. 

Reorganized into the ISD in January 2009, it continues 

to collect, store, analyze, and disseminate published 

and unpublished information on arthropod vectors and 

pests, hazardous and invasive organisms, and natural 

resources and environmental biology that is important 

to the DoD. Services include technical consultations 

on vectors, pests, environmental biology, and natural 

resources; development and distribution of Disease 

Vector Ecology Profiles that provide summaries of the 

bionomics of disease vectors and data on hazardous 

animals and plants for individual countries or 

biogeopolitical areas (eg, the Middle East); Technical 

Guides (formerly Technical Information Memoranda) 

that provide guidance on specific issues of interest to 

the DoD pest management community (eg, the 

surveillance and control of ticks that transmit disease); 

interactive teaching programs in CD (tick morphology) 

and DVD (mosquito morphology) format; and 

provision of subject-specific bibliographies, utilizing 

in-house and proprietary databases. Authorized ISD 

customers are all DoD medical, pest management, and 

natural resources personnel, as well as other DoD staff 

The Armed Forces Pest Management Board: 

Force Multiplier Through Policy, Guidance, Research, and Information 
 July – September 2009 81

THE ARMY MEDICAL DEPARTMENT JOURNAL

responsible for dealing with problems caused by 

disease vectors and pests. Also eligible are non-DoD 

members of the AFPMB, certain personnel of other 

federal or state agencies, and university faculty 

associated with the AFPMB. 

Since its inception, ISD has maintained a reference 

library that is now one of the world’s chief sources of 

information on what the late Ralph Audy called 

“medical zoology.”6

 The current library contains a 

quarter million accessions, of which about 108,000 are 

available as full-text, digital PDF files, together with 

some 2,300 books, 100 CDs or DVDs, and active 

subscriptions to over 60 periodicals in biomedicine, 

parasitology, and natural resources management. 

Central to ISD’s mission of information dissemination 

is its online Literature Retrieval System, a Boolean 

search engine that formerly provided only 

bibliographic literature summaries, but, with the 

advent of the internet, is now capable of supplying 

copies of all papers (PDF format) accessed by ISD 

personnel from the serial scientific literature. Users 

start at the basic search page (http://lrs.afpmb.org/

rlgn_app/ar_login/guest/guest), shown as Figure 2, 

where a journal search is the default option, although 

the book and CD collections as well as the former 

(1980-2000) AFPMB Technical Information Bulletin 

and papers in the online database of the Walter Reed 

Biosystematics Unit may also be searched, separately 

or concurrently. While any terms (authors, keywords, 

words from the title or text of a paper) can be typed 

into the basic search box, it is almost always preferable 

to select the Advanced tab which presents the 

advanced query composer page, Figure 3, where 

search parameters can be specified by terms in the 

document title, by author, by terms in the document 

text, by journal title, and by year range. Effective use 

of this system is dependent on practice and experience 

in its use. For example, one might search for papers on 

Figure 2. Literature Retrieval System basic search page. 

Figure 3. Literature Retrieval System advanced query composer page. 

Figure 4. Simple search entries in the query composer. Figure 5. False positives result from simple query terms. 
82 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

the ticks of Taiwan by typing the words “ticks” and 

“Taiwan” into The Document Text field (Figure 4) 

or into the basic search field. However, either method 

yields an unmanageable (and identical) number of hits, 

including many false positives (Figure 5). But in such 

a search it is evident that the focus is on Taiwan, 

which should therefore appear in The Document Title

box, while “ticks” remains in The Document Text

box (Figure 6). This strategy yields a much more 

manageable hit list, with virtually no false positives 

(Figure 7). Click the paper’s hypertext title (Figure 8) 

to view the entire document (Figure 9), which can then 

be printed, saved, or emailed. 

The Literature Retrieval System is not the only search 

tool available to ISD customers. Through contracts 

with ProQuest Dialog (Cary, NC) and Ovid 

Technologies, Inc. (New York, NY), customers enjoy 

free online access to such powerful biological 

databases as AGRICOLA (the National Agricultural 

Library’s catalog and article citation database), 

BIOSIS (Biosciences Information Service), CAB 

(Commonwealth Agricultural Bureaux) Abstracts, and 

MEDLINE (the National Library of Medicine’s 

premier bibliographic database). Hard copies of 

biomedical papers whose citations are retrieved via 

these proprietary databases are swiftly delivered 

(usually on a same-day basis) as web .pdf formatted 

documents through ISD’s DOCLINE® contract with 

the National Library of Medicine. For nonbiomedical 

literature, the ISD staff has access to the stacks of the 

nearby National Agricultural Library and Library of 

Congress. 

Living Hazards Database 

Maintained by ISD, the Living Hazards Database 

(LHD), publicly accessible at the AFPMB’s website, 

contains concise descriptive and bionomic information 

The Armed Forces Pest Management Board: 

Force Multiplier Through Policy, Guidance, Research, and Information 

Figure 6. Narrow the query by moving “Taiwan” to The 

Document Title box to return only those documents 

focused on Taiwan which discuss ticks in the text. 

Figure 9. The selected, downloaded document can be 

saved, forwarded, or printed. 

Figure 7. The modified query shown in Figure 5 produces a 

more manageable list of documents with virtually no false 

positive returns. 

Figure 8. Click the hyperlinked title of a document to 

download a PDF formatted version. 
 July – September 2009 83

THE ARMY MEDICAL DEPARTMENT JOURNAL

on most of the animals that have been reported to 

cause serious injury or death in humans. The LHD 

may be searched by species scientific name or by 

country, and is worldwide in scope, with each 

venomous animal discussed under the headers 

Identification, Description, Habitat, Activity and 

Behavior, and Venom Characteristics. Digital images 

are included for most of the 500+ listed venomous 

animals, which serve as aids to initial identification. 

Because the focus of the LHD is on injury by 

envenomization, most of the animals depicted are 

snakes. Birds, mammals, and plants are not currently 

included in the LHD. 

The LHD has been designed to materially assist medical, paramedical, and first-responder teams supporting 

US military and associated personnel throughout the 

world. The ISD therefore carefully reviews the LHD 

several times each year, and updates information and 

images whenever new material is published or in response to corrections by recognized technical experts. 

CONCLUSION 

The history of warfare has repeatedly shown that 

casualties during contingency operations are often 

caused by diseases, most of which are arthropodborne. The AFPMB is a force multiplier in the 

ceaseless campaign against arthropod-borne diseases, 

providing policies, guidance, research support, and 

information for US and allied Warfighters worldwide. 

Concurrently, the AFPMB ensures environmental 

stewardship and safety through careful management of 

pesticide products and the control of invasive species. 

Like the vectors and pests that it was established to 

combat, the AFPMB is an evolving entity, but one 

honed by over 50 years of accomplishment to face the 

challenges of the new century. 

ACKNOWLEDGEMENT

We thank our AFPMB colleagues LTC Jamie A. Blow, USA; Peter J. Egan, PhD; and Harold J. Harlan, PhD, 

for their assistance in preparing the sections on contingency pest management, environmental biology/

invasive species, and the Living Hazards Database, respectively. 

REFERENCES

1. Department of Defense Directive 4715.1E: Environment, Safety, and Occupational Health (ESOH). Washington, 

DC: US Dept of Defense; March 19, 2005. 

2. Department of Defense Instruction 4150.07: DOD Pest Management Program. Washington, DC: US Dept of 

Defense; May 29, 2008. 

3. Federal Insecticide, Fungicide, and Rodenticide Act, 7 USC §136 (1972). 

4. Wayland SH. Award Citation. Meritorious Achievement Award presented to the Armed Forces Pest Management 

Board: Deputy Assistant Administrator, Office of Prevention, Pesticides and Toxic Substances, US Environmental 

Protection Agency; August 1999; Washington, DC. 

5. Cope SE, Strickman DA, White GB. The Deployed Warfighter Protection Research Program: finding new methods 

to vanquish old foes. Army Med Dept J. April-June 2008:9-20. 

6. Audy JR. Red Mites and Typhus. London, England: Athlone Press; 1968. 

AUTHORS

Col Rogers is the Deputy Director of the Armed Forces Pest Management Board. 

Dr Robbins is an Entomologist with the Armed Forces Pest Management Board.

CAPT Cope is the Director of the Armed Forces Pest Management Board.
84 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

INTRODUCTION

Historically, disease and nonbattle injuries, 

particularly vector-borne diseases, have resulted in 

more casualties than have combat operations.1

 The 

impact of vector-borne disease on military operations 

is well-documented from the Revolutionary and 

American Civil Wars.2

 The incidence of these diseases 

in recent operations3-8 demonstrates that the threat has 

not diminished. Currently, the US military has a 

presence in over 130 countries9

 and is involved in a 

wide-range of operations, including stability and 

support operations, small scale contingency 

operations, and major theater wars. Military personnel 

remain exposed to a wide range of vectors and vectorborne diseases. The very nature of military operations 

(rapid deployments, troop movements, fluidity of the 

modern battlefield) often makes the conduct of areawide vector control operations impossible. In many 

tactical situations (eg, assault, bivouac, and 

entrenchment), vector control measures cannot be 

instituted, or are insufficient to prevent disease 

transmission. Thus, personal protective measures 

(PPMs) have been, and remain the first and best line of 

defense for military personnel against all vector-borne 

diseases. 

There are many types of PPMs available to military 

personnel, including permethrin for uniform and bed 

net treatment, and the Extended Duration Topical 

Insect and Arthropod Repellent (EDTIAR) with 33% 

N,N-diethyl-3-methylbenzamide (deet) in a polymer 

formulation.10 The Department of Defense Insect 

Repellent System, consisting of a permethrin-treated 

uniform, EDTIAR on exposed skin, and a properly 

worn uniform, is a system that, when employed 

properly, is very effective at protecting Soldiers from 

vector-borne disease threats.11 The EDTIAR is the 

standard military repellent which is designed to be 

used in all situations for protection against vector 

threats. 

Since concealment is important in many tactical 

situations, Soldiers use camouflage face paint. 

Although EDTIAR can be used in conjunction with the 

standard camouflage face paint, it requires 2 separate 

applications, an initial application of EDTIAR 

followed by the camouflage face paint.12 Recognizing 

the special needs of tactical situations, the Walter Reed 

Army Institute of Research (WRAIR) Repellent 

Program, in collaboration with Amon Re, Inc 

(Thomasville, Georgia), developed combined 

camouflage face paint with 30% deet.13 The addition 

of insect repellent to the camouflage face paint 

replaces 2 items with one, saves space, reduces the 

weight of the individual survival kit, and saves 

application time. 

An Operational Requirements Document (ORD) dated 

May 28, 1999 (internal use document) was issued to 

guide development of camouflage face paint combined 

with 30% deet in both compact and stick form. The 

compact form, with 5 colors of face paint (black, 

green, loam, sand, and white) was developed and 

Evaluation of Efficacy and Duration of the 

Stick Camouflage Face Paint with 30% Deet 

Against Mosquitoes in Belize 

MAJ Kendra L. Lawrence, MS, USA 

John Paul Benante 

Nicole C. Close, PhD 

Nicole L. Achee, PhD 

ABSTRACT

A combination of insect repellent, N,N-diethyl-3-methylbenzamide (deet), with camouflage face paint in a newly 

designed stick formulation was evaluated on human volunteers under field conditions in Belize during February 2007. 

The formulation provided over 90% protection against mosquitoes for 8 hours and at least 80% protection for 12 hours, 

with 100% protection for 2 to 4 hours after application. 
 July – September 2009 85

tested for efficacy and Soldier 

acceptability,14 and endorsed by 

the Ar me d Forces Pest 

Management Board. It was 

recommended for assignment of a 

national stock number (6840-01-

493-7334) in 2001. Development 

of the stick formulations to meet 

the requirements of the ORD 

began in 2006. 

The purpose of the study was to 

evaluate the repellent efficacy and 

duration of the stick camouflage 

face paint formulated with 30% 

deet (SCFPwD). The study was 

essential for further advanced 

development and processing of 

this product into the military 

supply system. 

MATERIALS AND METHODS

Study Site 

Belize (formerly British 

Honduras) is a Central American 

country with a geographic area of 

22,966 sq km and a population of 

approximately 290,000.15 The 

climate and general ecology of 

Belize is favorable for year round 

transmission of malaria. 

Extensive marshes, swamps, and rivers provide 

continuous larval habitats for malaria vector species, 

even during the dry seasons. Malaria incidence is 

significantly higher in the southern and western 

provinces of Toledo, Cayo, and Stann Creek than in 

the northern provinces of Corozal and Orange Walk.16

The attack rate of malaria is less than 1% per month, 

concentrated primarily in the south.17 The study was 

conducted in the town of San Roman in the northern 

Belize province of Orange Walk (Figure 1) from 

February 20 to February 22, 2007. The study site in 

San Roman (18° 17.8’ N, 88° 30.6’ W) was located 

about 100 m from the Rio Nueve (New River) in an 

open field (approximately 300 m2

) bordered on one 

side by a semiwooded area. Weather conditions during 

the 3 nights of collection were seasonal, with an 

average temperature of 24oC, 87% relative humidity, 

and wind speeds about 2 kph. 

Test Material 

The SCFPwD is a camouflage 

face paint in a hardened, tubeshaped form, comprised of the 

following ingredients: Puresyn 

M E 3 0 0 , P u r e s y n 1 0 0 0 

(Polydecene), N,N-diethyl-3-

methylbenzamide, Multiwax 

W835 (microcrystalline wax), 

white beeswax, light candelilla 

wax, propylparaben, Cab-O-Sil 

M 5 ( s i l i c a ) , T h i x ci n R 

(trihydroxystearin), Tenox 6 (Zea 

mays (corn) oil, glyceryl oleate, 

propylene glycol, BHA, BHT, 

propyl gallate, citric acid), 

titanium dioxide, black iron 

oxides, red iron oxides, yellow 

iron oxides, chromium oxide 

greens, ultramarines, and zinc 

oxide. The manufacturer of this 

p r o d u c t , I g u a n a , I n c 

(Thomasville, GA), received a 

formulation amendment dated 

July 11, 2007, from the Environmental Protection Agency (EPA). 

A formulation amendment is 

intended for products that are 

identical or substantially similar 

to a currently registered product. 

This product has the same EPA 

registration number (66306-11) 

and label as the camouflage face paint with 30% deet 

in the compact, originally approved on March 27, 

2001. 

Volunteers 

Volunteers in this study were recruited, screened, and 

enrolled under a human-use protocol reviewed and 

approved by the WRAIR Institutional Review Board.18

Volunteers were recruited from the villages of Orange 

Walk, August Pine Ridge, and San Roman, with the 

assistance of bilingual field liaisons. Interested parties 

were briefed on the nature of study participation. 

Participating volunteers signed informed consent 

forms prior to any study related procedures in 

accordance with research guidelines for studies 

involving humans.19 Volunteer recruitment, screening, 

and enrollment occurred February 17 through February 

20, 2007. 

Figure 1. Location of the study site was in 

the Orange Walk province of Belize in 

Central America. 
86 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

STUDY DESIGN AND PROCEDURE

All 5 colors of the camouflage face paint with 30% 

deet were evaluated on human volunteers at 6 time 

points: 2, 4, 6, 8, 10, and 12 hours postapplication. 

Peak biting activity occurred between 6 PM and 9 PM; 

therefore, only 2 mosquito challenges could occur each 

night, one at 6 PM and one at 8 PM. Three study nights 

were required in order for each volunteer to be 

challenged at all 6 time points. Therefore, a staggered 

application design was employed. Application times 

were at 8 AM, 12 noon, and 4 PM each day for 3 days. 

At the start of the study, volunteers were randomly 

assigned to a treatment group: black, green, loam, 

sand, or white camouflage face paint (n = 5 per 

treatment). Each volunteer rotated through all of the 

treatment times during the course of the study to 

measure all postapplication time points during peak 

biting activity. 

A 600 cm2

 treatment area from 

above the ankle to below the 

knee was determined for each 

volunteer. Five equally spaced 

circumference measurements 

were taken along each lower 

leg, averaged and divided into 

600 to get the length of the 

exposed area which was 

defined by an indelible marker 

on both legs. Each day of the 

study, the marked area from 

ankle to knee on one leg was 

treated with the assigned 

SCFPwD color and the same 

marked area on the opposite leg 

was left untreated to serve as a 

control. The EPA Product 

Performance Test Guidelines19

recommend using between 1.0 

g and 1.5 g of lotion or cream 

product over 600 cm2

 of skin 

surface area for testing 

repellents. Using these 

guidelines, 1.5 g of the 

SCFPwD was applied evenly 

on the treatment leg, which was 

s i m i l a r l y r e p e a t e d o n 

subsequent nights of testing. 

T r e a t m e n t a p p l i c a t i o n 

alternated between the left and 

right legs of each volunteer every night of the trial to 

minimize the number of bites on any one leg that 

served as the control. 

From February 20 through February 22, 2007, 

volunteers performed landing collections at the study 

site in San Roman starting at 6 PM and ending at 8:30 

PM each night. During the mosquito challenges, 

volunteers were covered (long sleeve shirts, long 

pants, jackets of Bug-Out® insect barrier material 

(Bug-Out Outdoorwear, Inc, Cedarville, IA), and 

footwear) except for the exposed experimental areas 

(treatment and control) on each leg. All mosquitoes 

landing in the marked areas of the exposed lower legs 

were counted and mouth-aspirated for a 20-minute test 

period or until 20 mosquitoes were counted and 

collected on the control leg. If 20 mosquitoes were 

collected from the control leg before the 20 minutes 

elapsed, the time was recorded and the challenge 

completed for the volunteer at that challenge point. If 

mosquito landing rates were 

low (<20 mosquitoes in 20 

minutes), the testing period was 

extended for an additional 10 

minutes. Collected mosquitoes 

were placed into screen-topped 

cartons marked with collection 

data (date, time of collection, 

collector number, etc). All 

insects were killed, labeled, and 

stored for identification. One of 

the coauthors, Dr Achee, 

identified the anophelines, and a 

taxonomist of the WRAIR 

Biosystematics Unit performed 

the remaining identifications. 

ANALYSIS

Data were analyzed by 

calculating percent protection 

(PP) of a particular subject, at a 

particular time point, using a 

particular camouflage paint 

stick color. Percent protection 

was calculated for each 

volunteer at each time point as: 

PP=100((LC-LT)/(LRC)) 

where LC represents the 

number landing on the bare skin 

control and LT the number 

Evaluation of Efficacy and Duration of the Stick Camouflage Face Paint 

with 30% Deet Against Mosquitoes in Belize 

Species Number 

Collected % 

Anopheles albimanus 2,742 75.02 

Mansonia titillans 243 6.65 

Anopheles vestitipennis 137 3.75 

Anopheles punctimacula 124 3.39 

Aedes scapularis 87 2.38 

Anopheles gabaldoni 81 2.22 

Culex erraticus 54 1.48 

Anopheles darlingi 49 1.34 

Psorophora confinnis 33 0.90 

Coquillettidia venezuelensis 32 0.88 

Anopheles crucians 23 0.63 

Culex sp 15 0.41 

Culex coronator 11 0.30 

Aedes serratus 5 0.14 

Psorophora varipes 5 0.14 

Psorophora sp 5 0.14 

Aedes sp 4 0.11 

Culex corniger/lactator 2 0.05 

Culex quinquefasciatus 2 0.05 

Aedes aegypti 1 0.03 

Total 3,655 100.00 

Table 1. Distribution of species across total 

mosquitoes collected from human volunteers 

at San Roman, Orange Walk, Belize (20-22 

February 2007). 
 July – September 2009 87

THE ARMY MEDICAL DEPARTMENT JOURNAL

landing on the leg treated with 

SCFPwD. The PP values were 

not normally distributed; 

t h e r e f o r e , t h e a r c s i n e 

transformation was applied to 

the calculated PP values to 

stabilize the variance. The 

transformed data were then 

analyzed using a mixed effects 

model, with both fixed and 

random effects. Fixed effects 

were stick color and duration of 

r e p e l l e n t . A v a r i a b l e 

representing the association of 

data within subjects was 

included to account for the 

variability of repeated 

measurements on subjects 

(random effects). The model was 

run first with the interaction 

term: stick color  duration. If 

the interaction term was not 

significant, the model was run again without the 

interaction term. The data analysis was generated 

using SAS System for XP Pro Platform, Version 9.1.3 

(SAS Institute Inc, Cary, NC). 

RESULTS AND DISCUSSION

Twenty-four male and 2 female volunteers participated 

in this study. Of those enrolled, 46% were hispanic, 

31% mestizo, and 23% other. The mean age of the 

volunteers was 29.7 years (range, 18-57 years). No 

adverse reactions or events were reported 

during the study and there were no deviations 

from the approved human-use protocol. 

During the 3 nights of collection (February 20 

through February 22, 2007), over 3,600 

mosquitoes from 20 species were collected 

from human volunteers, with Anopheles 

albimanus Wiedemann constituting the 

majority (75%) of those collected (Table 1). 

The number of mosquitoes landing per 

volunteer was consistent over each night and 

between challenge points (Table 2). The biting 

pressure, expressed as landing rate (number 

landing as a function of time), was also 

consistent in the control over each night and 

between challenge points (Table 2). The 

overall landing rates on control legs, averaged 

over all 3 nights, were 1.10 ± 0.04 (mean ± SE) and 

1.29±0.08 (mean±SE) at 6 PM and 8 PM, respectively. 

Thus, the biting pressure under which the study was 

conducted exceeds that recommended by the EPA.20

Percent protection (PP) of the SCFPwD was at least 

85%, with 4 of the 5 colors demonstrating an overall 

PP of at least 90% (Figure 2). Overall PP was the 

highest for green (0.94 ± 0.03, mean ± SE) and the 

lowest for sand (0.86 ± 0.04, mean ± SE). Percent 

protection was near 100% at 2 hours and 4 hours 

Table 2. Number of mosquitoes landing and landing rate (no. landing/minute) on 

treatment and control legs at each collection point over three nights of testing in 

San Roman, Orange Walk, Belize (2007). 

 Feb 20 Feb 21 Feb 22 All Nights

6 PM No. landing (mean ± SE)

 Treatment 1.88 ± 0.76 2.32 ± 0.67 3.32 ± 1.46 2.51 ± 0.59

 Control 23.04 ± 1.19 22.36 ± 1.39 25.56 ± 1.44 23.65 ± 0.78

Landing rate (mean ± SE)

 Treatment 0.09 ± 0.04 0.17 ± 0.05 0.11 ± 0.05 0.12 ± 0.03

 Control 1.08 ± 0.06 1.50 ± 0.06 0.97 ± 0.05 1.18 ± 0.04

Total landing 623 617 722 1962

 

8 PM No. landing (mean ± SE)

 Treatment 0.80 ± 0.26 3.96 ± 1.67 2.00 ± 0.91 2.25 ± 0.65

 Control 20.88 ± 0.44 21.72 ± 0.84 21.76 ± 0.85 21.45 ± 0.42

Landing rate (mean ± SE)

 Treatment 0.08 ± 0.03 0.22 ± 0.07 0.14 ± 0.06 0.14 ± 0.03

 Control 1.62 ± 0.15 1.76 ± 0.13 1.42 ± 0.16 1.60 ± 0.08

Total landing 542 642 594 1,778

Figure 2. Percent Protection for each of the 5 camouflage face 

paint stick colors averaged over all 6 postapplication collection 

time points. 

0 55

0.6

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

Black Green Loam Sand White 

0.55 

0.60 

0.75 

0.80 

0.95 

1.00 

0.65 

0.70 

0.85 

0.90 

Percent Protection 

Color of stick camouflage face paint-30% deet combination 
88 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

(Table 3), gradually declining over time (Figure 3) to 

0.85 ± 0.05 (mean ± SE) at 12 hours (Table 3). Percent 

protection was lowest (0.80 ± 0.06, mean ± SE) at the 

10 hour time point (Table 3) 

due to a decrease for 3 of the 

colors, as shown in Figure 2. A 

decrease in PP over time is 

expected as the product’s 

effectiveness declines; 

however, a more marked 

decrease in only 3 of the colors 

(green, sand, black) was 

unexpected. Furthermore, PP 

increased for those 3 colors at 

the 12 hour time point (Figure 

2) and overall PP increased to 

85% (Table 3). This decrease 

and subsequent increase in PP 

could be explained by the fact 

that all 10-hour challenges 

took place at 6 PM, the very 

beginning of the activity 

period. Landing rates on the 

controls were slightly lower at 

6 PM than at 8 PM on all 3 

nights (Table 2). Therefore, as 

the repellent wears off or loses 

effectiveness over the course 

of the day, small differences in 

landing rates, such as seen at 

10 versus 12-hour challenges, will be more obvious or 

amplified giving the appearance of a possible 

interaction between the 2 fixed effects, color and 

duration (time). However, in 

the mixed effects model with 

the interaction term, duration 

was the only significant factor 

(F5,120 = 5.44, P < 0.001) while 

neither color (F4,120 = 1.26, P =

0.29) nor duration  color 

(F20,120 = 0.53, P = 0.95) were 

significant (Table 4). When the 

model was run without the 

interaction term, duration was 

again highly significant (F5,140 =

4.54, P< 0.0001) and color was 

not significant (F4,140 = 1.35, P=

0.25) (Table 4). 

The new SCFPwD meets the 

threshold specifications of the 

ORD, to provide a minimum of 

8 hours of protection. It 

provided maximum protection 

for 4 hours and substantial 

protection for 8 hours when 

tested against the malaria vector 

Anopheles albimanus under 

field conditions in Belize. Data 

collected during this field study, 

Evaluation of Efficacy and Duration of the Stick Camouflage Face Paint 

with 30% Deet Against Mosquitoes in Belize 

Hours after application of face paint-repellent and corresponding times of day 

10 AM 12 NOON 2 PM 4 PM 6 PM 8 PM

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

2 hrs 4 hrs 6 hrs 8 hrs 10 hrs 12 hrs

Black

Green

Loam

Sand

White

0.0

Percent Protection 

0.65 

Figure 3. Percent Protection over time of each of the 5 camouflage face paint stick colors. 

Table 3. Number of mosquitoes landing on treatment and control legs and percent protection 

averaged over each postapplication collection 

timepoint. 

Time* N† Variable Mean ± SE 

2 25 Control 23.28 ± 1.51 

Treatment 0.44 ± 0.18 

Percent Protection 0.98 ± 0.01 

4 25 Control 20.40 ± 0.28 

Treatment 0.44 ± 0.15 

Percent Protection 0.98 ± 0.01 

6 25 Control 23.08 ± 1.33 

Treatment 2.20 ± 0.77 

Percent Protection 0.92 ± 0.02 

8 25 Control 21.48 ± 0.64 

Treatment 2.12 ± 0.92 

Percent Protection 0.91 ± 0.04 

10 25 Control 24.60 ± 1.25 

Treatment 4.88 ± 1.48 

Percent Protection 0.80 ± 0.06 

12 25 Control 22.48 ± 1.03 

Treatment 4.20 ± 1.66 

 Percent Protection 0.85 ± 0.05 

*Number of hours after application of face paint 

†Number of volunteers who participated 
 July – September 2009 89

THE ARMY MEDICAL DEPARTMENT JOURNAL

along with a laboratory study with mosquitoes and 

sand flies and Soldier acceptability surveys, will be 

compiled and submitted to the Armed Forces Pest 

Management Board for recommendation for a national 

stock number. Upon approval, the product, shown in 

Figure 5, will be available to all military personnel as 

part of the personal protective measures used to protect 

against arthropod bites. 

ACKNOWLEDGEMENTS

We thank Ireneo Briceno and Russell King of the 

Ministry of Health, Belize, for their field assistance and 

role in data collection, and Jim Pecor of the Walter 

Reed Biosystematics Unit, WRAIR, for performing 

mosquito identifications. 

Funding for this study was provided by the US Army 

Medical Materiel Development Activity. 

The SCFPwD used in this study was supplied by 

Iguana, Inc at no cost to WRAIR. 

REFERENCES

1. National Research Council. Health Effects of 

Permethrin-Impregnated Army Battle-Dress 

Uniforms. Washington, DC: National Academy 

Press; 1994. 

2. Macedo PA, Peterson RKD, Davis RS. Risk 

assessments for exposure of deployed military 

personnel to insecticides and personal protective 

measures used for disease-vector management. J 

Toxicol Environ Health Part A. 2007;70:1758-1771. 

3. Cutaneous leishmaniasis in U.S. military personnelsouthwest/central Asia, 2002-2003. MMWR Morb 

Mortal Wkly Rep. 2003;52:1009-1012. 

4. Sharp TW, Wallace MR, Hayes CG, et al. Dengue 

fever in U.S. troops during Operation Restore Hope, 

Somalia, 1992-1993. Am J Trop Med Hyg. 

1995;53:89-94. 

5. Wallace MR, Sharp TW, Smoak B, et al. Malaria 

among United States troops in Somalia. Am J Med. 

1996;100:49-55. 

6. Dengue fever among U.S. military personnel-Haiti, 

September – November, 1994. MMWR Morb Mortal 

Wkly Rep. 1994:43(46):845-848. 

7. Sanders JW, Putnam SD, Frankart C, et al. Impact of 

illness and noncombat injury during Operations Iraqi 

Freedom and Enduring Freedom (Afghanistan). Am J 

Trop Med Hyg. 2005;73:713-719. 

8. Coleman RE, Burkett DA, Putnam JL, et al. Impact 

of phlebotomine sand flies on U.S. military 

operations at Tallil Air Base, Iraq: 1. background, 

military situation, and development of a 

“leishmaniasis control program”. J Med Ent. 

2006;43:647-662. 

9. GlobalSecurity.org website. Where are the 

legions? global deployments of US forces. 

Available at: http://www.globalsecurity.org/

military/ops/global-deployments.htm. Accessed 

August 15, 2009. 

10. Gupta RK, Rutledge LC. Laboratory 

evaluation of controlled-release repellent 

formulation on human volunteers under three 

climactic regimens. J Am Mosq Control Assoc. 

1990;5:52-55. 

11. Soto J, Medina F, Dember N, Berman J. 

Efficacy of permethrin-treated uniforms in the 

prevention of malaria and leishmaniasis in 

Colombian soldiers. Clin Infect Dis. 

1995;21:599-602. Figure 5. Tubes of the camouflage face paint with 30% deet product 

used in the study. 

Effect df F-value P

Model with 

Interaction 

Duration 5,120 5.44 0.0002 

Color 4,120 1.26 0.2905 

Duration  Color 20,120 0.53 0.9491 

Model without 

Interaction 

Duration 5,140 5.84 <0.0001 

Color 4,140 1.35 0.2551 

Table 4. The results of the mixed-effects 

model ANOVA run with and without the 

interaction term. 
90 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

12. Personal Protective Measures Against Insects and 

Other Arthropods of Military Significance. Technical 

Guide No. 36. Washington, DC: Armed Forces Pest 

Management Board; April 18, 2002. 

13. Debboun M, Strickman DA, Klun JA. Repellents and 

the military: our first line of defense. J Am Mosq 

Control Assoc. 2005; 21:4-6. 

14. Debboun M, Coleman RE, Sithiprasasna R, et al. 

Soldier acceptability of a camouflage face paint 

combined with deet insect repellent. Mil Med. 

2001;166:777-782. 

15. The World Factbook. Central Intelligence Agency 

website. Available at: https://www.cia.gov/library/

publications/the-world-factbook/geos/BH.html. 

Accessed August 15, 2009. 

16. Hakre S, Masouka P, Vanzie E, Roberts DR. Spatial 

correlations of mapped malaria rates with 

environmental factors in Belize, Central America. 

International Journal of Health Geographics. 

2004;3:6-18. 

17. National Center for Medical Intelligence. Defense 

Intelligence Assessment, 6 March 2009: Food and 

Water-borne Diseases, Malaria. Available at: http://

www.intelink.gov/ncmi/product/idra.php?

id=65768#malaria. Accessed August 14, 2009. 

18. WRAIR Protocol #1324: Field Efficacy Study of 

Stick Camouflage Paint with 30% deet (SCFPwD) 

using Human Volunteers. Silver Spring, MD: Walter 

Reed Army Institute of Research; 2006. Internal use 

document. 

19. Guidelines for Investigators: Requirements for US 

Army Medical Research and Materiel Command 

Headquarters Review and Approval of Research 

Involving Human Volunteers, Human Anatomical 

Substances, and/or Human Data. Fort Detrick, MD: 

Human Research Protection Office, US Army 

Medical Research and Materiel Command; October 

1, 2007. Available at: https://mrmc.amedd.army.mil/

docs/rcq/guidelinesForInvestigators.doc. Accessed 

July 16, 2009. 

20. Environmental Protection Agency. Product 

Performance Test Guidelines: OPPTS 810.3700 

Insect Repellents for Human Skin and Outdoor 

Premises. December 1999. Available at: http://

www.epa.gov/opptsfrs/publications/OPPTS_ 

Harmonized/810_Product_Performance_Test_Guide 

lines/Drafts/810-3700.pdf. Accessed July 20, 2009. 

AUTHORS

MAJ Lawrence is Chief, Vector Control Department, 

Division of Entomology, Walter Reed Army Institute of 

Research, Silver Spring, Maryland. 

Mr Benante is a Biologist in the Vector Control 

Department, Division of Entomology, Walter Reed 

Army Institute of Research, Silver Spring, Maryland. 

Dr Close is Chief of Biostatistics, Division of Regulated 

Activities and Compliance, US Army Medical Research 

and Materiel Command, Ft. Detrick, Maryland. 

Dr Achee is a Medical Entomologist at the Henry M. 

Jackson Foundation for the Advancement of Military 

Medicine, Rockville, Maryland. 

Evaluation of Efficacy and Duration of the Stick Camouflage Face Paint 

with 30% Deet Against Mosquitoes in Belize 

The US Army Medical Research and Material Command 
 July – September 2009 91

INTRODUCTION

Mosquito-borne pathogens are generally acquired from 

vertebrate hosts and transmitted by blood-feeding 

female mosquitoes. Since pathogen acquisition and 

subsequent disease transmission require at least 2 

blood meals and one oviposition cycle to be 

completed, screening gravid 

female mosquitoes for virus 

infection provides the best 

estimate of the infected 

population.1

 Multiple techniques 

and methods are used to conduct 

mosquito surveillance, such as 

incandescent light traps, 

ultraviolet light traps, electric 

nets, CO2 traps, counterflow 

traps, human bait counts, 

oviposition traps, and Centers for 

Disease Control and Prevention 

(CDC) gravid traps. Of all the 

mosquito surveillance traps and 

methods, the CDC gravid trap is 

the only one that specifically 

targets and attracts gravid 

females. 2 Therefore, the 

likelihood of arbovirus detection 

significantly increases when using 

this trap. According to some 

surveillance studies, collections from gravid traps were 

estimated to contain from 57%3

 to 95%4 gravid 

females. The CDC gravid trap, shown in Figure 1, 

consists of a plastic rectangular basin that holds an 

infusion of organic matter that is attractive to some 

species of ovipositing mosquitoes. A vertical hollow 

cylinder with a battery-powered fan is mounted 

approximately 2.5 cm over the 

infusion. The action of the fan 

creates an upward, unidirectional 

air flow that vacuums the 

mosquitoes to the top of the tube 

and into a collection net. 

Both laboratory and field studies 

have shown that gravid mosquitoes exhibit significant preferences when selecting aquatic sites 

for oviposition.5,6 The physical 

characteristics such as color, substrate texture, odorants, and 

chemical cues were some of the 

factors identified to influence 

oviposition.7

 Additional studies 

have indicated that gravid females 

of different species used different 

factors for acquisition and selection of oviposition sites. For 

example, Aedes albopictus 

Comparison of the Attractiveness of Organic 

Infusions to the Standard CDC Gravid 

Mosquito Trap 

CPT Lee P. McPhatter, MS, USA 

Cara H. Olsen, DrPH 

COL Mustapha Debboun, MS, USA 

ABSTRACT

Field experiments were conducted in southeastern Texas in 2008 to compare the attractiveness of selected gravid-trap 

infusions to ovipositing female mosquitoes. Comparisons were made among the following infusions: Bermuda grass, 

oak leaves, acacia leaves, rabbit chow (alfalfa pellets) and green algae. Experiments were conducted at 6 trap locations 

in Fort Sam Houston military reservation in San Antonio, Texas. Four (Bermuda grass, acacia leaves, oak leaves, and 

algae) of the 5 infusions were effective in collecting Culex quinquefasciatus, Cx nigripalpus, and Cx erraticus. 

However, Bermuda grass attracted the greatest numbers of the mosquito species. Aedes albopictus female mosquitoes 

were collected in moderate numbers during this study; however the infusions were not determined to be significantly 

different from one another in their attractiveness for this species. 

Figure 1. The CDC gravid trap configuration (with battery) used in the study. 
92 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

(Skuse) females exhibited a strong preference to 

oviposit in artificial containers such as tires. Organic 

matter dissolved in water has been found to attract 

different mosquito species.8 Aedes aegypti (L) females 

were attracted to horse manure infusions8

 and Aedes 

triseriatus (Say) females to tree-hole water.9

 Infusions 

made with materials such as hay,10 grass,11 alfalfa 

pellets, bulrush,12 manure,8

 and oak leaves were 

reported as attractive substrates for Culex species. The 

purpose of this study was to compare the relative 

attractiveness of several organic infusions to different 

mosquito species in southeastern Texas. 

MATERIALS AND METHODS

Study Site 

The field study was conducted at six locations on Fort 

Sam Houston military reservation (29.42°N, 98.49°W, 

195 m elevation) (Figure 2). Fort Sam Houston is a US 

Army base located in the northeast of San Antonio, 

Texas. The installation comprises approximately 3,000 

acres and has a population of 35,000 people. Mosquito 

activity was prevalent throughout the installation from 

July to October 2008. 

Trapping Techniques 

A total of 6 mosquito gravid trapping sites were 

selected for this study (Figure 2). Trap site one was 

placed on the west side of the 

installation near the military horse 

stables adjacent to an active creek 

that is surrounded by urban terrain 

(residential). Trap two was placed in 

the northeast side of the installation 

near a low lying drainage channel 

that divides two urban communities. 

Trap three was placed near a large 

creek located on the edge of a 

recreational picnic area. Trap four 

was placed next to a house in a 

populated neighborhood, which had 

no immediate proximity to water. 

Trap five was placed at the edge of 

the wood line near an active athletic 

complex. Trap six was placed next to 

a tree near the golf course. The 

location of each trap was not less 

than 900 m from other traps. The 

traps used for this study were CDC 

gravid traps (model 1712, John W. 

Hock Company, Gainesville, FL). 

The tray of each gravid trap was filled 1⁄4 full with a 

different infusion bait (rabbit chow, Bermuda grass, 

live oak leaf Quercus virginiana (Mill), acacia leaf 

Acacia schaffneri (Wats), and filamentous green 

algae). All infusions except the green algae were 

prepared using 227 g of substrate added to 4 L of tap 

water. Each mixture was placed in closed Rubbermaid 

(Newell Rubbermaid Inc, Atlanta, GA) plastic 

containers and left outside in the sun to incubate for 5 

days prior to each trap week. The algae was collected 

from fresh water ponds and was incubated at outdoor 

temperatures (27°C - 29°C) for 7 days prior to each 

trapping week. The green algae infusion consisted of 

133 g of wet algae mixed with 4 L of pond water. 

Trapping was conducted 3 days per week from 

September 3 to November 22, 2008. The trapping 

cycle was divided into 2 experiments. Experiment one 

was conducted at locations one, two, and three during 

the first 6 weeks and experiment two was conducted at 

locations four, five, and six during the last 6 weeks. 

Trapping sessions commenced at 8 AM on Wednesday 

and ended 8 AM on Saturday. After the completion of 

each trap week, each infusion was rotated to a different 

trap site to ensure each infusion was tested once at 

each trap location. All of the mosquitoes collected 

were counted and identified to species using the 

morphological keys by Darsie and Ward.13 

Comparison of the Attractiveness of Organic Infusions to the Standard CDC Gravid Mosquito Trap 

Figure. 2. Location of the study area (Fort Sam Houston, Texas) and the 6 

sampling locations of the mosquito gravid traps (Sep 3 to Nov 22, 2008). 
 July – September 2009 93

THE ARMY MEDICAL DEPARTMENT JOURNAL

Statistical Analysis 

All data were analyzed using Stata release 10 for 

Windows (StataCorp LP, College Station, TX). 

Collection data was converted using the logarithmic 

scale. Counts of zero were replaced with a value of 0.5 

before taking the natural log. Histograms and normal 

quantile plots of the log counts were examined and no 

substantial deviations from normality were observed. 

Log-transformed counts of female mosquitoes 

collected by gravid traps were analyzed by 2-way 

analysis of variance (ANOVA) for variation among 

the most significant infusions, after adjusting for 

species. Multiple comparisons among infusions were 

made using Tukey HSD (honest significant difference) 

test at a 95% confidence level. A 3-factor ANOVA 

was also conducted to determine if the different trap 

sites affected the species of mosquitoes and the 

different infusions. 

RESULTS

A total of 2,003 females of 14 species of mosquitoes in 

3 genera (Aedes, Culex, Orthopodomyia) were 

collected. The Table shows the mosquitoes that were 

attracted to the 5 different infusion types. The most 

common mosquitoes collected were Culex 

quinquefasciatus Say (35%), Cx erraticus Dyar and 

Knab (34%), Cx nigripalpus Theobald (20%), Cx 

interrogator Dyar and Knab (6%), and Aedes 

albopictus (3%). The average numbers of Ae 

albopictus and Cx interrogator collected were 

significantly lower than those for the other species. 

Most of the mosquitoes collected (51%) were from 

traps containing the Bermuda grass infusion. Based on 

Tukey’s multiple comparison procedure, traps baited 

with Bermuda grass (F=23.57, df=3, P<0.0010) had 

a significantly higher number of mosquitoes than the 

other infusion types tested. Following Bermuda grass 

(51%), oak leaves (18%), algae (15%), and acacia 

leaves (12%) attracted the bulk of the remaining 

mosquito population. However, these 3 infusion types 

were not significantly different from each other. Of the 

3 genera represented by the collected mosquitoes, 96% 

were Culex. Fifty-three percent of the collected Culex

species were attracted to traps containing Bermuda 

grass infusion. Rabbit chow infusion collected the least 

number of Culex species (4%). The genus Aedes

represented 4% of the total mosquitoes collected. Most 

of the Aedes (39%) were collected by acacia leaf 

baited infusions. Traps baited with rabbit chow 

infusions attracted the least number of Aedes (3%). 

The total number of mosquitoes collected for each 

infusion by experiments one and two is presented in 

Figure 3. Experiment two had significantly lower 

numbers compared to experiment one. Bermuda grass 

infusion performance was still superior over all other 

infusions during this period. Averaging across species 

and sites, there was a significant main effect of 

infusion in both experiment one (P = 0.0017) and 

experiment two (P < 0.0001). In both experiments, the 

Bermuda grass infusions attracted the highest number 

of mosquitoes. In experiment one, the algae and oak 

infusions attracted nearly as many mosquitoes as the 

Bermuda grass infusion, and the differences among 

these infusions were not statistically significant. The 

Bermuda grass infusion attracted significantly more 

mosquitoes than the acacia infusion in experiment one 

(P = 0.0025). In experiment two, significantly more 

mosquitoes were collected using the Bermuda grass 

infusion than any of the other infusions (P<0.001 for 

all comparisons). There was a significant site to 

infusion interaction in both experiment one (P =

0.0070) and experiment two (P = 0.0074), indicating 

that the differences among infusions varied by site. 

Overall, in all sites, except site two (experiment one), 

the Bermuda grass infusion attracted the highest 

number of mosquitoes. After adjusting for multiple 

comparisons, the differences between Bermuda grass 

Distribution by species of female mosquitoes collected by 

5 different infusion types during 2 trapping occasions in 

2008 (Sep 3 to Oct 11, Oct 15 to Nov 22) at Fort Sam 

Houston Military Reservation, Texas. 

Mosquito Species Infusion Type 

Bermuda Rabbit 

Chow Acacia Oak Algae 

Aedes aegypti 0 0 0 1 1 

Aedes albopictus 6 2 26 8 17 

Aedes triseriatus 0 0 0 2 0 

Aedes vexans 3 0 2 2 0 

Aedes zoosophus 1 0 0 0 0 

Aedes atropalpus 0 0 0 1 0 

Culex coronator 0 0 0 0 1 

Culex erraticus 450 26 60 79 64 

Culex interrogator 38 3 19 42 24 

Culex nigripalpus 198 24 43 63 76 

Culex quinquefasciatus 336 30 84 154 107 

Culex salinarius 0 0 4 0 3 

Culex tarsalis 0 0 0 2 0 

Orthopodmyia alba 0 0 0 0 1 

Total 1,032 85 238 354 294 
94 http://www.cs.amedd.army.mil/dasqaDocuments.aspx?type=1

and the other infusions were not statistically significant in sites one, two and three, but were significant (P

< 0.05) in sites four, five, and six (experiment two). 

Significant species to infusion interaction was 

observed in experiment two (P = 0.0024) but not in 

experiment one (P = 0.0712). This finding suggests 

that the relative effectiveness of the 4 

(Bermuda grass, oak leaves, acacia 

leaves, and algae) infusions was 

similar for all species in experiment 

one. In experiment two, after adjusting for multiple comparisons, there 

was no significant difference among 

infusion with respect to the number 

of Ae albopictus mosquitoes 

attracted. The Bermuda grass infusion 

attracted significantly more of both 

Cx erraticus and Cx nigripalpus than 

any other infusion, and attracted 

significantly more Cx quinquefasciatus than any infusion except acacia. 

DISCUSSION

Our data supports reports from 

several other studies that Bermuda 

grass infusion is highly attractive to 

Cx quinquefasciatus.

2,7,14,15 The 

Bermuda grass infusion baited trap 

collected 2 to 3 times more Cx

quinquefasciatus than all of the other 

infusions. Over half of the Culex

species collected in this study were in 

the traps that contained Bermuda 

grass infusion. The Bermuda grass 

infusion also attracted more Cx 

nigripalpus and Cx erraticus

mosquitoes than the other infusions. 

In fact, the numbers of Cx erraticus

collected with the Bermuda grass 

infusion were higher than the 

numbers of Cx quinquefasciatus. 

Burkett-Cadena and Mullen1 6

reported, in contrast to our results, 

that small numbers of Cx erraticus

were collected with gravid trap, and 

inferred that the gravid trap was not a 

useful tool in collecting females of 

Cx erraticus. In their study, they used 

oak leaves, pine straw, red (dyed) 

hardwood mulch, and composted 

manure to make 4 different infusions. Similar to their 

results, the traps baited with oak leaf infusion used in 

our study collected modest numbers of Cx erraticus 

(Figure 3). Therefore, it is likely that the low numbers 

of Cx erraticus collected in their study were impacted 

by the selection of infusions. The infusions selected 

Comparison of the Attractiveness of Organic Infusions to the Standard CDC Gravid Mosquito Trap 

Figure 3. Total numbers of Cx erraticus (a, b), Cx nigripalpus (c, d), Cx 

quinquefasciatus (e, f), and Ae albopictus (g, h) female mosquitoes 

collected by gravid traps with 4 different experimental infusions during 2 

trapping occasions: experiment one (Exp 1), Sep 3-Oct 11, 2008, and 

experiment two (Exp 2), Oct 15-Nov 22, 2008. 
July – September 2009 95

THE ARMY MEDICAL DEPARTMENT JOURNAL

for this study collected low numbers of Cx coronator

Bayer, Cx interrogator, Cx salinarius Coq. and Cx 

tarsalis Coquillett. With the exception of Cx

interrogator, they all were commonly collected (in the 

vicinity of the trap sites) in moderate numbers using 

the CDC standard light trap. It is possible that the age 

of the infusions impacted the collection of these 

common species. Isoe et al17 showed that Cx tarsalis 

and Cx quinquefasciatus attraction to Bermuda grass 

infusion was affected by age. They suggested that Cx 

tarsalis preferred relatively clean water for oviposition 

sites, whereas Cx quinquefasciatus preferred more 

polluted and turbid waters. The oak, algae, and acacia 

infusions used in this study were the least turbid. Culex 

coronator, Cx salinarius and Cx tarsalis were only 

attracted to these 3 infusions. After the Bermuda grass 

infusion, the oak leaf infusion attracted the second 

highest number of mosquitoes. In addition, the oak leaf 

infusion attracted 11 different mosquito species, while 

the Bermuda grass infusion attracted 7 species. 

Aedes albopictus was the only non-Culex mosquito

species collected by all 5 infusions used in this study. 

Overall, the numbers of Ae albopictus were low. 

However, their presence in the traps was common 

when compared with other Aedes species collected 

during this study. Excluding the algae infusion, the 

acacia infusion attracted 2 to 3 times more Ae 

albopictus than the other 3 infusions. However, the 

mean number was low. This lack of preference for a 

certain type of infusion is most likely due to their 

oviposition behavior. Mogi and Mokry18 referred to 

this behavior as skip oviposition. This occurs when 

female mosquitoes lay their eggs in several containers 

as opposed to laying their entire clutch in one 

container.19-21

The rabbit chow infusion yielded the lowest results 

from all the infusions. Similar reports of low responses 

to this infusion were reported by Isoe and Millar,15

Allan et al,14 and Jackson et al.22 In contrast to the 

other infusions, the rabbit chow infusion attracted 

significant numbers of flies (Calliphoridae). It is 

possible that the attraction of these flies was 

antagonistic to the trapping efficiency. The high levels 

of calliphorid flies around the traps created an intense 

situation in which the flies were fighting over the 

oviposition media. The trapping location that had the 

most significant issues with the flies was the one at the 

horse stables. Ironically, the rabbit chow attracted the 

least amount of mosquitoes at this location. 

In conclusion, Bermuda grass, acacia leaves, oak 

leaves, and algae infusions were effective as gravid 

trap baits for the attraction of Cx quinquefasciatus, Cx 

nigripalpus, and Cx erraticus. Additional studies 

focusing on the concentration of organic material and 

age of these infusions might show how to increase 

attraction rates of low density gravid trap species such 

as Ae albopictus and Cx tarsalis. 

ACKNOWLEDGEMENTS

We thank Prabir Chakraborty and Annette Mitchell for 

assistance in data analysis; Samuel Melendez, Irene 

Brown, Jacob Caraway, Angela Moore, and Diego 

Cano for field assistance; and Dan Strickman, Dan 

Kline, and Sandy Allan for their constructive comments 

and review of this manuscript. 

REFERENCES

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18. Mogi M, Mokry J. Distribution of Wyeomyia smithii

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AUTHORS

CPT McPhatter is Chief, Entomology Section, 

Department of Preventive Medicine, Brooke Army 

Medical Center, Fort Sam Houston, Texas. 

Dr Olsen is an Assistant Professor and Biostatistics 

Consultant in the Department of Preventive Medicine 

and Biometrics, Uniformed Services University of the 

Health Sciences, Bethesda, Maryland. 

COL Debboun is Director, Center for Health Education 

and Training, Academy of Health Sciences, US Army 

Medical Department Center & School, Fort Sam 

Houston, Texas. 

Comparison of the Attractiveness of Organic Infusions to the Standard CDC Gravid Mosquito Trap 

The Brooke Army 

Medical Center 

Uniformed Services University 

of the Health Sciences 

US Army Medical Department 

Center & School 
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