More than three weeks after the first cases of equine herpesvirus-1 (EHV-1) related to the current outbreak were diagnosed, new confirmed cases are still being reported to state and provincial animal health authorities. The outbreak, which is believed to stem from horses attending an Odgen, Utah, cutting horse championship competition in early May, has now seen dozens of horses test positive for the disease, and more than 10 horses have been euthanized or died as a result.

Equine herpesvirus-1 is highly contagious and can cause a variety of ailments in horses, including rhinopneumonitis (a respiratory disease usually found in young horses), abortion in broodmares, and myeloencephalopathy (the neurologic form). The virus is not transmissible to humans. Clinical signs of EHV-1 myeloencephalopathy (EHM) include fever, ataxia (incoordination), weakness or paralysis of the hind limbs, and incontinence. The virus is generally passed from horse to horse via aerosol transmission (when affected animals sneeze/cough) and contact with nasal secretions.

New Confirmed Cases

At press time (4:00 p.m