In many horses, the first or only sign of EHV-1 infection is fever, which can go undetected | Photo: Stephanie L. Church/The Horse

On Aug. 21, California Department of Food and Agriculture (CDFA) officials confirmed a 17-year-old Thoroughbred gelding with neurologic equine herpesvirus-1 (EHV-1). The El Dorado County gelding, which had been vaccinated, presented with clinical signs on Aug. 13. Signs included fever, forelimb ataxia (loss of control of bodily movements), recumbency (inability to rise), and mild obtundation (diminished consciousness). He was subsequently euthanized.

Ten horses were exposed at the facility, which is now under quarantine. According to a CDFA statement, enhanced biosecurity measures have been enacted and exposed horses are undergoing twice-daily temperature monitoring. The gelding had not been shown or left the facility during the 14 days prior to his illness, and there is no connection to the EHV-4 case confirmed on Aug. 3 in Imperial County.

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 myeloencephalitis (EHM, the neurologic form)