Imagine walking through a market teeming with humans and nonhuman animals: monkeys, pigs, bats, pangolins, beavers, rats, deer and other creatures unknown and unappetizing to most Americans.
Smashed into this small area, half-a-million square feet – slightly more than 10 acres – is a dizzying kaleidoscope of species. These are animals that under more natural circumstances would rarely, if ever, interact.
You’re perusing, like all the other humans filtering in and out. Everything is for sale and you’re looking for food, fulfilling an evolutionary imperative that provides rhythm to our days.
Can you smell it? Can you hear the cacophony of animal shouts, trills and squawks? The human voices?
It’s early on an October day. The sun is rising, fog rolling off a distant ridge. You’ve been up for hours in Wyoming’s hill country and now you’re watching a monster bull elk saunter along the ridge 150 yards away.
Your heartbeat quickens. You take a deep breath, raise your hunting rifle, hover the crosshairs over the elk’s front shoulder.
It’s silent, the world’s sounds dampened by a dusting of snow. This is the largest elk you’ve ever seen. He’s grown big and strong nibbling the new growth that follows forest fires and logging. He’s been mostly unbothered by predators. In the cold, hard Wyoming winters, he eats feed put out by wildlife managers.
You slow your breath and gently squeeze the trigger.
These scenes have little in common.
The first is characteristic of the wet markets found in China and other countries. It also happens to be the kind of place where scientists believe the SARS-CoV-2 virus, which causes COVID-19, made the jump from bats to (maybe) pangolins before landing in humans.
And the second, a more familiar scene for readers of The Spokesman-Review, represents the front lines of a deadly neurological disease that’s slowly marched its way west through elk and deer herds: chronic wasting disease.
In the same way that these imagined scenes appear to be near opposites in tone and setting, the two diseases, CWD and COVID-19, apparently share little in common – other than being poorly understood.
One is a fast-acting virus that infects humans. The other, a simmering neurological disease found in deer and elk.
And yet, if you look closer, there are similarities.
“Of course, COVID-19 and chronic wasting disease are very different diseases,” said Margaret Wild. “But the way diseases spread has some commonalities.”
Wild would know.
A professor at Washington State University studying elk-hoof disease, Wild has spent her career researching emerging infectious diseases in wildlife. That mostly meant studying CWD. Now, at WSU she’s applying the knowledge and systems she learned studying CWD to the poorly understood elk-hoof disease found in Washington.
CWD is a neurological disease that kills deer and elk. It’s in a family of disease known as transmissible spongiform encephalopathies. These diseases are caused by oddly shaped proteins called prions (PREE-ons).
The effect is devastating. Infected animals stumble, drool, shed weight and, among other things, lose all fear of humans.
Then they die.
For obvious reasons, it’s often called the zombie deer disease.
What’s worse, infected animals shed prions, which can persist in the environment and remain infectious for at least two years, if not longer. In Colorado, where the disease was first documented in the 1960s, managers culled entire herds in hopes of stopping the disease. But as deer and elk returned to the landscape, they were reinfected by lingering prions.
Now, the disease is in 26 U.S. states, three Canadian provinces and Norway, South Korea, Finland and Sweden.
It has not been documented in Idaho or Washington, although some believe it’s simply a matter of time. Last year, Montana officials confirmed five cases of CWD less than 25 miles from the Idaho Panhandle.
Thankfully, as far as anyone knows, CWD has never jumped to humans.
That doesn’t mean it can’t.
Some ongoing research in nonhuman primates, most notably 18 hapless macaques at the University of Calgary, indicates that CWD may infect monkeys. The results of this study have not yet been published, and otherpublished research indicates human prions are resistant to the abnormal folding.
Still, if it turns out that CWD can infect primates, it’s one step closer to humans.
Adding to the worry, another prion disease found in cattle did make the jump. Creutzfeldt-Jakob disease is the human-variant of bovine spongiform encephalopathy, commonly known as mad cow disease.
Wild is quick to emphasize that it’s not a “given that (CWD) will make the leap.”
But two years ago the same could have been said of SARS-CoV-2.
The SARS-CoV-2 virus is in the coronavirus family of viruses. There are six other coronaviruses that are known to infect humans. Four of those are mild and cause roughly a third of all colds. The remaining two are rarer and more severe. They cause MERS (Middle East Respiratory Syndrome) and another strain of SARS (Severe Acute Respiratory Syndrome).
Meanwhile, there are at least 500 identified coronaviruses found in Chinese bats.
The coranaviruses are, of course, viruses. They are not prion diseases. They spread via respiratory droplets, not oddly formed proteins found in brain matter. And COVID-19, the disease caused by SARS-CoV-2, isn’t nearly as deadly as most prion diseases.
But, as Wild said, the way in which the diseases spread, and the process by which they make the jump to humans (known as spillover), is similar.
And the coronavirus pandemic has thrust these concerns into the spotlight. Words and phrases once used only by epidemiologists, veterinarians and public health officials – flattening the curve, social distancing, surveillance – are now common parts of the lexicon.
“Infectious disease is all around us,” writes David Quammen in his book “Spillover.” “Infectious disease is a kind of natural mortar binding one creature to another, one species to another, within the elaborate biophysical edifices we call ecosystems.”
Diseases, like animals, are trying to survive. Diseases are predators. But, unlike large predators – wolves for instance – they attack and eat their prey from the inside.
Like wolves, diseases have their favored targets, creatures with which they co-evolved, honing their predatory skills over millions of years.
Of course, things change. For most of life’s history on Earth, those changes were slow. Incremental. As land masses moved, or as the occasional intrepid individual traveled a great distance, species met and started sharing pathogens.
Diseases found new hosts. Hosts adapted.
Most efforts to jump species fail. Evolution is a brutal process, with many more dead ends than successes. But what it lacks for in finesse it makes up for in persistence.
And humans have accelerated the rate at which things change, giving the evolutionary process more chances to get it right. As we’ve expanded our footprint – as we’ve cleared forests, traveled around the world, displaced animals – we’ve come into contact with long-sequestered pathogens.
“Lots of these disease problems are caused by these stupid things that humans are doing to the planet,” said Andrew Dobson, a professor at Princeton University. “I think it’s really important for people to know that lots of the things we’re doing to disturb natural habitats carry this hidden cost.”
Dobson studies zoonotic diseases – that is, diseases infecting both animals and humans, like SARS-CoV-2. Much of his work has focused on the Greater Yellowstone Ecosystem, a place where large wild animals are sharing terrain with nonnative domestic animals.
He argues that ecologists traditionally have ignored the role pathogens play. And it’s a big one: 90% of the Earth’s biodiversity is parasitic, he said. Most species have between 10 and 20 parasitic species living inside them.
Scientists estimate that 75% of new infectious diseases originated in wildlife. And in the past 50 years, emerging zoonotic diseases have quadrupled, wrote a group of more than 100 conservation organizations in a letter to Congress last month. They urged lawmakers to include money in the stimulus package to address the underlying issues causing an increase in zoonotic disease
“COVID-19 is just the latest zoonotic disease to emerge that has its roots in the rampant habitat loss occurring around the world and the burgeoning wildlife trade,” the letter states. “Global pandemics will likely continue and even escalate if action isn’t taken.”
Congress did not allocate funding. And President Donald Trump’s administration has continued efforts to roll back Obama-era environmental regulations on drilling, mining and logging on public lands in the West.
That’s despite the fact a 2015 study found that land use changes such as development, mining and logging have driven many of the zoonotic outbreaks of the last century.
SARS-CoV-2 most likely started as one of the 500 known coronaviruses infecting a Chinese bat. Then, through incredible misfortune it found its way (with a stopover in some, as of yet unconfirmed, animal) into a highly social, globetrotting species: humans.
That spillover was facilitated by places like the wet market in Wuhan, where numerous species (and their parasites) come into intimate contact.
In the same way, it’s unlikely CWD will make the jump from elk and deer to cattle or humans.
But the more chances it has, the more likely it is to mutate and succeed. Imagine a gambler playing penny slots. If they play every day for a year, an unlikely event – hitting a jackpot – may happen.
It’s the same with weird wildlife diseases like CWD.
Over the past 100 years, elk and deer populations have grown, an incredible conservation success story. At the same time, Americans have expanded into former agricultural land. Elk, deer and other animals, attracted to succulent yards and shrubs, are coming out of the hills looking for an easier life.
Some states, like Wyoming, even go as far as feeding elk and deer in the winters to provide better hunting opportunity in the fall and keep elk out of farmer’s fields. Other states transport the animals, whether for research or profit. And elk and deer are living on a landscape that’s mostly free of predators, with herds managed by state agencies to maximize hunter success.
All of which expands the number of opportunities for something bad to happen. CWD, after all, was first identified in captive mule deer herds.
“If CWD is a relatively rare disease and people are infrequently exposed to it, then the likelihood of something bad happening is exceedingly rare,” said Wild. “The more CWD we have in deer and elk and the more people that are exposed to those animals, the more likely an exceedingly rare event could happen.”
In short, a disrupted ecosystem, one that is missing key parts, whether it’s species or habitats, increases the likelihood of diseases like CWD spreading.
Which brings us back to Washington and Idaho.
Social distancing and surveillance
The strategies used to slow the spread of CWD are nearly the same as those deployed by public health officials hoping to flatten the COVID-19 curve.
Last year, when five cases of CWD were confirmed in Libby, Montana, wildlife officials in Idaho started year-round surveillance in the Panhandle. The current surveillance strategy used by Idaho Fish and Game includes collecting samples from hunters and roadkill and responding to reports of deer behaving abnormally. The sampling model gives IDFG a 95% chance of detecting CWD if 1% of the population is infected.
In 2018, the state updated its CWD response plan, the third such plan IDFG has drafted. Additionally, last year the Idaho Fish and Game Commission banned the import of deer, elk or moose carcasses and urine from areas with documented cases of chronic wasting disease.
Washington is not doing that kind of surveillance and hasn’t since 2011, when federal funding ended.
But Melia DeVivo, a research scientist focusing on hoofed animals for the Washington Department of Fish and Wildlife, is working on the state’s CWD response plan. She hopes to have it finished this year. That plan will update surveillance techniques and incorporate the newest data on CWD.
“Our risk is pretty high,” she said. “It’s hard to say what exactly that risk level is. But we are seeing a slow spread of the disease from state to state. We know we have animals moving naturally across borders. We also have risk posed whenever we move live animals.”
Washington banned deer farming in 1993, a decision some think has kept CWD out of the Evergreen State.
“A deer in the wild is very rarely exposed to that prion,” Wild said. “But when we move an animal from across the country, alive or as a carcass, it’s just like someone with COVID-19 flying in to our city and infecting us locally.”
Prevention is the key. Once CWD is established in an area, it’s nearly impossible to eradicate.
DeVivo knows of only one instance when wildlife managers were able to rid themselves of CWD, and that was due to luck more than anything else.
Instead, the best offense is an aggressive defense. That means removing attractants that cause deer or elk to congregate, whether that’s baiting stations, salt licks or food lots.
“That poses a huge risk of the transmission of the disease, for sure,” she said.
Surveillance is also a key preventive tool.
But both Washington and Idaho may have a unique, albeit controversial, advantage: a nearly full suite of native predators.
Lions, wolves and bears (kind of)
Washington, the West’s second-smallest state geographically, is home to an impressive menagerie of wild animals: cougars, black bears, fishers, wolves, lynx and the occasional grizzly. It’s an unusual arrangement in the Lower 48 – 7 million people living alongside a rebounding carnivore population.
And when it comes to CWD, these predators could be Washington’s and Idaho’s saving grace.
“Predators do a very good job of removing sick animals from populations,” Dobson said. “And that reduces the rate of transmission.”
Some research indicates that predators, particularly wolves and cougars, naturally constrain the spread of wildlife diseases, CWD in particular.
“Cougars actually seem to selectively prey on CWD-positive deer,” DeVivo said, referencing research she’s done.
But wolves might be the best bet because of how they hunt.
They chase their prey, testing herds of deer and elk, hoping to pick out the weakest and slowest, which would likely mean CWD-infected animals. The CWD research isn’t conclusive, DeVivo said, and as of now it remains a theory.
“We don’t have a good example at this point of what it does in a population where you do have a full suite of predators,” DeVivo said. “I’m not going to say it’s going to be our saving grace for this disease. But I’m going to tell you it will be very interesting if CWD does show up in northeast Washington.”
‘The health of all species’
Back in Wyoming, you hit the bull elk. A clean shot. You spend the next 12 hours field dressing the animal and hiking it back to the car. It’s only five miles but you’re carrying hundreds of pounds of meat, after all.
It’s dark when you finish. But you’re anxious to get home to Spokane after 10 days gone. You know Washington prohibits bringing the heads of elk and deer into the state (unless all soft tissue has been removed) from CWD-positive places like Wyoming, but it’s late, you’re tired and this animal is as healthy-looking as they come.
So you drive through the night, the elk’s head and antlers wrapped up and tucked away.
The elk didn’t have CWD. Or maybe it did, but the prions didn’t, for whatever reason, linger. Washington stays CWD-free and the disease doesn’t jump species.
Or, perhaps in the chaotic wet market you make a conservative choice and don’t eat any exotic meat. Or maybe you do. Either way, you go back to your hotel. You fly home a week later. How was China? friends ask, and you answer in platitudes. You don’t get sick. There is no spillover.
This is the likely outcome.
Now scale it up. Thousands of hunters transporting carcasses. Hundreds of thousands of people flying, daily.
All interacting with landscapes, with ecosystems, that have been fundamentally altered by humans. Logged. Mined. Built upon. Each interaction representing a chance, however small, of something unfortunate happening.
There is no simple answer. No single solution. Instead, any response will require a shift in how we think about disease, argues Wild, the WSU professor.
“Really, health is about the health of all species,” she said. “By promoting the health of all species, and the environment, that’s how we can keep ourselves the most healthy.”
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