HETA 93-1121-2530 NIOSH INVESTIGATORS:

SEPTEMBER 1995 Ann M. Krake, M.S.

THE STATE OF NORTH DAKOTA Catherine L. Connon, M.N.

DEPARTMENT OF HEALTH 

AND CONSOLIDATED LABORATORIES USDA INVESTIGATOR:

BISMARCK, NORTH DAKOTA Thomas M. Gomez, D.V.M., M.S.

I. SUMMARY

From September 27 through October 2, 1993, investigators from the National Institute for

Occupational Safety and Health (NIOSH) and the United States Department of

Agriculture, Animal and Plant Health Inspection Service (USDA/APHIS), conducted a

health hazard evaluation (HHE) in the Sheyenne River valley of southeastern North

Dakota. The evaluation was in response to a request from the North Dakota State

Department of Health and Consolidated Laboratories, Division of Disease Control, Office

of the State Epidemiologist. The purpose of the evaluation was to investigate the potential

occupational transmission of anthrax among livestock producers during an anthrax

outbreak, or epizootic.

Because of severe flooding, approximately 75% of the state of North Dakota was

designated a federal disaster area in August 1993, including Barnes, 

La Moure, and Ransom Counties. Eight cases of confirmed livestock anthrax were

reported from seven production facilities located within those counties, which are situated

in and around the Sheyenne River valley. Affected livestock included beef and dairy

cattle, and swine. Prior to this outbreak there had not been a confirmed case of livestock

anthrax in this region for approximately 11 years.

The investigators visited 14 livestock production facilities in the Sheyenne River valley

region and conducted 18 interviews, including seven affected producers, seven unaffected

producers, and four veterinarians. Blood samples were collected from 2 producers with

infected livestock and 2 veterinarians with exposure to infected animals to determine

anthrax antibody titer, and environmental samples of soil, water, and feed were collected

in an attempt to identify any remaining potential sources of infection.

Although the state health department did not receive any confirmed reports of human

anthrax infection during the epizootic, producers and family members from three of the

seven affected farms received antibiotic therapy because of direct exposure to known or

suspect anthrax-infected livestock and/or because they experienced respiratory or other

illness potentially associated with anthrax infection. Although asymptomatic, two

veterinarians and a laboratory technician were also treated with antibiotics because of

direct contact with infected livestock. Four individuals were tested for serum antibody

titers to the anthrax organism; results were negative. Five of the 13 bulk samples of soil,

water, bedding, and feed collected were culture positive for anthrax. Interviews with

affected producers revealed that inconsistent and potentially hazardous work practices

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports
were fairly common among them. The investigators determined that producers overall had

very limited knowledge regarding the handling and disposal of anthrax-infected livestock

and carcasses, and that there was little or no communication between affected and

unaffected producers and their veterinarians concerning anthrax. All of these factors

contributed to increases in occupational exposure risks.

Evaluation of the state's surveillance and information dissemination techniques regarding

health issues indicated that test results and quarantines were shared between the diagnostic

laboratory, state veterinarian's office, and affected producers in a timely manner; however,

public and especially community awareness of anthrax and its effects was at best delayed,

and improvements here are necessary.

A higher than usual reported prevalence of livestock anthrax may have been related to the

flooding of the Sheyenne River and grazing pastures in the surrounding valley in southeastern

North Dakota. Environmental samples indicated that the anthrax organism was present and

viable at two of the affected animal production facilities at the time of this investigation. No

cases of human anthrax infection were identified. The state surveillance and notification

system for animal health issues was observed to be timely and efficient for the affected

producers; however, state notification efforts could be improved in the area of public

outreach.

KEYWORDS: SIC 0291 (Agricultural production—general farms, primarily livestock

and animal specialties), anthrax, zoonoses, epizootic, B. anthracis, farmer, producer,

veterinarian, livestock, beef, dairy, swine, flooding, agriculture.
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II. INTRODUCTION

On September 17, 1993, NIOSH received a request from the North Dakota State

Department of Health and Consolidated Laboratories, Division of Disease Control, Office

of the State Epidemiologist, to conduct an HHE in the Sheyenne River valley of

southeastern North Dakota where an anthrax epizootic was reported during August and

September 1993. In response to this request, NIOSH investigators, including an

occupational health nurse and an industrial hygienist, and a veterinary epidemiologist from

USDA/APHIS, conducted an evaluation of the epizootic from September 27 through 

October 2, 1993. Cooperation and assistance were provided by state and federal public

and animal health department officials and an agricultural health nurse working with the

NIOSH Occupational Health Nurses in Agricultural Communities (OHNAC) program. 

This report provides details of the anthrax epizootic investigation, including the medical

and environmental assessments and recommendations for reducing occupational exposure

to the anthrax organism.

The investigators met first with state health department officials, the state veterinarian, and

a representative of the North Dakota office of the USDA/APHIS in Bismarck, North

Dakota. A second opening conference was held in Valley City, North Dakota, with Barnes

County Health Department officials and Barnes County Cooperative Extension Service

representatives. Also included were two staff veterinarians from the North Dakota State

University (NDSU) Veterinary Diagnostic Laboratory in Fargo, North Dakota. 

Discussions at each opening conference focused on the investigators' plans to address the

state's request. It was decided that the focus of the investigation would be 1) to obtain a

detailed description of the epizootic that would include personal interviews of producers

with anthrax-affected (those with livestock that had culture-positive anthrax infection) and

unaffected livestock and their veterinarians; 2) to collect medical and environmental

samples; 3) to evaluate the efficacy of the current NIOSH OHNAC surveillance system; 4)

to determine methods for decreasing occupational exposure to anthrax; and 5) to evaluate

the need for a more extensive investigation. The investigation concluded with a closing

conference held in Bismarck, North Dakota, on October 2, 1993, with the North Dakota

State Department of Health and Consolidated Laboratories State Epidemiologist.
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III. BACKGROUND

During the 1993 summer, much of the midwestern region of the United States experienced

severe and prolonged flooding. In North Dakota, by late August 1993, 39 of the 52

counties (approximately 75% of the state) were designated federal disaster areas. Counties

in the northeast, central, and southeastern regions of the state were most affected,

including three within the Sheyenne River valley—Barnes, La Moure, and Ransom. The

statewide precipitation average for July 1993, was 7.9 inches, which is 5.4 inches (320%)

above normal; during the same month, Barnes County alone reported 8.7 inches of rain

(Figure 1).

The state of North Dakota historically averages one or two diagnosed cases of animal

anthrax annually, and these typically occur in the drier western section of the state. On

August 9, 1993, a blood specimen obtained from a heifer carcass was submitted for culture

to the NDSU Veterinary Diagnostic Laboratory. This case was the state's first confirmed

anthrax death for 1993; the cow was from near Adams County, which is located in the

southwest section of North Dakota (Figure 2). (Because this case appeared to be isolated,

and because several similar livestock anthrax deaths have been reported from the Adams

County area in years past, it was not considered part of the epizootic).

On August 16, 1993, a blood sample submitted to the NDSU laboratory by a veterinarian

practicing in the Sheyenne River valley revealed that anthrax was the cause of death of a

dairy heifer in Barnes County. From August 17 to September 16, 1993, the North Dakota

State Veterinarian received laboratory confirmation of seven additional livestock deaths

found to be directly attributable to anthrax infection. The cases originated from seven

different production facilities within and around the Sheyenne River valley (Figure 2), and

included beef cattle, dairy cattle, and swine (Table I).

The North Dakota State Department of Health received no reports of human anthrax

infection during this time period. However, one livestock producer with blackened sores

on his arm and who described having severe systemic illness was seen by a physician who

prescribed penicillin. In addition, several other farmers and their family members were

reportedly treated with antibiotics by a physician as a result of respiratory symptoms they

had experienced during the epizootic.
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Anthrax Epidemiology

Anthrax, which can infect both animals and humans, is caused by an aerobic sporeforming bacterium, Bacillus anthracis (B. anthracis). Retained as spores within soil, B.

anthracis can remain viable for decades until favorable conditions permit dispersion and

germination. Plains and grasslands that experience cyclic periods of drought and flood are

usually where spores are found, and anthrax can be dispersed when these environmental

conditions are moderately severe.1

 Periods of drought may cause livestock to forage much

closer to the ground, and spores may be ingested as the soil is eaten. After flooding, the

concentration of spores caught in standing water increases when preexisting or transitory

ponds begin to evaporate. Transmission to swine, horses, and ruminants (cattle, sheep,

and goats) occurs primarily through the ingestion of soil-borne spores, and animals

pastured on these plains or grasslands are more likely to ingest an infective dose. Contact

with infected carcasses may initiate secondary transmission to predators or carrion-eating

birds, and insects, such as biting flies, can potentially transmit infection to other livestock. 

Ruminants appear to be the most susceptible to anthrax infection, while swine tend to be

more resistant; pigs may become infected after ingesting anthrax-infected carcasses, and

are more likely than other animals to suffer the effects of chronic anthrax infection.

The incubation period for anthrax is from one to seven days, and animals infected with the

anthrax organism manifest disease symptoms in one of three ways: (1) Apoplexy (cerebral

hemorrhage) is observed most often in ruminants and is characterized by sudden onset and

death; (2) Acute or subacute infections are observed in horses and some ruminants, mainly

cattle and sheep; infected animals may stumble, appear lethargic, and will usually develop

moderate to severe swelling of the chin and neck (sublingual) areas. Death usually occurs

two days to one week following infection, decomposition is rapid, and carcasses may

display a bloody discharge from orifices, edema, bloating, and incomplete rigor mortis;2

(3) Chronic anthrax infection occurs primarily in less susceptible species (such as swine),

is characterized by pharyngeal and lingual edema, and usually results in asphyxiation.

Risk of infection to humans is correlated with disease incidence in animals and can occur

through direct contact with infected animals and contaminated animal products or through

ingestion of undercooked contaminated meat.2 Approximately 80% of all reported human

anthrax infections in the United States have been industry-related, while the remainder

were from exposures in the agricultural community.3 No cases have been reported in the

United States (U.S.) since 1978.4

As might be expected, anthrax infection associated with agriculture is more common in

less industrialized nations. Non-agricultural workers who become infected with anthrax

are primarily those employed in industries which process hides, hair, wool, bone and bone

products. Veterinarians and agricultural workers who handle infected animals and

carcasses are also at increased risk of becoming infected.5
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Human anthrax infection can present in one of three clinical forms. Historically the most

commonly observed, cutaneous anthrax represented approximately 95% of all reported

cases in the U.S.5

 Cutaneous infection can result when open wounds or insect bites

become contaminated with anthrax spores; the spores, having located a favorable medium,

germinate and multiply and subsequently release an exotoxin. Within one to seven days, a

small, red papular skin lesion develops; the lesion gradually becomes blue-black in color

as it develops into a fluid-filled vesicle which eventually ruptures. As surrounding tissue

is destroyed by the released toxins, eschars develop. Eschars heal naturally in

approximately 90% of cases involving untreated cutaneous anthrax lesions; 10% of

infected individuals go on to develop widespread infection and septicemia.5

Inhalation infection can occur if an infective dose is introduced and spores are deposited in

the alveoli. The bacteria and toxins enter the blood and cause septicemia and toxemia, and

the fatality rate has historically approached 100%. Inhalation anthrax infection accounts

for approximately 5% of reported human anthrax cases, and initial symptoms are generally

mild and nonspecific, making early diagnosis especially difficult. Patients may initially

present with common URI symptoms, but if left untreated, may develop acute respiratory

distress, fever, and shock within three to five days. Death follows shortly thereafter.3

Gastrointestinal anthrax infection can develop after the consumption of anthraxcontaminated meat. Once ingested, the organism penetrates the intestinal wall, multiplies,

produces a toxin, and causes ulcerative lesions and severe gastroenteritis. While cases of

gastrointestinal anthrax have been documented in the past in the United States, disease

control regulations in the meat industry have eliminated this form of infection.

When a prompt diagnosis is made and followed by immediate treatment, with penicillin

(preferably) or certain other antibiotics, individuals with anthrax usually experience rapid

recovery. Antibiotic therapy should be administered every six hours for a period of five to

seven days.5 

IV. EVALUATION METHODS

To enable comparisons between those who had infected livestock and those who didn’t,

producers from all seven affected farms were interviewed, as were neighboring but

unaffected producers—those whose herds had potential or actual fence-line contact with

affected herds, according to the affected producers. Additional interviews were conducted

with local veterinarians, the county health officer, and the necropsy and bacteriology staff

at the NDSU Laboratory, each of whom had potential occupational exposure to anthrax. 

Interviews addressed facility management practices, pasture characteristics, work practices

(including disposal and handling of animal carcasses and disposal of potentially

contaminated soil and clothing), a personal health history, and the producer's experience

with notification and dissemination of pertinent epizootic information. Information

regarding potential but unconfirmed livestock anthrax cases was obtained by review of
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records from the NDSU laboratory, from local veterinarians, through contact with county

extension personnel, and from affected and unaffected producers.

Medical Evaluation

The medical evaluation included interview questions pertaining to recent symptoms and

personal health history. Blood testing for antibody titer to anthrax was offered to those

producers, veterinarians, and laboratory personnel who reported respiratory or skin

symptoms, received post-"exposure" antibiotics, or had unprotected direct exposure to any

dead or infected livestock during the outbreak period. Participation was completely

voluntary, and participants gave written informed consent.

Blood specimens were collected in serum separator tubes according to standard

phlebotomy technique, centrifuged on-site, immediately refrigerated, and sent for analysis

to the United States Army Medical Research Institute for Infectious Diseases

(USAMRIID) on October 4, 1993. Serum samples were analyzed using both Western

Blot and enzyme-linked immunosorbent assay (ELISA) tests to identify serum precipitins

to B. anthracis.

Environmental Evaluation

Occupational and environmental evaluations included personal interviews regarding the

work practices of each producer and veterinarian, observation of affected farm pastures

and facilities, an inspection of livestock death and disposal sites, and environmental bulk

sampling of soil, water, bedding, and feed. Walk-through investigations were conducted

at facilities where the producer knew of potential exposure or death sites. Bulk samples

were obtained primarily as a service to producers and in cases where positive results were

strongly suspected. Work-practice evaluations included questions regarding the general

handling of sick and dead livestock; the handling of carcasses potentially contaminated or

diagnosed with anthrax; personal protective equipment (PPE) use during handling;

disinfection or disposal methods for PPE and other potentially contaminated equipment;

and each producer's methods for disposal of suspected or confirmed anthrax-contaminated

carcasses and surrounding soil.

Thirteen bulk environmental samples were collected from five of the seven affected farms

to include seven water samples, four soil samples, one combination used-bedding and soil

sample, and one swine feed sample 

(Table I). Eight samples (four each of soil and water) were collected in Barnes County

from both beef and dairy operations; four samples (one bedding/soil, one feed, and two

water) were collected from La Moure County and included beef and swine operations; and

one water sample was collected from a beef operation located in Ransom County. Sample

site selection criteria included livestock drinking ponds, death sites, especially those where

there had been no soil remediation, burial sites, and areas where producers felt most
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strongly that there were potential exposures to B. anthracis before and during the

epizootic.

Seven water samples were obtained from four farm operations (Table I); two from a pond

in a beef cattle pasture (site visit 2 in Figure 2); two from a dairy cattle pasture where this

particular section of pasture is usually dry (site 

visit 3); two samples from a beef pasture pond (site visit 5); and one other sample from

pasture water at a third beef production facility (site visit 6). Four soil samples, one

bedding/soil sample, and one feed sample were obtained from three different affected

farms. One sample was collected from the burial site of a confirmed anthrax-infected cow

where no soil remediation had been conducted (site visit 2). Three samples were collected

in a pasture where a dairy heifer had died approximately 3 weeks earlier (anthrax was

suspected but not confirmed); no soil remediation had been conducted and there were

visible traces of hair and exudate mixed with the soil (site visit 3). One feed sample and

one bedding/soil sample were collected from the swine operation (site visit 4), where three

hogs kept in confinement died, but only one carcass was submitted for testing; the

bedding/soil sample was collected from the approximate site of death in an old dairy barn

where the pigs were kept, and included straw and potentially contaminated soil (no

remediation had been conducted, and fresh straw had been placed on top of the soil). 

All soil, bedding, and feed samples were collected using sterile wooden tongue depressors,

and were placed into sterile plastic whirl bags. Water samples were collected in sterile

plastic containers. Both sample types were then sealed and hand-carried to the NDSU

Veterinary Diagnostic Laboratory for analysis.

Soil specimens were initially prepared with 1 gram of soil in 9 milliliters (ml) of sterile,

distilled water. This solution was heat shock-treated in a 62.5°C water bath to select for

spore-forming bacteria. Ten-fold serial dilutions (using distilled water) were prepared, up

to a maximum of 106

. At each stage of dilution, 0.1 ml of solution was streaked onto each

of the following—blood agar plates, PLET agar plates, and pour plates—with 40

micrograms (:g) of lysozyme added to a nutrient agar base. Water samples were prepared

by filtration through a 1.2 micron filter. The filtered specimen was then centrifuged, and

the sediment was cultured as a soil sample. A control was developed using a known B.

anthracis culture also streaked on agar plates, and conditions for the control were identical

to the corresponding bulk soil samples at all stages of plating. Growing colonies were

then analyzed for morphology, coliform characteristics typical of B. anthracis, gram stain,

penicillin sensitivity, and uniformity of colony lift with an inoculating loop.

Experts at the National Center for Infectious Disease (NCID), Division of Bacterial and

Mycotic Diseases, Centers for Disease Control and Prevention (CDC), recommended that

additional soil samples be collected from the swine facility. The purpose was to attempt to

determine the extent of soil contamination within this facility. Seven additional soil

samples were collected on November 8, 1993, by the state's regional OHNAC investigator
Page 9 - Health Hazard Evaluation Report No. 93-1121-2530

(Table I). The sample set collection and analysis methods were identical to those utilized

during the NIOSH investigation. A repeat sample was taken from the floor of the swine

facility where the three carcasses were found. The remainder of the samples included soil

from additional areas within the barn, roots of weeds fed to the pigs, and soil immediately

adjacent to the barn. 

Surveillance Notification

Anthrax epizootic notification data were collected from memoranda issued by the state

extension veterinarian, newspaper articles, notices of herd quarantine, NDSU specimen

submission records and laboratory reports, and personal interviews with producers and

veterinarians. Notification methods were evaluated primarily for timeliness, content, and

availability to intended readers.
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V. RESULTS AND DISCUSSION

Medical Evaluation

Despite numerous producer and veterinary accounts of direct contact with anthraxcontaminated livestock and carcasses, there were no confirmed cases of anthrax infection

reported for any of the residents of the Sheyenne River valley. Of five individuals

considered eligible for blood testing, samples were collected from four (Table II). Two

samples were collected from producers, both of whom had experienced respiratory

symptoms and one who had systemic illness and skin lesions; one was obtained from a

local veterinarian who had conducted a postmortem exam on an anthrax-infected cow;

and, the fourth was collected from a laboratory worker who had necropsied a subsequently

culture-confirmed anthrax-infected swine carcass. The blood was collected from all

individuals three to five weeks after the potential exposure or onset of symptoms, and in

one producer, a second sample was collected nine weeks following his potential exposure

to the organism. None had antibodies to B. anthracis. At the recommendation of

USAMRIID, a second blood specimen was collected on October 19, 1993, from the

producer who reported lesions on his left arm and hands beginning about August 20, 1993,

and a systemic illness about 12 days later. This repeat sample was collected to determine

whether there may have been a delayed rise in antibody titer. This test result was also

negative.

Of the 26 people interviewed by NIOSH investigators, 3 producers (all with affected

livestock), 4 of their family members, and 3 veterinarians took antibiotics either as a

prophylactic measure or as a result of the symptoms they had experienced. In all cases, the

antibiotics were taken from one to six days following exposure or development of

symptoms (Table II). About August 20, 1993, one producer noticed reddened fluid-filled

sores on the backs of both hands and on his left forearm and elbow. He said the sores

ruptured, oozed, and eventually scabbed over while gradually turning dark brown to black. 

He also reported a systemic illness beginning about September 1, 1993, following direct

contact with ill or deceased livestock during the previous week. On September 8, he

sought medical care from a local physician, but because of timing conflicts was not

examined. Later that day, the physician called the producer and prescribed penicillin. It is

unclear as to whether the producer started the therapy prescribed for him, but he did report

taking injectable penicillin September 5-6, and he reported full recovery from his illnesses. 

The producer had a physical examination September 9. The medical records described the

sores as 'small punctate healed lesions', and the physician decided that a specimen for

culture could not be obtained from them. At the time of the evaluation, NIOSH

investigators observed light brown to dark pink depressions in the areas described by the

producer of approximately 0.5 to 1 centimeter in size. These appeared to be newly-healed

lesions. Two post-exposure blood serum titers for B. anthracis collected from this

producer by the investigators were negative.
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Two additional producers and their immediate family members were treated with

penicillin. Both producers reportedly had direct contact with anthrax-infected carcasses,

but none of the family members had any contact with either sick or dead livestock. One

producer and his family members were given prescriptions for penicillin, and according to

the physician’s records, this was based upon family members’ respiratory symptoms and

the producer’s exposure to infected carcasses one day preceeding the onset of symptoms

and three days before penicillin was prescribed. The second producer, exposed twice to

infected livestock, experienced respiratory symptoms and took penicillin for five days,

starting four days after his first exposure. Approximately two weeks later, although he had

no symptoms, he began taking penicillin one day after his second exposure. Using a frontend loader, he had removed three swine carcasses from his confinement facility, blanketed

one, and placed it in the trunk of his car. He then transported the carcass to the NDSU

diagnostic laboratory, where anthrax was determined to be the cause of death. The

producer reported that he wore long-sleeved clothing and cotton gloves to protect himself

while handling the carcasses.

Three additional individuals were treated with antibiotics during this time period. Two

veterinarians, neither of whom had symptoms, treated themselves with ampicillin. One

did so a day after vaccinating livestock on 

an affected farm, and the other, a day after conducting a postmortem examination on a cow

subsequently found to have anthrax. Anthrax was not suspected at the time because the

carcass did not display any of the characteristics typical of an anthrax infection. Although

not his usual procedure when conducting postmortems, the veterinarian reportedly wore

coveralls, boots, and rubber gloves during the examination. A blood sample collected

from this individual was negative for antibodies to B. anthracis. 

A postmortem room technician at NDSU Veterinary Diagnostic Laboratory reported that

he was sprayed with blood from the head of a swine carcass as it was opened. The

technician reportedly wore the usual PPE provided by the employer for standard necropsy,

including latex rubber gloves and a three-quarter-length cotton laboratory coat. Anthrax

infection was not suspected, but the animal subsequently tested positive. Although the

technician had no symptoms, he took ampicillin beginning two days after his exposure.
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Environmental Evaluation

Of the environmental samples collected, all seven water samples were negative for B.

anthracis, while two of the four soil samples cultured positive for B. anthracis. Both of

these soil samples were obtained from the north pasture of the dairy producer (site visit 3). 

The third positive sample, a combination of used bedding and soil, was obtained from the

barn floor of the swine production facility. The feed sample, also obtained from the swine

facility, was negative. Seven additional soil samples, collected from the swine farm on

November 8, 1993, were negative for B. anthracis.

Each of the affected producers was asked to define their usual work-practice procedures

when handling dead livestock, and about work practices generally followed when

confronted with a potentially contaminated carcass. They were further asked to identify

where herds with affected animals had been pastured, where dead animals had been found,

and where they had been buried. Interviews conducted with each of the seven affected

producers indicated that when confronted with any dead livestock 57% (four of seven),

without handling the animal, immediately contact their veterinarian to conduct

postmortem investigations; if the death of the animal is suspect in any way, two of those

four producers usually transport the carcass directly to the NDSU laboratory for necropsy,

as they did during the epizootic; the other two producers either begin a postmortem

themselves or simply dispose of the carcass, usually by burial but potentially by using it

for feed for other livestock, depending upon factors such as the condition of the carcass,

the weather, etc.

When confronted with a potential anthrax-infected carcass, five of the seven affected

producers reported that they usually contact a veterinarian to conduct testing, then bury the

carcass approximately six feet deep; 29% (two of seven) of producers usually burn the

carcass before burial; one of those two producers adds quick-lime to the grave. None of

the producers initially removes the potentially contaminated topsoil; however, upon

veterinary or laboratory confirmation of anthrax infection, 43% (three of seven) of

producers return to the death site to remove and bury the topsoil where the affected animal

died or was necropsied.

During this epizootic, three of the producers (43%) and at least one of the four

veterinarians interviewed (lack of data is due to conflicting reports) were involved with

direct handling of both sick and dead livestock and were unprotected (did not use any

PPE). Also during the outbreak, all producers with anthrax-infected or suspect carcasses

reported that they eventually buried them, but only one used quick-lime, which kills any

remaining anthrax organisms, during burial. Two of the seven affected producers directly

handled anthrax-suspected or -confirmed carcasses, and neither of these producers wore

protective clothing, rubber gloves, or shoe covers while handling the carcasses. 

Furthermore, none of the producers wore personal protective gear during animal burial,
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soil removal, or soil treatment with quick lime. At least one veterinarian conducted

postmortems on livestock without using any protective clothing.

Producers were asked to comment on any changes they made in herd management

practices during the epizootic. Upon confirmation of anthrax infection in their herds, all

seven of the affected producers increased the frequency of herd observation. In addition,

three of the affected producers, all with beef cattle, moved their herds to different pastures: 

One producer moved his herd within a day after confirmation; another within one week;

and the third producer, who experienced multiple beef cattle deaths, moved his herd to

three separate pastures within two days after receiving two positive anthrax test results in

two days. All of the producers subsequently vaccinated their herds against anthrax. Two

of the local veterinarians used Thraxol - 2, which is administered as a single dose, to

vaccinate against anthrax on five of the seven affected farms; at the time of this

investigation, three of those five (60%) herds had received the recommended booster three

to four weeks after the initial dose. The two remaining affected herds were vaccinated

with the Colorado System, a two-dose vaccine, by local veterinarians.

In comparison, six of seven neighboring but unaffected producers, once notified, increased

their frequency of herd observation during the outbreak period. After being informed of

infected cattle in a neighboring pasture, on land with potential for fence-line contact, one

unaffected producer relocated his herd; one other producer reported that he would have

relocated his herd if he had been informed of infected neighboring cattle. As a precaution,

one of the seven unaffected producers vaccinated but did not booster his herd against

anthrax.

Potential Anthrax Sources for the North Dakota Epizootic

In general, an anthrax epizootic can occur as, 1) a result of introducing the 

B. anthracis organism into the area, 2) through re-emergence of the organism from a

previously established soil source, or 3) by mechanical transmission, such as through

insect bites. Results of this investigation showed that 2 of the 14 interviewed producers

added new livestock during the epizootic; five Holstein cattle were added to a herd which

ultimately remained unaffected, and an additional three head of cattle were introduced into

a beef facility, but pastured separately from cattle that ultimately became infected with

anthrax. Most of the affected and unaffected producers used feed supplements; however,

none were used that contained any animal by-products. Only one producer used fertilizer

on his pasture; however, the fertilizer was of inorganic origin and his herd remained

unaffected throughout the epizootic.

Because of the potential for transmission of the anthrax organism through biting insects,

producers were asked to comment on this year's fly and mosquito populations. Many of

the producers (8 of 14) felt that the number of flies remained about the same when

compared to past years, while two producers felt that there were more flies than usual. 
Page 14 - Health Hazard Evaluation Report No. 93-1121-2530

The other four producers had no comment. When questioned about the mosquito

population, 8 of the 14 producers felt that there had been a definite increase—4 of those 8

were affected producers.

Six of the affected producers pastured their livestock, as did all seven of the unaffected

producers. The single exception was the affected swine producer who kept his animals in

a partially-enclosed confinement facility (a converted dairy barn). All of the pastured

livestock had access to ponds or streams. No new water supplies were created as a result

of the flood; however, some of the pasture ponds, which are usually dry by late summer,

contained standing water at the time of the investigation in September 1993. One producer

reported increased wildlife deaths (foxes and coyotes) in his pastures where anthraxinfected cattle were found.

Quarantine and Notification

Six of the eight specimens submitted to the NDSU laboratory were collected from the

carcasses by veterinarians at the death sites. Two of the carcasses, a pig and a cow, were

transported by their owners to the laboratory for necropsy. All of the individuals who

submitted specimens for culture were notified by laboratory staff of an anthrax-positive

result within 24 hours of confirmation; the state veterinarian was also notified of positive

results the day of confirmation for all eight cases.

The state veterinarian issued quarantine notices to producers with confirmed anthrax

within 12-24 hours following laboratory notification. Each producer was then required by

the state of North Dakota to vaccinate all remaining farm livestock and to place the entire

herd under immediate quarantine for either 30 days after the last death loss or 30 days

following vaccination. According to the North Dakota State Board of Animal Health, the

vaccination must consist of at least two doses. The quarantine starting dates for each

affected herd were from August 17 to September 17, 1993. As no further anthraxconfirmed deaths occurred in any of the herds, all quarantined herds were released by

November 1993.

On September 3, 1993, a memorandum regarding the anthrax epizootic was issued by the

state extension veterinarian and was distributed to all county extension staff. Although

labeled as information only for extension staff and not for publication, it was prepared by

the same office that same day as a press release and was printed September 5, 1993, by

one local news publication. The memorandum included confirmation of five livestock

deaths due to anthrax and included a description of its symptoms and the potential for

infection in cattle. The memorandum also stated that anthrax could present a public health

risk to those working with infected animals and that unnecessary contact should be

avoided. Although the memorandum recommended that producers contact their

veterinarians immediately if anthrax was suspected, it did not instruct the recipients

(extension staff) to actually notify area producers or veterinarians of either the affected

livestock or the risks associated with exposure to anthrax.
Page 15 - Health Hazard Evaluation Report No. 93-1121-2530

Following confirmation of an additional livestock anthrax death in the Sheyenne River

basin, a second memorandum was issued September 9, 1993, by the state extension

veterinarian. This memorandum, again issued to all extension staff, contained

recommendations for area producers to check herds daily and to report to the herd

veterinarian any sudden livestock deaths. The memorandum also stated that prompt

diagnosis and correct handling of infected tissue were important for preventing disease

spread and human exposure. At this time, staff was advised to use information from either

memorandum "as you see fit," but again were given no specific information on making

contact with those potentially at risk.

Two announcements regarding the anthrax outbreak were distributed via newsprint to the

public in the Sheyenne River valley region. The first published article was written by a

local veterinarian and was based upon information contained in the first memo released by

the state veterinary office. The article appeared in a local newspaper on September 5,

1993, and suggested that producers closely monitor herds; it also warned against moving

any animal carcass because of potential human health risks. The second article, appearing

in another local paper on September 10, 1993, was written by the state's regional OHNAC

nurse and a local physician. The article provided recommendations on avoiding exposure

to anthrax and described the symptoms of anthrax infection in humans.

Only two of the affected and four of the unaffected producers recalled having read one of

the two published newspaper articles written during the outbreak period. One unaffected

producer reportedly read an article in a cattle producer's magazine. Three of the affected

producers first learned of the anthrax outbreak after being informed of positive laboratory

results by their veterinarians; three of the remaining four affected producers reportedly

learned of the outbreak from a neighbor, and one producer was first informed by reading

one of the newspaper articles. Three of the seven unaffected producers first heard of the

anthrax outbreak from their affected neighbors, while a fourth received the information

from another unaffected neighbor. The remaining three did not recall how they were

informed.

VI. CONCLUSIONS

Ten (all with potential exposure to anthrax) of the 26 individuals involved with the

NIOSH survey received antibiotic therapy during the anthrax epizootic; 6 were treated for

URI symptoms, 3 as a result of direct contact with infected livestock, and 1 individual,

who also had direct contact with infected livestock, treated himself as a result of systemic

illness and skin lesions he thought to be anthrax-related. While the URI symptoms were

most likely not related to the epizootic, his description of the lesions that developed on his

hands and left arm suggest the possibility of cutaneous anthrax, and he had several wounds

and much scarring (presumably from prior injuries, due to the nature of his occupation),

which is indicative that there may have been open wounds that could have provided entry

for the anthrax organism. Unfortunately, certain diagnostically important details about the
Page 16 - Health Hazard Evaluation Report No. 93-1121-2530

skin lesions are not available, and the negative serologic tests argue against the skin

lesions being anthrax-related.

Although the investigation was not designed to evaluate risk factors for herd or animal

infection with anthrax, results yielded a few conclusions regarding the potential etiology of

this anthrax epizootic. No fertilizers or feed supplements containing animal products were

used, no recent soil disturbances (such as plowing) were reported, no infected cattle were

introduced into any of the herds, and with one exception, all of the affected herds were

pastured during the outbreak. One group of affected swine was kept in confinement inside

a dairy barn prior to and throughout the epizootic, and it is likely that the anthrax organism

was introduced to them from an outside source. At the time of the NIOSH investigation,

however, the producer assured us that he knew of no potential sources, and a sample of his

feed was culture-negative for anthrax. Hypotheses included the potential for

contamination from the prior inhabitants of the barn, and that because the producer

neighbored his son's anthrax-affected beef facility, he had inadvertently introduced the

organism to his barn by entering with contaminated boots. Approximately six months

after the NIOSH investigation, the producers were interviewed by a state employee about

their experiences with the outbreak. At that time, the swine producer remembered he had

fed his pigs a beef cattle carcass which was probably contaminated with anthrax. 

Originally, this carcass was not suspected to be infected with anthrax and was never tested;

however, the producer of the herd from which this carcass originated subsequently lost an

additional six head of cattle; blood samples from two of those were submitted and tested

positive for anthrax. It is therefore likely that this epizootic was a result of pre-existing

soil-borne anthrax spores which germinated during the flood. It is not known why

outbreaks of this nature occur as inconsistently and infrequently as they do, nor why

livestock grazing similar pasture and separated only by a fence line can remain unaffected. 

Although anthrax in this region of the state is not known to be endemic, and affected

producers did not report prior knowledge of anthrax on their property or surrounding area,

many of these producers related similar stories about a massive buffalo herd that had died

many years ago in the Sheyenne River valley, reportedly of anthrax.

The North Dakota state anthrax surveillance system was observed to be efficient. Timely

laboratory notification was observed, as positive culture results were relayed within 24

hours of confirmation to producers, local veterinarians, and to the state veterinary office. 

The state office, in turn, promptly issued the required notice of herd quarantine, usually on

the day confirmation was received from the laboratory. There was, however, observed to

be a notification delay to the broader community. Although it is important to avoid

causing unnecessary alarm, efforts should be made to disseminate appropriate information

to those who need to know, including both affected and unaffected neighboring facilities. 

Once issued, announcements to the community regarding anthrax were observed to be

complete and informative and described risks to livestock and producers, clinical signs in

livestock and humans, exposure prevention strategies, and treatment and disposal of

suspect or affected carcasses, affected soil, and contaminated clothing.
Page 17 - Health Hazard Evaluation Report No. 93-1121-2530

VII. RECOMMENDATIONS

Those producers with positive soil samples (the dairy and swine facilities), local and

laboratory veterinarians and personnel, and the general community may all benefit from

information regarding the potential for anthrax infection, although very infrequent, during

periods of drought and flooding. The following recommendations provide methods for

reducing occupational exposure and infection while conducting treatment of potentially

infected livestock, proper burial procedures for known or suspected anthrax-infected

livestock, proper methods for soil remediation, and methods for disinfection or disposal of

contaminated personal protective equipment. Recommendations for increasing public

awareness for future outbreaks follow:

U If anthrax is suspected, aseptically collect a jugular blood sample for culture: Do not

necropsy the animal. If a necropsy is inadvertently performed, autoclave or

incinerate all implements. All animals at risk should be promptly vaccinated and

annually revaccinated. Symptomatic animals should be treated with penicillin or

tetracyclines and then vaccinated.5

U Producers with confirmed anthrax-infected livestock, especially those with anthraxpositive soil samples, should conduct immediate remediation of any soil remaining at

and around the death site(s) as follows: Ideally, the first 6 inches of any topsoil

contacted by the infected carcass, its exudate (blood, excrement, and hair), and any

necropsy waste, should be removed and buried along with the carcass, to a depth of

at least 6 feet. The carcass should then be covered with 5% lye or quick lime

(anhydrous calcium oxide). Prior to burial, contamination potential can further be

reduced by burning the carcass; burning should not be conducted in an open field,

where wind could potentially spread the organism. Burning also requires a fire of

approximately 700°F for sustained burning. Decontaminate the site by adding quick

lime to the grave, the carcass and the contaminated top soil during burial. Additional

lime should be mixed in with the replacement top soil to kill any remaining anthrax

organisms.5

U Producers should take every precaution to avoid skin contact with the potentially

contaminated carcass and soil. Protective, impermeable clothing and equipment

such as rubber gloves, rubber or leather apron, and rubber boots, with no

perforations, should be used. No skin, especially that which is compromised with

wounds or scratches, should be exposed. Disposable PPE is preferable, but if not

available, decontamination can be achieved by washing any exposed equipment in

hot water and detergent. Disposable PPE should be burned and buried with the

carcass.

 

U Although the likelihood of an anthrax respiratory infection is small, airborne

particulates, including anthrax-contaminated soil, can enter the lungs: Therefore,
Page 18 - Health Hazard Evaluation Report No. 93-1121-2530

producers should wear a NIOSH and Mine Safety and Health Administration (MSHA)

approved high efficiency-respirator, such as a half-face disposable respirator with a

high-efficency particulate air (HEPA) filter, when conducting soil remediation and

burial and when applying quicklime to soil. High efficency respirators provide

protection against particles of 0.3μm or greater in size. B. anthracis organisms range

from 0.5-5.0μm in size. Veterinarians and producers conducting postmortems should

also wear a HEPA-filtered respirator, especially on windy days. Various types and sizes

of respirators and filters are usually available through feed, hardware, or industrial

supply stores. Respirators should not be worn over a beard, as this greatly reduces the

respirator's effectiveness by not allowing a proper seal between the user's face and the

respirator.

U The appropriate state agency should consider developing an alert, which would include

these and any further recommendations, for distribution to producers with confirmed

anthrax infection and to any neighboring production facilities, especially those pasturing

livestock immediately adjacent to infected animals.

U The state health department, in cooperation with the media, should consider issuing a

periodic informational alert any time communities experience environmental conditions

conducive to anthrax proliferation, like droughts and floods. The full range of available

news media should be used to quickly reach the public. The warning may contain

general information on anthrax infection of livestock, including common symptoms,

and personal protective measures that can be used by the producer to reduce potential

occupational exposure to the anthrax organism.

U As soon as positive test results are received from the laboratory, the state animal health

department should contact all veterinarians in potentially affected areas, who in turn

would contact their clients. Local veterinarians should also alert neighboring veterinary

practitioners, should advise the affected producer to notify neighboring production

facilities, and should alert other susceptible clients of the potential for infection. 

Relayed information may include advice as to the potential for infection for each

producer's herd and infection prevention strategies. These strategies can include herd

relocation and herd vaccination against anthrax. The veterinarian can also provide

instruction and supervise proper cleaning, disinfection, and disposal of infected

carcasses. These precautionary measures should reduce the potential for occupational

exposure to anthrax.

 U A followup study is planned by the USDA to determine what environmental factors

may have contributed to the risk of anthrax infection in grazing animals and also to gain

a better understanding of anthrax bacilli and spore-retention in the soil of the

floodplain/grassland ecosystem and of the impact of flooding.
Page 19 - Health Hazard Evaluation Report No. 93-1121-2530

VIII. REFERENCES

1. Van Ness GB [1971]. Science 172:1303-1307.

2. Acha PN, Szyfres B [1987]. Zoonoses and communicable diseases common to man

and animals. 2nd ed. Pan American Health Organization, Pan American Sanitary

Bureau, Regional Office of the World Health Organization, pp. 10-15.

3. Brachman PS [1986]. Inhalation anthrax. In: Merchant JA, ed. Occupational

respiratory diseases. Cincinnati, OH: U.S. Department of Health and Human

Services, Public Health Service, Centers for Disease Control, National Institute for

Occupational Safety and Health. DHHS (NIOSH) Publication No. 86-102, pp. 693-

697.

4. CDC (Centers for Disease Control and Prevention) [1994]. Summary of notifiable

diseases, United States 1993. MMWR 42(53).

5. Benenson AS, ed. [1990]. Anthrax. In: Control of communicable diseases in man. 

15th ed. Washington, D.C: American Public Health Association, pp. 17-20.
Page 20 - Health Hazard Evaluation Report No. 93-1121-2530

IX. AUTHORSHIP AND ACKNOWLEDGEMENTS

Report Prepared By: Ann M. Krake, M.S.

Industrial Hygienist

Industrial Hygiene Section

Hazard Evaluations and Technical

 Assistance Branch

Catherine L. Connon, M.N.

Occupational Health Nurse

Medical Section

Surveillance Branch

Thomas M. Gomez, D.V.M., M.S.

Epidemiologist

Veterinary Services

Animal and Plant Health Inspection Service

United States Department of Agriculture

 at Foodborne and Diarrheal Diseases Branch

Division of Bacterial and Mycotic Diseases

National Center for Infectious Diseases

Field Assistance: Cheryl Hagen, B.S.N.

Community Health Center

Occupational Health Nurses

 in Agricultural Communities

Fargo, North Dakota

Analytical Support: North Dakota State University

Veterinary Diagnostic Laboratory

Fargo, North Dakota

United States Army Medical Research 

Institute for Infectious Diseases

Report Formatted By: Caren B. Day

Office Automation Assistant

Industrial Hygiene Section

Hazard Evaluations and Technical

 Assistance Branch

Originating Office: Hazard Evaluations and Technical

 Assistance Branch

Division of Surveillance, Hazard

 Evaluations, and Field Studies
Page 21 - Health Hazard Evaluation Report No. 93-1121-2530

X. DISTRIBUTION AND AVAILABILITY OF REPORT

Copies of this report may be freely reproduced and are not copyrighted. Single copies of

this report will be available for a period of three years from the NIOSH Publications

Office, 4676 Columbia Parkway, Cincinnati, Ohio 45226. To expedite your request,

include a self-addressed mailing label along with your written request. After this time,

copies may be purchased from the National Technical Information Service (NTIS), 5285

Port Royal Road, Springfield, Virginia 22161. Information regarding the NTIS stock

number may be obtained from the NIOSH Publications Office at the Cincinnati address.

For the purpose of informing affected individuals, copies of this report have been

forwarded to:

 1. North Dakota State Epidemiologist, Bismarck, North Dakota

 2. North Dakota State Veterinarian, Bismarck, North Dakota

 3. North Dakota State Animal Board of Health, Bismarck, North Dakota

 4. Barnes, La Moure, and Ransom County Health Officers, North Dakota

 5. Barnes, La Moure, and Ransom County Agent, North Dakota

 6. Barnes, La Moure, and Ransom County Health Unit, North Dakota

 7. Valley City Veterinary Hospital, Bismarck, North Dakota

 8. Hovland Veterinary Service, Lisbon, North Dakota

 9. Barnes, Ransom, and La Moure County participating producers

10. Community Health Center, Fargo, North Dakota

11. North Dakota State Veterinary Diagnostic Laboratory, Fargo, North Dakota

12. Center for Animal Disease Control, Fort Collins, Colorado

13. OSHA Region VIII
Page 22

TABLE I

DEMOGRAPHICS AND ENVIRONMENTAL SAMPLING RESULTS

SHEYENNE RIVER VALLEY, NORTH DAKOTA

HETA 93-1121

SEPTEMBER/OCTOBER 1993

Site County Operation

Type

Herd

 Size 

Total

Dead 

NDSUConfirmed

Anthrax

Deaths

Sample

Type

Total 

Samples

Results

1 Barnes Beef 1,650 5 1 None None N/A

2 Barnes Beef 25 2 1 Soil

Water

1

2

Negative

Negative

3 Barnes Dairy 240 11 1 Soil

Soil

Water

2

1

2

Positive

Negative

Negative

4 La Moure Swine 35 3 1 Bed/soil

Feed

Soil*

1

1

7

Positive

Negative

Negative

5 La Moure Beef 119 7 2 Water 2 Negative

6 Ransom Beef 249 2 1 Water 1 Negative

7 Ransom Beef 80 3 1 None None N/A

* Denotes the seven samples collected on November 8, 1993.
Page 23

TABLE II

MEDICAL DATA

SHEYENNE RIVER VALLEY, NORTH DAKOTA

HETA 93-1121

SEPTEMBER/OCTOBER 1993

Occupation Direct Contact with

Infected Livestock

Antibiotic Therapy Symptoms Blood Test

Results

Dairy 

Farmer

Numerous times during

burial and treatment of

infected animals

Self-treatment with penicillin for 2

days, unknown amount

Skin lesions

Negative*

250 mg penicillin, 4 per day for 10

days (unknown if taken)

 Systemic illness

Beef Rancher Burial and treatment of

infected animals

250 mg penicillin, 4 per day 

for 7 days

Upper respiratory Negative

Swine Farmer

Fed infected carcass to

swine

500 mg penicillin, 4 per day 

for 5 days

Upper respiratory

No sample

taken

 Transported dead swine

to clinic

500 mg penicillin, 4 per day 

for 5 days

None

Veterinarian Postmortem of infected

cow

Self-treatment with 500 mg ampicillin,

3 per day for 7 days

None Negative

Veterinarian Vaccination of affected

beef herd

Self-treatment with 500 mg ampicillin,

3 per day for 6 days

None No sample

taken

Veterinary

Pathologist

Postmortem of infected

swine carcass

Yes, details unknown None Negative

* A second blood sample, collected approximately one month later, was also negative.
Page 24