Equine Infectious Anemia (EIA)

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Article By: Margaret Ross
Photo Credit: en.wikipedia.org

Adapted from: NCDA & CS Veterinary Division – Animal Health Programs – Equine Infectious Anemia (EIA) & information from Dr. Linnea Theisen, Eastern Equine Associates Mobile Veterinary Service


            Have you ever heard of Equine Infectious Anemia or EIA? According to an article from the North Carolina Department of Agriculture and Consumer Services…

            EIA is a viral and infectious disease found in equids. It can accompany an illness that may be acute, subacute or chronic and can also be subclinical in some cases. EIA is a worldwide problem and has been reported in all of the mainland states. The only known natural hosts of this disease are ponies, horses, mules and donkeys. Typically, the outbreaks occur during late summer or early fall and also overlap with the peak of biting insect populations. However, if EIA is transmitted via a hypodermic needle, new infections can be produced at any time during the year.

            A retrovirus is what causes EIA and it is related to the lentivirus that causes AIDS in humans. At this time, it is thought that the equine virus does not affect people. EIA has been found in milk, saliva, and blood of diseased horses but typically loses its efficacy outside of the horse’s body. Boiling, sunlight, and most chemical disinfectants destroy the virus. However, once a horse has the virus, they carry it for life – regardless of how severe their symptoms are.

            The disease is transmitted by intravenous, intramuscular, or subcutaneous injection of blood contaminated with the disease. Insects that suck blood can also be a source of infection transfer. The incubation period for the virus is around 14 days but could be much longer. Symptoms often include a high fever of 104 – 108 degrees F., lessened appetite, drastic loss of physical condition, severe depression, incoordination, jaundice, increased heart rate, swelling of legs and lower abdomen, and a yellowish or bloody discharge from the nose, along with other symptoms.

            Clinical diagnosis is very difficult and needs to include regular observations of the horse as well as recording body temperature twice daily. EIA should also be distinguished from babesiosis, which is a blood disease that is transmitted from ticks. It can be diagnosed by blood studies and is rare in North Carolina.

            An antibody test that is positive is thought to be the same as being infected, even if symptoms do not concur with diagnosis. How severe the symptoms are depends on the amount of virus in the blood at any particular time. Currently, a vaccine is not available and there is no treatment or cure, other than supportive care. If your horse is showing signs of EIA, isolate them until testing is complete. If the immunodiffusion test comes back positive, immediate euthanasia must be considered. At this point, the state veterinarian takes over and the horse must be either euthanized or isolated by a certain number of miles from other horses. In addition, the horse must never be moved from that property or change owners without getting approval from the state veterinarian.

How can you be safe? You should only buy horses known to be negative with the immunodiffusion test and require a copy of those records. Be extremely careful with equipment that can transmit blood from one horse to another. Fly / insect control, cleanliness, and careful use of pesticides are all encouraged. If an EIA-positive horse must be kept, that horse should be isolated from the others. Horse owners who have known EIA-positive horses need to be aware of federal regulations when moving these horses.

In addition, it is important to note that you should always have proof of a current Coggins anytime you move your horse from your property, even if you’re just going to trail ride. Barns that board horses are also required to have current Coggins on all the horses. Don’t purchase horses without a current negative Coggins test or transport horses without one. If a horse owner brings a horse onto their farm without a current Coggins, they should separate that horse (quarantine) until the test results return. In order to get a health certificate, a current Coggins test is required; health certificates are required for horses crossing state lines. If you do not have a current Coggins and health certificate in this case, your horses, truck, and trailer can all be confiscated!

            Horse owners can have their veterinarian submit a sample to test for EIA to the North Carolina Department of Agriculture and Consumer Services. Visit http://www.ncagr.gov/vet/FactSheets/equine.htm for more information and the full article. If you would like more information on EIA, please contact your veterinarian.

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