Saint Paul, Minn - The Board of Animal Health responded to two horses with West Nile virus in Kandiyohi County this week. One horse, a one-year-old quarter horse colt was unvaccinated and died from complications related to the illness. The other horse is a 21-year-old mare who recently received a West Nile virus booster dose prior to its infection and is recovering. The detections stem from separate farms, and the virus appears to be circulating in mosquitoes in the county. Infected horses cannot spread the virus to people or other horses.

“Vaccination is the best way to protect horses from West Nile virus,” said Dr. Heather Damico, senior veterinarian in charge of equine. “Historically, a lot of the reported cases we deal with in horses are either unvaccinated or under vaccinated, which means they didn’t receive their annual booster shot. Vaccines can prevent infection or reduce severity of disease if the horse is infected.”

West Nile virus is regularly found in Minnesota during the summer and birds serve as the primary host of the disease. The virus circulates between infected birds and mosquitoes. Once infected, the mosquitoes can transmit the virus to horses or people. Infected horses cannot spread the virus to people or other horses. The virus can cause inflammation of the brain and spinal cord. Infected horses may or may not show neurological symptoms including muscle tremors and incoordination.

In addition to vaccinations horse owners can reduce environmental risks of West Nile virus by reducing mosquitoes:

• Change water in drinking troughs every week.
• Mow long grass.
• Drain stagnant water puddles.
• Remove items mosquitoes use for breeding grounds, like old tires and tin cans.
• Place and maintain screens over windows and stable doors.
• Use mosquito repellents to protect horses and people from mosquito bites.

This is a high-risk time of year for West Nile virus transmission. The Metropolitan Mosquito Control District has already reported West Nile virus in routine mosquito samples in several metro counties this summer. The virus has been detected, don’t wait to vaccinate. Non-negative test results for West Nile virus disease must be reported to the Board of Animal Health.

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