Washington has reported its first cases of equine infectious anemia in seven years, as two horses from Yakima County tested positive for the disease.

The horses are from separate farms but were together on one of the farms this summer, the State Department of Agriculture reports.

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, according to the WSDA.

After the National Veterinary Services Laboratory confirmed the positive test, 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.

A bloodborne illness

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 percent 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.”

Lifelong carriers

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:

For more information about Equine Infectious Anemia: EIA Factsheet or on USDA’s website.

Source: Washington State Department of Agriculture