In many horses, the only sign of EHV-1 infection is fever, which can go undetected. | Photo: Alexandra Beckstett/The Horse

A 17-year-old Thoroughbred gelding from an Orange Country, California, facility has been diagnosed with equine herpesvirus myeloencephalopathy (EHM, the neurologic form of equine herpesvirus-1 ) after developing neurologic signs of disease, the California Department of Food and Agriculture (CDFA) reported April 13.

“The gelding has been isolated and placed under quarantine,” the CDFA’s statement said. “Exposed horses will be monitored for clinical signs and temperatures will be taken twice daily. Any horse displaying a fever or compatible clinical signs will be tested.”

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