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Mosquito-borne horse disease found in Minnesota grouse

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Eastern equine encephalitis has been found in three ruffed grouse in Itasca County, the first time the mosquito-borne virus has been confirmed to sicken a Minnesota wild animal, state conservation officials said Monday.

The disease is rare in humans. People bitten by infected mosquitoes seldom develop any symptoms, although the virus can be serious if they do, the Minnesota Department of Natural Resources said in a statement.

Nationwide, 36 people have been confirmed infected this year, with 13 deaths, according to the federal Centers for Disease Control.

Earlier this year, the Minnesota Board of Animal Health reported a Belgian mare in Otter Tail County had to be euthanized after being diagnosed with the disease. The previous case in Minnesota dated back to 2001.

"It's the first time we've ever actually determined clinical illness in a wild animal in Minnesota from triple-E,” said Michelle Carstensen, the DNR’s wildlife health program leader. “ It just shows that these mosquito populations that have the virus do occur in places in Minnesota and that the virus does periodically show up here."

With only one year of sampling, it’s too early to say how widespread the virus might be in grouse populations, the DNR said.

Grouse hunters brought the birds to DNR staff in late October after they noticed the birds didn’t or couldn’t fly away. When field dressing the birds, the hunters also noticed reduced muscle mass, the agency said.

People typically are infected with the disease through a mosquito bite, not through wild birds, but DNR still recommends handling game safely and not eating any sick wildlife Carstensen said.

The EEE virus is typically found in the eastern United States and along the Gulf Coast but also has been found in Michigan and Wisconsin.

Prior to this discovery, the DNR had confirmed that wolves and moose in northeastern Minnesota had been exposed to the virus but never found animals of either species sick with the disease.

In 2018, the DNR began asking hunters to submit grouse samples for West Nile virus testing. Samples collected the first year showed 12 percent of the birds had been exposed to West Nile virus but none had been exposed to EEE.

MPR News reporter Elizabeth Shockman contributed to this report.