Canadians are being warned about the spread of a deadly animal disease that has the potential to infect humans especially after some of the animals were released for human consumption.

Chronic wasting disease (CWD) is similar to mad cow disease (formally known as bovine spongiform encephalopathy or BSE). It infects deer, elk, and moose and it's spread by a protein — called a prion — which has the unusual ability to spread between animals causing a deadly wasting disease.

There is no direct evidence that it can spread to humans, but recent research showing transmission to non-human primates (macaques) has heightened concerns.

Until last fall, CWD had only shown up in wild and farmed deer and elk in Alberta and Saskatchewan.

But in September 2018, a deer farm in Quebec had a major outbreak; 2,788 animals were destroyed and 11 animals were found to have been infected.

According to the Canadian Food Inspection Agency, the rest of the animals that tested negative, along with younger animals under 12 months — 2,777 deer — were released for human consumption, a decision that remains controversial.

'Should have destroyed the meat'

"They should have destroyed the meat," said Alain Cossette.

He's the executive director of the Quebec Federation of Hunters and Fishermen. He said he's surprised the younger animals who were not tested were released into the food chain. (Deer under one year of age are not tested as this disease is less likely to be detected in young deer).

(Daniel Rofusz/CBC News)

Although CWD is not a known health or food safety risk, Cossette won't take the chance of eating an infected animal.

"I will tell you, something that attacks your brain, I will never take that chance to eat an animal that can be contaminated, or maybe contaminated. I will never try that."

Health Canada recommends that people avoid eating meat from animals known to be infected with the prion protein. There are precautions for hunters, too. They're encouraged, when handling carcasses, to have those animals tested before eating the meat.

But experts say it's likely that Canadians are already eating deer and other wild game that is infected with CWD.

"Human exposure to CWD is quite widespread, in my opinion," said Michael Coulthart, who tracks prion diseases with the Public Health Agency of Canada.

The more CWD there is, the more likely humans are exposed to it through consumption of meat. - Michael Coulthart, Public Health Agency of Canada

Although he said that humans don't appear to be highly susceptible to disease after being exposed to CWD, he is fairly certain that exposure is taking place. "The more CWD there is, the more likely that humans are exposed to it through consumption of meat mostly."

This week, a letter signed by more than 30 experts, including scientists, doctors, wildlife biologists and Indigenous leaders was sent to the prime minister calling for greater effort to control CWD.

Dr. Neil Cashman was one of the signatories. He's a professor at the Faculty of Medicine at the University of British Columbia and has researched prion diseases for over 20 years.

"I think CWD has the possibility of having more negative impact for Canada and its economy then did … mad cow disease," he said. "I think we're teetering on the edge of a catastrophe."

The directives listed in the letter include:

Contain the geographic spread of CWD, for example, by banning the movement of deer, and potentially infected carcasses.

Prevent human exposure.

Fund independent, evidence-based initiatives to prevent the transfer of CWD via food and feed chains.

"I think the Canadian consumer should be very worried," Cashman said. "The problem is the positive carcasses are being consumed all the time, with no knowledge, and no planning about how to reduce this risk."