The teaser at the top of Forum News Service outdoors columnist Brad Dokken's Wildlife managers pinpoint a numbers problem with chronic wasting disease testing forecasts what's going to come in the article:
Convincing hunters that a deer can look perfectly healthy but still have CWD is an ongoing challenge when it comes to testing. Typically, infected deer don’t display the classic emaciated, listless symptoms until the last four months or so before they die. While the numbers are down in North Dakota, the dropoff in sampling was even more striking in Minnesota.
Fifteen paragraphs down column, there's this:
The dropoff in sampling was even more striking in Minnesota, where the DNR drastically scaled back its testing efforts to minimize the COVID-19 risks. Instead of mandatory testing with staff on hand at sampling sites – the program in 2019 – the DNR switched to voluntary testing without staff in the permit areas targeted for testing, similar to the system used in North Dakota.
In 2019, when testing was mandatory in the CWD-positive permit areas, the DNR saw 98% compliance and collected about 18,000 samples, said Carstensen, the DNR’s Wildlife Health Group leader.
In 2020, by comparison, hunter participation dropped to about 20% in many areas and less than 10% in some of the new permit areas with more recent cases of CWD, Carstensen said.
“In some of our areas that we’re working, we still got enough with 20% of the available harvest being submitted to have a good sense of what was happening with the disease,” she said. “In other areas, we fell far short of deriving any meaningful conclusions based on the low sample volume, so it was a little bit of a hit or miss in some of our zones.
“We still got over 8,000 samples in our state, so we did OK, given those constraints. But it was a marked difference from the year before.”
The question, of course, is how much testing is enough to give an accurate picture of CWD prevalence in a given area. Minnesota has documented 111 cases of CWD in wild deer since the first report in 2010, DNR statistics show.
“It’s hard to say what the proper sample is across the board because it really depends on the number of deer you have available,” Carstensen said. “It doesn’t require testing every deer; it requires testing enough deer in the right areas to have good information, and so we’re trying to achieve that.”
In North Dakota, the Game and Fish Department’s Bahnson says he’d like to test about 300 animals in each unit targeted for surveillance.
“If we get to like 12% or 13% of our hunters in each unit, then that would be fine,” Bahnson said.
Convincing hunters that a deer can look perfectly healthy but still have CWD is an ongoing challenge when it comes to testing, Bahnson and Carstensen say; typically, infected deer don’t display the classic emaciated, listless symptoms until the last four months or so before they die.
“The vast majority of the deer that we have that are positive in Minnesota look totally fine to you and I,” Carstensen said. “It’s a very short window where they become emaciated. Trying to harvest them in that window is tough.”
While North Dakota likely will return to a more traditional testing regimen next fall, Minnesota’s plans are a work in progress, the DNR’s Carstensen said. There’s a fair chance sampling efforts will be a mix of mandatory – which is “very expensive,” Carstensen says – and voluntary. That should be finalized in the next few weeks.
“We’re in the middle of working on that,” she said. “I'm trying to see if we can come up with a hybrid model where we maximize our efficiency, costwise, but still get enough of a sample to have good information about the disease.”
A tweet by Minnesota House Environment and Natural Resources Finance and Policy Committee chair Rick Hansen brought this column to our attention :
When it is considered “voluntary” it will be. When there are no staffed testing stations...less participation🦌🦌🦌
— Rep. Rick Hansen (@reprickhansen) February 21, 2021
Let's hope for the sake of the wild herd that the DNR is able to return to mandatory testing by the fall hunting seasons.
Photo: This Minnesota whitetail buck, which appeared perfectly healthy to the eye, later tested positive for chronic wasting disease. Source: Minnesota DNR, via Forum News Services. Photo rotated.
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