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

Authorities placed the premises under quarantine in October when one horse, a gelding with unreported vaccination status, tested positive for the neurologic form of EHV-1, also known as equine herpesvirus myeloencephalopathy (EHM). The affected horse first experienced clinical signs of ataxia (incoordination), fever, nasal discharge, and recumbency (inability to rise) on Oct. 12.

Nine other horses on the affected farm were quarantined and monitored for signs of illness. Two horses subsequently spiked mild fevers that resolved, and an additional horse on the premises exhibited fever and neurologic signs that resolved spontaneously after three days. No other horses or premises have been reported in connection with the index case.

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 EHM