Chronic wasting disease a growing threat, even to soil

Posted on April 27, 2023 by Vauxhall Advance

By Samantha Johnson

Southern Alberta Newspapers

Local Journalism Initiative Reporter

In Alberta, Chronic Wasting Disease is present in mule deer, white-tailed deer, elk and moose. It’s a significant concern to wildlife managers and hunters in the province but, at this point, there is no solution to the problem. Data for the 2022-23 hunting season shows a province-wide contamination of 23.4 per cent.

Joel Nicholson, senior wildlife biologist with Fish and Wildlife in Medicine Hat, said, “There are pockets of prevalence that are unbelievably high (in Saskatchewan). We are headed in the same direction. We’re pushing one in four from a mule deer standpoint. The prevalence only seems to go one direction without major intervention.”

The leading edges of the known distribution are being monitored, along the westward and northern spread. Since CWD was first confirmed in Alberta in 2005, the level of control, from aggressive to less so, has varied.

The head collection program is currently focusing on the leading edge of the disease as well, with the number of freezers provided decreasing. Online information (https://www.alberta.ca/chronic-wasting-disease-information-for-hunters.aspx) states that opportunities for submitting heads outside the target areas are limited.

“We did have freezers in the Medicine Hat area last year at a lower number,” stated Nicholson. “I don’t know what the status of the program will be this fall.”

While it is recommended that any animal infected with a prion disease, such as CWD, not be eaten, some are not concerned about it said Nicholson. CWD spreads by animal-to-animal contact and through bodily fluids. As it can take years to kill off an animal, there is significant opportunity for the disease to spread.

Debora Voll, who lives on an award-winning multigenerational farm in Saskatchewan, is concerned about soil contamination from CWD.

“I’m very passionate about this and I’m watching the devastation of the deer. We have 55 per cent base of contamination or infection in mule deer. That is a risk to our soil and why I started my research. The more I research, the less I know. I think we need to drive home that soil contamination is a potential devastating outcome to the environment and the agriculture community. Not just for Saskatchewan but for Western Canada.”

Soil becomes contaminated with the CWD prion via saliva, urine and feces from infected animals.

“Studies show plants uptake the prion responsible for CWD. Tomatoes, corn, alfalfa, and wheat. Who is going to buy produce grown in potentially contaminated soil? That is not being addressed,” stated Voll.

A 2021 paper states the CWD prion can persist in a bioavailable state for years and certain soil microparticles enhance the transmissibility of the disease (https://veterinaryresearch.biomedcentral.com/articles/10.1186/s13567-021-00986-y). When deer consume soil, particularly in areas adjacent to mineral licks, they can ingest the CWD prion.

A plant sprayed with urine from an infected animal will also remain infectious for two years or more. The paper states that results regarding the uptake of prions by plants are not conclusive. One study showed grass plants do uptake prions from the soil and transport them to above ground vegetation and another showed wheat does not.

The first reported case of CWD was in 1967 and it is now confirmed in 30 states and four provinces, according to March 2023 information from the US Geological Survey. Norway’s first documented case was in 2016 with Finland and Sweden also reporting cases in wild Moose. The disease was shipped to Korea from Canada through imported deer in 1997. Given the impact on wildlife management, studies into CWD are ongoing.