Equine diseases hit Otter Tail, 2 other counties

ST. PAUL — Three different equine diseases have been detected in three separate Minnesota counties as state animal experts stress this is the time of year horses are the most prone to diseases.

The Minnesota Board of Animal Health said horses in Otter Tail, Pine and Swift counties have been euthanized since eastern equine encephalitis, equine infectious anemia and West Nile virus were detected.

Eastern equine encephalitis was reported in a 14-year-old Belgian mare in Otter Tail County. That horse was euthanized Aug. 1, the animal board said. EEE is a viral disease that causes inflammation of the horse's brain and spinal cord. While rare in the Midwest, there were also three cases reported in Minnesota in 2001.

EEE can cause fatal infections in horses and people, the animal health board said. The virus circulates between mosquitoes and birds, but when horses are bitten by mosquitoes carrying the virus, horses are unable to transmit the disease. EEE causes death to horses in more than 90 percent of the cases.

“Mid-July through early September is the highest risk time for EEE, WNV (West Nile virus) and other mosquito-transmitted diseases in Minnesota,” said Dave Neitzel, Minnesota Department of Health epidemiologist. “Minnesotans can protect themselves by wearing mosquito repellents and taking other precautions outlined on the MDH website.”


In Pine County in east-central Minnesota, a veterinarian confirmed the viral disease equine infectious anemia during a routine screening of a horse shortly after the animal's purchase from another part of the state. EIA affects horses, donkeys and mules but poses no known risk to humans, the animal board said. The affected horse was quarantined and put down. EIA is primarily spread through horse and deer fly bites.

The Minnesota Board of Animal Health requires EIA infected horses be euthanized or quarantined for life because there is no vaccine or treatment, and once a horse is infected it remains a carrier for life and may not display any clinical signs.

“The Board’s testing rules are in place to survey for this disease and prevent it from spreading,” said Dr. Courtney Wheeler, equine program director. “Even if you own a horse that never leaves your property, we encourage testing for EIA routinely and avoiding shows or events where there are no testing requirements.”

A 25-year-old mare suspected to have West Nile virus was euthanized in Swift County in west-central Minnesota. The horse had no documented history of vaccination against West Nile and after the horse was put down, a blood sample confirmed exposure to the virus.

State animal experts say steps can be taken to reduce the risk of these diseases, including:

  • 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.

Positive test results for West Nile virus disease, eastern equine encephalitis and equine infectious anemia must be reported to the Board of Animal Health (domestic animals) and Minnesota Department of Health (humans), the animal board said.

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