Equine herpesvirus type 1 (EHV-1) has been confirmed as the cause of illness in three Thoroughbreds that were stabled in a training barn at Turfway Park in Florence, Ky. Tuesday's announcement follows treatment and elimination of several EHV-1 outbreaks in Ohio and Pennsylvania since January.
The EHV-1 organism can cause three different forms of disease, including rhinopneumonitis (a respiratory disease often affecting young horses), abortions in pregnant mares, and neurologic disease. Horses in the Ohio and Pennsylvania outbreaks showed fevers, respiratory illness, and neurologic deficits. In the Kentucky cases, horses have shown fevers, and two of the horses showed neurologic signs several days later. There are at least seven other strains of equine herpesviruses. Horses can survive the neurologic form of EHV-1 with supportive care, but if a horse becomes recumbent (stays down), it is difficult to nurse the horse back to health. The virus doesn't live long in the environment, and it can be killed with bleach.
The first two sick horses from Turfway were sent to Rood and Riddle Equine Hospital in Lexington March 6. The third horse developed a fever over the March 15-16 weekend and is under treatment in isolation at Turfway.
Dr. Bonnie Barr of Rood and Riddle treated the two EHV-1 cases, a 3-year-old gelding and a 4-year-old filly. According to Barr, the horses showed acute neurologic signs upon referral to the hospital, and were placed immediately in an isolation facility.
"I was suspicious from the clinical signs, but we did further testing to rule out other neurological diseases," she said. "They were in our isolation facility the whole time they were here."
"Both of them had pretty much symmetrical posterior paresis or ataxia, and one of them actually was recumbent when it got here," she said. "They both did progress to the point where they had bladder paralysis," a common clinical manifestation of EHV-1.
Barr and veterinary staff administered anti-inflammatories, an antiviral drug called acyclovir, and supportive care for the horses. They collected serum and nasal swabs from the horses, and virus isolation was completed on the blood at the Gluck Center March 11.
Barr explained that the blood test takes about five days to complete. "The blood was the first test to come back positive, but that was enough to give us our diagnosis (EHV-1)."
Back at Turfway Park, the third horse is recovering, and the barn has been quarantined. Only certain people are allowed in and out of the barn, and must use disinfection protocol. Handlers are regularly taking the temperatures of all horses which came into contact with horses in the particular barn, and looking for any unusual signs of illness.