The Equine Disease Communication Center (EDCC) reported Oct. 10 that additional New York horses have tested positive for Eastern equine encephalitis (EEE) and West Nile virus (WNV).

The New York State Department of Agriculture and Markets (NYSDAM) reported that an Oswego County horse tested positive for EEE and has been euthanized, the EDCC said.

Meanwhile, NYSDAM has confirmed four additional WNV cases. One horse from St. Lawrence County is still alive but was not vaccinated for the disease, the EDCC said, while the three other horses—which resided in Cayuga, Erie, and St. Lawrence counties—have been euthanized. The EDCC said two of those three were not vaccinated, and the other horse had been vaccinated but not enough time had elapsed for the vaccine to be protective.

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