Ruffed grouse exposure to West Nile Virus drops
In the second year of a regional study, 20% of ruffed grouse sampled in 2019 in Wisconsin showed exposure to West Nile Virus, down from 29% the previous year.
But for the second consecutive year, grouse in the Badger State showed on average twice the exposure to the virus than birds in Michigan and Minnesota.
The results provide additional evidence, as with virtually all viruses and species, ruffed grouse can survive exposure to WNV.
They do not allow an estimate of the number of birds that may have died from it.
“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 with the Wisconsin Department of Natural Resources.
The project, scheduled to run from 2018 through 2020, was initiated after grouse populations in the Upper Midwest showed signs of an unexpected and unexplained population decline in late 2017 and 2018.
Results of 2019 testing were released last week by the natural resources agencies in the three states.
The work provides a rear-view look at WNV in the grouse population. Although the disease was documented in Wisconsin since 2002 and known to cause mortality among birds, no grouse had been tested.
But after a Pennsylvania study concluded in 2016 that “WNV clearly kills ruffed grouse and as many as 80% of grouse exposed to the virus are killed outright or might have reduced survival” and the surprise downturn in regional grouse numbers in 2017, wildlife officials in Wisconsin, Michigan and Minnesota decided to begin a coordinated effort to assess the virus in the popular upland bird.
The study design relied on hunters to provide blood and heart samples from birds they killed. The testing was conducted at the Southeastern Cooperative Wildlife Disease Center in Athens, Georgia.
In Wisconsin, hunters submitted samples from 188 grouse taken last year. Twenty percent had antibodies consistent with WNV exposure, including 9% with confirmed exposure and 11% with likely exposure.
None had evidence of the virus present in the heart tissue.
In 2018 29% of the 235 samples submitted from Wisconsin grouse had antibodies to WNV either confirmed or likely, and two had evidence of the virus in their hearts.
The year-over-year decline is consistent with data from the Wisconsin Department of Health Services, which showed just two cases of WNV in humans in 2019 in Wisconsin, down from 33 in 2018 tied for second lowest since 2002. The state average is 19 cases.
By comparison, activity of the virus in Wisconsin was high in 2017 (51 human cases, third highest on record), the same year grouse drumming counts were high in spring but hunters reported seeing fewer birds in fall.
Is it possible WNV had a populationlevel effect on ruffed grouse in Wisconsin in 2017?
That question will likely never be answered. But the study is providing data to show grouse can survive and recover from the virus.
“Here in the Upper Great Lakes, the top three harvest states for ruffed grouse in the country, we are very interested in this species and want to know as much as we can,” said Al Stewart, upland game bird specialist with Michigan Department of Natural Resources. “At what levels could (WNV) impact the population overall? That’s a piece of the puzzle we’re looking at.”
Stewart said biologists believe WNV has the most serious health impacts on birds that are weaker or have compromised immune systems.
To that end, wildlife managers have long espoused the value of maintaining the highest quality habitat on the landscape. For grouse, that’s young forest habitat.
In 2019 data from the other states, WNV exposure was detected in 12% of the 317 samples submitted in Minnesota. Exposure
to the virus was confirmed in 3 (or 1%) and likely in 36 (11%). Viral genetic material was not found in any of the Minnesota heart samples.
In Michigan, exposure was detected in 8% of the 247 ruffed grouse blood samples, including 7 (3%) confirmed and 13 (6%) likely. Viral genetic material was found in one heart sample.
As a result of the coronavirus pandemic, the number of samples submitted this year is likely to take a big downturn.
No new WNV test kits will be distributed this fall, according to the Wisconsin DNR. Due to COVID-19 operational changes, the agency said it will rely on hunters who possess unused kits from previous years to fill them and send them in for processing.
The DNR issued a request to hunters who have an unused kit and don’t plan to utilize it in 2020 to give it to another hunter who might.
Lake Michigan whitefish meeting: The DNR will host a video meeting from 6 to 8 p.m. Tuesday on potential changes to commercial fishing regulations for Lake Michigan whitefish.
The agency said it is developing new regulations for lake whitefish for the commercial industry and would like stakeholder participation from a wide variety of sources. Tuesday’s meeting will be the first of several public meetings over the next year and will discuss current information and how to develop a path forward, according to the DNR.
To view or participate in the meeting, logon to the Zoom video conferencing website or call (312) 626-6799 and use the meeting ID 957 6595 4593.