Eastern Equine Encephalitis Confirmed in Marathon County
Saturday, October 18th, 2025 -- 7:32 AM
The Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) confirms that a 5-month-old colt in Marathon County has tested positive for Eastern Equine Encephalitis (EEE). It is the state’s first confirmed case of EEE in a horse this year. In 2024, DATCP documented 10 cases of EEE in horses.
EEE and West Nile Virus (WNV) are viruses that can cause inflammation of the brain (encephalitis). Symptoms of EEE in horses include altered mentation, impaired vision, head pressing, circling, inability to swallow, lack of coordination, seizures, and death. Affected horses are often found down and unable to rise. EEE is fatal in most horses showing signs of illness. Equine owners should contact their veterinarian if they observe any of these signs.
EEE and WNV are not contagious between horses and do not pass directly between horses and humans. Mosquitoes carry the virus from infected birds, and the only route of transmission is from a mosquito bite. The infections confirm that there are mosquitoes infected with EEE in the state that can transmit the virus to people and animals.
More information on EEE can be found at: https://datcp.wi.gov/Pages/
Feel free to contact us with questions and/or comments.