Experts warn of CWD in humans



The U.S. needs to get serious about the risk of chronic wasting disease (CWD) infecting humans, a group of leading disease experts from across the country warned. “A comprehensive strategy, with national leadership and support, is needed to address this important public health risk,” the experts wrote in a paper published by the American Society for Microbiology last month.

CWD is an always-fatal brain disease that affects cervids — a family of animals that includes deer and elk. The disease is rampant in central Wisconsin, and it is spreading right outside Winona, too. Dozens of deer in Fillmore County have been infected. The herd at a deer farm in Cedar Valley south of Winona contracted CWD, and this year, three wild deer near Cedar Valley and Pickwick were found with the disease.

While there are no known cases of CWD spreading to humans, some studies have found that primates contracted the disease after eating infected meat. Famously, a similar disease — Mad Cow Disease — is believed to have spread from cattle to humans in Britain via meat. There’s a risk for the same thing to happen with CWD and people should be “very seriously concerned,” said Mike Osterholm, the paper’s lead author and the director of the University of Minnesota’s Center for Infectious Disease Research and Policy.

Osterholm travelled to England during the early days of Mad Cow Disease to help advise authorities there. “At the time, I felt there were far too many reassurances that there wouldn’t be a health problem with it,” he said. At the time, U.K. Minister of Agriculture John Gummer tried to feed a burger to his young daughter on TV to prove British beef was safe, despite the spread of Mad Cow Disease among cattle. Years later, scientists found strong evidence Mad Cow Disease did in fact spread to humans and scores of Britons died as result. “It took a decade of incubation time before we realized what happened,” Osterholm said. Britons were getting sick despite Gummer’s assurances; it just took many years for any signs of the disease to emerge.

Both CWD and Mad Cow Disease are believed to be caused by misshapen proteins called prions. The mis-folded proteins cause other proteins in individuals’ bodies to become malformed in the same way. Because they are not technically alive, prions are extremely hard to destroy — making it almost impossible to sanitize infected meat or contaminated surfaces. Both prion diseases have long incubation periods, meaning that infected individuals can carry the disease for years before showing any symptoms. When they do show symptoms, both diseases slowly attack the brain.

The U.S. Centers for Disease Control (CDC) has recommended that hunters “strongly consider” getting deer and elk tested for CWD before eating venison, while also advising that hunters follow the advice of their state agencies.

A Minnesota Department of Natural Resources (DNR) spokesman gave hunters less cautionary advice in 2018: “The bottom line is, it really gets into an individual’s comfort level and risk level approach.” No one can say with absolute certainty that eating venison from CWD-affected areas is safe, he said. “At the same time, no one can say there is no risk when you get in your car and drive home today,” the spokesman pointed out. “People should be informed and make their own decision about this,” he said.

“I find that kind of parsing, not helpful,” Osterholm said of the DNR’s advice. “The average citizen is not trained in risk analysis. They’re looking for guidance. They’re looking for information.” People should not stop hunting — because hunting helps suppress deer populations and control CWD — but Osterholm said he would sooner drive without a seat belt than eat CWD-infected meat. “If people don’t take it very seriously or even discard the kind of information that says, ‘Don’t eat CWD products in venison,’ and they wait until we have evidence of CWD transmission to humans, I feel like then we’ll really fall off the cliff on CWD,” he stated.

Experts from the Prion Research Center at Colorado State University, the Prion Disease Pathology Surveillance Center at Case Western Reserve University, and the Minnesota Department of Health joined Osterholm in writing the recent paper. In it, they point to evidence that CWD strains are emerging that are more capable of crossing species barriers. “The strains that are changing are changing to be much more like the human-prion proteins that we worry about,” Osterholm stated. The paper also points to the ongoing spread of CWD in cervids, evidence of its transfer to monkeys, and the lessons of past prion diseases in humans, such as Mad Cow. “If you put that all together, you have to be very concerned about the potential for transmission to humans,” Osterholm said.

The authors call for a national response to the threat of CWD. Testing animals for CWD in CWD-affected areas should be mandatory in more states, they argue. Improved regulations of captive and wild deer are needed to prevent the disease’s spread, the authors recommended. More research into CWD, including possible treatments or vaccines, and especially better tests for CWD are needed, they wrote.

Current CWD tests take weeks to get results. In the meantime, what do hunters do with their possibly infected deer? If the deer is sent to a meat processing plant before the test comes back, that plant could become contaminated with prions. Osterholm said his dream would be for scientists to develop “a home pregnancy test” for CWD, a little test strip that could tell hunters right away if an animal is CWD-positive. “If it takes two or three weeks to get back results, that’s almost an ineffective test,” Osterholm stated.

The Minnesota DNR is doing a great job on trying to control CWD, but a lot of its funding and a lot of other states’ funding comes from hunting licenses, Osterholm said. “There are a number of bills before Congress, and they need to act … We need strong national leadership. We can’t be taking all of these resources out of license fees,” he argued.

Remember the old saying, Osterholm continued, “You can pay me now or you can pay me later. I guarantee if we don’t do anything on this issue now, we will pay later.”


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