Chronic wasting disease sparks public health concerns and lobbying

Recent concerns about the spread of chronic wasting disease (CWD) has some calling for Canada-wide regulations and monitoring to support hunters, as well as a ban on game farms to ensure public safety and protect wildlife health. Wildlife officials aren’t as convinced.

Darrel Rowledge is one of 34 signatories of a letter sent to Prime Minister Justin Trudeau and senior cabinet ministers in June, urging the federal government to act. The group includes researchers specializing in public health and economics, First Nations leaders, hunting and fishing associations and public health organizations.

“The underlying story is that we have been creating most of the infectious pathogens that are killing us,” Rowledge said. “It’s related to bringing animals, especially new species, into captivity. It’s just a disease factory.”

CWD does not affect humans, but Rowledge and some of his colleagues fear this might change, with possible catastrophic effects to Canada’s food and blood supplies.

Dr. Iga Stasiak, veterinarian and provincial wildlife health specialist with the Saskatchewan Ministry of the Environment, said this fear should be tempered with current scientific knowledge. While some studies have shown CWD can infect non-human primates such as macaques, these animals are not closely related to humans. Real-world studies in Canada and areas of the United States where CWD is present seem to bear this out.

“There’s been some research on the incidence of prion diseases such as chronic wasting disease or mad cow disease in humans in areas in Canada and the U.S. where the disease has been present for over 30 years,” she said. “We haven’t found any increase in the incidence of those diseases. So there’s some evidence that suggests that if there is any risk, it’s likely very low.

CWD arrived in Canada in the 1980s via animals imported from South Dakota to a game farm near Lloydminster. Invariably fatal, it attacks brains and nervous systems, causing listless behavior, drooling and excessive thirst in affected animals. CWD has spread across Saskatchewan, Alberta and into the Yukon. There have been three cases of CWD on game farms so far in 2019, all in Alberta.

More troubling, in fall 2018, a case was detected at a game farm in the Laurentians in Quebec. Meat from some animals entered the food chain.

The discovery doesn’t surprise Ellen Goddard, a researcher from the Faculty of Agricultural, Life and Environmental Sciences at the University of Alberta. Goddard specializes in public policy and consumer behaviour related to food. While she said it’s not necessary to shut down game farming in Canada, testing of all farmed animals should be mandatory.

“Given we have the capacity to do that, I don’t see why we aren’t doing it,” she said. She added that currently only Saskatchewan, Alberta, Manitoba and the Yukon test all farmed animals before they enter the food chain.

“I don’t know why Ontario and Quebec wouldn’t do that,” she said.

These gaps in regulation and monitoring need to be filled if there is to be a Canada-wide response to CWD; there are simply too many unknowns. For example, Stasiak said there have been three moose in Saskatchewan that have tested positive for CWD. These are suspected to be “spillover” cases from contact with infected deer, but since moose aren’t typically tested, it’s unknown if these cases are anomalies.

There is much at stake not only for recreational hunters (Rowledge is one), but also for people in rural and remote communities who rely on wild game as an important part of their diet. This means First Nations, federal and provincial governments must co-ordinate their efforts because wildlife moves across arbitrary international borders. CWD is also present in 26 U.S. states, some bordering Canadian provinces.

Stasiak said that while it may have been possible to eradicate the disease decades ago, the task now is to control the spread of CWD to keep it out of unaffected areas and species, such as boreal caribou which are likely susceptible.

“It’s endemic in our wildlife populations in southern Saskatchewan, in some areas at very high prevalence — around 40 percent,” she said. “Those are really high prevalence rates. I think some of the most critical needs are to prevent further expansion or spread of the disease.”

What is chronic wasting disease?

Chronic wasting disease (CWD) is one of a group of maladies called transmissible spongiform encephalopathies (TSE), which include scrapie in sheep, transmissible mink encephalopathy on mink farms and BSE (mad cow disease) in cattle. CWD affects cervids, a family of animals that includes deer, elk, moose, and caribou.

All TSEs are caused by prions, misfolded proteins which transmit their distorted shape to normal proteins. These misshapen proteins cause distinctive “holes” in brain tissue, giving it a spongy appearance (hence “spongiform”).

BSE is perhaps the best known TSE for its link to variant Creutzfeld-Jakob disease (vCJD) in humans, a degenerative brain disease that leads to dementia and death. Creutzfeld-Jakob does occur naturally, but it is rare — about one person in a million worldwide.

In the late 1980s and early 1990s, British researchers found that prion-infected cattle feed was behind a spike in vCJD cases in people. This prompted a massive cull of British cattle, and sporadic bans on the import and export of cattle involving countries in which BSE appears, including Canada.

While BSE prions tend to be limited to the nervous system, CWD prions are present throughout the animals’ bodies. Studies show prions can be impervious to virtually all decontamination methods, from disinfectants to high heat, so they persist indefinitely in the environment. For this reason, more than 30 former game farms in Saskatchewan are under indefinite quarantine.

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