The California Department of Food and Agriculture (CDFA) has confirmed that a 15-year-old Warmblood mare from Sacramento County tested positive for equine herpesvirus-1 (EHV) after exhibiting severe neurologic signs of disease.

“The mare initially showed signs of colic on Friday, April 21, and was transported to a veterinary clinic for veterinary care,” the CDFA’s April 28 update noted. “While in isolation at the veterinary clinic, the mare started displaying neurologic signs, became recumbent, and was subsequently euthanized due to the severity of signs. Quarantine biosecurity measures were immediately implemented at the home premises.

“With neurologic signs and detection of EHV-1, this horse meets the case definition for an equine herpesvirus myeloencephalopathy (EHM) case, which is reportable and actionable in the state of California,” the CDFA continued. “CDFA issued a quarantine for 31 exposed horses which requires implementation of biosecurity measures including twice daily temperature taking and observation of horses. No exposed horses have displayed signs of disease. (The) CDFA continues to monitor the situation onsite.”

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 (the neurologic form). In many horses, fever is the only sign of EHV-1 infection, which can go undetected