A Contra Costa County, Calif., mare has tested positive for neuropathogenic equine herpesvirus-1 (EHV-1), the California Department of Food and Agriculture (CDFA) reported July 5.

"A 4-year-old Quarter Horse mare in Contra Costa County displaying severe neurologic signs has been confirmed positive for the neuropathogenic strain of equine herpesvirus-1," the CDFA said in a statement. "Due to the severity of clinical signs in this case of equine herpes myeloencephalopathy (EHM), the mare was euthanized. Initial epidemiologic investigation indicates no exposed horses as the mare was the sole horse on a pasture with cattle. The CDFA continues with the epidemiologic investigation and to monitor the situation."

Equine herpesvirus-1 is highly contagious among horses and camelids and is generally spread via aerosol transmission (when infected animals sneeze and cough) and through contact with nasal secretions from infected animals. The disease can cause a variety of problems in horses, including rhinopneumonitis (a respiratory disease usually found in young horses), abortion in broodmares, and EHM (the neurologic form of EHV-1).

Fever, ataxia (incoordination), weakness or paralysis of the hind limbs, and incontinence are signs of EHM. If a horse that has possibly been exposed to EHV-1 begins to display any of the aforementioned signs, call your veterinarian immediately