Between May 23 and May 27, the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) confirmed four horses on a Dufferin County, Canada, farm with the neurologic form of equine herpesvirus-1 (EHV-1). Two of the horses were euthanized due to the severity of their clinical signs, and the other two were referred to an equine hospital for treatment. On May 23, a fifth horse on the farm was euthanized due to severe, progressive neurologic signs; however, that horse was not tested for EHV-1.

On May 17, the attending veterinarian and the farm manager imposed strict biosecurity procedures and restricted horse and human movement on and off the farm. The disease has been contained to the farm’s main barn.

According to OMAFRA, the outbreak is linked to a racing facility in the city of Toronto where an outbreak was reported on May 18. At that facility, four horses were confirmed with equine herpesvirus myeloencephalitis (EHM, the neurologic form) and treated at an equine hospital, and a fifth horse presumed to have EHM was euthanized. The outbreak there was limited to a single barn.

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