Eastern Equine Encephalitis (EEE) has been confirmed in the United Counties of Prescott and Russell, Ontario. On September 22, 2024, a 15 year old Quarter Horse cross developed acute neurologic signs (severe ataxia, muscle tremors, reduced PLR, obtunded). The horse was euthanized later that evening due to progressive neurologic signs. EEE was confirmed on October 7, 2024. The horse was not vaccinated against EEE. This is the 22nd case of equine EEE in Ontario this year.