Wildlife-to-human crossover possibility heightens concerns
Each fall, millions of hunters across North America make their way into forests and grasslands to kill deer. Over the winter, people chow down on the venison steaks, sausage, and burgers made from the animals.
These hunters, however, are not just on the front lines of an American tradition. Infectious disease researchers say they are also on the front lines of what could be a serious threat to public health: chronic wasting disease.
The neurological disease, which is contagious, rapidly spreading, and always fatal, is caused by misfolded proteins called prions. It currently is known to infect only members of the cervid family — elk, deer, reindeer, caribou, and moose.
Animal disease scientists are alarmed about the rapid spread of CWD in deer. Recent research shows that the barrier to a spillover into humans is less formidable than previously believed and that the prions causing the disease may be evolving to become more able to infect humans.
A response to the threat is ramping up. In 2023, a coalition of researchers began “working on a major initiative, bringing together 68 different global experts on various aspects of CWD to really look at what are the challenges ahead should we see a spillover into humans and food production,” said Michael Osterholm, an expert in infectious disease at the University of Minnesota and a leading authority on CWD.
“The bottom-line message is we are quite unprepared,” Osterholm said. “If we saw a spillover right now, we would be in free fall. There are no contingency plans for what to do or how to follow up.”
The team of experts is planning for a potential outbreak, focusing on public health surveillance, lab capacity, prion disease diagnostics, surveillance of livestock and wildlife, risk communication, and education and outreach.
Despite the concern, tens of thousands of infected animals have been eaten by people in recent years, yet there have been no known human cases of the disease.
Many hunters have wrestled with how seriously to take the threat of CWD. “The predominant opinion I encounter is that no human being has gotten this disease,” said Steve Rinella, a writer and the founder of MeatEater, a media and lifestyle company focused on hunting and cooking wild game.
They think, “I am not going to worry about it because it hasn't jumped the species barrier,” Rinella said. “That would change dramatically if a hunter got CWD.”
Other prion diseases, such as bovine spongiform encephalopathy, also known as mad cow disease, and CreutzfeldtJakob disease, have affected humans. Mad cow claimed the lives of more than 200 people, mostly in the United Kingdom and France. Some experts believe Parkinson's and Alzheimer's also may be caused by prions.
First discovered in Colorado in captive deer in 1967, CWD has since spread widely. It has been found in animals in at least 32 states, four Canadian provinces, and four other foreign countries. It was recently found for the first time in Yellowstone National Park.
Prions behave very differently than viruses and bacteria and are virtually impossible to eradicate. Matthew Dunfee, director of the Chronic Wasting Disease Alliance, said experts call it a “disease from outer space.”