Every fall, millions of hunters across North America enter forests and prairies to kill deer. During the winter, people eat the venison steaks, sausages and burgers made from the animals.
These hunters, however, aren’t just at the forefront 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. Currently, it is known to infect only members of the cervid family – moose, deer, reindeer, caribou and moose.
Animal disease scientists are concerned about the rapid spread of CWD in deer. Recent research suggests that the barrier to spread to humans is less formidable than previously thought, and that the prions that cause the disease may be evolving to become more capable of infecting humans.
The response to the threat is intensifying. 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 the future challenges are if we see a spillover into humans and food production,” said Michael Osterholm. , an infectious disease expert at the University of Minnesota and a leading authority on CWD.
“The main message is that we are quite unprepared,” Osterholm said. “If we saw a spill right now, we’d be in freefall. There are no contingency plans for what to do or how to proceed.”
The expert panel plans for a potential outbreak, focusing on public health surveillance, laboratory capabilities, prion disease diagnosis, livestock and wildlife surveillance, risk communication, and education and outreach.
Despite the concern, tens of thousands of infected animals have been consumed by humans in recent years, yet there have been no known cases of the disease in humans.
Many hunters have struggled with how seriously to take the threat of CWD. “The prevailing view I come across is that no human has contracted this disease,” said Steve Rinella, author and founder of MeatEater, a media and lifestyle company focused on hunting and cooking wild game.
They think, ‘I’m not going to worry about it because it hasn’t crossed 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 Creutzfeldt-Jakob disease, have affected humans. Mad cow has claimed the lives of more than 200 people, mostly in the UK and France. Some experts believe that Parkinson’s and Alzheimer’s disease may also be caused by prions.
CWD was first discovered in Colorado in captive deer in 1967, and 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 from viruses and bacteria and are almost impossible to eradicate. Matthew Dunfee, director of the Chronic Wasting Disease Alliance, said experts were calling it “disease from space”.
The symptoms are terrifying. The brain wears down to a spongy consistency. Sometimes nicknamed “zombie deer disease,” the condition causes infected animals to stumble, drool and stare blankly before dying. There is no cure or vaccine. And it is extremely difficult to eradicate, either with disinfectants or high heat — it even survives autoclaving or medical sterilization.
Cooking does not kill prions, Osterholm said. Unfortunately, he said, “cooking concentrates the prions. It makes it even more likely” that people will consume them, he said.
Although CWD is not known to have passed to humans or domestic animals, experts are very concerned about both possibilities, which Osterholm’s team just received more than $1.5 million in funding to study. CWD can infect more parts of an animal’s body than other prion diseases, such as mad cow disease, which could make it more likely to spread to people who eat deer — if it can jump to humans.
Researchers estimate that between 7,000 and 15,000 infected animals are unknowingly consumed by hunting families each year, a number that is increasing each year as the disease spreads across the continent. While testing wild game for CWD is available, it is cumbersome and testing is not widely used in many places.
A major problem with determining whether AD has affected people is that it has a long latency. People who ingest prions may not contract the resulting disease until many years later – so if someone did get sick, there may not be an obvious connection to having eaten deer.
Prions are extremely resistant to the environment. They can remain in the soil for many years and even be taken up by plants.
Because the most likely route of spread is through humans eating venison, rapid testing of venison and other cervical carcasses focuses on prevention. Right now, a hunter can drive a deer to a check station and send a lymph node sample to a lab. It can take a week or more for results to come in, so most hunters skip it.
Montana, for example, is famous for its deer hunting. CWD was first detected in the wild there in 2017 and has now spread across much of the state. Despite warnings and free testing, Montana wildlife officials haven’t seen much concern among hunters. “We haven’t seen a decline in deer hunting because of this,” said Brian Wakeling, chief of the game management office for the Montana Department of Fish, Wildlife and Parks. In 2022 Montana hunters killed nearly 88,000 deer. Only 5,941 samples were taken and 253 of them tested positive.
Experts believe a rapid test would greatly increase the number of animals tested and help prevent the spread.
Because of the deer’s importance to Native peoples, several tribal nations in Minnesota are working with experts at the University of Minnesota to find ways to monitor and manage the disease. “The threat and potential for the spread of CWD on any of our three reservations has the potential to negatively impact the Ojibwe deer hunting culture and traditions, providing deer for our participation,” said Doug McArthur, tribal biologist for the White Earth Nation, in the announcement about the program. (The other groups listed are the Leech Lake Band of Ojibwe and the Red Lake Band of Chippewa.) “Tribes must be prepared with a CWD management and mitigation plan … to ensure that the long-standing and culturally significant practice of the harvest the deer are preserved for future generations.”
Peter Larsen is an assistant professor at the University of Minnesota College of Veterinary Medicine and co-director of the Minnesota Center for Prion Research and Research. The center was created to study many aspects of prions as part of a push to prevent potential spread. “Our mission is to learn what we can about not only cardiovascular disease but also other prion-like diseases, including Parkinson’s and Alzheimer’s,” he said. “We’re studying the biology and ecology” of the misfolded protein, he said. “How do prions move in the environment? How can we help mitigate risk and improve animal health and welfare?”
Part of that mission is new technology to make testing faster and easier. Researchers have developed a way for hunters to do their own tests, although it can take weeks for results. There is hope for, within the next two years, a trial that will reduce the waiting time to three to four hours.
“With all the doom and gloom surrounding CWD, we have real solutions that can help us fight this disease in new ways,” said Larsen. “There is some optimism.”
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This article was reprinted by khn.orga national newsroom that produces in-depth health journalism and is one of KFF’s core operating programs – the independent source for health policy research, polling and journalism.
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