Horses that have been vaccinated against EEE and WNV in past years will need an annual booster shot; in areas with a prolonged mosquito season, veterinarians might recommend two boosters annually—one in the spring and another in the fall. | Photo: Anne M. Eberhardt/The Horse

North Carolina Agriculture Commissioner Steve Troxler is encouraging horse owners to have their animals vaccinated against mosquito-borne diseases—including Eastern equine encephalomyelitis and West Nile virus—and rabies.

“April until November is prime mosquito-breeding season in North Carolina and when horses are at risk if not properly vaccinated,” Troxler said. “EEE is fatal 90% of the time in horses and WNV has a fatality rate of 30%. Both diseases are preventable by vaccination.”

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