The Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) has been notified of two confirmed cases of Equine Herpes Myeloencephalopathy (EHM), caused by equine herpes virus 1 (EHV-1). The horses from Durham Region were referred to the Ontario Veterinary College with neurological signs and are receiving treatment. Three other horses on the farm have tested positive for the mutated (neuropathogenic) strain of EHV-1 on nasal swabs, but are not demonstrating neurological signs at this time. The farm owner has voluntarily placed the premises under a self-imposed quarantine to reduce the risk of viral spread.

These are the first cases of EHM diagnosed in Ontario this year; however, cases of EHM have been diagnosed in California, Kentucky, Louisiana and Michigan since the beginning of the year. In 2015, there were three laboratory-confirmed cases of EHM in Ontario.

EHV-1 infection in horses can cause respiratory disease, abortion, neonatal foal death, and/or neurological disease. EHV-1 is not a federally reportable disease but is immediately notifiable by laboratories under the reporting regulation of the provincial Animal Health Act. Attending veterinarians suspicious of EHM should contact OMAFRA as soon as possible.

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