Ruffed grouse are exposed to West Nile but flushing it from bodies, study finds
MADISON, Wis. (WKBT) — Ruffed grouse are being exposed to the West Nile Virus but are surviving and flushing the virus out of their bodies, according to a surveillance project.
Blood samples collected from ruffed grouse that hunters harvested in 2019 indicate that 20% of the samples submitted from Wisconsin had antibodies consistent with West Nile exposure, according to the Wisconsin Department of Natural Resources.
Of these samples, 9% showed confirmed WNV and 11% showed likely exposure, the DNR reported Wednesday after receiving the 2019 test results from the second year of the ruffed grouse West Nile Virus (WNV) surveillance project.
None of the 188 samples had evidence of the virus present in their hearts, according to the results.
“These findings indicate that, while ruffed grouse are being exposed to WNV, there are birds that are surviving and clearing the virus from their bodies,” said Alaina Gerrits, assistant upland game ecologist.
Humans also can be infected with the West Nile Virus, which mosquitoes spread. However, 80 percent do not develop any symptoms, according to the federal Centers for Disease Control and Prevention.
About 1 in 5 people who are infected develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea or rash, the CDC says.
“Most people with this type of West Nile Virus disease recover completely, but fatigue and weakness can last for weeks or months,” according to the CDC
About 1 in 150 infected people develop a severe illness affecting the central nervous system such as encephalitis (inflammation of the brain) or meningitis (inflammation of the membranes that surround the brain and spinal cord), the CDC says.
The multi-year ruffed grouse study aims to provide biologists with more information about West Nile exposure and infection in the birds in the western Great Lakes region.
Ruffed grouse harvested in Wisconsin, Minnesota and Michigan during the 2019 hunting season were sent to the Southeastern Cooperative Wildlife Disease Study in Athens, Ga., to be analyzed.
“We are grateful to the passionate grouse hunters of Wisconsin who took the time to submit samples from their harvested birds,” Gerrits said. “Without their support, this study would not be possible.”
Hunter-submitted samples underwent two types of testing to help determine if the birds were exposed to WNV:
• One test sought traces of viral genetic material in heart tissue.
• A blood test aimed to determine whether the grouse had developed an immune response from exposure to the virus.
Similar to humans, ruffed grouse can develop antibodies as an immune response to viruses they encounter. When the body fights off WNV, these antibodies can be found in the blood.
Hunters who submitted samples and provided contact information will be provided test results via email as soon as possible — regardless of whether results were negative or positive.
In 2018, 29% of the 235 samples submitted had antibodies to WNV either confirmed or likely, and two had evidence of the virus present in their hearts. Both of these birds also had developed antibodies to the virus and the results do not directly indicate these two birds were sick at the time of harvest.
The study may help identify future research needs in Wisconsin, such as a potential survival study to investigate sources of mortality, with WNV being one of many stressors examined.
West Nile Virus’s effects on birds can vary. Signs can range from no clinical disease or illness to heart lesions and inflammation of the brain, the lining of the brain and of the spinal cord.
Many factors can influence how severely the virus affects an individual bird. There is no evidence that it can be spread by handling dead birds or by consuming properly cooked game.
In Michigan, West Nile Virus exposure from 2019 samples was detected in 8% of the 247 ruffed grouse blood samples with exposure to the virus either confirmed (7% or 3%) or likely (13% or 6%). Viral genetic material was found in one heart sample.
In Minnesota, exposure was detected in 12% of the 317 blood samples submitted. Exposure to the virus either confirmed (3% or 1%) or likely (36% or 11%). Viral genetic material was not found in any of the Minnesota heart samples.