A horse at Arapohe Park racetrack in Colorado has tested positive for equine infectious anemia (EIA).
Quarantine measures have been put in place, but authorities believe the risk of transmission is currently low.
The virus that causes the disease is spread by bloodsucking insects. Horses may not appear to have any symptoms of the disease, although it can also cause high fever, weakness, weight loss, an enlarged spleen, anemia, a weak pulse and even death.
There is no cure, so infected animals have to be quarantined for life or euthanized.
The Colorado Department of Agriculture’s state veterinarian’s office was told of the positive test on June 23. Confirmatory tests are being run.
The racetrack, in Arapahoe County, is currently under a hold order that restricts the movement of horses until an initial investigation is completed by the state agriculture department.
The affected horse had been in Colorado fewer than 60 days and came from an out-of-state track.
It appears the horse was infected before coming to Colorado and previously tested negative for the disease in May last year.
Because the disease is most commonly spread by biting flies, and it is early in Colorado’s fly season, the risk of transmission to other horses at the track appears to be relatively low, authorities said.
The state agriculture agency and the US Department of Agriculture’s Veterinary Services division is working with Arapahoe Park officials and the horse owner to gather more information to respond to the initial positive test.
Horses in the US must be tested annually for EIA before they can be transported across state lines. The test for EIA is commonly called a Coggins test.