CWD: ‘It’s kind of a genetic roulette table’

March 22, 2019
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The Minnesota Department of Natural Resources says chronic wasting disease seems to be spreading along river corridors, where deer can easily travel.

The Center for Infectious Disease Research and Policy at the University of Minnesota announced Tuesday that it has launched the Chronic Wasting Disease Response, Research and Policy Program.

Dr. Michael T. Osterholm, the director of CIDRAP, said the new program has multiple objectives, but the biggest one is to raise national awareness of what he believes is a real threat to human health.

“We believe it is possible that human cases of chronic wasting disease associated with the consumption of CWD-contaminated meat will be documented in the years ahead,” he said. “There is an immediate and critical need for national leadership on addressing CWD, and the CWD Program establishes the University of Minnesota as both the national and international center for CWD response, research, education and policy.”

Osterholm is very familiar with diseases caused by prions, which are abnormally shaped proteins. In the 1980s, he was on the front lines in England when bovine spongiform encephalopathy (mad cow disease) was detected in cattle.

“Everybody rushed to reassure the public that this would not be a problem, that there was this species barrier that would prevent the prion from infecting humans,” he said. “If you said otherwise, you were told, ‘Oh, you’re just fearmongers. This isn’t going to happen.’ And then it did. Ten years later, we learned that it transmitted to humans through the consumption of contaminated beef.”

Since 1996, 231 people worldwide have died of mad-cow disease, which in people is called variant Creutzfeldt-Jakob disease.

Osterholm said the similarities between Britain then and the United States now are too real to ignore.

“We’re kind of at a deja vu-like moment with what’s happening with the rapid spread of CWD and the subsequent consumption by humans of contaminated venison, and what happened in Great Britain,” he said. “Granted, we don’t have any evidence that it’s happened here yet, but we’re talking about potentially a 10-year incubation period. So anything we find in the future will reflect back potentially as much as 10 years earlier in terms of exposure.”

Southeastern Minnesota is “ground zero” for Minnesota’s battle against chronic wasting disease. More than 40 wild deer have tested positive for CWD, most of them near Preston.

But Minnesota is far from alone. CWD has been found in deer and elk in 26 states. That means that each year, more and more hunters and their families are unknowingly eating meat from infected animals, which can carry prions for several years before showing symptoms of the disease.

With great numbers, Osterholm said, comes greater risk.

“It’s kind of a genetic roulette table,” Osterholm said. “One of the things we worry about is that as more and more transmission occurs within the cervid population, you have more chances for genetic changes to occur in the prions, which could make them more likely to infect humans.”

To protect hunters, Osterholm said the new CWD program will press for the development of an easy-to-use field test that would allow hunters to quickly determine whether the deer they just shot is infected with CWD. Currently, the testing process requires lymph tissue to be removed and sent to a lab, where the testing process can take several days.

“If hunters could test their deer themselves, right there in the field, not only would that keep the animal from being consumed, but it would also keep that animal out of meat processing plants,” Osterholm said. “An infected deer could contaminate equipment at a meat processor, and then anything that comes down the pike later — a deer, a hog, a cow — could be contaminated as well.”

Osterholm stressed that while the new program’s goal is to raise awareness about CWD’s potential risks to humans, it doesn’t want to discourage hunting. Quite the opposite, in fact.

“Hunting plays such an important role in controlling the size of the deer herd, which helps contain transmission of the disease,” he said. “If we didn’t take 200,000 deer out of the herd each year by hunting, that would only exacerbate the potential for transmission.”