ST. PAUL — There’s no conclusive evidence that chronic wasting disease is transmissible to humans who eat meat from infected animals, but the possibility can’t be dismissed, either, health experts say.
In a paper titled “Chronic Wasting Disease in Cervids: Implications for Prion Transmission to Humans and Other Animal Species,” senior author Michael Osterholm and five contributing authors say “the risk of CWD transmission to humans is low but not zero.”
A renowned Minnesota public health expert, Osterholm is director of the Center for Infectious Disease Research and Policy — CIDRAP, for short — at the University of Minnesota.
Citing research by the Alliance for Public Wildlife, the paper estimates that humans consume “7,000 to 15,000 CWD-infected animals annually, a number that may increase by 20% each year.”
Previous research has shown the prions that cause mad cow disease in cattle can transmit to different animal species and humans, Osterholm said in a phone interview.
“The prions that are in these deer are of note in that they’re changing, they’re constantly mutating,” Osterholm said. “In the mad cow situation, the prion was primarily in the central nerve — the brain and the spinal cord. Here in these deer, it’s surely in the central nerve, but there also are prions located in the lymphatic system; they’re actually right in the muscle.”
Prions in the muscle are more “zoonotic,” meaning they potentially are more likely to transmit to other species, including humans, than prions in the central nerve, Osterholm said.
Cooking the meat has no effect, since prions can withstand temperatures of 1,500 degrees or more.
“It has to give us pause at this point to say, ‘Yes, could it happen? It might, we don’t know,’ ” Osterholm said. “But it surely is more than just a theoretical risk.”
As part of continuing efforts to learn more about CWD and other prion diseases, CIDRAP last spring formed the CWD Expert Advisory Group, a 47-person panel Osterholm describes as a “who’s who” of the top prion researchers from around the world, along with wildlife managers and leaders from conservation and hunting organizations, including Craig Engwall, executive director of the Minnesota Deer Hunters Association.
CIDRAP also has a section on its website dedicated to the latest CWD-related news and developments. The goal is to foster a “cross education effort” between constituencies, Osterholm said.
“It’s where we can all come together, and we don’t just have a prion biology research meeting and we have a wildlife meeting and we have a hunter education meeting,” he said. “Those are all great, but what you need to do is talk across to each other, not around each other.”
That’s important because the disease is constantly changing, Osterholm said.
“Studies that were done five to seven years ago looking at the potential for the transmission of this prion to humans found, in many cases, at least the initial lab data didn’t support that might happen,” Osterholm said. “Those were well-done studies — really well-done studies. The problem is we have new strains today; they’ve emerged.
“That’s why the website we have is such an important resource because it really is the one resource for current comprehensive and authoritative information on CWD for the world.”
During the last legislative session, Minnesota lawmakers approved $1.87 million from the state’s general fund and $2.85 million from the state’s Game and Fish fund to combat CWD, John Myers of Forum News Service reported in June.
Still, too much of the work being done in the area of CWD research has fallen on the shoulders of deer hunters and state agencies such as the Minnesota Department of Natural Resources, Osterhom says.
“I think it’s fair to say Minnesota has done an incredible job on a relative lack of resources,” Osterholm said. “This last legislative session did provide some additional resources, but it’s one where we need federal activity and support soon.
“I mean, right now.”
On the Web: