Growing Plague Of "Mad Deer" Baffles Scientists

May 24, 2002 The Wall Street Journal by Antonio Regalado
FORT COLLINS, Colo. - There's trouble on the other side of the chain-link fences surrounding the state government's Foothills Wildlife Research Facility. The dusty pastures are ground zero for a deer-killing plague that is frighteningly similar to mad-cow disease.

It was here that the condition, known as chronic wasting disease, or CWD, was first identified decades ago, and where animal-management practices may have fueled an epidemic. Now, scientists are conducting research in the pens and laboratories here in their search for ways to stop it.

They are racing against a disease that has rapidly spread across eight states and parts of Canada. The U.S. Department of Agriculture has called CWD an "emergency." In Colorado, sharpshooters, some working from helicopters, have slaughtered 10,000 deer in the past year trying to contain its spread. Identified first only in captive animals, it has leapt the fences, infecting a small but growing number of the nation's more than 20 million free-ranging deer. Fears that CWD could devastate regional hunting and tourist economies have sent states scurrying to Washington for financial aid. Last week, in congressional hearings on the outbreak, Wisconsin Gov. Scott McCallum pleaded for financial assistance and declared that CWD "is threatening our way of life."

Brain tests following last fall's hunting season in Wisconsin suggested that about 3 percent of white-tail deer are infected in a large region straddling two counties. Those findings have generated shock waves in a state where hunters killed 446,000 deer last year, generating more than $1 billion in economic activity and countless venison dinners.

Much about the illness remains a mystery. A little-understood protein known as a "prion," a form of which is behind mad-cow disease, causes chronic wasting disease. In ways scientists don't yet fully grasp, prions enter the brain and set off a chain reaction, causing some of the brain's own proteins to assume an aberrant form. In humans, such rogue prion proteins are blamed for a rare, naturally occurring human illness called Creutzfeldt-Jakob disease, and a related disease linked to eating contaminated beef from "mad cows."

There's no evidence that meat from deer or elk has infected humans. But alarms have been raised recently over five unusual cases of brain-wasting disease in young people living in the U.S., and researchers are probing the cases for possible links.

One involves Doug McEwen, a 30-year-old hunter from Kaysville, Utah, who died in 1999 of Creutzfeldt-Jakob disease. The condition is extremely rare, and, when it occurs naturally, almost always strikes late in life. An early onset has been one of the hallmarks of the disease linked to cattle. The McEwen case caught the attention of activist groups that were lobbying for stricter surveillance in the U.S. of mad-cow disease. The Center for Food Safety, a consumer watchdog group in Washington, called Mr. McEwen's case the first possible case of "mad deer" disease.

Researchers haven't been able to document a link. The Centers for Disease Control and Prevention in Atlanta studied Mr. McEwen's case and those of two other people 30 years old or younger who died of Creutzfeldt-Jakob disease between 1997 and 2000. An analysis of their brain tissue ruled out mad-cow disease as the cause. But two were hunters and one was the daughter of a hunter, and all had regularly consumed elk or deer meat. Intrigued by the possibility that wild game caused their disease, epidemiologists quizzed family members about the victims' lifestyles and eating habits. But researchers said they found "no strong evidence for a causal link" to CWD.

Meanwhile, scientists in Fort Collins and elsewhere are conducting federally funded tests to figure out how the animals are becoming infected. In mad-cow, the disease source was traced to cattle feed containing bone meal from contaminated livestock. But no one knows how CWD moves from animal to animal. One thing is clear: The infectious agents are hard to kill off. The grounds at the 35-acre Foothills facility have been dug up, disinfected and even temporarily closed. Still, when the animals return, they invariably lose weight, salivate copiously, behave oddly, and die.

"We know very, very little. We don't understand the transmission, we don't understand the origin, we don't understand any of this," says Stanley Prusiner, the University of California, San Francisco neurologist who won a Nobel Prize for developing the prion hypothesis.

Chronic wasting disease has been around for at least 35 years, but until the mad-cow outbreak, it was of interest to only a handful of wildlife biologists. Elizabeth Williams was one of them. Just out of veterinary school in 1977, she learned about the trouble researchers had been having since the mid-60s at the animal research pens on the edge of Fort Collins. The deer there were doing poorly in captivity, mysteriously losing weight and dying. Biologists suspected a nutritional problem, or perhaps poisoning, and termed the syndrome "chronic wasting."

Dr. Williams soon found the problem. Peering at thin slices of the animals' brains through a microscope, she recalls seeing "a lot of lesions." The sponge-like patterns of decay she found reminded her of a video she'd seen as a student about the human cannibals of Papua New Guinea. An adventurous scientist named D. Carleton Gajdusek had won a Nobel Prize for showing that the ritual acts of eating human brains were causing a rare condition, called spongiform encephalopathy, that was killing the islanders.

The deer were dying of something similar. Dr. William's classification of CWD as a spongiform disease in 1977 was a career-making finding, although CWD remained an obscure wildlife problem.

An early sign that CWD was infectious came two years later, when veterinarians detected a case at another research facility in Sybille Canyon, Wyo., about 120 miles northwest of Fort Collins. That site, a jumble of open paddocks on a steep hillside, sometimes exchanged animals with the Fort Collins pens.

Two years after the Sybille case turned up, biologists diagnosed the first case in a wild animal - a sick elk found in Rocky Mountain National Park. It may never be known for sure if the disease actually started in the Fort Collins pens, or was simply first identified there. "The pens are like microscopes for mule deer," says N.T. Hobbs, an ecologist at the Colorado State University, who now leads a major study of CWD funded by the federal government. "Just because you see something, that doesn't mean you created it."

The Foothills Wildlife Research Facility, Colorado's main center for studying diseases of wild animals, is surrounded by a double ring of eight-foot-high fencing, and none of the animals now being studied there is ever allowed to leave alive. But security wasn't always so tight. For years after Dr. Williams' findings about CWD, deer were often brought into the pens to breed, then released back into the wild. The pens only had a single fence line then, and especially during rutting season wild bucks would come to the perimeter to nose with the females inside.

By 1985, however, it became clear that the Fort Collins pens and Sybille Canyon had become deadly reservoirs of sickness. Whatever was causing CWD was somehow loose in the dirt enclosures. That led to what Dr. Hobbs calls a "grisly" clean-up effort at the Foothills facility. The deer, big horn sheep and other animals being studied on site were all destroyed, and six inches of topsoil hauled away. The out buildings were washed with bleach, then left vacant for over a year. But when new deer were brought to the Foothills pens, the disease came back too.

Today, both Fort Collins and Sybille Canyon are considered hopelessly contaminated. Terry Kreeger, the Wyoming state veterinarian who lives at Sybille with his family, says when an elk or deer dies of CWD, he hauls the carcass in his pick-up truck to Dr. Williams' laboratory near Laramie. The corpse is dissected and incinerated, but few other precautions are taken. Dr. Kreeger, for instance, says he washes his truck out with a hose without worrying about putting more prions into the environment. "This horse is long out of the barn," he shrugs.

Initially, CWD had been spreading slowly, since wildlife in the main infection area of about 20,000 square miles between Fort Collins and Laramie were contained by natural barriers, such as the slopes of the Rocky Mountains. But CWD's jump from deer into local elk gave the disease an unpredictable new way to spread: via man-made transport as part of the trade in elk. In 1996, CWD turned up on a commercial elk farm on Saskatchewan, Canada. Three years later, elk-breeding operations in four U.S. states had found sick animals as well.

At the time, commercial elk farming was booming among small ranchers looking for new income. Elk require little food or space to thrive, and ranchers can make money from their meat and antlers, which are sawed off in the spring, then ground and sold as nutritional supplements. So-called velvet antler is exported to Asia where it is considered an aphrodisiac, and is also sold in U.S. chains such as General Nutrition Centers, where it retails for about $17 an ounce.

Since 2000, only 259 farmed elk have died or been diagnosed with CWD, according to the North American Elk Breeders Association. This is just a small percentage of the 160,000 elk it estimates are in captivity on 2,300 U.S. and Canadian elk ranches. But the disease has an incubation period of two to three years. Since 1998, elk farmers have destroyed 4,432 elk known to be exposed to the sickness.

Some researchers speculate that the elk trade brought the disease to wild deer in Wisconsin. Discovery of those infected animals sharply escalated CWD concerns nationwide, because the new region of infection is so far from where the disease was first identified. But the truth is, nobody knows.

Scientists in Colorado and Wyoming are now urgently trying to determine just how CWD is spread, partly funded by a $2.2 million grant from the National Science Foundation. At Sybille Canyon, researchers have infected three young deer with CWD by feeding them the brains of deer that died of the disease. Blood, saliva, feces and urine collected from the animals every six months will be injected into the brains of laboratory mice to see if they cause infection.

A separate set of experiments will confirm whether prions can lurk in the environment, as the team suspects. At the Fort Collins pens, Michael Miller, a Colorado Division of Wildlife biologist, has overseen the construction of isolation rooms to test different theories. In one room, two fawns are living alongside the decomposed carcass of a CWD deer. Others are being reared in rooms that previously housed animals with CWD.

The unknowns worry some consumer advocates. "I think that we have to assume the worst of CWD - that it could be even more dangerous and costly than mad cow because of its unique ability to spread through the environment and animal to animal," says John Stauber, the author of "Mad Cow U.S.A.," a book arguing the U.S. hasn't done enough to keep bovine spongiform encephalopathy, as the disease is known formally, out of the country. "With BSE there was a feeding loop that could be shut down. Here, it seems to spread like a cold or the flu."

Some laboratory studies suggest CWD could theoretically infect people. Byron Caughey, a prion researcher at the National Institutes of Health's Rocky Mountain Laboratory in Hamilton, Mont., found that CWD prions could convert human prion proteins to their deadly form in a lab dish. However, the efficiency of such "conversion" was extremely low, evidence of a substantial species barrier.

So far, few steps have been taken to reduce people's exposure to CWD prions. In Colorado, where hunting and wildlife sightseeing generate nearly as much economic activity as skiing, there are no special regulations governing how deer carcasses are handled. Hunters in Fort Collins have been asked to sever the head of any deer they bag and deposit it in a steel drum outside the Division of Wildlife's offices across from the Holiday Inn. A couple of weeks later, a state lab reports whether the kill was infected.

Margy Constantino, a Brooklyn native who makes her own bullets in the basement of her ranch house near Fort Collins, says some hunters haven't waited for test results before eating their kills. Ms. Constantino, who lives in an area with rates of CWD as high as 15 percent, shot a buck through the heart last year and waited about three weeks for results.

Though the results came back negative, she'd already had the animal butchered in the meantime. Since the local butchers tend to give customers ground meat made from pooled scraps, often there's no guarantee a hunter's kill won't be mixed with that of an animal that turned up positive for CWD.

"The processor takes scraps and turns it into hamburgers," says Jim Widmier, the proprietor of Arrow Dynamics, a shop in Fort Collins that caters to bow hunters. "That is a scary situation. The hamburger and sausage you get is going to be ground up with other people's."

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