Chronic wasting disease remains relatively rare in Minnesota’s wild white-tailed deer herd, but cases found in northern Minnesota in the past couple of years have ramped up the Department of Natural Resources response.
“This year alone, we’re going to have 239 DNR staff, at least, coming out to work at sampling stations, 120 students from seven different state and tribal colleges and universities,” DNR wildlife section manager Kelly Straka recently told a legislative committee.
Straka said the agency has tested more than 120,000 deer since 2002 and to date has found 217 positive cases, a positive rate of just under two percent of deer tested.
The statewide wild white-tailed deer population is estimated at nearly one million animals.
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CWD is spread through prions from infected animals. The neurological disease is always fatal in cervids, including deer and elk.
Spreading across the state
The disease was largely contained to southeastern Minnesota counties for years. A CWD outbreak in farmed white-tailed deer in Beltrami County in 2021 raised concerns about spread in northern Minnesota.
That fall a hunter killed deer in Polk County became the first positive CWD case in northwest Minnesota. New cases have also been confirmed near Grand Rapids, Minn., over the past two years.
On opening weekend of firearms season, there is mandatory testing of deer killed by hunters in management and surveillance zones across the state. There are also voluntary testing options.
The DNR provided 10,000 free CWD test kits hunters could request. Some taxidermists and meat processors across the state will also collect samples.
The DNR considers surveillance an important tool for managing CWD.
“But once you have a disease in a wild population surveillance alone is not going to manage that disease, just testing is not going to help,” said Straka. “So what can we do to actually try to prevent the introduction of disease to areas or slow the spread where we know it currently exists?”
The DNR restricts the movement of deer killed in CWD management zones. The agency is providing dumpsters at more than 40 sites across the state where hunters can dispose of deer carcasses after the meat is removed. There are also restrictions on movement of deer carcasses across state lines.
The DNR has spent more than $21 million on chronic wasting disease response since 2003. In recent years the annual cost has increased rapidly, approaching $4 million this fiscal year.
The Minnesota Center for Prion Research and Outreach at the University of Minnesota is working on new testing options to more effectively surveil for CWD in wild deer.
Testing is now done after deer are killed, but the researchers have developed a test that can be used on live animals. The test has yet to be approved by the U.S. Department of Agriculture, which oversees CWD programs.
Minnesota researchers are also developing other methods to test for CWD in live wild deer herds as a way to increase early detection of the disease.
And the U of M Center has expanded education and outreach efforts.
“We worked with community members from the Twin Cities Hmong and southeastern Minnesota Amish communities, and seven Tribal Nations in Minnesota, Michigan and Wisconsin to gather data on existing knowledge, perspectives and impacts of CWD,” said co-director Tiffany Wolf.
That data helped create targeted CWD information brochures.
The Center for Prion Research and Outreach has also worked with Tribal Nations in Minnesota, Wisconsin and Michigan to test for CWD and to begin developing Tribal CWD management plans.
While chronic wasting disease is now more widely found in wild deer across the state, the disease prevalence is still low.
Monitoring hunter concerns
Research shows concern about CWD is having little effect on hunter participation in the annual deer season.
DNR research scientist Adam Landon has worked on several research projects over the past five years examining hunter response to CWD.
Hunters play an important role in managing deer populations, so the agency wants to keep engaged in the annual deer season.
Landon said hunters that seek out information about chronic wasting disease tend to perceive a higher risk, while those who depend on experts at the DNR for information perceive lower risk.
Data show a low rate of chronic wasting disease does little to deter hunters, who perceive a low risk from hunting and consuming deer.
“Barring some dramatic change in our understanding of the risks of CWD to human health, hunters are likely to maintain participation in hunting and seek testing to ensure that they’re consuming safe venison,” said Landon.
The Federal Centers for Disease Control and Prevention says there have been no reported human cases of CWD. There has been research showing transmission of prions in monkeys eating infected venison.
The CDC states that there is no strong evidence for the occurrence of CWD in people, and it is not known if people can get infected with CWD prions. The agency says “These experimental studies raise the concern that CWD may pose a risk to people and suggest that it is important to prevent human exposures to CWD.”
Michael Osterholm with Center for Infectious Disease Research and Policy at the University of Minnesota is leading a new international project to develop a response plan if the disease is found in humans.
“CWD is an evolving situation with an increasing number of infections in cervids and ever changing prion strains. If you knew CWD five years ago, it doesn't mean you know it today,” Osterholm recently told lawmakers. “That’s what I think is really an important message to get across.”
Osterholm said the CWD response planning group will report back to the legislature early next year.