ALBERTA — Researchers from the University of Calgary published a study in the journal Science Advances detailing the potential for chronic wasting disease prions to transmit from asymptomatic cervids to other species in laboratory environments. The disease continues to spread across North America, including regions of Alberta.

The scientists conducted controlled laboratory experiments to investigate cross-species transmission of the disease. They detected low levels of prions in the tissues of study animals that exhibited no symptoms. Transferring tissue samples from these asymptomatic animals subsequently caused the recipients to develop symptoms of the disease.

Assistant Professor Samia Hannaoui said, "These findings show that even without obvious clinical signs, infectious prions can still be present and transmissible." The disease is a fatal neurological illness caused by infectious proteins known as prions.

Professor Hermann Schaetzl said, "We are not dealing with a single, fixed agent. Prion strains can evolve, and that evolution can influence how the disease behaves." Infected animals can shed infectious prions into the environment for months or years before exhibiting clinical symptoms. Shed prions contaminate soil and vegetation through animal urine and feces.

Schaetzl said, "By the time you see clinical signs, the animal has often been infectious for a long time. That is what makes this disease particularly challenging to control." The disease affects cervid animals such as deer and elk.

Current evidence indicates that the transmission barrier between the disease and humans remains strong; there has never been a confirmed case of the disease in humans. Schaetzl said, "Our findings do not indicate an immediate risk to humans, but they suggest the situation is more nuanced than previously understood. As the disease becomes more widespread, understanding these dynamics becomes increasingly important." He said, "The more the disease spreads in animals, the more opportunities there are for exposure. Risk is linked to prevalence."

Researchers at the University of Calgary are also investigating methods to slow disease transmission in cervid populations. Early vaccine studies using mouse models, designed to mimic cervid infections, showed that vaccinated animals shed fewer infectious prions. Vaccinated mice also survived longer after exposure to the disease. Hannaoui said, "If we can reduce shedding, we may be able to reduce transmission. That could have important implications at the cervid population level."