Some hunters deterred by growing CWD rates in province

A disease harmful to Saskatchewan’s deer population has grown significantly in the province over the past decade — and it’s causing some hunters to reconsider whether the pursuit is worth the time and cost.

Chronic wasting disease (CWD) is a progressive and fatal nervous system disease that affects animals in the cervid family, including deer, elk and caribou.

“These animals that are infected typically don’t survive longer than two years in deer and three years in elk,” said Dr. Iga Stasiak, a wildlife health specialist with Saskatchewan’s Ministry of Environment.

“The animal actually just wastes away and eventually falls prey to other predators or the disease itself,” explained Darrell Crabbe, executive director of the Saskatchewan Wildlife Federation.

He called it “pretty gruesome to see.”

Stasiak said there has been a dramatic jump in cases since its first decade in the province.

In the first 15 years — between 2000 and 2015 — Stasiak said about 500 total cases in the province were recorded. She said the same total has now been seen each year for the past three years.

There were 466 positive cases detected in the almost 3,000 submissions between 2020 and 2021, according to the province’s reported CWD surveillance program results posted to its website.

Stasiak said it was a high year.

“Ten years ago, we were seeing areas that had less than five per cent infection rates. Now, those are up to 50 per cent in some of those areas,” Stasiak said.

The growth is not unexpected, however.

“Infection rates do increase over time,” Stasiak said, adding that even areas of Saskatchewan with low infection rates currently could see a rise in the disease in the coming years.

CWD in Saskatchewan

More significant population impacts begin when infection rates reach around 30 per cent; that’s when Stasiak said concern begins to rise for a certain area, but it’s not an exact number.

“We know that when infection rates increase … is when we start seeing impacts on the population as a whole and population decline,” Stasiak explained.

At that point, older animals begin to die off because they’re more likely to be infected and younger populations start to take over. That can impact how well a population survives and their presence in certain areas.

Hunting in Saskatchewan is allocated based on wildlife management zones. That’s also how CWD rates are monitored.

The highest CWD infection rates in the province currently are along the South Saskatchewan River Valley in the central-west portion of the province.

Stasiak said those rates are very high, with more than 50 per cent infection rates in the male mule deer population and about half that in females. About 20 to 30 per cent infection rates are present there in the white-tailed deer populations.

Crabbe agreed, noting the federation has seen the disease most prevalent in areas around the South Saskatchewan Valley, as well as the Saskatchewan Landing and Swift Current areas.

Infection rates radiate out from that area and decline, Stasiak said, moving eastward and north into the boreal forest areas.

“It really does depend on where you’re hunting and we do have that information available online for hunters,” she said.

Stasiak said the first cases of CWD in the province surfaced in 1996 on a captive elk farm. It was believed to have come to Saskatchewan in animals that had been imported from South Dakota in the late 1980s.

In 2000, the first case was found in the wild deer population — first in a mule deer, then a white-tailed deer.

Stasiak said the disease has spread across the province since then.

CWD is transmissible most highly through animal-to-animal contact. It can be spread through bodily fluids, including urine, feces and saliva, and can spread more quickly in animals that live in congregation.

“The more gregarious the species is — like mule deer or elk — the chances are much better that transmission is going to occur because they congregate in large herds,” Crabbe said.

Contaminants can also be deposited in soil, water and feed to be spread amongst cervid populations. Crabbe said the late winter and early spring can be especially bad for the disease because white-tailed deer, mule deer and elk congregate to feed.

“Once it’s shed through urine or feces … it can actually be retained in certain soil types, especially clays, and it can actually then be brought up into vegetation,” Crabbe said.

“It’s pretty difficult to get rid of the disease once it has itself entrenched in an area.”

The disease affects the nervous systems of animals and has the potential to spread through meat to humans. Crabbe said the disease incapacitates animals, boring holes through their brain and brain stem and causing the animal to become lethargic.

Despite coming from the same family of diseases as bovine spongiform encephalopathy (more commonly known as mad cow disease), there have not been any documented cases of CWD in humans.

“It appears to only be transmissible among members of the deer family,” said Stasiak.

In Saskatchewan, that would encompass mule deer, white-tailed deer, elk and moose. Caribou can also be susceptible, though there haven’t been any cases in caribou in the province yet, Stasiak said.

She said CWD has shown to be transmissible to other species too, in experimental settings.

But while the disease doesn’t currently pose a risk to human health, it does harm the province’s ecosystem. It also raises concerns for possible food safety issues.

“People are concerned about the safety of the meat for consumption (even though) there hasn’t been any cases in humans, because there’s still a lot we don’t know about the disease and because it is in the same family as mad cow disease,” Stasiak explained.

She said it is recommended not to eat meat that is known to be infected with CWD, “more as a precaution.”

New numbers to be reported

Stasiak said there likely won’t be a significant increase in the new CWD rates that will be reported later this month. A year-to-year change is not typical, with a shift more likely to take place over a period of two to three years. She does, however, expect to see some increase.

Samples taken from this year’s CWD surveillance program are being tested and analyzed now.

Data from previous surveillance years, captured through hunters providing samples of their kills to test for the presence of CWD, helps the province pinpoint where the disease is most prevalent in Saskatchewan.

Crabbe said some zones have seen as high as 60 per cent prevalence of the disease in recent years, which he called “very unfortunate.”

Stasiak anticipated some new zones could appear or additional cases could be seen in the more eastern portion of the province or the boreal transition zone where she said there haven’t been many documented cases before.

Managing CWD

Different from other provinces, Saskatchewan is looking at long-term management solutions for dealing with the disease.

That can include measures like harvest management — which would include harvesting more animals or targeting older bucks in specific areas to reduce infection rates — and restricting baiting and feeding, which can attract wildlife.

As the disease is transmissible between animals, steps to limit transmission at congregation sites can be helpful.

Crabbe noted the general population doesn’t lend support to eliminating parts of a population.

Other measures include limiting carcass movement and mandating proper carcass disposal by hunters to prevent infected carcasses from being left in Saskatchewan ecosystems.

Crabbe said the most obvious form of control for the disease is nature itself, with extreme kinds of weather likely to push infected animals towards death. He said that gives healthy animals a better chance to survive, especially in the winter.

Research is in the works now too for a possible oral vaccine that could be distributed amongst cervids in the province to eventually help eliminate the disease from Saskatchewan ecosystems — ideally in populations that have not yet been infected.

Stasiak said that’s a large, multi-agency collaborative effort that multiple provinces are currently engaged in.

“That’s likely years in the making but we’re looking at all options,” she said.

Crabbe added the logistics of trying to get existing herds receiving a potential vaccine is “a pretty daunting possibility.”

The province’s surveillance program is a significant help in ensuring CWD cases across the province are tracked and recorded.

“The information we receive through the surveillance program is really critical to helping guide future management actions,” Stasiak explained, adding the contributions of hunters who participate in the testing program are appreciated.

Once hunters have submitted a sample from their animal for testing, it can take somewhere between four and six weeks on average to get a sample back, according to Stasiak. It is not recommended that meat infected with CWD be consumed but given the time for testing, that discretion is left to hunters.

“It’s up to them whether they want to wait for the testing results,” Stasiak said.

Crabbe said any hunter whose kill ends up being infected with CWD is recommended by the Canadian Cooperative Wildlife Health Centre to dispose of the carcass in a controlled landfill or another way that the disease cannot be dispersed back into the environment through disposal.

Hunters deterred

Generally, Crabbe said hunters will try to avoid zones where CWD is most prevalent because of the cost of hunting, only to return with an animal destined for disposal.

“When you spend all that time and effort and resources to go hunting and harvest an animal and bring it home and then get it tested and end up having to dispose of the meat … it certainly makes you try to determine whether it’s feasible or not to continue doing that,” Crabbe explained.

“Our major concern right now is a combination of chronic wasting disease and where we see the prevalence rates at and a lot of the other new things … like the new trespassing legislation.”

He said the combination of higher CWD rates in the province and the new trespassing legislation — which he said has not yet put a system in place that identifies landowners for hunters to be aware of — presents a scenario requiring a lot more logistical caution than most hunters want to deal with.

“We’re hearing (from) a lot of hunters that they’re very much contemplating perhaps not hunting next year,” Crabbe said.