Using forensic science techniques, a team led by University of Minnesota scientists recovered samples from a remote Beltrami County site used by a nearby deer farm to discard white-tailed deer carcasses. Testing for the presence of chronic wasting disease (CWD)-causing prions has found one bone marrow sample to be positive.
The rapid testing was completed using RT-QuIC technology, a highly-sensitive assay 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.
“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,” said Peter Larsen, Ph.D., who led the team and co-directs the Minnesota Center for Prion Research and Outreach (MNPRO) at the University. “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.”
Sweeping across the site on May 2, the team collected bones, hides, soil and plant samples. Their expertise in cervid anatomy and mortality investigations of wildlife allowed the discovery of portions of ten or more deer. Additionally, the team’s 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 (USDA) 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 forensic recovery team included Larsen, Tiffany Wolf, DVM, Ph.D.; Roxanne Larsen, Ph.D.; Marc Schwabenlander, MPH; and Gage Rowden, M.S., all from the University of Minnesota College of Veterinary Medicine. Joining the team was Jason Bartz, Ph.D., from Creighton University’s School of Medicine. Bartz will independently verify the results of the RT-QuIC testing performed by the MNPRO laboratory.
The MNPRO team also recently developed a new assay 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 this.
CWD originated roughly 50 years ago and affects white-tailed deer, mule deer, red deer, sika deer, caribou, reindeer, elk, and moose — all animals known as “cervids.” The disease produces small lesions in an animal’s brain and ultimately results in abnormal behavior, weight loss, loss of bodily functions, and death. While it is yet unknown whether the disease can spread to humans, the Centers for Disease Control and Prevention recommends against eating meat from CWD-infected animals. In 2020, both the Food and Drug Administration and the USDA declared CWD-positive venison unfit for human or animal consumption.
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 can also persist in the environment for years. Advances made on CWD could inform other prion-related diseases in humans and animals alike.
MNPRO’s research is supported by the MN Agricultural Experiment Station Rapid Ag Response Fund and the Minnesota Environment and Natural Resources Trust Fund, as recommended by the Legislative-Citizen Commission on Minnesota Resources. Additionally, various entities at the University of Minnesota have provided support, including the University’s Department of Veterinary and Biomedical Sciences, the Office for the Vice President of Research, and the College of Veterinary Medicine.