A horse in Nassau County, Florida, has tested positive for Eastern equine encephalitis (EEE), the Equine Disease Communication Center (EDCC) announced Feb. 26. According to Florida Department of Agriculture and Consumer Services statistics, this is the first EEE case for the county and the second for the state in 2018.

“The 7-year-old Quarter Horse mare became clinical on Jan. 31 and was euthanized due to a poor prognosis,” the EDCC said. “The vaccination history is unknown.”

The positive EEE test result came in on Feb. 12, the EDCC said.

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