A team led by University of Minnesota researchers using forensic science techniques has documented the presence of prions that cause chronic wasting disease at a remote Beltrami County site where a nearby deer farm discarded white-tailed deer carcasses.
The Minnesota Board of Animal Health in early April confirmed a 3-year-old whitetail doe on a Beltrami County deer farm had tested positive for CWD. The case marked the farthest north in Minnesota the fatal deer disease had been confirmed in Minnesota.
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According to a news release from the U of M, the university scientists found the CWD-causing prions in a single bone marrow sample, using a technology known as RT-QuIC that can be used to identify CWD prions in carcasses and the environment.
Faster, accurate testing that can be used on a wide variety of sample types is critical to improving efforts to limit the spread of CWD, a transmissible neurological disease that is always fatal to white-tailed deer, the scientists said.
“This is a rapidly evolving situation. We are glad that we were able to assist our collaborators at the Minnesota Department of Natural Resources, the Minnesota Board of Animal Health and the U.S. Department of Agriculture with RT-QuIC testing of the carcasses,” Peter Larsen, who led the team and co-directs the Minnesota Center for Prion Research and Outreach (MNPRO) at the university, said in a news release. “Our work helps everyone respond more quickly with actions to safeguard our collective white-tailed deer resources. Identification of a positive carcass within an area that is frequented by wild white-tailed deer is highly concerning. Our MNPRO team is ready to assist with securing the dump-site to try and prevent CWD from spreading to the surrounding wild herds.”
The team on May 2 collected bones, hides, soil and plant samples at the site. Their expertise in cervid anatomy and mortality investigations of wildlife allowed them to find portions of 10 or more deer, the news release stated. Additionally, their knowledge of the conditions that promote the survival of CWD-causing prions allowed them to focus on collecting and processing samples obtained from highly deteriorated and desiccated materials with a high likelihood of retaining the prions months or years after their deposition.
The nearby deer farm herd was depopulated last week, and samples from those deer have been collected by the U.S. Department of Agriculture for official CWD testing. MNPRO obtained additional research samples from the depopulated animals.
Further testing of the carcass samples in-hand, as well as future collection and testing of additional samples from the carcass site, is dependent on MNPRO receiving additional funding, the university news release stated.
Following the recent finding of CWD in Beltrami County, the DNR is developing a response plan that will include stepped-up surveillance and a deer feeding ban to be implemented sometime before this fall's deer hunting season. Minnesota has documented about 115 cases of CWD in wild deer since the first confirmed report in 2010, DNR statistics show.
“That’s such a geographic jump in where we have seen the disease, and that now means we’re going to have to do surveillance activity up in that area surrounding that facility in Beltrami County,” DNR Commissioner Sarah Strommen said last week in a Herald interview. “That’s the heart of deer country there, so it’s concerning and we want to be proactive on that.”
The MNPRO team also recently developed a new test that generates a color change of red for a positive CWD result and blue for negative. They have named the test “MN-QuIC” to honor the state of Minnesota, where the test was developed. The new test is cheaper than those using traditional equipment and uses field-deployable equipment to garner preliminary results in just 24 hours. The team is striving for a test that could be used at individual stations, cutting down on testing bottlenecks during deer hunting season.
MN-QuIC is another tool that holds promise for rapid sample screening in forensic investigations such as the one in Beltrami County.
Fatal to members of the deer family, collectively known as cervids, CWD is spread by misfolded prion proteins, the same process that causes scrapie in sheep, bovine spongiform encephalopathy in cattle (sometimes called “mad cow disease”) and sporadic Creutzfeldt-Jakob disease in humans. CWD-causing prions are not alive and can only be destroyed with specialized equipment or strong chemicals, which is what makes CWD so difficult to mitigate. They also can persist in the environment for years. Advances made on CWD could inform other prion-related diseases in humans and animals alike.