Highly sensitive test capable of detecting CWD prions in venison
August 18, 2021
ST. PAUL, MN — University of Minnesota researchers have harnessed a highly sensitive test to detect the presence of chronic wasting disease (CWD)-causing prions in commonly consumed muscle tissue like backstrap and tenderloin—signaling the test could have future utility as a venison screening tool.
The test is an in vitro amplification technology called real-time quaking-induced conversion (RT-QuIC), which researchers have previously used to find CWD in various tissues and biological samples. However, this is believed to be the first time the test has been used to analyze skeletal muscle tissues that are commonly consumed to look for evidence of CWD.
Although current standardized CWD-testing methods have been able to confirm the disease in muscle tissue, those methods have a high threshold for disease detection and present technical challenges that prevent them from screening many samples at once—making them poorly suited for food-safety tests.
Now, for the first time, researchers have proof of concept of a highly sensitive CWD test that could be used as a venison-safety screening tool. Currently, there are no federal guidelines for testing for CWD in venison during processing, nor are there validated CWD tests for food safety in the United States.
“There is growing concern that particular strains of CWD have the potential to cause disease in both humans and livestock,” said Assistant Professor Peter Larsen, PhD, who co-led the study, published this week in the journal Scientific Reports. Larsen has also co-founded the Minnesota Center for Prion Research and Outreach, which actively studies the disease. “We must identify technologies, like RT-QuIC, that can be leveraged post-harvest to prevent CWD prions from entering the food chain.”
The study's findings are important for a number of reasons. As of 2020, the Food and Drug Administration and the United States Department of Agriculture consider venison from CWD-positive animals as adulterated and unsuitable for human and animal consumption. At the same time, the Alliance for Public Wildlife has estimated that between 7,000 and 15,000 CWD-infected deer are consumed each year. Household pets also consume venison, as the ingredient is common in commercial cat and dog food.
Although no human infections from CWD have been documented, current data support that the risk is not zero, according to the University's Center for Infectious Disease Research and Policy.
CWD is a progressive neurodegenerative disease—a member of a family of diseases called transmissible spongiform encephalopathies. It was first documented in 1967; by 2019 it was confirmed in 26 states and three Canadian provinces, as well as in Sweden, Norway, Finland, and South Korea. It affects white-tailed deer, mule deer, red deer, sika deer, caribou, reindeer, elk, and moose—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. CWD-causing prions lack genetic material and can only be destroyed with specialized equipment or strong chemicals, which is what makes CWD so difficult to mitigate.
The research team, led by PhD-candidate Manci Li and Larsen, tested a variety of CWD-positive and CWD-negative tissues in white-tailed deer culled by the Minnesota Department of Natural Resources and the United States Department of Agriculture APHIS Wildlife Services. They also tested tongue, backstrap, tenderloin, forelimb, and hindlimb muscles, and found statistically significant CWD prion-seeding activity.
“Our results, based on a sampling of various muscle groups, suggest that CWD prions are distributed across CWD-infected (white-tailed deer) skeletal muscles,” the researchers wrote in the paper. They add that additional research is needed to determine the full extent to which CWD prions occur within particular muscle tissue types of infected animals throughout the course of disease.
Said Li: “This research is very exciting because we believe it will lead to technologies capable of the high-throughput screening of CWD in a variety of venison products.”
The study was funded by a combination of state and University sources, including the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources; the Minnesota Agricultural Experiment Station Rapid Agricultural Response Fund; and the Minnesota Agricultural, Research, Education, Extension and Technology Transfer program.