CWD Prions Spread Silently Across Species, Study Finds
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- University of Calgary researchers published a study in Science Advances showing chronic wasting disease prions were detected in tissues of non-cervid animals that never developed clinical symptoms, and those prions transmitted disease when injected into other species.
- Dr. Samia Hannaoui, first author and UCVM assistant professor, said the findings demonstrate that 'even without obvious [clinical signs], infectious prions can still be present and transmissible.'
- Dr. Hermann Schaetzl, UCVM professor and last author, warned that prion strains 'can evolve' as they move between hosts, producing new strains with unpredictable behavior.
- The study noted infected animals can shed prions through urine and feces for months or years before symptoms appear, contaminating vegetation and soil long before the disease is visible.
- Researchers emphasized no immediate human risk exists, but cited bovine spongiform encephalopathy (BSE, or 'mad cow disease') as a precedent for prion diseases crossing species barriers from animals to humans.
- Separate early-stage vaccine studies at UCalgary using mouse models showed vaccinated cervids shed fewer infectious prions and survived longer after exposure, suggesting a potential path to reducing transmission in wild populations.
- CWD continues expanding across North America, including new regions of Alberta, with researchers linking greater prevalence to greater exposure opportunities.
Why it matters: If prions can circulate silently in non-deer species without visible illness, wildlife managers lose their primary detection tool — clinical surveillance — at exactly the moment CWD's range is expanding. The BSE precedent means a low current risk to humans is not the same as a zero future risk, particularly as the disease spreads across more regions of North America.
