Several states affected by the neurologic equine herpesvirus-1 (EHV-1) outbreak saw more horses test positive for the disease Thursday, while other states saw their totals remain steady. Now, nearly two weeks after the conclusion of the competition believed to be the point of origin for the outbreak (the National Cutting Horse Association’s Western National Championships, held April 29-May 8 in Ogden, Utah), veterinarians are diagnosing and treating both confirmed and suspected EHV-1 cases in an attempt to slow or stop the spread of the virus.

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 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.

At press time, the state and province totals of positive and suspected EHV-1 cases were as follows:

Washington – Debra C. Sellon, DVM, PhD, Dipl. ACVIM, a professor of equine medicine at Washington State University (WSU), confirmed today that two horses at the WSU Veterinary Teaching Hospital tested positive for EHV-1