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State Veterinarian Statement on Eastern Equine Encephalitis-Positive Eaton County Horse

Preventing mosquito bites is the first step to protecting your animals, yourself, and your family

LANSING, MI — Today, State Veterinarian Nora Wineland, DVM, released the following statement due to the discovery of Eastern Equine Encephalitis (EEE) in a two-year-old Paint cross gelding from Eaton County. This is the first case of EEE in Eaton County this year.

“On September 8, 2022, the gelding became ill with neurologic signs—including leaning, wobbling, and stiffness/trying not to move. The horse was unvaccinated against EEE and was humanely euthanized due to the severity of his condition.

This case shows the virus is present in the area’s mosquitoes and highlights the need to take precautions. Protect animals against mosquitoes by placing livestock in a barn under fans during peak mosquito activity (from dusk to dawn), eliminating standing water on one’s property, using an insect repellant on animals that is approved for the species, and contacting a veterinarian to vaccinate horses against EEE and other mosquito-borne diseases.

Also, please contact a veterinarian if a horse shows signs of the illness: mild fever and stumbling, which can progress to being down and struggling to stand.”

EEE is a viral disease transmitted through the bites of mosquitoes to both animals and people; it is typically seen in late summer to early fall each year in Michigan. The disease is not spread by horse-to-horse or horse-to-human contact. Overall, the mosquitoes that carry EEE will remain alive and active until there has been at least one hard freeze where the temperatures fall below 28 degrees Fahrenheit. 

EEE is one of the most dangerous mosquito-borne diseases in the U.S. with a 90 percent fatality rate among horses that become ill and a 33 percent fatality rate among humans who become ill.

For 2022, the gelding is Michigan’s third case of EEE in a domestic animal; the other cases occurred in Roscommon and St. Joseph counties. Also, there are currently no reported cases of EEE in humans. 

For more information about EEE, please visit