A Standardbred horse at The Meadows Racetrack and Casino in Washington County tested positive yesterday (Wednesday, Jan. 24) for equine herpes virus, or EHV-1, making it the second confirmed case in the state this month.

Last week, veterinarians with the Pennsylvania Department of Agriculture and the University of Pennsylvania School of Veterinary Medicine confirmed a case at the school’s New Bolton Center in Kennett Square, Chester County.

The Washington County horse tested positive after it was moved to the Ohio State College of Veterinary Medicine for diagnostic tests. Veterinarians report that the horse is responding well to treatment.

As a precaution, two barns at the Meadows racetrack have been quarantined to control any potential spread of the virus. Trainers are monitoring two of approximately 60 potentially exposed horses in the quarantined barns that presented with elevated temperatures. No additional horses at the racetrack have shown signs of clinical illness, but the movement of horses into or out of the track has been restricted until all horses receive a clean bill of health.

The Meadows Racetrack was closed yesterday due to a power outage and poor track conditions, but reopened today (Jan. 25). Clinically healthy horses are being allowed to jog around the track to stay in shape. Pending improvement in track conditions, all non-quarantined horses should be eligible to race again on Saturday.

In the New Bolton Center case last week, a 30-year-old horse developed symptoms compatible with equine herpes myeloencephalopathy, or EHM, then tested positive for EHV-1 on January 16. A second horse, housed in an adjacent barn, also developed a fever and later tested positive for EHV-1. The second horse was moved to a state-of-the-art, on-site isolation facility with dedicated staff who are entirely separate from personnel handling other horses.

The Pennsylvania Department of Agriculture contacted owners and quarantined other potentially exposed horses that left the New Bolton Center prior to confirming the EHM diagnosis. To control the spread of the virus, Orders of Special Quarantine were posted at other Pennsylvania premises that had recently received potentially exposed horses. In addition to increased biosecurity, these locations are required to conduct twice daily temperature checks, monitor, and report any horses showing signs of EHV-1 infection. No new cases have been identified since the original diagnosis.

EHV-1 is a highly contagious virus that commonly circulates in horse populations. Depending on the specific strain of the virus, the equine herpes virus can cause a variety of clinical signs in infected horses, including respiratory disease or abortion in pregnant mares. The EHM form of the disease can cause horses to suffer varying degrees of paralysis and ataxia; in severe cases, the infected horse may be euthanized. While EHV-1 can cause illness in horses, other equine animals and camelids (llamas and alpacas), it does not pose a health threat to people or other animals.

Unless a new case is detected, all horses can be cleared after 28 days without symptoms, or after 21 days with confirmation of negative test results for both blood samples and nasal swab tests.

Experts note that many horses carry a latent form of the herpes virus, and symptoms may not appear unless the animal is stressed. Although horses are vaccinated for other strains of the equine herpes virus, there is no existing vaccine for the EHV-1 strain of the virus.

(PA Dept. of Agriculture)