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Equine Infectious Anemia (EIA)

What is Equine Infectious Anemia (EIA)?

Equine Infectious Anemia (EIA) is a viral disease affecting only members of the equidae family (horses, ponies, zebras, mules, and donkeys). There is no vaccine or treatment for the disease.   Infection is often in-apparent and results in a lifelong carrier state if the horse survives the acute phase of the infection.  
EIA is found widely throughout the world. There is no evidence that EIA is a threat to human health.  EIA is a reportable animal disease in all states.

The clinical signs are often nonspecific and of variable severity. Clinical signs in an acute case can range from fever and decreased appetite to severe anemia and sudden death. It is often difficult to differentiate EIA from other diseases.  Incubation period is a week to 60 days or longer.  Additional clinical signs in an acute case can include:

  • Jaundice (yellow discoloration of mucous membranes)
  • rapid breathing, rapid heart rate
  • swelling of limbs
  • bleeding from the nose, or red/purple spots on mucous membranes
  • blood-stained feces

Horses that survive the acute phase of the disease become chronic, in-apparent carriers.  Some carriers may develop recurrent flare-ups, often following another stress – illness or strenuous work. While donkeys and mules have the ability to contract this virus, most remain non-clinical.

Samples to collect

  • Serum should be collected and submitted to an EIA APHIS-Approved Laboratory using a VS Form 10-11 or approved electronic EIA submission system.  EIA is a reportable disease in all states.
  • Sample of Form 10-11 and Instructions.  Note that VS 10-11 forms are only available to accredited veterinarians and there are no approved fillable pdfs of the form for submissions. 

Post Mortem Lesions

  • Spleen, liver and abdominal lymph nodes may be enlarged. Mucous membranes can be pale. In chronic cases, emaciation may also be noted. However horses that die between clinical episodes may have no gross lesions.

Natural transmission of EIA is by blood feeding flies (horse flies and deer flies) and is limited to relatively short distances. This virus is frequently transmitted via unclean or re-used needles and syringes, blood transfusions and contaminated instruments (IV sets, dental instruments, tattoo equipment).  Mares can transmit the virus to foals in utero, and, less likely, transmission can occur via milk or semen.

There is no treatment for EIA. Because infected animals become lifelong carriers they must be permanently isolated and quarantined or euthanized.

Reducing exposure to biting flies through management practices may reduce the spread of infection. To prevent iatrogenic spread, never reuse needles, syringes or IV sets, use only new, clean needles with injectable medicines and use only licensed and approved blood products. Blood transfusions should be performed only by licensed veterinarians using donor horses tested negative for EIA and other blood-borne infections like equine piroplasmosis.

Surveillance and testing are the best methods of prevention. Since EIA control efforts began over 40 years ago the reactor rate has fallen from 4% to .004% in 2017 among tested animals. USDA recommends testing every equid annually.

There is no vaccine approved for use in the U.S.

  1. Call your veterinarian
  2. Move suspected horse at least 200 yards away from other horses
  3. Reduce exposure to biting flies

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