States Release First Year Results of Ruffed Grouse West Nile Virus Study in Great Lakes States

States Release First Year Results of Ruffed Grouse West Nile Virus Study in Great Lakes States

Early results from a multistate study on the prevalence of West Nile virus (WNV) in ruffed grouse in three Great Lakes states suggests that while the virus is present, some birds exposed to the virus can survive. WNV is spread mostly through the bite of an infected mosquito that can cause inflammation of the brain and sometimes inflammation of the lining of the brain and spinal cord. WNV was first detected in the U.S. in 1999 in New York and quickly spread across the country. Birds are the reservoir hosts of WNV and the virus has been documented in over 250 species of birds; crows, blue jays, and ravens are the most susceptible to the disease.

WNV has been detected in ruffed grouse, and the state fish and wildlife agencies in Michigan, Minnesota, and Wisconsin are collaborating on a three-year study to evaluate the potential impacts to ruffed grouse populations. Using more than 700 hunter-provided samples, researchers analyzed blood samples looking for antibodies that would indicate exposure to the virus, and heart tissue to determine if the virus was present. The following are the first-year results:

  • During the 2018 season, Michigan hunters submitted 213 samples from four study areas in the Upper and northern Lower peninsulas. Of these, 28 (13%) tested positive for exposure, with antibodies to West Nile virus confirmed in nine (4%) birds and likely in 19 (9%). Four birds (one adult and three juveniles, all from the northern Lower Peninsula) tested positive for the presence of viral material in their hearts.
  • In Wisconsin, 68 (29%) of the 235 samples were positive for antibodies consistent with virus exposure, with exposure being confirmed in 44 (19%) and likely in 24 (10%). Two birds tested positive for the virus in the heart tissue.
  • In Minnesota, 34 (12.5%) of the 273 samples were positive for antibodies, while exposure was detected in 10 (3.7%) and likely in 24 (8.8%). The virus was not found in heart tissue from any of the Minnesota samples.

Ongoing research in Pennsylvania suggests that regions with high-quality, abundant young forest habitat show a stronger recovery of grouse population between peak West Nile virus periods, compared to regions with lower-quality, less abundant, and more fragmented habitat. Also, individual birds in high-quality habitat regions seem to have a higher survival rate after contracting West Nile, compared to birds in areas with lower-quality habitat.

November 15, 2019