Equine Infectious

Anemia:

Implications for

Public Land

Managers and

Horse Owners

by Dr. Charles J. Issel, DVM, PhD.

University of Kentucky

Department of Veterinary Science

Background

Equine infectious anemia (EIA) is a

disease caused by a virus that produces anemia, intermittent fever,

and severe weight loss. Horses,

ponies, mules, and donkeys are the

only known animals affected by the

virus. When the virus enters the

bloodstream, it invades lymphocytes (white blood cells) that are

important in the body’s defense

against disease. Once an animal is

infected with the virus, it is infected for life, regardless of the severity

of the symptoms.

At present, there is no vaccine or

cure available. Because the virus is

highly infectious, the infected animals are usually euthanized. BLM

officials have euthanized over 90

wild horses in the Uintah Basin of

eastern Utah in the past 2 years

because they carried the deadly virus. 

Other common names for EIA are

swamp fever, mountain fever, slow

fever, and Coggins disease.

Discussion

Initial signs of EIA may include: an

intermittent or continuous fever

(sudden rise from100 degrees F. to

105 degrees F.), profuse sweating,

rapid breathing, depression, and

weight loss even though the animal

continues to eat well. Disease signs

occur 7 to 21 days after primary

infection.

The initial signs of EIA pass quickly

into one of four patterns:

1. Acute cases are more the exception than the rule. These animals

rarely survive and can die within

3 to 10 days after the virus enters

the bloodstream.

2. Subacute cases can also be very

sick and then become chronic.

These animals exhibit no signs

of the disease for a long time,

then progress to a state of continuing weight loss, rough hair

coat, and anemia. Relapses of

increasing severity are common.

3. Chronic cases may have occasional attacks and develop classic

symptoms of the lower legs,

chest, and abdomen. These signs

will later subside but may never

recur. These symptoms commonly develop after stress from

hard work, hot weather, pregnancy, or from other diseases.

4. Carrier animals appear to be

healthy but harbor the agent of

the disease. An animal will carry

the virus for its entire life and

never show signs of the disease,

but it is potentially able to transmit the disease. These animals

may develop into acute or chronic cases after hard work, severe

stress, or from other diseases.

Infection and Transmission

EIA is transmitted by the exchange

of certain bodily fluids, usually

blood, from an infected to a noninfected animal. One mode of

transmission is through insect bites.

Horseflies, stable flies, and deer

flies are blood feeders. A fly, having

bitten an infected animal, will have

residual blood on its mouth parts.

If the fly moves from an infected

animal to a non infected animal,

the virus may be introduced into

the non-infected animal when the

insect pierces the skin of that animal.

The virus is also transmitted by

mechanical means. Instruments,

such as hoof knives, needles,

syringes, etc., that were previously used and contaminated with

blood from an infected animal

may unknowingly infect a healthy

animal.

If the levels of virus in a mare’s

blood are high enough, transplacental infection of a foal is possible.

Approximately 10 percent of foals

delivered from infected mares are

infected at birth and remain lifelong carriers of the virus.

Detection of the Disease

The AGID test, also known as the

Coggins Test, is the most commonly

used official test to detect antibodies from the equine blood against

the EIA virus. It is extremely likely

that an animal that tests positive on

one occasion will do so for the rest

of its life (except young foals who

absorbed antibodies from their positive dam’s colostrum). In most

states, when an animal is diagnosed

as EIA positive, the individual and

others on the same premises are

placed under quarantine. Those

animals, whether wild or domestic,

remain under quarantine until all

positive animals are either euthanized or test negative.

Four options are available to the

owner whose animal has tested

positive:

1. Move the positive individual(s)

to a location that is preapproved

by agricultural authorities, is a

minimum of 1/4 mile away

from the other equine, and

quarantine the individuals at

this new location. The 1/4 mile

RESOURCE NOTES

NO. 40 DATE 08/17/00

Range

Wild Horse andBurro Program
separation is intended to minimize the contact by biting flies,

reducing the risk of infection.

2. Move the positive individuals to

an insect-free enclosure; place the

individuals under quarantine.

3. Euthanasia with the proper

disposal with approval of

appropriate agricultural officials

and/or accredited veterinarian.

4. Ship to slaughter under procedures approved by agricultural

officials and with the appropriate

state and federal shipping papers.

There are only a few slaughter

facilities in the United States

that are approved to accept EIA

positive horses. If not euthanized

or shipped promptly, equids

must have a “34A” freeze

brand applied to the left side

of the neck.

Once infected animals are removed,

further testing of the remaining animals (usually at 30 to 45 days) must

continue until tests are negative.

Reducing the Risk of

Infection

1. Reduce flies in the barns or stables and pastures as much as

possible.

2. Avoid exposing your animal to

sick animals.

3. Use a new, sterile needle on

each animal. The simple rule

of thumb is “one horse, one

needle.”

4. Clean and sterilize all instruments thoroughly after each use.

This will prevent the spread of

disease by knives, needles, and

dental and surgical equipment.

5. Do not share saddles, bridles,

and other pieces of equipment

between any animals with open

or bleeding wounds or sores.

6. Do not breed mares or stallions

that you suspect or know are

infected.

7. Observe your animals daily. At

the first appearance of any of

the disease signs - fever, depression, or loss of appetite - isolate

the sick animal and call your

veterinarian.

8. Purchase animals only after they

have been tested and found to

be free of any evidence of disease. Insist on being furnished

with a copy of the test report.

9. Only participate in events (show,

sale, rides, etc.) that require prior

testing for all animals.

10. Request that all other event

managers/promoters require

proof of negative EIA status.

11. Establish a routine EIA testing

schedule for your equid with

your veterinarian.

Conclusion

EIA is a serious and deadly threat

to all horses, burros, ponies, mules,

and donkeys. BLM personnel

involved in the Wild Horse and

Burro program and owners of these

animals or other domestic animals

should take time to be familiar

with this disease and be able to recognize it in the animals they have

responsibility for. Testing is

required for BLM animals and

equine owners should follow suit.

More information can be found at

http:www.aphis.usda.gov/vs/eia/eia.

html.

Contact

Dr. Charles J. Issel, DVM

Wright-Marker Professor of Equine

Infectious Diseases

University of Kentucky, Dept. of

Veterinary Science

Gluck Equine Research Center

Lexington, JY 40546-0099

or

Glenn Foreman, Public Affairs

Utah State Office

Bureau of Land Management

324 So. State Street

Salt Lake City, UT 84111

phone (801) 539-4023

fax (801) 539-4013

email: gforeman@blm.gov

or

Glade Anderson

Wild Horse Specialist

Salt Lake Field Office

Salt Lake City, UT

phone (801) 977-4376

fax (801) 977-4397

email: g1anders@blm.gov

Range

Resource Notes are intended to be early

announcements of technical and informational topics for

Bureau of Land Management personnel and some of their customers.

Information in this Resource Note is based on the opinion and

experience of the author and has not been peer-reviewed. Conclusions

and opinions expressed herein do not

necessarily represent those of BLM. Use of trade names does not

imply U.S. Government endorsement of commercial products.

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