CHRONIC WASTING DISEASE is a wildlife plague so strange and novel that it baffles even experts. It also eventually kills nearly every one
CHRONIC WASTING DISEASE is a wildlife plague so strange and novel that it baffles even experts. It also eventually kills nearly every one of its hosts in excruciating and prolonged agony.
Somehow, this diabolical disease has become one of my regular beats. I try to follow updates from researchers and to report on new information that can help wildlife managers and hunters understand and respond to the emerging knowledge of its origins and implications. Along the way, I’ve tried to find slivers of hope in the research while also reminding hunters that CWD is the biggest threat to our traditions of deer hunting.
But all that traditional reporting is often not impactful. I’ve come to realize that hunters don’t like to either receive or respond to bad news. It’s way easier to perpetuate our traditional deer camp, or to keep our trophy-buck management program in place, or to dismiss the research into CWD as “junk science” than it is to recognize that chronic wasting disease will—sooner or later—impact the way we hunt deer in North America.
It may also impact our own health. While there’s no evidence that humans can become infected with CWD, it’s a member of what are called transmissible spongiform encephalopathies (or TSEs) that include Mad Cow Disease in Britain and a brain-wasting disease called Creutzfeldt-Jakob Disease that can infect humans.
Part of the problem with communicating the urgency of CWD is that its science is dense and complicated. The disease is caused by a bent protein, called a prion, that is not alive but which can infect deer or elk that come in contact with it through licking a branch or sniffing a butt. But curiously not every deer (or elk, caribou, or moose; the disease affects all members of the deer family) gets infected. Another complication is that transmission is invisible. And the disease’s impacts are further obscured by the fact that CWD-infected deer and elk, whose brains are being worm-eaten by this rogue protein, often die from something else. They’re hit by cars or killed by predators or die of dehydration because they’ve been transformed into hollow-eyed hulls.
Compounding all those problems is the fact that science is often nuanced. There is often not a single answer to a simple question. Conclusions about CWD’s causation, distribution, and prevalence are qualified by margins of error and statistical uncertainty. The situation is further muddied by the corrupting influence of profit. Commercial deer farms are a repository for CWD, and while the industry has helped advance our knowledge of the disease and its transmission, deer farmers have been resistant to regulations designed to keep our wild herds healthy.
But if you talk to enough CWD researchers, and listen closely, they often have a lot more to say about the disease than their science—or supervisors—allow. Some of them have wild fantasies about how our deer herd will recover, and others are willing to share their opinions about whether the disease could infect humans, but none of them are willing to comment on the record.
What you’re going to read here is the most speculative, and poorly attributed, story you’ll likely ever read about chronic wasting disease. But it also may be the most important, because this is what CWD researchers, protected by anonymity and free from their requirement to defend their positions, want you to know. These are outtakes from a series of interviews, or they’re the hushed revelations shared in a bar at the end of a professional conference.
But why publish a bunch of quotes and predictions if researchers won’t have their names printed alongside them? Because these perspectives hint at where CWD research is headed, how very far it still has to go, and why we should care a lot more about its implications.
CWD Is Confusing
We have vaccines to protect us from smallpox and polio, and more recently, immunizations for Covid-19 and evolving strains of the common flu. So why can’t we cure CWD?
“Honestly, I don’t even know what we’re fighting,” said one biologist in a moment of candor. “I get that it’s a bent protein, but what is it? It’s not a virus or a bacteria. It’s not alive but it’s not really dead, either. And you can’t detect it until its host is dead. That doesn’t make any sense.”
If there’s no realistic hope for a cure, there actually has been a good deal of work on detecting CWD in live animals, at least in the controlled environment of commercial deer farms. Veterinarians have figured out that they can detect CWD in tissue punched out of a captured deer. They can also detect CWD in tissue taken from the rectum of a captive deer.
But getting a sample from a wild live deer? That’s still years away.
“It’s actually pretty easy to get a sample from a captive deer, but that’s because they can be captured, tested, marked, recaptured, and then we can follow its disease progression inside a fence,” said another researcher. “Imagine doing all that with a wild deer. It could be done, I guess, but it would be so expensive and the sample size would be necessarily small because of the expense and hardship.”
“Until we learn how to efficiently and cost-effectively collect samples from wild animals then we’re going to be guessing which individuals have CWD and which don’t. There is some promising evidence that fecal testing can detect CWD in a wild population, but that doesn’t tell us which individual is infected.”
We May Be Killing the Wrong Deer
That practical difficulty of recognizing diseased deer is important to acknowledge, because it affects state game agencies’ response to CWD. In some cases—Wisconsin comes to mind—states have pursued an eradication policy, aiming to kill every deer within a certain radius from a disease outbreak. Other states have been more restrained, aiming to kill a certain number of deer to reduce densities and therefore prevalence of the disease. But in either case, healthy deer are being culled. And some of those deer may have a natural resistance to CWD. So are we inadvertently removing a possible solution with these remove-and-test operations?
“I’d be really unpopular for giving props to the game-farm industry, but one thing they’ve done pretty well is they’ve mapped and sequenced the genotypes of deer,” says one wildlife researcher. “That’s what you do if your business depends on selective breeding, right? The industry has screened tens of thousands of deer for unique genotypes and then tried to link them to resistance to CWD, and they have a handle on three or four [genetic] mutations that are pretty resistant. But in terms of knowing, or even guessing, genotypes of wild populations? We have no idea. So when you’re culling animals you always risk killing the golden goose, that one animal that might be the key to developing generational resistance.”
Many researchers compare CWD to sheep scrapie, a TSE that affects domestic sheep and goats.
“Years ago they recognized there were some sheep that were fully resistant to scrapie,” said one CWD researcher. “Agriculture being what it is, they selected those and effectively bred sheep scrapie out of the population by selective breeding. The deer farmers are doing the same thing. They will have some success. But in the wild setting? You have this bad deal where you have some hunters accidentally spreading it. You have populations [of animals] spreading it through normal migration, and there’s no eliminating it once you’ve got it.”
The researcher added what he called a blasphemous observation.
“This idea of selective breeding might be a key to surviving CWD over the long term,” the researcher said. “Stay with me here, but I can see a future where selective breeding for resistance could develop a strain of disease-resistant deer inside a captive population. If our wild deer are wiped out by CWD, then it could be that releasing these captive deer is the only way to return cervids to some landscapes.”
CWD Will Affect Deer Hunting
The researcher is suggesting that some deer and elk herds will be wiped out by CWD. It’s already happening in isolated herds of both mule deer and elk in Wyoming and Colorado, where 20 percent of the population dies every year from CWD-related causes.
“Those places where we’re losing 10 to 20 percent of our deer populations every year to CWD? Those are the places with naturally low population dynamics, because there are so many environmental pressures, from predators to other diseases to poor habitat conditions or tough winters. Before CWD infected those herds, hunters were given about 10 to 20 percent of the surplus to hunt. If CWD is now taking that surplus, then the sportsmen lose out, because I don’t think any game agency wants to hammer these struggling populations so they’ll restrict human harvest, instead.”
Researchers have noticed an interesting population dynamic that may inform how we manage CWD into the future.
“Those populations with low recruitment, like those infected herds in Wyoming and Colorado, may just go away over the next couple decades, but other areas, like the agricultural land in Wisconsin, is showing that they can have a lot of CWD in their deer populations but they’re not seeing a major decrease in overall numbers,” the researcher said. “What they are seeing is a decrease in older animals, and not just old bucks. Old does, too. Their age structure has really shifted down to where most of their population is very young. I think we’re going to have to adjust our expectations to be happy with shooting forkhorns.”
“I haven’t done these studies personally,” said the researcher, “but people with fancy ecological modeling are looking at how long an infected population will take to have a herd rebuilt with genetically resistant animals. Their models are saying 50 to 100 years. It’s possible that we’ll see deer go away in our lifetimes. Maybe their recovery won’t happen in our lifetimes, but might happen in our children’s lifetimes. It’s going to happen so slowly in the wild because we can’t accelerate the change like we can in a captive environment. I’m all about wildlife doing what wildlife need to do without a lot of human intervention. But if you’re in the West and you’re used to hunting some of these marginal herds, then my best advice is to start getting used to hunting pronghorns.”
CWD Management Is Expensive
State agencies are spending millions of dollars on CWD monitoring, testing, and public information campaigns. Wisconsin spent $32 million in its first five years of combating the disease. Idaho spent $110,000 on CWD monitoring even before the first positive case was detected last November. Many more millions are being poured into researching the disease. In many cases, states have been using hunting-license accounts to cover the work, but this year Congress appropriated some $70 million for research as well as management and control efforts.
Some of those funds—to the tune of $9.4 million—was distributed to states and tribes just last month. But there are proposals and research projects that could easily consume the balance of the appropriation. When you consider the size and economic consequence of America’s $23 billion deer-hunting industry, funding projects that can slow or stop this existential risk makes good economic sense.
“We have some research projects that are on hold simply because we don’t have the funding or the personnel to launch them,” said one research advisor. “These are not small or quick studies. It can take years just to do the clinical work, and more years to determine our findings. Meanwhile, the CWD [distribution] map just gets more colors on it.”
Human Infection Is Still Unknown
“Our biggest victim of CWD, besides the deer themselves, is contributions to our Hunters For The Hungry program,” said one wildlife manager who says uncertainty and concern about eating potentially infected venison has cratered donations to food banks in her state. “A lot of processors have dropped out of the program because they don’t want to accept the expense of holding an animal until a clean test comes back or take the chance of processing and distributing a diseased animal.”
As for the underlying question of whether humans are at risk of contracting CWD from diseased meat, the jury is still out, despite tons of research into the topic. Some researchers have gone so far as to inject folded prions from infected deer into the brains of research animals ranging from monkeys to mice, and haven’t been able to detect cross-species transmission. Others have found some transmission, but that study may have been flawed.
Most researchers say the current public-health advisory from the Centers for Disease Control is sound. It includes recommendations to not shoot sick deer, to wear protective gloves when handling deer, to have animals tested for CWD before eating the meat, and to discard meat from an infected animal in an approved landfill.
Proper Carcass Disposal Is Our Best Defense
If there’s a lot of uncertainty and disagreement about detecting, slowing, or managing the spread of CWD among scientists, there’s one point of vocal unanimity: hunters must help contain CWD by disposing of deer and elk carcasses properly.
“I think there’s pretty wide agreement that CWD is spread by trucks,” said one biologist. “Either the stock trailers that game farms use to haul live deer or the pickups that hunters use to haul dead deer.”
Each state has its own rules governing carcass transport and disposal, but they often share a few details. Don’t move brain or nervous tissue from one area to another. That’s doubly critical when moving from a CWD endemic area to a state or place where CWD hasn’t been detected, but it’s good practice anytime and everywhere. Don’t discard carcasses on the landscape. Instead, take them to a Class II landfill. And have your deer or elk tested for CWD. There are plenty of resources where you can find details about doing this yourself or taking your harvest to a CWD testing station.
“Bottom line: there’s no getting rid of CWD once you have it in a population or on a landscape,” said one wildlife manager. “Believe me, you don’t want it. But it’s ultimately up to hunters to hold the line.”
CWD Is Awful
“Imagine watching your grandma with Alzheimer’s, and recording her transformation from a person into a ghost. Every. Single. Day. And you can’t help her or intervene. That’s what it’s like watching these deer die from CWD.”
That’s the day-to-day life of a CWD technician in a major research lab, observing and recording clinical signs of the disease. Most hunters have never seen a deer in the final stages of CWD, because they often seek solitude or are killed by secondary agents before most of us can observe their last days.
“I wouldn’t wish this on my enemies,” says the technician. “It’s like [these deer] are just gone while they are still alive.”
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