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The original item was published from 10/19/2021 8:37:42 PM to 11/30/2021 8:05:04 PM.

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Health Department

Posted on: October 19, 2021

[ARCHIVED] First domestic animal from Lenawee County to test positive for West Nile Virus



October 19, 2021

 Adrian, Michigan- Cases of West Nile virus (WNV) are being seen once again in Michigan animal, mosquito and human populations.  WNV typically circulates between birds and mosquitoes, but an infected mosquito can also transmit the disease through a bite to people and animals, especially horses and other equids. In Michigan, the disease is typically a concern every summer to early fall. 

The Lenawee County Health Department has been notified of a horse from Lenawee County testing positive for WNV.  The case occurred in a 13-year-old grey mare.  The mare became ill on October 7, 2021 with neurological signs including ataxia, a reluctance to move, muscle fasciculations(twitching), muzzle tremors, and grinding of the teeth. While the horse was vaccinated by the owner, it is unclear if the horse was vaccinated against West Nile Virus.  This is the first known case of WNV ever in a domestic animal from Lenawee County, and the fifth horse case statewide for 2021.  The horse is alive and recovering.  This is a reminder that WNV and other arbovirus that can be spread by mosquitoes are still circulating in the state and in our community.   

In addition to animal cases, there have been 40 confirmed human cases of WNV in Michigan so far this year. These cases are spread over 8 counties, with the majority located in Macomb County, Oakland County, and the City of Detroit. Lenawee County does not have any known human cases of WNV at this time. 

Lenawee County residents are reminded that the best way to protect against West Nile Virus and other mosquito-borne illnesses is to protect themselves and their pets, and livestock from mosquitoes.   

To combat the spread of this disease, animal owners can:

  • Talk to their veterinarian about vaccinating their horses against WNV and other mosquito-borne illnesses like Eastern Equine Encephalitis (EEE). There are highly effective, safe vaccines available.
  • House their livestock in a barn under fans (as mosquitoes are not strong flyers) during peak mosquito activity from dusk to dawn.
  • Use insect repellant on animals that is approved for the species.
  • Eliminate standing water on the property-i.e., fill in puddles, repair eaves, and change the water in buckets and bowls at least once a day.
  • 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. Please also note that various mosquito-borne diseases are reportable to MDARD. Cases can be reported by completing and submitting a Reportable Disease Form to

Residents can stay healthy outdoors by following steps to avoid mosquito bites:

  • Apply insect repellents that contain the active ingredient DEET, or other U.S. Environmental Protection Agency-approved product, to exposed skin or clothing, and always follow the manufacturer’s directions for use.
  • Wear long-sleeved shirts and long pants when outdoors. Apply insect repellent to clothing to help prevent bites.
  • Maintain window and door screening to help keep mosquitoes outside.
  • Empty water from mosquito breeding sites around the home, such as buckets, unused kiddie pools, old tires or similar sites where mosquitoes may lay eggs.
  • Use nets and/or fans over outdoor eating areas.

Even though it is now October, the mosquitoes that carry WNV and other mosquito borne diseases such as EEE, will continue to pose a threat until there has been at least one hard freeze where the temperatures fall below 28 degrees Fahrenheit for several hours. Due to this year's mild fall temperatures, the mosquitoes are continuing to circulate in the environment and spread the virus.

For more information about mosquito-borne diseases, visit

For more information regarding equine disease, please visit




Contact: Cindy Merritt

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