Chronic wasting disease, or CWD, is usually associated with wild animals such as deer, elk and moose. But a new study from the University of Calgary and international researchers looked at whether the disease might have the potential to infect species beyond cervids.
So far, there has never been a confirmed case of CWD in humans. Still, scientists say the findings show why continued research and monitoring are important as the disease spreads into more areas.
CWD is a deadly neurological illness caused by prions, which are infectious proteins that damage the brain and nervous system. The disease has been expanding across North America, including parts of Alberta.
In the study, published in Science Advances, researchers used controlled lab experiments to examine whether CWD prions could cross species barriers. Most of the animals studied did not show symptoms. However, scientists found small amounts of infectious prions in their tissues.
When those tissue samples were passed on to other species, some of the recipient animals developed signs of CWD.
Researchers said this suggests that infectious prions may be present even when an animal appears healthy. That could make the disease harder to detect and control.
Prion diseases are especially difficult to predict because prions are not fixed in the same way as many other infectious agents. As they move between hosts, they can change and potentially form new strains with different traits.
CWD also creates another challenge because infected animals can shed prions long before they look sick. These infectious proteins can be released through urine and feces for months or even years, contaminating soil, plants and the surrounding environment.
By the time an infected animal begins showing symptoms, it may already have been spreading the disease for a long time.
The researchers stressed that the new findings do not suggest an immediate danger to people. Current evidence still points to a strong barrier between CWD and humans.
However, scientists know that some prion diseases have crossed species barriers before. One example is bovine spongiform encephalopathy, better known as mad cow disease, which spread from cattle to humans.
Because CWD is becoming more common in wildlife, researchers say it is important to keep studying whether prions could adapt over time in ways that affect transmission or disease development.
They also warn that as CWD spreads among animals, opportunities for exposure increase. In other words, the higher the prevalence in wildlife, the greater the need for surveillance and prevention.
University of Calgary researchers are also exploring possible ways to reduce CWD transmission in deer and elk populations. Early vaccine studies in mouse models designed to mimic infection in cervids have shown encouraging results. Vaccinated animals shed fewer prions and survived longer after exposure.
If scientists can reduce how much infected animals shed, they may be able to slow the spread of the disease in wild populations.
As CWD continues to expand, researchers say understanding how prion diseases evolve, spread and sometimes remain hidden will be essential for protecting wildlife and supporting future public health efforts.