State Veterinarian Statement on Detection of West Nile Virus in Missaukee County Horse

Mosquitoes will continue to be active until there has been a hard freeze; take precautions to protect your animals, yourself and your family

LANSING, Mich. - State Veterinarian Nora Wineland, DVM, MS, DACVPM, released the following statement after the detection of West Nile virus (WNV) in a two-year-old horse from Missaukee County. This is the first case of WNV reported in a domestic animal for 2025.

"On August 20, 2025, the horse became ill with neurologic signs, including being down with an inability to rise. Subsequent testing revealed the horse was positive for WNV. The horse was unvaccinated and was humanely euthanized due to the severity of its disease.

"Despite the cooler nightly temperatures being experienced around the state, the mosquitoes that carry WNV and other mosquito-borne diseases will remain alive and active until there has been at least one hard freeze where the temperatures fall below 28 degrees Fahrenheit. Until this occurs, it is important to continue taking precautions to keep mosquitoes away from animals."

WNV is a viral disease transmitted through the bite of an infected mosquito. While the disease typically affects horses, humans and birds, it can sometimes cause illness in other animals. The disease is not spread by horse-to-horse or horse-to-human contact. Cases of WNV are typically seen in the late summer through early fall each year in Michigan.

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 WNV and other mosquito-borne diseases are all vital measures to take in order to keep animals healthy.

MDARD encourages owners to contact a veterinarian if a horse shows signs of illness including mild fever and stumbling, which can progress to being down and struggling to stand. If a Michigan animal is suspected of having WNV, funding is available under an arbovirus grant to cover the testing costs. Please contact the Michigan Department of Agriculture and Rural Development at 800-292-3939 for more details.

As of September 5, 2025, WNV was also detected in 27 wild birds and 154 mosquito pools throughout Michigan. In addition, 13 people in Michigan have been sickened by WNV in 2025.

For more information about WNV, please visit michigan.gov/EmergingDiseases.

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