The Wisconsin Department of Agriculture, Trade and Consumer Protection (WDATCP) confirmed on Aug. 23 that a 12-year-old Warmblood mare tested positive for Eastern equine encephalitis (EEE). The mare experienced onset of clinical signs, including fever, muscle fasciculations, and recumbency, on Aug. 19. She had no history of vaccination and was humanely euthanized.

This is Wisconsin’s third case of EEE in 2019.

EEE 101

Eastern equine encephalomyelitis is caused by the Eastern equine encephalitis virus, for which wild birds are a natural reservoir. Mosquitoes that feed on EEE-infected birds can transmit the virus to humans, horses, and other birds. Horses do not develop high enough levels of these viruses in their blood to be contagious to other animals or humans. Because of the high mortality rate in horses and humans, EEE is regarded as one of the most serious mosquito-borne diseases in the United States