Eastern Equine Encephalitis (EEE) has been confirmed in the Regional Municipality of Halton, Ontario. A 16 year old Draft mare was clinically normal on the morning of August 21, 2025, but by late afternoon had developed acute, progressive neurologic signs and she was euthanized the following day despite supportive therapy. The horse was not vaccinated against EEE. Three additional horses were exposed.
This is the sixth 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.