Bent Out Of Shape, Part 1: A Mysterious Animal Epidemic

Apr 22, 2019

Heather Swanson and Ryan Prioreschi monitor wildlife with the City of Boulder. They're standing in knee-high golden grass on a slope where the Rocky Mountains start slumping into the plains — the epicenter of a now-international animal epidemic. The ecologists have their binoculars out and they’re staring right at the problem.

A fawn is running circles around the rest of the herd, with the boing of a muscular slinky toy.

"He's wired," says Swanson, laughing. "He's doing laps."

A few others are rearing up on their hind legs and kicking each other. The rest of the herd of mule deer are just hanging out in the shade. It looks like a beautiful spring morning and the animals look sleek and healthy. But all is not what it seems.

"That is buck number 46," says Prioreschi, pointing to a deer. "He is positive."

Doe number 22, currently laying in the grass, is also positive for chronic wasting disease.

"Doesn't show any symptoms. She looks perfectly fine," says Prioreschi.

The mountain lions know that something is wrong. A number of years ago, Swanson and her colleagues studied which deer mountain lions prefer to attack.

Mule deer in Table Mesa, Colorado.
Credit Rae Ellen Bichell / KUNC

"The mountain lions were definitely preferentially selecting deer that had chronic wasting disease over those that were negative," she says. "And for most of the ones that they had killed, we had not detected any chronic wasting disease symptoms yet. So certainly the lions were able to key in on far more subtle cues than we were."

Unlike us, the lions know that while a deer might look sleek and alert, it's actually a ticking time bomb. That's one of the weird things about this disease. It isn't like the usual viral or bacterial illness. The infection can sit in a herd, crawling from animal to animal, for years before people notice anything is wrong.

"Through time (it) degrades, essentially, their brain tissue," says Swanson.

Then, things can go downhill fast. Swanson says it could be a matter of weeks before buck 46 or doe 22 starts to droop and drool, as an infection gnaws holes into its brain.

"That seems to happen pretty rapidly," she says. "To our eyes they look fairly healthy and within a number of weeks they reach that point and then they're gone."

Scientists have called chronic wasting disease a nightmare and a state of emergency. Lawmakers are calling it a crisis. Lately, the media’s been calling it "zombie deer disease." There are at least three bills being considered at the national level right now to combat the disease.

A few weeks ago, Wyoming Senator John Barrasso got in front of a congressional hearing to introduce one of them.

Unchecked, this disease could truly be catastrophic for wildlife and for local economies. -Wyoming Sen. John Barrasso

"Today I'm here to talk about a different kind of health crisis that's facing our nation," said Barrasso.

The neurodegenerative disease infects deer, elk and moose.

"It's highly contagious and always fatal," said Barrasso. "Unchecked, this disease could truly be catastrophic for wildlife and for local economies."

Barrasso's bipartisan bill is cosponsored by senators from across the country, including Idaho, Wyoming and Colorado. It would give federal dollars to the National Academies of Sciences to identify major gaps in scientific understanding of CWD and to better identify how to keep the disease from spreading further among animals, including from those in Canada to the U.S.

On the same day that Barrasso addressed his colleagues in Congress, epidemiologist Michael Osterholm spoke to state lawmakers in Minnesota.  

"This is kind of a worst-case nightmare," said Osterholm.

It's a nightmare that's hard to explain. Chronic wasting disease is not your garden variety infectious disease. It's not bacterial, viral or even fungal. It's caused by something we all have inside our bodies — something called prions.

As Osterholm put it to Minnesota lawmakers, "If Stephen King could write an infectious disease novel, he'd write it about prions."

Osterholm might not be far from the truth with his sci-fi reference. A book by Kurt Vonnegut, Cat's Cradle, comes up a lot in reference to prions. In it, there's a fictional substance called Ice Nine, a strange form of water that is solid at room temperature. When it touches liquid water, it turns the liquid to ice, too. That's very close to how prions cause disease.

"They're just very different from traditional pathogens," said Kaitlyn Wagner, who researches prions at Colorado State University. She says the prions that cause chronic wasting disease start out as normal proteins. All mammals have normal prions, sitting on the surfaces of our healthy cells. The difference between a good prion and a bad one is the shape.

Ryan Prioreschi uses a radio receiver to search for deer that have been previously tagged and sampled for the disease.
Credit Rae Ellen Bichell / KUNC

Mark Zabel, who is associate director of the Prion Research Center at Colorado State University, says one way to think about it is origami. Healthy proteins are shaped like origami cranes. If an abnormal origami crane comes along with a bent wing, the normal origami cranes will start to copy it. One by one, their wings will bend as well.

Eventually, when a badly folded prion has, as Zabel puts it, "coerced" enough healthy proteins to get bent out of shape, they can gather in clumps, killing off cells and leaving the brain full of holes like a sponge.

In the case of other prion diseases, including bovine spongiform encephalopathy — also known as mad cow disease — the badly folded proteins tend to stay contained in the brain and nervous system, but animals infected with chronic wasting disease leave behind infectious proteins all over the place. They've been found in urine, feces, blood and saliva. And those misshapen proteins can stick around.  

Zabel says a virus might be able to survive for a few hours outside its host. A bacterium might be able to make it for a week or two. A prion, on the other hand, would be capable of sticking around for years — decades, even.  

To complicate things, studies have shown that plants can suck them up through their roots and harbor them in their leaves, potentially infecting the next animal that comes around for a snack.

There's a lot that’s still unknown. What researchers do know is that it was first identified in Colorado way back in the 1960s and now chronic wasting disease has crawled its way across the country, infecting deer, elk and moose in at least 26 U.S. states and three Canadian provinces.  It's also turned up in South Korea, Finland, Sweden and Norway.

And it all started here, in the Mountain West. Or did it?

This story is part one of "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.