F U N D E D B Y U N D E R W R I T E R S AT L LOY D ' S , LO N D O N

APRIL 2016
Volume 25, Number 2

C O M M E N TA RY
IN THIS ISSUE
Commentary
International
Fourth Quarter2015  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 2EquineHerpesvirus  .  .  .  .  .  .  .  .  . 3National
Eastern Equine
Encephalitis .  .  .  .  .  .  .  .  . 3Syndromic
Surveillance .  .  .  .  .  .  .  .  . 4KentuckyKentuckyMosquitoes .  .  .  .  .  .  .  .  .  . 5You can’t believe everything you read, hear,or see.
Critical thinking is more important than ever,and I am continually amazed at the erroneous,misleading information to which we are exposed.
Always be wary of grandiose statements.
When Zika virus made the headlines in the
U.S., an “expert” on the national news stated “allwe have to do is kill the mosquitoes” to keep thedisease out of North America. And, he wasn’t making a joke.
One only has to look online at news reports
from late 1999 to find reassurances by publichealth officials that citizens didn’t need to worry
about the “new” West Nile virus returning in summer 2000 due to a full-scale campaign to spray
insecticides to kill mosquitoes. Look how well thatworked.
Mosquito-borne illnesses are difficult to control
because of the resilience and breeding efficiency ofthese insects. While there is no evidence that Zika
virus affects horses, other mosquito-transmitted
viruses such as WNV affect hundreds of horses
each year, despite available effective vaccines andannual reminders to horse owners about mosquito
control.
More grandiosity …
A national Sunday newsmagazine supplement
recently published an article stating that Good
Samaritan laws in every state protect people against
liability if they try cardiopulmonary resuscitation(CPR) on a person. The article also went on tostate that “you can’t be sued for trying [CPR].”
Both statements are completely wrong. Kentuckylaw (for example) does not protect everyone who
attempts CPR, and lawyers can sue for anything.
Learn how to perform CPR and know the laws
and liability protections in your state.
Who is a veterinary “specialist?”

I’ve seen several websites that tout the sponsoring veterinarian as a “specialist in sport horse
medicine” (for example). According to the American Veterinary Medical Association, a veterinary
specialist is a veterinarian “who has completed
additional training in a specific area of veterinary
medicine and passed an examination that evaluates
their knowledge and skills….” Considering the
rigorous training involved in obtaining “Diplomate” status, veterinary specialists almost always
include this in their educational background, suchas Diplomate, ACVS for veterinary surgeons, or
Dipl. ABVP (Equine) for American Board of
Veterinary Practitioners in Equine Practice. The
term “specialist” means additional education,
training, rigorous examination, and continuing
education. Many exceptionally skilled veterinarians have practices that involve primarily sport
horses. However, if they are not board certified,they are not “specialists.”
Let’s talk about “certifications.” Business cards
or websites for some people boast an impressive
list of certifications and letters after the individuals’
names. But, are they legitimate, meaningful indications of advanced, specialized education or experience? Or simply that the person paid money for aweekend’s worth of training that barely scratched
the surface, but resulted in being presented witha “certificate?” Investigate the organization online
to determine what training, testing, and “certification” was actually involved. You may be surprised.
Critically evaluate what you read, see, and hear.
Ask questions. Assume nothing, and if it is toogood to be true, it usually is (but find out anyway).
CONTACT:
Dr. Roberta Dwyer
rmdwyer@uky.edu(859) 218-1122
Department of Animal and Food Sciences
University of Kentucky, Lexington, Kentucky

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I N T E R N AT I O N A L

Fourth Quarter 2015

T

Equine Disease Quarterly
Editors

Alan LoynachanPeter Timoney

Staff

Diane Furry
Tawana Brown
Dennis Duross

Correspondence should be
addressed to the editors,
Department of Veterinary
Science, Maxwell H. Gluck
Equine Research Center,
University of Kentucky,
Lexington, Kentucky USA,40546-0099
Telephone (859) 257-4757
Fax (859) 257-8542
Internet address:
http://www.ca.uky.edu/
gluck/index.htm
Material published in the
Quarterly is not subject tocopyright. Permission istherefore granted toreproduce articles, althoughacknowledgment of thesource and author is requested.
The University of Kentucky
is an Equal Opportunity
Organization.

Printed on recycled paper

he International Collating Centre, Newmarket, United Kingdom; Equine Disease
Communication Center, USEF, Lexington, KY,
USA; and other sources reported the following
disease outbreaks.
Vesicular stomatitis continued to spread during
the period under review, with 134 virus-confirmed
premises and an additional 485 premises on which
the disease was clinically diagnosed but not virologically confirmed. All confirmed outbreaks havebeen caused by the New Jersey serotype. New outbreaks were diagnosed in each of the eight affectedstates: Arizona, Colorado, Nebraska, New Mexico,South Dakota, Texas, Utah, and Wyoming; thegreatest increase of cases were detected in Colorado
and Wyoming.
Influenza was reported by the UK and the USA.
Isolated cases were diagnosed on four premises in
the UK, of which the majority were in unvaccinated horses. A fifth premises in the UK involved
an outbreak of five cases, all Andalusians. Influenza
was considered endemic in the USA with diseaseconfirmed in Florida, Kentucky, Michigan, Ohio,
Oregon, and Texas.
Equine herpesvirus (EHV) 1- and 4-relateddiseases were recorded in France, Germany, Ireland, Japan, the UK, and the USA. Respiratory
disease caused by EHV-1 was confirmed in France(a single outbreak), Ireland (seven cases), and theUSA (activity recorded in several states). EHV-1
abortion was reported by Japan (eight cases invaccinated mares on seven premises), the UK(two cases in Thoroughbreds), and the USA (threecases). Two outbreaks of equine herpesvirus 1
myeloencephalopathy were recorded in the USA,
both in Pennsylvania—one at a racetrack and theother at a riding stable; the latter resulted in threedeaths. France and Germany reported outbreaksof EHV-4 respiratory disease. Nineteen outbreaks
were confirmed in France, most in French Trotters,
and single cases were confirmed on three premisesin Germany. A small number of cases of infection
with EHV-2 and/or -5 were diagnosed in the USA.

A single case of equine coital exanthema (EHV3) was confirmed in the USA.
Strangles was reported by Australia (24 outbreaks involving 48 cases), France (11 outbreaks),
Germany (single cases on three premises), Ireland(20 cases involving three provinces), Switzerland(one outbreak), United Arab Emirates (eight caseson two premises), and the USA (disease is endemic;
17 outbreaks in seven states).
Canada confirmed 13 cases of equine infectious anemia. These occurred on seven premises
located in British Columbia (2), Alberta (3), andSaskatchewan (2), both of which were linked
epidemiologically.
Equine piroplasmosis was reported by France(disease endemic) and Switzerland (a case of dual
infection with Babesia caballi and Theileria equi in
an imported animal).
The USA confirmed outbreaks of salmonellosis, some associated with Group B Salmonella
spp and others with Group C1 Salmonella spp.
Multiple cases of proliferative enteropathy causedby Lawsonia intracellularis were diagnosed in several states in the USA. A single case of clostridial
enteritis associated with Clostridium perfringens
type A toxin was confirmed in Kentucky.
France and the USA reported cases of leptospiralabortion. A single case was diagnosed in France
and 12 cases were diagnosed in Kentucky, USA.
A total of 23 cases of Eastern equine encephalomyelitis were confirmed in the USA, with thegreatest numbers recorded in Florida, Texas, andGeorgia. France and the USA reported outbreaksof West Nile encephalitis. A total of 45 cases
involving 34 outbreaks were diagnosed in France.
The USA recorded 160 cases, most of which wereconfirmed in Texas, Washington, Missouri, andCalifornia.
A single case of Hendra virus infection wasreported in Queensland, Australia during the third
quarter of 2015.

Equine Herpesvirus Associated Ocular DiseaseHerpesviruses are widely disseminated in natureand renowned in equine medicine for inducing respiratory, reproductive and neurological diseases. The most important biological characteristicof these viruses is their ability to remain latent.
Reactivation of latent virus can occur and resultin virus replication, shedding, and disease. While
the precise mechanisms of reactivation are unclear,
it is believed to be triggered by stressors such us
exercise, pregnancy, changes in management,
or concurrent disease. The equine herpesviruses(EHV) that have been implicated in ocular disease,
to date, are EHV-2 and EHV-1.
Equine herpesvirus-2 has been proposed as theputative and primary cause of viral keratitis in thehorse. Nevertheless, the virus has been inconsistently found in corneal and conjunctival scrapesof affected animals and can be frequently foundin asymptomatic horses. In addition, co-infection
with EHV-5 is common, not only in ocular disease
but also in respiratory cases, making it difficult toattribute causation of disease to a particular virus.
Evidence for EHV-2 induced ocular disease isbased on several reports of successful virus isolation from outbreaks and single cases of keratoconjunctivitis, conjunctivitis, or corneal edemain foals; however, despite such reports its role asa pathogen is still debatable. In contrast to otherviral etiologies, herpetic keratitis is not usually accompanied by systemic disease. Clinically, horses
have sporadic, multifocal, subepithelial, punctate
opacities that stain variably with fluorescein but
commonly with Rose Bengal. Superficial vascularization is associated with the opacities, and horses
exhibit persistent to moderate ocular pain that canlead to reflex uveitis. Continuation of the epithelial
lesions into the corneal stroma is possible as a consequence of viral antigens extending from epithelial

lesions or from viral replication in stromal cells.
Evidence of virus in corneal and/or conjunctival
scrapes may be challenging as viral inclusion bodies, within injured epithelium, are rarely seen at
the time of sampling. PCR techniques are morereliable in detecting viral DNA; however, the presence of herpetic DNA is not diagnostic of itself.
Corneal lesions in the horse seem to resolve quickly
after antiviral treatment or heal spontaneously,
which is in contrast to human and feline induced
herpesviral ocular disease. Treatment with topical antivirals is often recommended if there is astrong suspicion of herpesvirus involvement andsubsequent PCR confirmation. Topical ganciclovir
gel in combination with topical corticosteroids has
been recommended as the treatment of choice.
Chorioretinal lesions have been described following experimental EHV-1 infection in several
studies. Focal and multifocal lesions, either unilateral or bilateral and located in the non-tapetal
fundus as donut-shaped depigmented regions withpigmented centers were observed several weeks
after infection. This type of lesion is most likely
caused by ischemic injury of the chorioretina withdeath of the overlying retinal pigment epithelium.
These findings do not seem to impact vision, but
are a main concern during pre-purchase examination, particularly if previous history is unknown.
Although there is sufficient evidence to support
the role of EHV-1 in chorioretinitis, the implication of any member of the equine herpesvirus
family in corneal disease remains controversial.
CONTACT:
Sonia Gonzalez-Medina
Ldo Vet, CertAVP(EM), MRCVS
44-2032148025 (Ext. 4025)
Royal Veterinary College
London, United Kingdom

N AT I O N A L

Eastern Equine EncephalitisE

astern equine encephalitis (EEE) is an annual disease threat to horses in the Gulf andAtlantic Coast states and the Great Lakes region.
Occasional cases have been reported as far northas Canada and from some inland states such as
Iowa, Arkansas, and Kentucky. The causative

agent, Eastern equine encephalitis virus (EEEV),
is silently maintained by a songbird/mosquito
transmission cycle. Infected ornithophilic (“birdloving”) Culiseta melanura mosquitoes living near
freshwater hardwood marshes transmit EEEV tonestling songbirds; subsequently, new hatches of3

4mosquitoes acquire the virus by biting the infectedbirds. The ecological range of C. melanura limits
the westward extent of EEEV infections.
While songbirds do not become ill from theinfection, transmission of EEEV to other birds,
horses, or humans can cause disease. Transmissionof EEEV to mammalian hosts involves mosquito
vectors with broader feeding habits such as Aedes
spp. In temperate regions, EEE cases in horses
have a summer/fall seasonality with few cases occurring in cool months and complete cessation in
the winter. In subtropical regions such as Florida,
there is year-round risk of EEE transmission witha peak in the summer months. Horses and humans
are not part of natural maintenance of EEEV asthey do not produce sufficient viremia to allow
transmission to mosquitoes. They are considereddead-end hosts.
Once an equid is infected by a mosquito bite,clinical signs can appear in 5-15 days. EEEV infections in horses, mules, or donkeys are typicallysevere and up to 90% of ill horses do not survive
the infection. Clinical signs range from fever and/or dull mentation (thus the old name “sleeping
sickness”) to blindness, loss of coordination, headpressing, inability to rise, seizures, and death. Fevers in the acute clinical phase may be very high(e.g. 105-106°F).
Clinical signs associated with EEE can overlap those observed with West Nile encephalitis
or equine herpesvirus 1 myeloencephalopathy(EHM), thus laboratory confirmation of EEE
is critical. A combination of clinical signs, appropriate environment, and lack of appropriate
vaccination history along with a positive EEE
IgM Capture ELISA serologic test confers a strong
presumptive diagnosis of EEE. For horses that dieor are euthanized, PCR identification of EEEV
nucleic acid in the brain, isolation of EEEV frombrain tissue, or specific staining of fixed brain tissue
confirms the diagnosis.

Despite widely available and effective USDA licensed vaccines, each year horses in North America
succumb to EEE. The American Association of
Equine Practitioners considers EEE vaccination
among the core vaccines and has specific risk-based
guidelines established by age and residence of thehorse. As the vaccines are killed virus products,
adherence to a 2- or 3-dose primary series is criticalto engender protective immunity in foals.
In 2014, a total of 136 equine cases of EEE
were reported from 15 states. The USDA Animal
and Plant Health Inspection Service (APHIS)
Veterinary Services (VS) branch collaborates with
the U.S. Centers for Disease Control and Prevention (CDC) and state veterinary and public healthofficials to facilitate communication about EEE
disease cases in horses and confirm equine casesin each state. CDC collects EEE case information
using its ArboNET reporting system, an electronic
surveillance and reporting system used to track
and report arboviral activity, including EEE, inhumans and animals. During the transmission
season, VS disseminates the equine arbovirus caseinformation to state animal health officials forconfirmation and posts the number of confirmed
cases to the USDA equine infectious anemia disease information website (http://www.aphis.usda.
gov/animal-health/equine-health).
Contact:
Eileen N. Ostlund
eileen.n.ostlund@aphis.usda.gov(515) 337-7551
National Veterinary Services Laboratories
STAS/VS/APHIS/USDA
Ames, Iowa
andRebecca Jones
rebecca.d.jones@aphis.usda.gov(970) 494-7196
Surveillance Design and Analysis
Center for Epidemiology and Animal Health
STAS/VS/APHIS/USDA
Fort Collins, CO

Syndromic Surveillance and Spatial Epidemiology

Syndromic surveillance is the use of existing
health data to provide real-time analysis andfeedback to epidemiologists in the investigationof disease outbreaks. Spatial epidemiology is asubfield of health geography that allows the studyof the distribution of disease and health outcomes.
Utilizing both approaches allows for the mappingof disease geographically for correlation studies
and detection of disease clusters (e.g. unusuallyhigh incidence of a particular disease or syndrome

occurring in close proximity in terms of both
geography and time). These methods are used to
improve early detection of disease outbreaks or biologic terrorism in human and veterinary medicine.
Over the last ten years, the University of
Kentucky Veterinary Diagnostic Laboratory (UK
VDL) has established an epidemiology section andimplemented multiple surveillance, reporting, andalerting systems to monitor animal health. Utilizing a custom syndromic event simulator, the UK

5

VDL uses test results and syndromic events (e.g.
abortions, cases of respiratory disease, number ofdeaths) to monitor the health of Kentucky’s animal population to predict and model early disease
outbreaks. This simulator monitors each day’s
syndromic events combined with the previous 29
days of data to create a “moving” 30-day window.
These data are then compared with historical data
during the same time frame over the last 5 years(e.g. background rate of disease bounded by timeand space). This mathematical approach allows us
to statistically calculate if increased levels of specific
events are occurring. Any data set that indicatesan increased level of disease is then geocoded into
map coordinates to alert UK VDL epidemiologists
of a potential outbreak. Any indication by the
program of a possible outbreak is then investigatedand verified by the epidemiology section. Upon
verification of an increase in sickness or deaths,
the UK VDL then alerts Kentucky veterinarians
and officials.
Aside from surveillance, the UK VDL utilizes
necropsy and test data to generate a Kentucky
animal health map that is published on our website
at vdl.uky.edu. This map allows users to click on
any county in Kentucky and see what diseases havebeen diagnosed during the last month. If a county

lacks information, then it means no cases have been
diagnosed in that county at the UK VDL. The map
does not identify owners or the specific location inwhich the disease was diagnosed, only the countyof the submitting veterinarian. This allows us tomaintain client confidentiality while at the sametime providing users with a method of determining the diseases in their area, so that biosecurity
measures can be implemented or increased.
While syndromic surveillance and spatial methods of epidemiology are always evolving and beingrefined, it should be noted that there are somechallenges to these methods. Spatial epidemiology
is almost always based on data analysis. Because ofthis, data collection must be routine and accurate.
Syndromic surveillance currently used by the UK
VDL depends upon the data collected solely atthis laboratory; the inclusion of field data fromveterinarians or other laboratories would further
enhance this important surveillance technique.
CONTACT:
Dr. Jacqueline Smith
jsmit8@uky.edu(859) 257-7559
University of Kentucky
Veterinary Diagnostic Laboratory
Lexington, Kentucky

KENTUCKY

Kentucky Mosquitoes

K

entucky is home to more than 50 species ofmosquitoes with a range of breeding sites andsurvival strategies. Some thrive when above-normal
rainfall creates temporary ground pools; others
develop in small accumulations of stagnant water
during dry periods.
Many of our mosquito species spend the winteras freeze-resistant eggs that can survive prolonged
harsh conditions. A few, such as the house mosquito (Culex pipiens), spend the winter as adults
in protected places. They are vulnerable to severe
cold, but like most insects have the reproductive
capacity to build numbers by late summer, even
if winter mortality is high.
Several mosquito species feed on horses withvaried effects that range from adverse skin reactions to disease transmission. Proteins injected inmosquito saliva can produce irritating bites thatcan cause skin reactions in sensitive individuals.

The inland floodwater mosquito (Aedes vexans) isa widespread pest that can develop in any groundpool that lasts 10 to 14 days. It causes a significant
and chronic problem in some parts of the stateand can give rise to several generations each year.
Females rest on vegetation and shaded grass during
the day and bite viciously at dusk and after dark.
They can live for several weeks and may travel
several miles during that time. Feeding by large
numbers of these mosquitoes at night can produce
dermatitis and itching in horses on pasture.
Feeding habits, the ability to sustain and passviruses, and host preferences for blood meals affect the potential for some mosquito species toserve as disease vectors. Some mosquito species
feed primarily on mammals, others on birds, andsome are opportunistic. Ornithophilic mosquitoes (Culex pipiens group) can maintain an avian
cycle of Eastern equine encephalitis, Saint LouisEquine Disease Quarterly Newsletter
Department of Veterinary Science
Maxwell H. Gluck Equine Research Center
University of Kentucky
Lexington, Kentucky 40546-0099
Address Service Requested

encephalitis, and West Nile viruses among various
bird species. Some of these mosquitoes serve as
bridge vectors for viruses when they initially feed
on infected birds and then take blood meals frommammals.
The rapid spread of West Nile virus across the
U.S. required quick action to manage vector mosquitoes in an effort to protect equines and humans.
Mosquito management takes a multi-pronged
approach including source reduction, screens, andprotection using repellents and insecticides. Fortunately, a combination of factors—selection for
immunity in the avian population, development
and registration of a vaccine, and mosquito management—were instrumental in quickly reducing
the annual number of equine cases from a high of
513 in 2002 to 8 in 2004. A few cases have been
diagnosed each year since 2004, but vaccination
has played a significant role in keeping the inci-

dence low. A sound prevention program, which
includes mosquito management is an importantpart of keeping the disease in check.
The Zika virus and yellow fever mosquito (Aedes aegypti) have captured the headlines in recent
weeks. The yellow fever mosquito is not a part of
Kentucky’s mosquito population, and there is no
indication that Zika virus affects equines. However,there are human health concerns. The larvae of
this mosquito can develop in small accumulationsof water (as little as 1/4 inch deep) in artificial or
natural containers. It is an aggressive day biter thatis most active in early morning and late afternoon.
Usually, it moves only 100 to 300 yards from its
breeding site, so breeding-site reduction can be
an important aspect of managing this species.
Repellents containing DEET are very effective at
protecting people from being bitten in late August,when this mosquito is most abundant.
Contact:
Dr. Lee Townsend
Lee.Townsend@uky.edu(859) 257-7455
Department of Entomology
University of Kentucky
Lexington, Kentucky