SCOTT SIMON, HOST:

In at least 26 states across the country, deer, elk and moose are coming down with a harrowing fatal disease. It starts with weight loss and ends with stumbling and drooling as the animal's brain tissue deteriorates. It's bad for them. It's bad for hunting. It could even be bad for human beings. KUNC's Rae Ellen Bichell reports.

RAE ELLEN BICHELL, BYLINE: Crisis, state of emergency, zombie deer disease - chronic wasting disease is being called all of these things. It's an illness that's spreading in deer, elk and moose. And there are at least three bills being considered at the national level right now to provide funds to research and fight it. Wyoming Senator John Barrasso got in front of a congressional hearing to introduce one of them.

(SOUNDBITE OF ARCHIVED RECORDING)

JOHN BARRASSO: Today, I'm here to talk about a different kind of health crisis that's facing our nation.

BICHELL: He explained to lawmakers that the neurodegenerative disease is now spreading far beyond the Mountain West, where it was once believed to be based. It's very contagious.

(SOUNDBITE OF ARCHIVED RECORDING)

BARRASSO: And always fatal.

BICHELL: He worries there's still a lot we don't know about the disease, including exactly how it spreads and whether it's a danger to humans. But we do know this.

(SOUNDBITE OF ARCHIVED RECORDING)

BARRASSO: Unchecked, this disease could truly be catastrophic for wildlife and for local economies.

BICHELL: The disease has actually been around for a long time. Researchers first identified it way back in the 1960s. Soon after, Michael Miller got sucked into working on it.

MICHAEL MILLER: Well, yeah, sucked into it is really right.

BICHELL: Miller is a veterinarian with Colorado Parks and Wildlife. Back then, his colleagues were studying captive mule deer, but the animals kept getting sick and dying. Miller says it didn't make any sense. Finally, they looked at pieces of the animals' brains and saw something disturbing - they were full of holes, a pattern similar to mad cow disease. They soon discovered it was hard to kill, too.

MILLER: So in the mid-'80s, they gathered up and killed all the captive deer and elk that they had and did what at the time seemed like a very thorough job of cleaning up the facility grounds.

BICHELL: They turned over the soil where the deer had been kept, had a helicopter drop chlorine onto the site, left it alone for a full year, then brought in healthy wild elk.

MILLER: And (laughter) we failed, basically.

BICHELL: Within a couple of years, the disease was back. Miller and his colleagues worked hard to figure out how to contain it in northern Colorado. But over the next few decades, it just seemed to keep spreading, first in captive animals, then it turned up 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.

MILLER: 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.

BICHELL: Researchers used to think the disease started here in the Mountain West and then moved everywhere else, but it's becoming clear that's not the case. Just ask Mark Zabel, who studies this type of disease at Colorado State University.

MARK ZABEL: 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 and Canada, to the Midwest and Wisconsin. But then there are some that have no known connection.

BICHELL: Like Norway in 2016, followed by Finland and, just a few weeks ago, Sweden. Kaitlyn Wagner, a Ph.D. candidate in microbiology, works in Zabel's lab.

KAITLYN WAGNER: So I think this question of what's going on has kind of opened up again.

BICHELL: They think there isn't necessarily one chronic wasting disease. There could be a bunch of different strains. And those different strains could be emerging at different times across the globe, which brings us into the laboratory today. Wagner's running an experiment.

WAGNER: So today, we're going to look at the brains from Texas and a brain from an elk in Colorado. So we're going to look at those two and see how they're different.

BICHELL: Step one is to see if the pathogens in the brain are just as easy to chemically destroy. They're huddled around a computer waiting, and then the results come up.

ZABEL: Unlike anything we've seen before.

BICHELL: The image shows that the pathogens from the Texas deer are a lot harder to destroy using chemicals - like, a lot.

ZABEL: Which means that it has a completely different structure than we've ever seen before.

BICHELL: And that suggests it might be a different kind of chronic wasting disease. Now, these are only the preliminary results from a few animals, but it suggests their hypothesis about multiple strains of chronic wasting disease may be correct. Wagner and Zabel have a lot more work to do. But if more experiments come to the same conclusion, it could mean that this disease will be an even trickier challenge than it is already. And, Zabel adds, there's something else.

ZABEL: If it's still evolving, it may still evolve into a form that could potentially, eventually affect humans.

BICHELL: Mark Zabel is not the only one worried about that possibility. A number of studies have shown that chronic wasting disease shouldn't be a problem for people, but others leave that possibility open. In the meantime, there's one thing that researchers from across the continent can agree on. If you're eating deer from an area where the disease is prevalent, get it tested.

For NPR News, I'm Rae Ellen Bichell.

(SOUNDBITE OF TYCHO'S "SOURCE")

SIMON: And this story comes to us from the Mountain West News Bureau, a public radio collaboration.

Transcript provided by NPR, Copyright NPR.