Would you feed your child a food if there was a possibility that it could slowly eat away at their brain 10 years from now leaving them dying, demented and wracked with painful body spasms?
That’s the question facing hunters and eaters of wild game in Wyoming as chronic wasting disease spreads.
The risk of a person contracting chronic wasting disease is, for the time being, low. We don’t even have any evidence that humans can catch the disease. However, the situation with wild game in Wyoming is eerily similar to that of mad cow disease in the U.K. 20 years ago, and things didn’t turn out so well for humans there.
Chronic wasting disease, like mad cow disease, is a transmissible spongiform encephalopathy. Both are thought to be caused by an utterly unique class of pathogens called prions.
Prions are not bacteria, viruses or parasites. They are a type of malformed protein, the basic building blocks of all cells. They are produced by the cells in the nervous systems of their hosts, but they are misconstructed — they do not fold into their proper shape. What makes prions contagious is that the particular shape they take causes a chain reaction, causing other proteins around them to become misconstructed as well, turning normal host proteins into more prions. This eventually causes the cell to die, and the prions affect the other cells surrounding them.
It is as if one faulty light bulb in a house not only malfunctioned, but also caused the other wiring and electronics to malfunction as well. The home’s electrical systems would eventually fail and spread their problems through the grid to the other homes in the neighborhood.
Chronic wasting disease was first discovered in deer in Fort Collins, Colorado, in 1967. In now infects more than 40 percent of deer, elk and moose in parts of Colorado and southeast Wyoming and has spread to 24 states and parts of Canada. Animals are thought to spread the disease usually through contact of bodily fluids, but the infectious proteins can remain in the environment for years and are highly resistant to human eradication efforts.
The first case of CWD in Teton County was discovered in a road-kill mule deer in 2018. Since then, state and local officials have been pondering ways to limit the disease’s spread in our region through means such as increasing natural predation, phasing out feed lots, and incinerating affected carcasses. While these approaches may limit the disease in cervid herds, none are likely to keep CWD entirely out of our region.
CWD is a slowly progressive illness — most infected hosts show no sign of illness for two years or more, until the prions become so prolific that their nervous systems start to malfunction. This affects the hosts’ cognitive and motor functions. They then waste away.
No human has been known to catch CWD after eating wild game, even game known to be infected with CWD. Spongiform encephalopathy also occurs randomly and sporadically in humans, at a rate of once in every one to two million people. Health officials in Colorado have been surveilling hunters since the 1970s and have not seen an increase in spongiform encephalopathy since CWD became widespread there. The first known spongiform encephalopathy, scrapie, which affects goats and sheep, has been known for hundreds of years and never crossed into humans.
Scientists have performed various experiments to see if CWD might be transmissible to humans, with mixed results. Two studies on squirrel monkeys provided evidence that transmission of prion disease is possible under experimental conditions and seven test-tube experiments showed that CWD prions can convert human protein to a misfolded state.
Regardless, prions hold the potential to mutate over time, which might make the CWD capable of crossing into humans.
For many years mad cow disease, another transmissible spongiform encephalopathy, was thought to be limited to cows. It spread largely unchecked through herds in the U.K. despite warnings from scientists that the disease could someday cross over into humans. It did.
Mad cow disease was discovered in the U.K. in 1986, and over 750,000 affected cattle entered the human food chain. Due to its long incubation period, the first case of mad cow disease didn’t occur in a human until 1996. There have been 228 human cases; it isn’t over yet, though — prion diseases can have an incubation period of over 50 years.
The most likely way for a person to contract CWD would be from eating the meat of an infected deer, elk or moose. The World Health Organization, U.S. Centers for Disease Control and Prevention, Health Canada and other health agencies recommend against eating meat from CWD-positive animals.
Wyoming Game and Fish is expanding its testing program and advising (although not requiring) hunters to have their game tested.
In the meantime the carcass is likely to end up in the hands of a processor. Game meat processors, which are regulated by the Wyoming Department of Agriculture, are not required to perform testing at their facilities, which could be a potential site of spread. Destroying prions requires either high heat or special enzymatic detergent or prolonged bleach submersion, far beyond standard hygiene practices of meat processors. There are also no restrictions on transport of processed game meat.
Once an animal with CWD dies the infectious prions can be found in soils and grasses for at least 16 years. This occurs particularly in places where ungulate herds congregate, such as in feeding grounds like the National Elk Refuge, which sits directly above the Town of Jackson’s drinking water wells.
So what’s a red-blooded, connected-to-the-land, meat-loving Wyomingite to do? Hunting is not only a pastime in much of Wyoming, but an important source of protein for many families.
There are certainly local physicians who, having become aware of the potential risk, have begun to avoid game meat. I think at this point that’s a decision best left to individual families armed with up-to-date information. The bottom line is that nearly all foods we consume come with some inherent risk of contamination of one sort or another. Game meat is certainly less dangerous than raw milk. It is likely less dangerous than produce contaminated with proven-harmful yet still-legal pesticides like chlorpyrifos. It is probably riskier than any theoretical harm conferred by genetically modified organisms.
Hunters can reduce their risk of exposure to CWD by following recommendations set out by the CDC (CDC.gov/prions/cwd/prevention.html).
In the meantime, we need a national strategy to study and manage what the Mountain Journal has called “Greater Yellowstone’s coming plague.”