An unvaccinated Mustang residing in Osceola County, Florida, was euthanized after testing positive for Eastern equine encephalitis (EEE), the Equine Disease Communication Center (EDCC) reported May 13.

The EDCC stated that the 2-year-old, who had not left the property in over a year, began exhibiting clinical signs on May 6 and was euthanized for humane reasons on May 7.

This is the first confirmed EEE case in Osceola County and the second confirmed case in Florida for 2016. The first was in an  unvaccinated 18-month-old Quarter Horse residing in Polk County in April.

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