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Equine Infectious Anemia
An Equine Health Risk
By Diane Ursu

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 causing anemia.

According to the Michigan Department of Agriculture, Animal Industry Division article, "Equine Infectious 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.

Signs and Symptoms of 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 that are contaminated by the blood of an infected horse.

Symptoms associated with equine infectious anemia:

• 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

Testing and Treatment for Equine Infectious Anemia

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 Coggins test is requires blood to be drawn. 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 entrance to many horse-related events.

Laws regarding EIA may vary from state to state. To find the laws in your state, you may go to the following web site that lists the laws by state.

Statutes and administrative regulations by state dealing with EIA.

Resources for Equine Infectious Anemia

• 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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