The Equine Disease Communication Center (EDCC) reported Feb. 28 that a recently imported Warmblood mare now residing in Kentucky has tested positive for equine herpesvirus-1 (EHV-1).

“On Monday Feb. 26, the Kentucky Office of the State Veterinarian received notification confirming the diagnosis of equine herpes myeloencephalopathy (EHM, the neurologic form of the virus) in a Warmblood mare that had imported through the USDA’s New York Animal Import Center and consigned to a private quarantine facility in Kentucky to complete CEM (contagious equine metritis) quarantine,” the EDCC said. “The mare arrived at the Kentucky facility on Feb. 18 and first developed acute neurologic signs during the evening on Sunday, Feb. 25. The mare was referred and transported to a local equine hospital the following morning where she was diagnosed positive for EHV-1 neuropathogenic strain.

“This mare had no direct exposure to resident horses while in quarantine and no other horses in the facility are exhibiting clinical signs of EHM,” the agency continued. “The population of horses will continue to be monitored and horses identified or considered to have had indirect exposure will test negative prior to being released from quarantine. Transport cohorts have been identified and notices given to appropriate personnel. USDA officials and transport staff have been notified of the diagnosis.”

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 EHM. In many horses, the 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 the neurologic form 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.