West Nile Virus (WNV) has been confirmed in Grey County, Ontario. On August 16, 2025, an 8 year old Standardbred gelding developed acute neurologic signs ataxia, hyperesthesia, intermittent to persistent recumbency). Serum WNV IgM ELISA was positive. The horse was euthanized. The horse was not vaccinated against WNV.
This is the third confirmed case of equine WNV in Ontario this year . To see past and present WNV cases in Ontario go to: https://www.oahn.ca/resources/ontario-equine-disease-alerts/ and enter the disease surveillance portal.