The question of where chronic wasting disease came from reopened in the spring of 2016.
Roy Andersen was monitoring reindeer in Norway. He’s a research technician with the Norwegian Institute for Nature Research. On a rare, sunny day, Andersen and his colleagues were doing what they often do in the spring: blasting across a snowy plateau, chasing a herd of about 500 wild reindeer.
Reindeer are big and fast and skittish, so the researchers don’t mess around. They dart them with tranquilizers from a helicopter.
"Everything is going really fast, of course. They're running quite fast," he said.
The group's veterinarian was hanging out the side of the helicopter, dart gun in hand. Andersen says he shot one dart and missed, then tried again.
"And he also missed on that dart, too, so that's when we had to stop," he said.
They landed the helicopter. Andersen and the others got out to track down the darts. The copilots were waiting by the helicopter when one of them spotted something.
"He mentioned that he saw something down the hill about 200 meters away," said Andersen, who decided to take a look.
It was a reindeer.
"It was lying on the side, flat out — not very common for reindeer. And it had all these bubbles and stuff coming out of his mouth,"” he said.
Three or four minutes later, it was dead. Andersen and his colleagues thought they had accidentally killed it — that maybe a dart had hit it in a weird way, or that it was just stressed out from the helicopter chase. So they zipped it up in a giant duffel bag.
"And we brought the animal with us down from the mountains to find out what had happened to it," said Andersen.
Samples from the sick reindeer eventually made their way over to the laboratory of Sylvie Benestad with the Norwegian Veterinary Institute.
"And it was really strongly positive," she said — positive for chronic wasting disease. "That started the problem."
Benestad says Norway has some of the only wild reindeer in Europe. If it spread to semi-domesticated reindeer, it could cause a cultural crisis.
"We are all aware of the threat if CWD spreads to semi-domesticated reindeers. It could easily wipe out the entire Sami reindeer husbandry culture," said Randi Skum with the Sami Reindeer Herders' Association of Norway.
Based on how it quickly and viciously it spread in the U.S., the Norwegians knew they had to do something.
"If we didn't do anything, it would be enormous consequences, so we felt that we had to react immediately," she said.
The Norwegians sent sharpshooters out in helicopters and snowmobiles to kill all the reindeer where the infection had been found — about 2,400 of them.
Among those euthanized animals, 19 tested positive for chronic wasting disease. Luckily, Benestad says, the area is fairly isolated, with roads on one side and mountains on another. They built a fence for good measure and started intensive surveillance of animals across the country. It's now forbidden for reindeer herders to gather lichen and plants from certain areas to feed their animals.
Did those control measures work? Call back in ten years, says Benestad, and maybe then she'll have an answer.
"We still don't know how it came to Norway," she said.
Norway has strict rules about importing live animals, so Benestad says CWD couldn't have arrived that way. One hypothesis was that it came from the U.S. way back in the 1930s and '40s when Finland imported white-tailed deer to populate its forests. (Fun fact: all white-tailed deer in Finland are descended from less than 10 American animals.) But that was long ago, and there didn't seem to be any problem with Finnish deer. Maybe, Benestad says, it came from lures made of deer pee, which hunters can buy online.
But then something else happened.
"About two months after the first case in reindeer, we discovered two moose," she said.
Again, Benestad analyzed the samples.
"And I noticed immediately that it was something different," she said. "The brain distribution of this abnormal prion protein was different."
She concluded this version of the disease was not the same as the one circulating in North America. And upon closer inspection, the disease in reindeer was different, too.
Then last year, a moose in neighboring Finland tested positive as well, way over by the Russian border, and in March 2019, the illness showed up in Sweden. A hunter came across a moose that was in bad shape. It was thin and confused, walking in circles.
"The hunter thought that perhaps it was blind," said Maria Noremark, a veterinarian and epidemiologist with the National Veterinary Institute in Sweden. "And that was the first case we have detected in Sweden."
It's worth mentioning something important, though. That moose was 16 years old. The other cases of chronic wasting disease in moose have also occurred in elderly animals. On top of that, the infection shows up in fewer places in the body than it does in deer and reindeer. It also seems to be a lot less contagious than the CWD circulating among deer.
Scientists are trying to figure out what all this means.
Maybe, Benestad and Noremark say, moose are like people in that a certain amount of prion disease will naturally (albeit very rarely) arise in older mammals, and because it’s contained in the brain and spinal cord, there’s very little concern for contagion.
But that doesn't explain the reindeer, which, like deer, seem to experience the disease much younger and in a much more contagious form. Could there be multiple kinds of chronic wasting disease? And where are they coming from, anyway?
"I mean, the first cases in North America also came from somewhere," said Noremark.
This story is part two "Bent Out Of Shape," a four-part special report about chronic wasting disease.
Part One: A Mysterious Animal Epidemic
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.