The weather in Wisconsin is starting to change from winter to spring, reminding us that mosquitoes will soon be spreading diseases among horses, including Eastern equine encephalitis (EEE) and West Nile virus (WNV).

In 2016 Wisconsin had 19 confirmed EEE cases and seven WNV cases in horses, but there could have been more unconfirmed cases.

"Until we see our first mosquito, it’s easy to forget about vaccinations against these diseases," says Julie McGwin, DVM, equine program manager for the Wisconsin Department of Agriculture, Trade, and Consumer Protection’s Division of Animal Health. "We’ve seen the sun emerge to warm things up and the mosquito population will multiply before you know it.

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