Equine herpes myeloencephalopathy has been confirmed in the Regional Municipality of York, Ontario. A 15 year old mare became acutely recumbent on February 10, 2026. She was assisted to stand and moved to an isolation area, treated supportively, remained stable overnight, became recumbent the following morning but has improved since then. Her ataxia is markedly improved but she still appears to have some urinary incontinence. Nasal swab and blood samples were positive for equine herpesvirus 1 (EHV-1) by PCR. The horse was vaccinated against EHV-1.
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.