Twenty-five cases of Eastern equine encephalitis (EEE) have been confirmed in Wisconsin horses since mid-August, mostly in north central Wisconsin, State Veterinarian Robert Ehlenfeldt, DVM, said Friday (Sept. 23). It has been detected in Price, Lincoln, Taylor, Clark, Marathon, and Dunn counties to date.

A viral disease, EEE affects the central nervous system and is transmitted to horses by infected mosquitoes. The fatality rate for EEE in horses is 75-95%. The course of EEE can be swift, with death occurring two to three days after onset of clinical signs despite intensive care. Horses that survive might have long-lasting impairments and neurologic problems.

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.

Ehlenfeldt advised horse owners to call a veterinarian if their horses show any signs of central nervous system disease: depression, loss of appetite, drooping eyelids and lower lip, aimless wandering and circling, blindness, and sometimes paralysis