Equine Infectious Anemia

Equine Infectious Anemia is a disease among equines that is much like AIDS. It is a virus that attacks the immune system and destroys red blood cells thus causing anemia:

When the virus enters the bloodstream, it invades lymphocytes (a form of white blood cells that are important in the body's defense against disease). The virus then reproduces in the lymphocyte, increasing in numbers until the lymphocyte bursts releasing more virus into the bloodstream to repeat the cycle. The animal attempts to fight off the viral infection by producing antibodies against the virus. However, this antibody is not effective in eliminating the virus from the body, and enough lymphocytes are destroyed over time to reduce the effectiveness of the immune system. When the animal reaches this stage, it usually succumbs to other bacterial or viral infection. The death rate of infected equidae varies from 30 to 70 percent, and is usually higher when the virus is introduced into a new geographical region.

The anemia that sometimes accompanies this disease is caused by the animal's immune system attacking the cells that produce red blood cells in the bone marrow. The reasons for this event are unknown.

--Michigan Department of Agriculture, Animal Industry Division. Equine Infectious Anemia

Horses infected with EIA may show signs from one week to one month from the date of infection. Some horses may show no signs and become carriers of the virus. It is transmitted through biting flies and mosquitoes previously exposed to a carrier. It can also be transmitted through instruments such as needles which are contaminated by the blood of an infected horse.

Symptoms Associated With EIA

Rise in temperature to 104° to 106°	General weakness	Loss of appetite
Small hemorrhages in the mouth and at the base of the tongue	Swelling of the legs and ventral midline	Significant decrease in the horse's performance level
Paleness of the mucous membranes	Chronic weight loss

There is no cure or vaccine for EIA. It is suggested that infected horses be euthanized to prevent the spread of the virus. It is recommended that horses be tested regularly through the use of the Coggins test. The veterinarian draws blood and sends it to a lab to be tested. After testing, the owner receives a copy of the test stating that the horse tested negative or positive. The test is a requirement for the entrance to many horse-related events. Laws may vary from state to state. To find out what the laws in your state are, regarding EIA, you may go to the following web site which lists the laws by state.

Statutes and administrative regulations by state dealing with EIA.

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Equine Infectious Anemia. Michigan Department of Agriculture, Animal Industry Division.

Equine Infectious Anemia Attacks Horse's Immune System. Illinois Veterinary Bulletin. University of Illinois, College of Veterinary Medicine.

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Last revision: May 5, 2002