On May 4 the Colorado Department of Agriculture (CDA) State Veterinarian’s Office received notice from the USDA National Veterinary Services Laboratory that a Weld County horse tested positive for equine infectious anemia (EIA).

The horse’s home facility has been placed under a quarantine order that restricts movement of horses until the CDA completes further testing.

“Because the disease is not curable, the affected horse has been euthanized,” said Colorado State Veterinarian Keith Roehr, DVM. “The remaining horses on the facility will be observed and retested in 60 days. The disease is most commonly spread by biting flies and it is very early in Colorado’s fly season; therefore, the risk of disease transmission to other horses at this time is relatively low.”

Equine infectious anemia is a viral disease that attacks horses’ immune systems. The virus is transmitted through the exchange of body fluids from an infected to a noninfected animal, often by blood-feeding insects such as horseflies, and more rarely through the use of blood-contaminated instruments or needles.

A Coggins test screens horses’ blood for antibodies that are indicative of the presence of EIA, and most U.S. states require horses to have proof of a negative Coggins test in order to travel.

Once an animal is infected with EIA, it is infected for life and can be a reservoir for the spread of disease. Obvious clinical signs of the disease include progressive loss of condition along with muscle weakness and poor stamina. An affected horse also could show fever, depression, and anemia.