Researchers first identified chronic wasting disease way back in the 1960s. Soon after, Michael Miller got sucked into working on it.
"Yeah, sucked into it is really right," he said.
Miller is a senior wildlife veterinarian with Colorado Parks and Wildlife. Back then, local wildlife scientists were studying captive mule deer at a facility in Fort Collins, Colorado. They were trying to figure out how to help mule deer in the wild survive harsh winters, but the animals kept getting sick and dying.
It didn't make any sense. Finally, they looked at pieces of the animals' brains and saw something disturbing: the brains were full of holes, a pattern similar to what happens with mad cow disease. They soon discovered it was hard to kill, too.
"The folks who were running these research operations decided to try to get rid of the disease, so in the mid-80s they gathered up and killed all the captive deer and elk they had and did what, at the time, seemed like a very thorough job of cleaning up the facility grounds," Miller said.
They cleaned the pens where the animals had been kept, turned the soil, brought in a helicopter to drop chlorine onto the site, and left it alone for a full year. Then, they brought in healthy wild elk calves.
"And we failed," said Miller.
With a couple years, the disease was back. Miller and his colleagues worked hard to figure out how to contain it in northern Colorado.
"The idea at the time was that we would do what we needed to here, locally, to keep it from spreading to the Western Slope. What we didn't realize is that it was actually more widespread. It was a really nice idea that was probably 10, 15, maybe 20 years too late," he said.
Over the next few decades cases kept showing up in new places, first in captive animals, then in the wild. Cases mushroomed across the U.S. and Canada. It even jumped continents, flying from Canada to South Korea in a shipment of infected elk.
Early modeling work hinted at the possibility that chronic wasting disease might make deer go extinct.
"That's probably not going to happen. It's certainly not going to happen any time very soon. What is more likely is that we will have a deer herd that is unable to grow," he said.
A bad winter, for example, could do some real damage to herds if enough animals among them are infected.
People in Canada, the U.S. and Nordic countries are scrambling to keep the disease under control. Idaho is trying to tighten rules about moving animals across its borders. In Wyoming, environmental groups are suing the U.S. Fish and Wildlife Service for feeding elk in the winter, which they believe could contribute to the spread of chronic wasting disease.
Colorado just came out with its latest management plan, which includes testing animals, thinning out overly infected herds in some cases, scoping out the possibility of investing in incinerators to dispose of infected carcasses, and warning hunters and taxidermists about how to handle infectious material.
"We're not talking about going in and annihilating deer over large tracts of land," said Miller about the plan in Colorado, where 57 percent of deer herds and 37 percent of its elk herds are infected. "We've actually done that," he said, adding that it was only once and not on a very big tract of land. "It was under the misguided notion that it had just gotten there, and we could actually stamp it out if we did something quickly. And again, we were wrong."
"It isn't something that lends itself to a quick fix, and we don't need to do draconian things but we need to do something," said Miller.
Historically, a lot of these plans have rested on one big assumption: That the disease started here in the Mountain West and then moved everywhere else. But Mark Zabel, who studies the disease, says that could be wrong in a big way.
"Most of the outbreaks in the U.S. can be traced back to movement of animals on the game farms from the Front Range to places like Saskatchewan in Canada to the Midwest and Wisconsin to South Dakota, repopulation in Arkansas," said Zabel, associate director of the Prion Research Center at Colorado State University. "But then there are some that have no known connection."
For example, scientists were mystified in 2016, when the disease showed up in Norway and then later in Finland and Sweden.
"I think this question of what's going on is kind of opened up again," said Kaitlyn Wagner, a PhD candidate in microbiology at Colorado State University.
Wagner and Zabel have a hypothesis. They think there isn't necessarily one chronic wasting disease, but instead a bunch of different strains of it. Those different strains, they say, could be emerging at different times across the globe.
On a February morning in the lab in Fort Collins, Colorado, Wagner and Zabel are comparing the prions from the brains of CWD-infected deer in Texas and elk in Colorado, as part of a project looking at samples from seven states. They want to know if they're different.
"If they are different, this would suggest that we have different strain properties which is evidence as we're building our case that we might have multiple strains of CWD circulating in the U.S.," said Wagner.
Step one is to see if they're just as easy to destroy using a chemical called guanidine. The shape of a prion dictates everything, including the way it interacts with an animal's cells and the ease with which chemicals can unfold it.
"Moment of truth," said Wagner, as she and Zabel huddled around a computer, waiting for results to come through. When they did, Zabel was surprised.
"Unlike anything we've seen before," he said. "Awesome."
The prions from the Texas deer are a lot harder to destroy than the ones from the Colorado elk. In fact, they're barely damaged at all.
"We've never seen that before in any prion strain, which means that it has a completely different structure than we've ever seen before," said Zabel.
And that suggests it might be a very different kind of chronic wasting disease. The researchers ran the same test on another Texas deer, with the same results.
Now, these are only the preliminary results from a few animals. Wagner and Zabel have a lot more experiments to do. But if future tests come to the same conclusion, it would support their hypothesis that there are multiple strains of chronic wasting disease with different origins. That, in turn, could mean that this disease will be an even trickier challenge to manage than it already is.
And, Zabel adds, there's something else.
"If it's still evolving, it may still evolve into a form that could potentially, eventually affect humans," he said.
It turns out, Zabel is not the only one worried about that possibility.
This story is part two "Bent Out Of Shape," a four-part special report about chronic wasting disease.
Part One: A Mysterious Animal Epidemic
Part Two: An Animal Epidemic Goes Global
This series was produced by the Mountain West News Bureau, a collaboration between Wyoming Public Media, Boise State Public Radio in Idaho, KUER in Salt Lake City and KRCC and KUNC in Colorado, and published in collaboration with High Country News.