Study finds silent prion infections may complicate wasting disease control
University of Calgary researchers say chronic wasting disease prions can be infectious even when animals show no outward symptoms.
By Priya Raghavan · Science Reporter
3 min read
A new University of Calgary-led study suggests chronic wasting disease can spread in harder-to-detect ways than researchers previously understood. The finding matters because the fatal wildlife disease is expanding in North America, while scientists continue to assess whether it could move beyond deer-family animals.
The research, published in Science Advances, examined the potential for chronic wasting disease, or CWD, to cross species barriers. The University of Calgary said the work found infectious prions in some animals that did not show clinical signs of disease, and that material from those animals could cause CWD-like illness when transferred to other species in controlled laboratory experiments.
Silent infection raises surveillance questions
CWD affects cervids, including deer and elk. According to the University of Calgary, it is a fatal neurological disease caused by prions, which are infectious misfolded proteins, and it has spread across parts of North America, including more areas of Alberta.
Samia Hannaoui, a researcher and assistant professor at the university’s Faculty of Veterinary Medicine and first author of the study, said the results show infectious prions may be present and transmissible even when an animal has no obvious clinical signs, according to the university.
The university said most animals in the experiments did not become visibly sick. Researchers still detected low levels of infectious prions in tissues, and disease appeared after samples from those animals were passed to other species.
No confirmed human case
The researchers said the study does not show an immediate threat to people. The University of Calgary said there has been no confirmed case of CWD in humans, and current evidence points to a strong species barrier between CWD and people.
Hermann Schaetzl, a professor at the University of Calgary Faculty of Veterinary Medicine and senior author of the paper, said the findings make the risk picture more complex as CWD spreads, according to the university. The researchers said continued monitoring is needed because prions can change as they pass between hosts, potentially producing strains with different behavior.
The University of Calgary also noted that prion diseases have crossed species barriers before. It cited bovine spongiform encephalopathy, known as mad cow disease, which spread from cattle to humans.
Environmental shedding adds control challenge
Researchers said CWD is difficult to control because infected animals can shed prions before symptoms are visible. According to the University of Calgary, prions can be released through urine and feces for months or years, contaminating soil and vegetation.
Schaetzl said animals often have been infectious for a long period by the time clinical signs appear, the university reported. That long presymptomatic period can make visible illness a late signal rather than an early warning.
The researchers said increasing prevalence in wildlife increases opportunities for exposure. They called for continued surveillance and disease-control work as CWD spreads in animal populations.
The University of Calgary said its researchers are also studying possible ways to reduce transmission among cervids. Early vaccine work in mouse models designed to mimic infection in deer and elk found that vaccinated animals shed fewer infectious prions during early and later disease stages and lived longer after exposure, according to the university.
Hannaoui said reducing shedding could lower transmission at the population level, the university reported. The researchers said further work is needed to understand unusual or silent infections and how prion diseases evolve as they move through hosts.
This story draws on original reporting from ScienceDaily.