The outbreak of neurologic equine herpesvirus (EHV-1) continues as new cases were confirmed over the weekend. The source of the outbreak is believed to be the April 29-May 8 National Cutting Horse Association’s (NCHA) Western National Championships in Ogden, Utah. Horse owners and veterinarians remain on the lookout for clinical signs associated with EHV-1 in exposed horses.

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.

The USDA released its last situation report Thursday, May 19. At press time today (May 22), the case counts by state were as follows:

Arizona – Both the USDA situation report and the state Department of Agriculture indicate that as of May 18, there has only been one positive case of EHV-1 reported in Arizona. The horse reportedly displayed severe neurologic signs, and the USDA situation report suggested that he was euthanized