A new American study has shown the infectious prions that cause chronic wasting disease have been found in the muscle meat of infected animals.
“We know definitely infectious material is in the muscle of infected animals,” said Glenn Telling, a University of Kentucky scientist who launched the study to address concerns about the safety of meat from infected animals.
CWD is a contagious neurological disease that affects deer, elk and moose. It is in a group of diseases known as transmissible spongiform encephalopathy that includes scrapie in sheep and goats and BSE in cattle.
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Until now, widely held scientific opinion was that muscle cuts of meat did not harbour CWD-causing prions.
There have been no documented cases of humans getting CWD, but Telling said these findings should be a warning to hunters and others to take extra precautions.
“Are people going to die if they eat meat from infected deer? I would say at the moment we don’t know. Even though we’ve been studying these diseases for a number of years, there are still no rules to predict whether or not a CWD prion will cause a disease in human beings.
“I would err on the side of caution. We know now for the first time meat from these infected animals does contain not insignificant levels of infectivity.”
CWD was first diagnosed in captive deer and elk in Colorado in the 1970s and moved to wild deer and elk in the 1980s. It has also been found in farmed and wild elk and deer populations in Saskatchewan and Alberta.
During the study, researchers replaced the gene for the normal prion protein in mice with the normal gene from deer so the mice produced normal, healthy deer protein. Then researchers injected the mouse brains with tissue from infected deer. One year to 18 months later, the mice developed encephalopathy.
Tissue from the infected deer’s brains and high muscle caused disease. Muscle took slightly longer to cause disease than brain tissue.
Telling said many unanswered questions remain about CWD. Scientists know little about the origins of the disease or how it’s spread. They don’t know if there are different strains within the deer species, nor do they know whether livestock sharing contaminated pastures would be at risk.
“We know the most likely means of exposure human beings would have to CWD would be either consuming or handling infected meat,” said
Telling.
“What it says is that this is a risk material. That people who are going to be handling or consuming or some other way exposed (to) meat from infected deer or elk or other species are at risk to being exposed to prions.”
Glenda Elkow, chair of the Alberta Elk Commission, said she is skeptical about research that has manipulated a mouse prion to draw conclusions about CWD in elk.
“That’s not really very natural. I have a wonderment when they genetically modified a mouse to try and do research on it, do they weaken some other aspect of the mouse to make it more susceptible to certain things,” she said.
“I’m a bit suspicious. Has the research proved anything? It’s only one researcher and it isn’t a deer. It’s a mouse that’s genetically turned into a deer. I would question that,” said Elkow.
Trent Bollinger, a veterinary pathologist with the Western College of Veterinary Medicine in Saskatoon, said because of the unpredictability of prion disease, it would be prudent to not eat CWD or prion infected food.
Bollinger said the animal should be tested for CWD before the meat is eaten, especially if it was killed in an area of the province where CWD has been found in wild deer.
Elkow said there is no need for hunters to eat an untested infected deer or elk because in Alberta it takes very little time to test the animals’ heads.
