A scary, incurable neurodegenerative wildlife sickness officially landed in Jackson Hole last fall after decades of movement across the landscape toward northwest Wyoming.
After chronic wasting disease’s arrival, made official by a mule deer buck that was road-killed near Kelly, the dialogue quickly turned to what land and wildlife managers should and would do to limit spread among the malady’s usual hosts, deer, elk and moose. Concurrently, a global discussion is underway about whether human beings — specifically people who eat wild game — can contract CWD, which is closely related to two diseases we can acquire: mad cow and Creutzfeldt-Jakob.
“The best available evidence suggests that people shouldn’t be eating CWD-positive meat,” National Elk Refuge biologist Eric Cole said, “but there’s very little evidence that people can contract it environmentally, or contract it at all.”
Although a human case has never been confirmed to date, research on interspecies transmissibility is underway. One high-profile Canadian study suggests there’s no absolute barrier protecting primates from the always deadly disease. The decadelong study exposed 18 macaque monkeys to CWD’s vector, misfolded proteins called prions, in different ways: Some had it injected into their brains, some were fed infected meat and given blood transfusions, and others were cut and had wounds wrapped in infected deer brain tissue to simulate what would happen to a hunter while field dressing.
“At this point what we would like to stress — my collaborators and I — is that we have some evidence that it might infect nonhuman primates,” Canadian Food Inspection Agency lab researcher Stefanie Czub recently told High Country News for a story titled “The disease devastating deer herds may also threaten human health.”
Four of Czub’s test subjects have shown clinical signs of CWD, two monkeys whose brains were injected with prions and two that ate infected meat.
But other research has found less evidence that the strain of CWD North American ungulates carry can cross over to humans. Research at the University of California-San Diego and UC-Davis, according to the High Country News story, suggests that human prions are not capable of misfolding in the way that chronic wasting disease corrupts deer and elk prions.
Further muddying the waters is the newfound realization that there are several strains of CWD, which may have different abilities to be transmitted from one species to the next. New strains appear to have recently emerged in European cervids.
Even if the book is not yet closed on whether people are truly at risk, the general consensus is that eating meat from infected animals is ill-advised. The Centers for Disease Control and Prevention advises hunters to have all game meat tested and to not eat animals that turn up positive. The Wyoming Game and Fish Department echoes that advice.
Jackson Hole filmmaker and big-game hunter Shane Moore is one local who would “absolutely not” consider eating infected meat.
“I’m not thrilled with the idea of having an animal processed in a facility that has other animals going through that are positive,” Moore said.
The horror-movie-esque nature of chronic wasting disease stems partly from its durability. Prions can survive for years outside their animal hosts, embedding in soil, moving through water and even uptaking into grass that grows over infected ground. Detoxifying an infected landscape is exceptionally difficult, which is part of the reason that Teton County and other land managers are exploring the acquisition of a large incinerator that can burn over 1,000 degrees to dispose of carcasses.
For now the discussion of CWD in Jackson Hole will continue to revolve around steps that can be taken to reduce its impact on wildlife populations. The Wyoming Game and Fish Department, National Elk Refuge and other wildlife managers are in the throes of modifying management plans and trying to figure out how to limit high concentrations of animals like elk by reducing or eliminating feeding programs.
Arguably, there are some linkages between wildlife management and the human health side of chronic wasting disease.
In Cole’s view, the British breakout of mad cow disease in the late 1980s offers a cautionary tale. Prions were being spread through commercial feed that infected millions of cattle that, in turn, millions of people consumed. At some point the misfolded proteins mutated into a prion disease that humans could contract, and eventually 177 people died.
“The best way to prevent that from happening with CWD is to maintain low prevalence rates in the native ungulates,” Cole said. “It’s not unprecedented. It has happened with other prion-based diseases.”