NO. 40 DATE 08/17/00
by Dr. Charles J. Issel, DVM, PhD.
University of Kentucky Department of Veterinary Science
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 bodys 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.
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:
Infection and Transmission
EIA is transmitted by the exchange of certain bodily fluids, usually blood, from an infected to a non-infected 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 mares 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 life-long 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 dams 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:
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
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.
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
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
Wild Horse Specialist
Salt Lake Field Office
Salt Lake City, UT
phone (801) 977-4376
fax (801) 977-4397
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