Prevalence of deadly chronic wasting disease in some Alberta deer hits 23%

An incurable disease found in deer, elk, and moose is spreading across Alberta, according to new provincial surveillance results — and certain populations have reached a 23 per cent positivity rate. 

Chronic wasting disease, nicknamed zombie deer disease, is a fatal and incurable illness that affects deer family members.

Animals with chronic wasting disease often experience brain and nervous system deterioration. 

Surveillance results put out by the province, collected during the 2022-23 hunting seasons, found CWD in 23.4 per cent of 2,457 mule deer, 8.3 per cent of 1,556 white-tailed deer, 1.6 per cent of 320 elk and 2.9 per cent of 175 moose.

Overall, evidence of CWD was detected in 15.8 per cent of wild deer, elk and moose. 

"Any animal that gets CWD is always going to die. At this point, it's just a mess," said Debbie McKenzie, an associate professor in the department of biological sciences at the University of Alberta in Edmonton.

"It's one of the things that happens with CWD. The numbers don't appear to go down with time." 

She added that infection rates are the highest around the Alberta-Saskatchewan border, with close to 50 per cent positivity rate. 

"Basically, every other deer that's shot during the hunting season is CWD-positive, and there's areas now in the South Saskatchewan River valley just across the provincial border in Saskatchewan where it's greater than 85 per cent." 

McKenzie said hunters can take their deer to be tested by the province, and if a deer is positive for CWD — it's strongly recommended not to consume its meat. 

While there hasn't been anything in humans that looks like any neurodegenerative disease that is linked specifically to chronic wasting disease, it remains a concern for researchers, she said. 

"We don't know if it's going to jump to humans, but given that there's really long incubation periods with these diseases, by the time we know that it has jumped — if it does — it's going to be 10 years after people were infected, for example, maybe more." 

Along with the numbers going up, it looks like the disease is moving westward, toward many of the province's national parks, McKenzie said. 

Sabine Gilch, professor at the University of Calgary's faculty of veterinary medicine and CWD researcher, agreed the disease is closing in on Alberta's national parks as infected deer have been found in surveillance west of Cochrane. 

"The distance is getting shorter," Gilch said. 

"The deer do not recognize the borders of the national parks, so it's certainly a concern that at some point the disease moves into Banff National Park or Jasper." 

Gilch, who last year was given more than $4 million to research CWD vaccines and environmental remediation, says an infection rate of around 23 per cent in mule deer shows how much more difficult the disease will be to tackle. 

She said that when she started researching chronic wasting disease at the University of Calgary 10 years ago, the prevalence of CWD in the province's deer was below two per cent. 

"The higher the prevalence gets in deer and the wider the distribution of CWD gets, the harder it becomes to mitigate the disease," Gilch said. 

"It's really hard to get rid of the disease once it's established in the wild deer populations."