Equine Infectious Anemia Reported In Two Washington Horses

For the first time in seven years, the Washington State Department of Agriculture has confirmed equine infectious anemia in two horses. The two horses come from separate farms in Yakima County but were together on one of the farms earlier this summer. A private veterinarian tested the first horse, a 7-year-old quarter horse gelding, after the owner became concerned about possible exposure to EIA while recently stabled at an out-of-state facility. After that test returned positive, WSDA veterinarians tested horses at the second farm and an 8-year-old quarter horse gelding also tested positive for the disease. Both locations are under quarantine and testing and contact tracing efforts are underway. WSDA field vets are working closely with the owners and local veterinarians to monitor potentially exposed horses and implement biosecurity measures to prevent further infection.

EIA, also known as Coggins disease, is a bloodborne illness affecting only members of the Equidae family (horses, ponies, donkeys, mules, and zebras). Historically the virus has been transmitted between horses by blood-feeding insects, most commonly horse flies, deer flies, and stable flies. However, more recently, iatrogenic (human caused) transmission has become more common through shared, blood-contaminated equipment, needles, syringes, or multidose vials of medication. In 2020, 80% of all EIA infections in the U.S. were in quarter horse racehorses and were human caused.

Both infected horses were actively involved in the quarter horse and bush track racing circuits in both Washington and California. Some of the iatrogenic transmission cases in the quarter Horse racehorse population are found in horses participating in unsanctioned racing. However, there are also recognized crossover cases between unsanctioned and sanctioned racing in some parts of the United States.

WSDA urges anyone who has reason to believe their horse may have been exposed at a race and rescue groups that have taken in retired racetrack horses to consider contacting their veterinarian and proactively testing their horses for EIA. Often these horses are also co-infected with Piroplasmosis, a bloodborne protozoal infection.

“Although it does not affect people,” Dr. Amber Itle, Washington State Veterinarian said, “EIA is a very serious disease in horses that can quietly spread through a herd for many months to years prior to detection and there is no treatment for it. I would strongly encourage anyone with a quarter horse with an unknown history to proactively test your horse.”

Infected horses may die from the disease, but more often, they show little to no symptoms and recover, becoming chronically infected lifelong carriers of the virus. These horses serve as a reservoir of the virus and continue to spread it. Therefore, EIA-positive horses must be euthanized or held under strict isolation and quarantine for the remainder of their lives.

WSDA suggests all horse owners follow these USDA tips to prevent the infection and spread of EIA:

Separate symptomatic horses from others and contact your veterinarian immediately.
Keep the area in and around your barn clean and dry to reduce the insect population.
Apply fly sprays and insect repellants as needed.
Only use sterile needles and licensed blood products; never reuse needles or syringes.
Use a sterile needle each time you puncture a multi-dose medication bottle.
Do not share surgical or dental equipment that is contaminated with blood or debris between horses.
Allow only licensed veterinarians using blood from confirmed EIA-negative donor horses to perform blood transfusions.
Disinfect bits and lip chains between horses.
Clean and cover open wounds.
Test every horse at least annually.
Require proof of a recent negative EIA test for new horses entering the premises or when purchasing a new horse.