What is Equine Infectious Anemia?

board of animal health

Reportable Disease of the Month

Equine Infectious Anemia

What is it?

Equine Infectious Anemia (EIA) is a viral disease affecting horses, donkeys, and mules. It is spread primarily by large biting flies, and is found worldwide. The Minnesota Board of Animal Health quarantines infected horses for life because they remain a reservoir for the disease after they’re infected. Horses must have a negative blood test (Coggins test) within 12 months of importation into Minnesota or exhibition at a public event.

How is it transmitted?

EIA is primarily a blood borne infection. There are several routes for the virus to spread, and the most common is through horse and deer fly bites. The virus can be spread by in-utero passage from mare to foal. People can spread it to horses by the use of contaminated needles or other equipment not sanitized after working with infected horses, mules or donkeys. Researchers have also found the virus in milk and semen. Infected horses are lifelong carriers and can shed the virus even if they appear healthy.

What are the clinical signs?

Unfortunately, EIA can be difficult to spot because infected horses may not appear to have any clinical signs of the disease. Severely sick horses are most likely to exhibit clinical signs including high fever, fatigue, fluid build-up in the legs and under the chest, anemia, and loss of appetite.

How is it treated?

There is no vaccine or treatment for EIA. Once a horse is infected, it remains infected for life and is always a potential reservoir for spread of the disease. EIA infected horses must be permanently quarantined and isolated or be euthanized.

Is there a risk to people?

There is no known risk to people and EIA is not a zoonotic disease.

How can it be prevented?

Biosecurity is the best option of preventing many diseases from affecting horses and other animals. Insect and pest control is a proactive step owners can take to reduce potentially infected flies from biting their animals. Other measures, like cleaning and disinfecting equipment and supplies, and isolating new horses until they’re tested for EIA are recommended. Minimizing or eliminating contact between non-exposed and infected horses is instrumental in preventing spread of the disease. Horse owners are encouraged to test for EIA routinely, stable or pasture horses at facilities that require testing, and avoid shows or events where testing is not a requirement. Report cases of EIA to the Minnesota Board of Animal Health.

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