Officials at the California Department of Food and Agriculture (CDFA) confirmed a 13-year-old Quarter Horse mare from San Bernardino County, California, with equine herpesvirus-1 (EHV-1). | Photo: Wikimedia Commons

The mare began showing clinical signs of fever, hypermetria (cerebellar dysfunction in which voluntary muscular movements tend to result in the movement of bodily parts beyond the intended goal), and neurologic signs on Oct. 29. She was euthanized the same day due to the severity of her signs and confirmed positive upon necropsy on Nov. 5.

Twenty exposed horses on her home premises have been quarantined and enhanced biosecurity measures enacted, including twice-daily temperature monitoring. The positive horse is not linked to any other California EHV-1 cases and had not recently moved off the premises. CDFA continues to monitor the situation.

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 myeloencephalopathy (EHM, the neurologic form)