First it was West Nile Virus, now biologists working at the University of Minnesota Veterinary Diagnostic Laboratory have confirmed they have also discovered eastern equine encephalitis (EEE) in two and possibly a third ruffed grouse shot in Itasca County. This is the first time researchers have found EEE in Minnesota, which like West Nile Virus, is carried by mosquitoes.
The DNR reported that the hunters who shot the birds noticed they didn’t, or couldn’t fly. Also, when the birds were field dressed, they didn’t have as much muscle mass as a normal ruffed grouse.
“It is rare for us to find EEE in Minnesota, but this year we’ve diagnosed the virus in these grouse and a horse,” said the VDL’s Dr. Arno Wuenschmann. “I initially suspected that West Nile virus caused the encephalitis but molecular tests conducted on the grouse in collaboration with the Animal Health Diagnostic Center at Cornell University proved EEE virus was to blame.”
The EEE virus is typically found in the eastern United States and along the Gulf Coast but also has been found in other states, including 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.
“We’ll keep testing samples that hunters submit for both viruses,” Carstensen said. “Hunters who harvest sick grouse also can help us by contacting a nearby DNR area wildlife office so they can submit those samples for testing, too.”
As with any wild game, care should be used when processing the animal to avoid cuts that could cause potential infection. Any game that appears abnormal – either in the field or after dressing – should not be consumed. Hunters with questions about what they harvest can contact a nearby DNR area wildlife office.
Grouse sampling information can be found on the DNR website.
About the EEE virus
Eastern equine encephalitis is a viral illness that is transmitted by mosquitos and can cause encephalitis, which is inflammation of the brain.
The virus primarily moves between passerine (perching) birds and a specific species of mosquito in freshwater hardwood wetlands. Birds in this cycle usually remain healthy despite being bitten and infected.
Illness caused by the EEE virus in humans, horses, dogs and other types of birds is rare because the mosquito that transmits the virus feeds almost exclusively on passerine birds. But if a mammalian host or other type of bird is bitten and encephalitis develops, the fatality rate can be high.
Symptoms of illness may include a sudden onset of fever, chills and muscle or joint aches. Cases with severe illness may begin with fever; headache and vomiting that may progress into disorientation, seizures and coma.
No human cases of EEE have been reported in Minnesota but the Board of Animal Health reported that the virus was found in a horse this year and three horses in 2001. Most of the horse cases occurred near tamarack bogs or hardwood swamps in northern and eastern Minnesota.
The Minnesota Department of Natural Resources (DNR) tested for the EEE virus in Cook County in the summer of 2013.
DNR sent workers out into the field to capture mosquitoes for a study that could help explain why the moose were dying in northern Minnesota.
According to Erika Butler, who at that time was the D.V.M. Wildlife Veterinarian for the DNR, 54,319 mosquitoes representing 29 species were collected and sent to the Minnesota Department of Health for Eastern Equine Encephalitis (EEE) and West Nile Virus (WNV) testing.
The results indicated at that time none of the mosquitos that had been tested were carrying the EEE virus, which Butler described as, “West Nile Virus’ evil sister.”
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