Wisconsin Confirms First Equine EEE Case of 2026

By Blake Jackson

The Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) has confirmed the state’s first equine case of Eastern Equine Encephalitis (EEE) this year.

A 4-year-old grade mare in Portage County tested positive for the mosquito-borne virus. Wisconsin recorded one confirmed EEE case in a horse in 2025.

EEE and West Nile virus (WNV) are viral diseases that can cause inflammation of the brain in horses and people. In horses, EEE may cause serious neurological symptoms, including changes in behavior, impaired vision, head pressing, circling, difficulty swallowing, poor coordination, seizures and an inability to stand.

Most horses that develop clinical signs of EEE do not survive. Horse owners should contact a veterinarian immediately if they notice possible symptoms.

EEE is not transmitted directly between horses and humans. Instead, infected mosquitoes spread the virus after feeding on birds, which serve as natural reservoirs. Because mosquitoes are most active from mid- to late summer through the first killing frost, the risk of infection typically increases during this period.

The confirmed equine case indicates that mosquitoes carrying EEE are present in Wisconsin and may pose a risk to both animals and people.

DATCP recommends that horse owners consult their veterinarians about EEE vaccination. The American Association of Equine Practitioners considers EEE and WNV vaccinations part of the core vaccine program for horses, regardless of their activity level.

Previously unvaccinated adult horses generally require an initial two-dose series, followed by yearly booster vaccinations.

Along with vaccination, owners can reduce mosquito exposure by eliminating standing water around barns and pastures. This includes removing old tires, buckets and unused containers, maintaining rain gutters, turning over wheelbarrows and wading pools, and regularly replacing birdbath water. Pools and other outdoor water features should also be properly maintained.

Keeping horses indoors from dusk until dawn, when mosquito activity is generally highest, can provide additional protection.

Horse owners should remain alert for neurological symptoms and work with veterinarians to reduce the risk of mosquito-borne disease.

Photo Credit: gettyimages-patrick-jennings