West Nile Virus Found In Ruffed Grouse In Minnesota, But Results Show Some Are Able To Survive

Test results from the first year of a multi-state study on West Nile virus in ruffed grouse found that the virus is present in Minnesota, Michigan, and Wisconsin, but exposed grouse can survive.

According to the Minnesota Department of Natural Resources, in 273 samples from grouse that hunters harvested in Minnesota during 2018, 34 samples (12.5 percent) had antibodies consistent with West Nile virus exposure. The results were confirmed in 10 samples (3.7 percent) or deemed likely in 24 samples (8.8 percent). The tests did not find the presence of the virus in any of the ruffed grouse hearts, meaning the birds were not sick when harvested.

“The study tells us that some birds that have been exposed to West Nile virus are surviving – both juvenile and adults – and they are not sick when harvested in the fall,” said Charlotte Roy, grouse project leader with the Minnesota Department of Natural Resources. “But this study does not tell us about birds that may have died from the disease over the summer.”

Research in other states points to good grouse habitats as one factor that can produce birds in better condition and better able to survive stressors like West Nile virus.

The DNR had asked grouse hunters to collect two types of samples to help determine if the birds were exposed to the virus: a blood sample to determine if the grouse had developed an immune response to the virus, and the heart to look for traces of viral genetic material.

Sample collection is continuing during the 2019 grouse hunting season. Ruffed grouse hunters can voluntarily submit samples if they are willing to collect blood on filter paper strips within 30 minutes of harvest, hearts, and a few feathers for sex and age determination, and are willing to provide harvest location information.

West Nile virus has been present in Minnesota since the early 2000s, but interest in effects on ruffed grouse increased following a study in Pennsylvania documenting relationships between habitat quality, populations and virus exposure. Some bird species recover quickly and become tolerant to the virus while others, such as blue jays and crows, suffer higher rates of mortality.

West Nile virus is carried by infected mosquitoes. Not all people or animals bitten by an infected mosquito will contract West Nile virus. There have been no documented cases of people contracting West Nile virus from consuming properly cooked meat.

For more information about ruffed grouse hunting and sampling, visit the DNR grouse hunting page.