A study led by University of Calgary researchers reports that chronic wasting disease (CWD) prions can be detected in some animals that show no obvious symptoms, and that material from those animals was able to transmit infection in laboratory experiments. The authors say the findings do not indicate an immediate threat to people but add to evidence that CWD’s behavior across species warrants continued monitoring.
The research, published in Science Advances, examined how chronic wasting disease—a fatal neurological illness caused by misfolded proteins known as prions—might behave when it encounters new hosts.
In controlled laboratory experiments, most of the animals studied did not develop clinical symptoms. Even so, the team reported detecting low levels of infectious prions in tissue samples from some of these apparently healthy animals. When those samples were transferred to other species in subsequent experiments, the recipients developed signs consistent with CWD.
“These findings show that even without obvious (clinical signs), infectious prions can still be present and transmissible,” said Dr. Samia Hannaoui, a researcher and assistant professor at the University of Calgary’s Faculty of Veterinary Medicine and the study’s first author.
The study also highlights why prion diseases can be difficult to forecast. According to the researchers, prions can change as they move between hosts over time, potentially producing new strains with different characteristics.
“We’re not dealing with a single, fixed agent,” said Dr. Hermann Schätzl, a University of Calgary professor and the study’s senior author. “Prion strains can evolve, and that evolution can influence how the disease behaves.”
The researchers noted that infected animals can release prions into the environment before illness becomes visible, with prions shed through urine and feces for months or even years—contaminating vegetation and soil.
On human health, the researchers stressed that there has never been a confirmed case of CWD in people and that their results do not point to an immediate risk. Still, they said the growing geographic spread of CWD in wildlife increases the importance of surveillance and research, particularly because prion diseases have crossed species barriers in the past—most famously bovine spongiform encephalopathy, or “mad cow disease,” which was transmitted from cattle to humans.
The authors argued that understanding silent or atypical infections could be important for managing the disease in wildlife and for informing long-term public health preparedness as CWD becomes more widespread.
