Eastern Equine Encephalitis (EEE) has been confirmed in Simcoe County, Ontario. On September 1, 2025, a 10 year old Miniature Horse mare was euthanized after becoming acutely recumbent and developing seizures. EEE was confirmed on October 3, 2025. The horse was undervaccinated against EEE. Another miniature horse had died after developing similar signs two weeks prior to September 1, and is a suspected case.
This is the 8th confirmed equine EEE case in Ontario this year. To see past and present EEE cases in Ontario go to: https://www.oahn.ca/resources/ontario-equine-disease-alerts/ and enter the disease surveillance portal.