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Chronic Wasting Disease

Air Date: Week of

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An illness similar to mad cow disease is affecting deer and elk populations in the mid-west and western part of the U.S. There’s no proof yet that chronic wasting disease can affect people. But wildlife managers are worried that the disease could decimate deer and elk numbers, so they’ve taken some controversial measures to stop it. Eric Whitney reports.


CURWOOD: It’s Living on Earth. I’m Steve Curwood.

About 10 million Americans hunt deer each year. But these days, an epidemic among deer has hunters worried that their sport will never be the same.

Chronic wasting disease is a cousin to so-called mad cow disease. It’s spreading faster than biologists predicted and has the potential to devastate wild deer populations. There’s also a concern that it could infect humans, as well.

There’s no known treatment or cure for chronic wasting disease. And wildlife managers are being forced to take radical and controversial steps to control it. Eric Whitney reports from disease hot spots in the Rocky Mountains and Midwest.


WHITNEY: It takes a special kind of person to do work like Elizabeth Williams does, especially at 8:00 in the morning.

WILLIAMS: What I’m doing is cutting the ribs. That’s so I can get in to look at the thoracic cavity.

WHITNEY: Dr. Williams is a University of Wyoming pathobiologist, a scientist who studies the cause of animal deaths. Today, she opens up the body of a dead mule deer found by the side of the road.

WILLIAMS: Must’ve been hit with real tremendous force. You can see how the liver is just all fragmented. That’s part of, I presume, being hit by something pretty big.

WHITNEY: There’s no murder mystery here. It’s obvious that this deer was killed by a car. But tissue samples from this animal offer a glimpse into the overall health of the state’s entire deer heard, so Dr. Williams carefully collects small pieces of the animals organs for further analysis.

This type of routine surveillance work is how Dr. Williams discovered a new and enigmatic wildlife illness called chronic wasting disease, or CWD. She says at the time, 25 years ago, it didn’t seem like a big deal.

WILLIAMS: It wasn’t anything that special, believe me. We find new things all the time, and this just happens to be one that’s kind of gone forward, and in retrospect has turned out to be something maybe more important than we thought initially. But there wasn’t anything that special.

WHITNEY: That’s because CWD had only been observed in a handful of captive deer at a research facility in Colorado. Inexplicably, deer there began behaving erratically, drooling and losing interest in food until they wasted away and died. Since then, the disease has been found in 11 states and two Canadian provinces. And the more biologists have looked for CWD, the more they’ve found.

But, even so many years after its discovery, some very basic questions about the disease still remain unanswered. For instance, scientists have no idea where CWD came from, nor are they even sure exactly how the disease is transmitted.

WILLIAMS: Somehow, the agent gets out of the animal. It gets into the environment, and then, presumably, there’s enough of the agent present that a susceptible animal can pick it up. We don’t know very much about the dynamics of that. We don’t even know for sure if that happens, but we think it does.

WHITNEY: The agent that scientists believe causes CWD is called a prion. It’s not a living organism itself, like bacteria or a virus, but a malformed protein molecule. Prions are incredibly resilient. They’ve been shown to remain infectious in the outdoors for more than a decade. They’re resistant to chemical disinfectants and even the high-temperature autoclaves used to sterilize surgical instruments. And once they infect a deer, Dr. Williams says, they’re 100 percent lethal.

WILLIAMS: We’ve looked at lots of deer and we don’t recognize any genetic resistance. And animals don’t develop antibodies, so they don’t develop the kind of immunity to these diseases that you would like to a viral disease or a bacterial disease. It’s an entirely different kind of response and, unfortunately, none of the research shows that in deer there's any resistance to CWD.

WHITNEY: Exactly how prions work is poorly understood. Scientists most often find them in brain tissue, where they appear to cause adjacent healthy proteins to become twisted and misshapen, too. Slowly, the brains of victims become riddled with microscopic holes.

Last fall, in an effort to better understand the disease, wildlife managers in Colorado launched an unprecedented effort to examine tissue from the brains of thousands of deer across the state. That meant asking deer hunters to bring the severed heads of the animals they killed into collection stations. They were kept in walk-in refrigerators like this one in Denver.

MALE 1: This is actually where we keep the heads.

MALE 2: How many you think you got in there?

MALE 1: We had 50 turned in this morning and probably at least another 30 since then, so probably 70 or 80 heads today. While we didn’t get as many heads as we expected, I think we’re pleased with the kind of data that we are getting.

WHITNEY: State officials expect the data from this growing collection to tell them not only where the disease is most prevalent, but also how fast it is spreading. Because there’s no known treatment for, or vaccine against CWD, wildlife managers here are trying to control it by drastically reducing the size of deer herds in diseases hot spots. In the most extreme case, this means killing more than half the deer in a 2,000-animal herd.

MALMSBERRY: When people think about what Colorado represents, they think of the mountains, they think of skiing, but they also think of big game herds.

WHITNEY: Todd Malmsberry is a spokesman for the state’s Division of Wildlife. He says the culls are justified in order to stave off the devastation of those big game herds, and what they mean to Colorado culturally and economically.

MALMSBERRY: We can’t think of anything more irresponsible right now than to simply sit on our hands and do nothing, and watch this disease progress through the western United States and actually potentially through all of North America.

WHITNEY: Colorado’s culling strategy has drawn criticism from a broad spectrum of citizens, but it pales in comparison to what’s being done in Wisconsin.


WHITNEY: Tucked away in a ravine near the village of Black Earth is what’s officially known as a wildlife registration area. Most people, however, call it a head lopping station, because this is where Wisconsin, like Colorado, is collecting deer heads to test them for chronic wasting disease.

Lee Arjuket is known informally as a head lopper, for obvious reasons. The blood smeared on his blue plastic coveralls indicates that he’s been busy. Archugit says he’s lost count of the number of animals he’s decapitated.

ARJUKET: Dozens, easily. Sometimes they bring in four, five, seven at a time and we just work through them all. So, I don't know. I wouldn’t be able to tell you.

WHITNEY: This station is in the middle of Wisconsin’s CWD hot zone, a two-county area in the Southwest part of the state that so far is the only place the disease has been observed here. Because it appeared less than a year earlier, wildlife managers think they have a shot at eradicating the disease. Their strategy is to kill every potential carrier within 400 miles of where CWD was found. That’s 25,000 deer: bucks, does, fawns, everything.

Killing this many animals to control a disease is one of the most radical acts ever undertaken by wildlife managers in the U.S. They say the action is justified because Wisconsin’s deer population density is far greater than Colorado’s. That means CWD has the potential to spread much more rapidly in the Midwest. The massive herd reduction has been endorsed by leading wildlife biologists, like Dr. Thomas Yuill, Director of the Institute for Environmental Studies at the University of Wisconsin.

YUILL: In situations like this, it’s prudent to run the risk of reducing the population more than is necessary, than underestimating the relative transmissibility and not quite reducing the population enough to break that chain of transmission.

WHITNEY: Scientists also point out that killing 25,000 deer in Wisconsin will hardly make a dent in the state’s estimated population of a million and a half animals, a number some say is already too high. But Wisconsin’s disease-control strategy is not without its critics in the scientific community.

SOUTHWICK: It’s almost an archaic procedure to control a disease by killing the organisms that might contract the disease.

WHITNEY: Charles Southwick is Professor Emeritus of Environmental and Population Biology at the University of Colorado. Now retired, he has studied animal population dynamics for 50 years.

SOUTHWICK: I think Wisconsin’s program is unrealistic. And I would still say to them, go in and do selective culling of sick-looking animals. Get this population down to the point where it’s in reasonable balance with its habitat, but don’t try to kill every animal in a given area.

WHITNEY: Wisconsin officials say that just killing sick-looking animals won’t work. It takes years for deer to begin showing symptoms of CWD. They say targeting only deer that look sick virtually guarantees that a reservoir of disease will remain undetected within the herd, spreading to more animals. But because of the huge genetic diversity within the species, Southwick continues to believe that there may be some deer out there with genetic resistance to CWD. If that’s true, mass killings would eliminate the very animals that would be the basis of a new, healthy deer herd.

Southwick’s theories remain the minority opinion. Most wildlife biologists continue to support actions like those being taken here in Wisconsin. But killing every deer inside 400 rugged square miles of dense woods is no small task, even in a state where some schools still take a break for deer season and couples have been known to plan pregnancies around the annual fall ritual.

This hunter, who gave his name as Mike, says he doesn’t plan to take more deer than normally allowed.

MIKE: No, no. Take a couple of them, sure, I’ll help out. Sure. I won’t go crazy with it, though.

WHITNEY: For generations hunters have been taught that it’s wasteful and wrong to shoot more deer than your family can eat. But this year Mike says he won’t be bringing any venison home at all.

MIKE: No, I’m going to dump this out. It’s got the wife scared also. I don’t know.

WHITNEY: A lot of hunters say their wives don’t want them bringing deer home this year. That’s because CWD is similar to so-called mad cow disease, which has been proven to cause a lethal infection in people who eat contaminated beef. No studies have ever linked chronic wasting to human illness, but Wisconsin and Colorado are letting hunters and their disease hot zones know whether the animal they shot tested positive.

Many discount the health risk and eat the meat, but the Centers for Disease Control recommend against it. Worried that disease fears would keep hunters home this fall, Wisconsin took the unusual step of actually encouraging people to go hunting, with radio ads like this one.

RADIO AD: Freeze em, test em, fry em. I ain’t afraid of no twisty little prion here. Keep fighting CWD. And it won’t take long. There’ll be a flash of white, and there it was…gone. The Wisconsin D&R, CW-free in 2003.

WHITNEY: The campaign appears to have worked. Official say hunter numbers were only off by about 10 percent.


WHITNEY: Kevin Hayvey and his buddies are among those who came out. Tonight, they’re having steaks and beers after a day of hunting. Hayvey says they were disappointed when they learned that their favorite hunting spot fell within Wisconsin’s CWD hot zone. They’re hunting here again anyway, but Hayvey doesn’t like to think beyond this year.

HAYVEY: Because I was like, okay, if they’re going to kill every deer in a spot, like I say, I’ve been hunting for 26 years. I’m like, what am I gonna do? Where am I gonna go? I guess once you get locked into a spot, locked in with a group of guys you’ve been with and all of the sudden it could be all like sort of yanked out from your feet. I was really depressed.

WHITNEY: The goal of killing all the deer in Wisconsin’s hot zone has proven difficult to achieve, even with strong support from hunters. Only about a third of the 25,000 animals targeted were brought in. In response, the state is allowing two extra months of hunting in the hot zone. It’s also sending state and federal sharpshooters into the area who will work at night using bait, spotlights and guns equipped with silencers to kill the animals.

For Living on Earth, I’m Eric Whitney in Black Earth, Wisconsin.



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