EHV-1 Confirmed in Michigan Standardbred Horse

A Standardbred racehorse residing in Genesee County, Mich., has tested positive for neurologic equine herpesvirus-1 (EHV-1), state veterinarian Steve Halstead, DVM, confirmed Jan 2.

Halstead told that the affected horse participated in a race at Sports Creek Raceway, a haul-in only racetrack in Swartz Creek, Mich., on Dec. 22, 2012, and began showing neurologic signs of disease on Dec. 23, 2012. That day, the animal's owner/trainer contacted their veterinarian, who took samples and sent them for evaluation at the state diagnostic lab, Halstead said. He was informed of the positive test results Dec. 28, shortly before 5:00 p.m., he said.

"(The horse's condition) worsened through the first part of that week; in fact the veterinarian thought it was pretty much over on Wednesday (Dec. 26), but he since has recovered," Halstead said. "There's one other horse in the same stable, but there's no indication that it's ill."

Halstead noted that both horses had previously received rhinopneumonitis vaccinations, "which is normal procedure for this veterinarian and this trainer. It wasn't following infection, just a routine vaccination."

Halstead said both horses have been placed under quarantine, which will last at least 21 days.

The Sports Creek harness meet has concluded, Halstead said, and harness racing does not resume in Michigan until mid-January. Several harness racing tracks across the country, including The Meadowlands Racetrack in New Jersey and Balmoral Park in Illinois, have placed entry restrictions on horses that have raced at Sports Creek in recent days. The Meadowlands, for instance, is denying horses that raced at Sports Creek after Dec. 1, 2012, until further notice.

"Right now we're just waiting for the quarantine period and monitoring the horses," Halstead said, noting that the horses' veterinarian and owner/trainer are working closely with officials to monitor the situation.

Although it's not transmissible to humans, EHV-1 is highly contagious among horses and camelids, and it is generally passed from horse to horse via aerosol transmission (when affected animals sneeze/cough) and contact with nasal secretions. The disease can cause a variety of ailments in equines, including rhinopneumonitis (a respiratory disease usually found in young horses), abortion in broodmares, and myeloencephalopathy (EHM, the neurologic form).

Myeloencephalopathy is characterized by fever, ataxia (incoordination), weakness or paralysis of the hind limbs, and incontinence. Should a horse with potential EHV-1 exposure display any of the aforementioned clinical signs, a veterinarian should be called to obtain samples and test for the disease. will continue to provide updates as more information becomes available.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.