CLARE COUNTY, Mich. – A horse in Clare County has tested positive for West Nile virus.
The horse is a 5-year-old standardbred mare. This is the second case of West Nile virus reported in a domestic animal this year.
West Nile virus is transmitted through the bite of an infected mosquito. The disease typically affects horses, humans, and birds, but can sometimes cause illness in other animals. The disease is not spread by horse-to-horse or horse-to-human contact.
The mosquitoes that carry WNV will remain alive and active until there has been at least one hard freeze where the temperatures fall below 28 degrees.
State Veterinarian Nora Wineland, DVM, released the following statement:
“Around September 18, 2023, the mare became ill with a lack of coordination and weakness in her hindlimbs. Subsequent testing revealed the mare was positive for WNV. The horse was unvaccinated against the disease.
“This case fundamentally highlights why animal owners need to continue taking precautions to protect their animals from mosquito-borne diseases. With warmer temperatures being experienced across the state, keeping mosquitoes away from animals remains essential.
“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.
“Also, please contact a veterinarian if a horse shows signs of illness: mild fever and stumbling, which can progress to being down and struggling to stand. Funding is available to test animals suspected of having WNV or other mosquito-borne diseases. Please contact MDARD at 800-292-3939 for more details.”
West Nile virus (WNV)
Most people who become infected with WNV do not develop any symptoms. When people do become ill symptoms include headache, body aches, joint pains, vomiting, diarrhea or rash. Most people with that type of WNV recover completely.
About 1 out of 150 people infected will develop a serious neurologic illness. Symptoms include, headache, high fever, neck stiffness, disorientation, coma, tremors, seizures or paralysis.
As of Sept. 28, WNV has been detected in 10 wild birds and 127 mosquito pools throughout Michigan. There were 10 cases of WNV reported in humans.
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Preventing mosquito bites
Michigan officials suggest taking the following steps to prevent mosquito bites:
- When used as directed, Environmental Protection Agency (EPA)-registered insect repellents with one of the active ingredients below are proven safe and effective, even for pregnant and breastfeeding women: DEET, Picaridin (known as KBR 3023 and icaridin outside the US), IR3535, Oil of lemon eucalyptus (OLE), Para-menthane-diol (PMD), and 2-undecanone.
- Wear light-colored, 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 lay eggs.
- You could also hire a mosquito control business. Mosquito control businesses are required to be licensed to apply pesticides in Michigan. A list of Michigan firms licensed to apply pesticides is available online.
Mosquitoes lay eggs in or near standing water
Mosquitoes need standing water to reproduce. That’s why you should empty, scrub or cover any items that hold water.
Standing water is often found in old tires, buckets, planters, toys, pools, birdbaths, flower pot saucers or trash containers.
Mosquitoes can complete their life cycle in about a week. The CDC recommends using an outdoor insect spray made to kill adult mosquitoes. Mosquitoes are often found in dark, humid areas.
Can’t remove standing water? Larvicides are an option
If you’re unable to remove the standing water where you live then you’ve got one other option: Larvicides.
Larvicides work by killing mosquito larvae and pupae before they grow into pesky adults. According to the CDC, if you use larvicides correctly they do not harm people, pets or the environment.
Larvicides come in liquids, tablets, bits, pellets, granules and briquettes. You use them by applying them where mosquitoes lay eggs (that means anywhere that holds standing water). That can include buckets and rain barrels, fountains, gutters or downspouts, non-chlorinated swimming pools, pool covers that collect water, tires and tree holes.
Use larvicides to treat standing water that will not be used for drinking and cannot be covered, dumped or removed.
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