Equine Infectious Anemia (EIA)

 

Equine Infectious Anemia (EIA) is a viral disease affecting only equidae (horses, ponies, zebras, mules, and donkeys). It was mistakenly believed to only occur in wet, humid regions of the southern United States thus earning the moniker of “Swamp Fever”. Its actual distribution is nearly worldwide, regardless of climate. There is no vaccine or treatment, and infection is often in-apparent and results in a lifelong carrier state if the horse survives the acute phase of the infection. Since there is no treatment for EIA – infected animals must be permanently isolated, quarantined, or euthanized. There is no evidence that EIA is a threat to human health and is a reportable animal disease in all states.

USDA APHIS - Equine Infectious Anemia (EIA)


  • Jaundice
  • Rapid breathing
  • Rapid heart rate
  • Depression
  • Muscle weakness
  • Swelling of the limbs
  • Bleeding from the nose, or hemorrhage on mucous membranes
  • Blood-stained feces

Clinical signs are often nonspecific and variable – making EIA difficult to differentiate it from other diseases. Incubation period is often variable as well ranging from one week to 60 days or longer.


Transmission of EIA naturally occurs through blood feeding flies (horse, deer flies, etc…) and is frequently transmitted through re-used needles, syringes, and/or contaminated instruments. Mares can transmit the virus to foals in utero and less likely via milk or semen.


Awareness and prevention of EIA is best accomplished through good biosecurity practices such as:

  • Insect control using insect repellents, fly control mediation – managing manure piles.
  • Eliminate standing water where possible (gutters, old tires, open containers/equipment).
  • Never sharing needles and other medical equipment between horses.
  • Routine EIA testing to determine the status of new horses before introduction into your herd.