Michigan's first cases of West Nile virus in 2021 confirmed in horse, birds

Mark Hicks
The Detroit News

The first cases of West Nile virus this year have been reported in Michigan animal and mosquito populations, state officials announced Tuesday.

The Michigan Department of Agriculture and Rural Development recently confirmed the first case in a 28-year-old Quarter Horse mare from Midland County. On July 15, the mare, which had been under-vaccinated, "became ill with a sudden onset of neurologic disease and was humanely euthanized," representatives said in a statement.

“With the discovery of WNV in a Michigan horse, this signals that the virus is circulating again in the state,” said State Veterinarian Nora Wineland. “Its presence underscores the need to take all the necessary steps to protect animals from this disease.”

The cases follow none reported in domestic animals last year, officials said Tuesday.

The virus has been detected in mosquito and wildlife populations. It has been identified in five wild birds from Berrien, Calhoun, Cass and Ingham counties, as well as three mosquito pools in Calhoun, Kent and Oakland counties, according to the release.

“We urge Michiganders to continuously take precautions to protect themselves (in addition to their pets and livestock) against mosquitoes. It only takes one bite from an infected mosquito to cause a severe illness,” said Dr. Joneigh Khaldun, the state's chief medical executive and chief deputy for health at the Michigan Department of Health and Human Services. 

“Steps like using an EPA-registered insect repellent when outdoors, avoiding areas where mosquitoes are present (if possible), and wearing clothing to cover arms and legs to prevent bites can help.”

Last year, 32 human cases were reported. That included one in Barry County, two in Clinton County, one in Gratiot County, two in Ingham County, four in Kent County, two in Macomb County, eight in Oakland County, seven in Wayne, and five in Detroit, the report found.

In 2019, there were 12 human cases and two deaths, the state has said.

There were no reported West Nile cases in domestic animals last year and one confirmed in a Lapeer County horse in 2019, state officials said.

According to a year-end report the Michigan Department of Health and Human Services

Bureau compiled, the virus was reported in 2020 in 10 birds in Bay, Delta, Dickinson, Lapeer, Oakland, Ogemaw and Saginaw counties. It also was reported in 74 mosquito pools in Arenac, Bay, Kent, Lapeer, Midland, Oakland and Saginaw counties.

The virus typically circulates between birds and mosquitoes, but infected insects also can transmit the disease to people and animals through bites, according to the state.

Summer and early fall are when the risk is greatest in Michigan, experts say.

To combat the spread, animal owners are urged to take steps including using insect repellant, housing livestock in a barn under fans during peak mosquito activity between dusk and dawn, as well as eliminating standing water.

"Contact a veterinarian if an animal shows signs of the illness: mild fever, lack of appetite, lethargy, weakness, stumbling, tremors and a droopy lip and/or head tilt," state officials said Tuesday.

Mosquito-borne diseases are reportable to MDARD by completing and submitting a Reportable Disease Form to MIReportableAnimal@Michigan.gov.