The Equine Disease Communication Center (EDCC) reported Aug. 29 that a horse from Ulster County, New York, has been euthanized after contracting Eastern equine encephalitis (EEE).

“An unvaccinated 11-year-old mare was diagnosed with EEE this week,” the EDCC statement read.

The owner first noticed clinical signs on Aug. 22 and a vet came out to examine on the same day. Clinical signs included depression, trembling, stumbling, blindness, and fever, the EDCC said. The veterinarian treated the horse symptomatically and returned the next day to find the horse down and unresponsive, the EDCC said. The horse was euthanized on Aug. 23. West Nile virus and rabies tests were negative, the statement noted.

A viral disease, EEE affects the central nervous system and is transmitted to horses by infected mosquitoes. Clinical signs of EEE include moderate to high fever, depression, lack of appetite, cranial nerve deficits (facial paralysis, tongue weakness, difficulty swallowing), behavioral changes (aggression, self-mutilation, or drowsiness), gait abnormalities, or severe central nervous system signs, such as head-pressing, circling, blindness, and seizures. The course of EEE can be swift, with death occurring two to three days after onset of clinical signs despite intensive care; fatality rates reach 75-80% among horses. Horses that survive might have long-lasting impairments and neurologic problems