Equine herpesvirus 1 (EHV-1) has been confirmed in a 24 year old mare, in Wellington County, Ontario, at a boarding facility. On July 7, 2026, the mare developed acute ataxia in all four limbs with muscle fasciculations and hyperesthesia. Clinical signs progressed and she was euthanized. Nasal swab and blood samples tested positive for EHV-1. There was no history of recent travel.
The facility owner, working with their veterinarian, has instituted voluntary animal movement restrictions and biosecurity protocols. To see past and present EHV-1 neurologic (EHM) cases in Ontario go to: https://www.oahn.ca/resources/ontario-equine-disease-alerts/ and enter the disease surveillance portal.