By Blake Jackson
The Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) has confirmed the state’s first case of Eastern Equine Encephalitis (EEE) in 2025, involving a 5-month-old colt in Marathon County. In comparison, there were 10 confirmed EEE cases in horses across Wisconsin in 2024, according to DATCP’s online tracking map.
EEE, along with West Nile Virus (WNV), is a mosquito-borne illness that causes brain inflammation (encephalitis) in horses. Common signs of EEE include confusion, loss of coordination, difficulty swallowing, circling, seizures, and sometimes death.
In many cases, infected horses are found lying down and unable to rise. Because the disease is often fatal, DATCP urges horse owners to contact their veterinarian immediately if such symptoms appear.
EEE and WNV cannot spread directly from horse to horse or from horses to humans. Both viruses are transmitted exclusively through mosquito bites that have previously fed on infected birds. The presence of EEE in horses confirms that infected mosquitoes are active in Wisconsin and pose a risk to both people and animals.
Mosquito activity and the risk of infection typically peaks from mid to late summer and lasts until the first hard frost.
DATCP strongly advises horse owners to vaccinate against EEE and WNV. The American Association of Equine Practitioners (AAEP) lists these vaccines as core, meaning all horses should receive them regardless of lifestyle or location.
To help reduce mosquito exposure, owners should eliminate standing water sources such as buckets, tires, or troughs, maintain clean gutters, refresh birdbath water weekly, and keep horses indoors from dusk to dawn when mosquitoes are most active.
For more details, visit DATCP’s website at https://datcp.wi.gov/Pages/Programs_Services/HorsesEEEWNV.aspx
Photo Credit: gettyimages-patrick-jennings
Categories: Wisconsin, Livestock