On March 31, Kentucky Department of Agriculture (KDA) officials reported negative results from all horses at Blackwood Training Center’s Barn B for equine herpesvirus-1 (EHV-1). This testing followed an EHV-1 outbreak in Woodford County, Kentucky, that began with one horse on March 6 at Blackwood Training Facility and escalated to six positive horses, including two at Turfway Park on March 14.

In addition to the negative findings, more than 14 days have elapsed since any horse in Barn B was potentially exposed to a positive case. Officials released the Barn B horses from quarantine to resume normal activities beginning April 2.

In Blackwood’s Barn A, daily monitoring continues. No fevers or other clinical signs have occurred and officials have tentatively scheduled these horses for PCR testing of nasal swabs and whole blood later this week.

EHV 101

Herpesvirus is highly contagious among horses and can cause a variety of ailments in equids, including rhinopneumonitis (a respiratory disease usually found in young horses), abortion in broodmares, and equine herpesvirus myeloencephalitis (EHM, the neurologic form).

In many horses, the first or only sign of EHV-1 infection is fever, which can go undetected. In addition to fever, other common signs of EHV-1 infection in young horses include cough, decreased appetite, depression, and a nasal discharge. Pregnant mares typically show no signs of infection before they abort, and abortions usually occur late in gestation (around eight months) but can be earlier. Abortions can occur anywhere from two weeks to several months following infection with EHV-1.

Horses with EHM usually have a fever at the onset of the disease and might show signs of a respiratory infection. A few days later, neurologic signs such as ataxia (incoordination), weakness or paralysis of the fore- and hind limbs, urine retention and dribbling, loss of tail tone, and recumbency (inability to rise) develop.

Herpesvirus is easily spread by nose-to-nose or close contact with an infectious horse; sharing contaminated equipment including bits, buckets, and towels; or clothing, hands, or equipment of people who have recently had contact with an infectious horse. Routine biosecurity measures, including hygiene and basic cleaning and disinfection practices, should be in place at all times to help prevent disease spread.

Current EHV-1 vaccines might reduce viral shedding but are not protective against the neurologic form of the disease. Implementing routine biosecurity practices is the best way to minimize viral spread, and the best method of disease control is disease prevention.