1. Home
Send to a Friend via Email

Equine Infectious Anemia

Learn About Swamp Fever




2006 Gabor Bibor

EIA is an alarming disease because if a horse has recovered from the initial infection, it remains a carrier of the virus, although it appears very healthy. This can cause problems for the owner who must now find ways to keep it quarantined. Many horses don’t recover though, and for them, EIA is fatal. Or, the recurring symptoms cause debilitating, life-long health problems. For those living in areas where EIA is prevalent, mosquito control and vigilance are a must. EIA has been diagnosed world-wide, although some areas where testing is not required, that have a large population of horses and mosquitoes are more likely to have outbreaks of EIA. To prevent the spread of the disease many events require a negative Coggins (AGID) or ELSA test to be presented.


EIA, Swamp Fever, Equine Infectious Anemia

Causes of Swamp Fever:

EIA is a virus carried from horse to horse by biting insects such as mosquitoes. There is also a slight risk it could be transmitted via un-sterilized needles and other veterinary medical equipment, from mare to nursing foal, or the virus may be ingested. Mares can get the virus from breeding stallions. Fetal foals may also get the virus through the placenta resulting in spontaneous abortions or the foal dying within weeks of birth.


Symptoms include listlessness, elevated temperature, respiration and pulse, weakness, loss of coordination, abortion in broodmares and decline in overall health and vitality. The fever tends to spike then decrease, sometimes within a short time. Jaundice and fluid retention may develop. Small lesions may form on the tongue and other mucous membranes such as cheeks and inner nostrils.



The virus damages the horse's immune system and is closely related to the human HIV virus. During the early stages of the disease, horses suffer from fever and hemorrhaging. About 30% will die within the first stage of the disease. Those who survive may experience a return of symptoms, recover then experience the symptoms again with less severity. The symptoms may return in response to stress such as hot weather, hard work, drug sensitivities or breeding.


In some horses symptoms may disappear so the horse seems to have fully recovered.  However, the horse will remain a carrier. Even though the horse appears healthy, the virus remains in its bloodstream. Horses don't have outward signs of the virus after they recover. The only sure way to make a diagnosis is with a 'Coggins' blood test or ELSA test. Both tests can be done by your veterinarian and are often required for competitions.

Prevention of Equine Infectious Anemia:

Swamp fever can only be prevented by stopping the spread of the virus. Testing can identify possible carriers of the virus so that the individual can be appropriately dealt with. Insect control on horses and around stables can help destroy the flies and mosquitoes that transmit the disease.


There is no cure or vaccination for swamp fever. If the horse survives the initial infection, it’s health care to treat the cyclic symptoms will be ongoing. Horses that are found to be carriers, but present to symptoms, must be kept in quarantine that makes it impossible for a carrier such as a mosquito to transfer it to another horse. This means the horse must not be kept within several miles of other horses, and never be brought into contact with other horses at any time. The horse cannot be used for competition or breeding. This can be very difficult, and it is unhealthy for a horse to be kept alone. However, if adequate quarantine measures are impossible, the horse must be euthanized.

©2014 About.com. All rights reserved.