
Recently, fifteen horses at a facility in Stanislaus County, California, tested positive for equine infectious anemia (EIA). Due to this, euthanasia was chosen by the owners for these horses, and it was carried out in the presence of California Department of Food and Agriculture veterinarians on March 24 and April 7. Additionally, twelve other horses that were exposed will remain quarantined until their 60-day retest.
EDCC Health Watch is a marketing program by Equine Network that uses information from the Equine Disease Communication Center (EDCC) to generate and share verified equine disease reports. The EDCC is a nonprofit organization that relies on industry donations to provide accessible infectious disease information.
Understanding EIA
Equine infectious anemia is a viral disease that targets horses’ immune systems. The virus spreads through the exchange of body fluids from an infected animal to an uninfected one, often via blood-feeding insects like horseflies. It can also be transmitted through the use of blood-contaminated instruments or needles.
A Coggins test screens a horse’s blood for antibodies that indicate the presence of the EIA virus. Most U.S. states mandate horses to have a negative Coggins test proof for interstate travel.
Once a horse contracts EIA, it remains infected for life and can serve as a source for disease transmission. While not all horses display symptoms, those that do may show:
- Progressive weight loss;
- Muscle weakness;
- Reduced stamina;
- Fever;
- Depression; and
- Anemia.
EIA lacks a vaccine or cure. An infected horse either succumbs to the disease, is euthanized, or must be placed under strict quarantine conditions (at least 200 yards away from healthy equids) for its lifetime.

