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Horse dies from rare virus, a sign mosquitos in MN are carrying it

EEE is a rare virus spread by mosquitos that can infect humans.

A horse in Aitkin County died after contracting a disease that is spread by mosquitos, indicating that mosquitos carrying Eastern equine encephalitis (EEE) are in the area and could also infect people.

The 7-year-old crossbred gelding horse was confirmed to have EEE last week, and before it died it was staggering, had impaired vision and was excessively drooling - all clinical signs of neurological disease, the Minnesota Board of Animal Health said in a news release Thursday.

The horse, who had no history of travel over the past three months, tested negative for other diseases, including rabies, West Nile virus encephalitis and Western equine encephalitis, the release noted. It was last vaccinated for EEE 18 months ago.

“The diseases EEE, WEE, and WNV in horses can be limited through vaccination protocols and decreased exposure to mosquitoes,” Board Senior Veterinarian Dr. Brian Hoefs said in a news release Thursday. “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.”

On the property where the horse lives there are at least 11 other horses, who all appear healthy and have since received initial vaccinations for EEE/WEE/WNV with boosters pending, the release said. 

EEE can cause fatal infections in horses, with EEE being fatal in more than 90% of cases. Clinical signs of the virus include fever, lethargy, not eating and walking aimlessly.

EEE and people

EEE, which is primarily transmitted by mosquitoes, can also cause fatal infections in people. (Horses and people are "dead-end hosts," meaning they can't transmit the disease to other horses or people.)

The state animal board says cases of EEE involving horses are a "clear indication" that mosquitos infected with the virus are in the area and can infect humans.

According to the Mayo Clinic, EEE is a rare virus that can cause swelling of the brain, with symptoms typically starting 4-10 days after being bitten by an infected mosquito. Symptoms may include headache, fever, chills and vomiting. Signs and symptoms can worsen to disorientation, seizures and coma and lead to brain damage or, in some cases, death.

The only way to lower your chance of getting EEE is to prevent mosquito bites, especially if you spend time outdoors and in the woods, Mayo says. 

Mayo suggests using bug spray with DEET or picaridin, wearing long pants and long-sleeved shirts when outside, emptying standing water from outdoor containers, having screens on windows and doors, and using permethrin to treat clothing as ways to prevent mosquito bites.

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