Equine Infectious Anemia Leave a comment

Infection Anemia in Horses

Sometimes referred to as horse malaria or swamp fever, Equine Infectious Anemia (EIA) is a virus that causes destruction of the horse’s red blood cells, causing anemia, weakness, and death. EIA has become endemic in certain parts of the world, but is very uncommon in the United States. In fact, EIA is a reportable disease in the U.S., which means that if it is diagnosed in a horse in this country, the veterinarian is required to notify the USDA.

There is no cure for Equine Infectious Anemia. It is spread by the horsefly. Horses are required to be tested for this disease for entry into shows and for transport across state lines. This is a simple routine blood test called a Coggins test.


EIA can present as an acute form or chronic form. The acute form is usually fatal. If the horse survives, it will become a chronic carrier of the disease. Once infected, the virus remains in the horse’s body for the rest of its life. Chronic carries are referred to as “swampers”.

  • Anemia
  • Lethargy
  • Weight loss
  • Fever
  • Enlarged spleen
  • Swollen belly and legs (edema)
  • Depression
  • Decreased athletic performance
  • Death (in acute cases)


EIA is caused by a retro virus and transmitted by horseflies. However, the infection can also be spread through blood-contaminated items such as unsterilized needles, syringes, etc.


Your veterinarian will usually conduct a Coggins test on the suspected animal, which is a laboratory-run blood test to diagnose EIA in horses.



There is no treatment or vaccine available in the U.S. at this time for EIA, though most horses that survive the acute form of this disease may have flare-ups from the symptoms episodically. Interestingly enough, there have even been studies done relating the human HIV virus and EIA, as they are both retroviruses.

Living and Management

If a horse in the U.S. is diagnosed with EIA, there are three options mandated by the USDA. Since it is a reportable disease and there is no cure, the first and most common option is euthanasia. Secondly, the infected horse can be donated to a research facility. Thirdly, the owners can construct a completely enclosed barn covered in wire mesh that does not allow horseflies to enter and the horse is forbidden any contact with other horses. Due to the costs and limitations of the third option, and the limited number of labs that will accept EIA positive horses, most cases result in euthanasia.


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