Aitkin County horse death linked to disease spread by mosquitoes

A 7-year-old crossbred gelding horse in Aitkin County died and was confirmed to have had Eastern equine encephalitis (EEE) last week. The Minnesota Department of Health reported the EEE-positive results to the Board of Animal Health, and also reported the animal was negative for other diseases of concern including rabies, Western equine encephalitis (WEE) and West Nile virus encephalitis (WNV).

Before the horse died it was showing clinical signs of neurologic disease including staggering, impaired vision, and excessive drooling. Samples were initially submitted to the University of Minnesota Veterinary Diagnostic Laboratory for rabies testing. The rabies samples were negative and additional tests were ordered for the other diseases.

“The diseases EEE, WEE, and WNV in horses can be limited through vaccination protocols and decreased exposure to mosquitoes,” said Board Senior Veterinarian, Dr. Brian Hoefs. “While COVID-19 has restricted many equine related activities, it is imperative to be vigilant about annual preventative care, including core vaccinations. We encourage all horse owners to work with their veterinarians to develop strategies for preventing EEE/WEE/WNV exposure and illness in their horses.”

The horse had no history of travel over the past three months and a reported last vaccination for EEE 18 months ago. At least 11 other horses remaining on the premises appear healthy at this time and have subsequently received initial vaccinations for EEE/WEE/WNV with boosters pending.

EEE can cause fatal infections in horses and people. The virus is primarily transmitted by mosquitoes. Horses and people are considered “dead end hosts” meaning they are unable to transmit the disease to other horses or people. In horses, EEE is fatal in more than 90-percent of cases, and clinical signs can include fever, lethargy, not eating and walking aimlessly.

Even though people cannot contract the disease from horses, cases in horses are a clear indication that infected mosquitoes are in the area and can infect humans. Clinical signs of EEE in people can include high fever, muscle pain, altered mental status, headache, photophobia, and seizures, which occur between three and 10 days after the bite of an infected mosquito. Consult your healthcare provider for additional information about EEE in people.

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