Night of the hunter

What the government isn't telling you about mad deer disease.

By Fran Smith

Published October 21, 2002 7:02PM (EDT)

As British cattle began dying of a mysterious wasting disease in the late 80's, the agriculture minister tried to reassure a nervous public that eating beef was safe. John Gummer posed for cameras with his 4-year-old daughter, Cordelia, each clutching a burger. When the girl refused to eat, Gummer took a bite of hers. "Delicious!" he proclaimed. By the time the European Union banned exports of British beef six years later, the cattle industry was devastated and several people in England had already died from a deadly, brain-wasting disease.

Flash forward to Wisconsin.

Chronic wasting disease (CWD), an illness strikingly similar to mad cow, is spreading to deer in the state, its first appearance east of the Mississippi. Many frightened hunters are sitting out the season, and demand for hunting licenses is down 22 percent.

To kick-start the deer season, hunter and Republican Gov. Scott McCallum, up for reelection this year, boasts that he'll stalk his prey with bow and arrow. Not to be outdone, Ed Thompson, the Libertarian gubernatorial candidate (and brother of Tommy Thompson, secretary of the Department of Health and Human Services), stages a venison chow-down at a meat processing plant inside the disease hot zone. Thompson wolfs down two deer bratwursts with sauerkraut, smacks his lips, then commands: "Go ahead and hunt. Eat your venison."

It couldn't happen here -- could it? The British experience demonstrated how critical it is to move fast to contain a health threat. So-called "new variant" Cruetzfeldt-Jakob disease (vCJD), a particularly brutal illness linked to mad cow that erodes brains and quickly drives its victims mad, has already claimed 130 lives. The first U.S. victim, a 22-year-old Florida woman born and raised in Britain, was identified last week.

It could happen here. Though scientists once almost uniformly scoffed at the idea that CWD posed any threat to domestic animals or humans, many are worried now. CWD prions -- the family of mutant proteins that cause the disease -- may have already claimed human lives in this country. There's no physical evidence yet, but the rapid spread of the disease among elk and two different species of deer, its jump east across the Mississippi into dense populations of game and farm animals, and a rash of suspicious deaths among hunters are raising alarms.

Some health professionals and activists argue that not enough is being done to protect consumers, hunters, and the beef cattle and dairy cows that sometimes share pasture with infected game animals and were fed road-kill deer as recently as seven years ago.

The Wisconsin Department of Natural Resources, which relies on fees from hunting and fishing licenses, continues to reassure hunters there's no evidence that humans can catch CWD from consuming venison. It cautions hunters to avoid obviously ill animals (though deer may be infected without showing symptoms), and to wear rubber gloves when butchering deer and avoid cutting into or consuming neurological tissue. Some hunters too squeamish to eat their kill are donating the venison to pantries for the homeless.

"My son and I went bull hunting this weekend," boasted Tom Hauge, director of the Wisconsin DNR program on chronic wasting disease. "We had a perfectly grand time. We have always butchered our deer ourselves. I may very well be having venison for supper."

But Judd Aiken, a CWD expert at the University of Wisconsin in Madison, believes no deer anywhere in Wisconsin should be consumed until sample carcass test results are in, which could take months. "The safest approach is not to consume venison where we know there's CWD," he said.

The spread of the disease to Wisconsin is particularly worrisome. Scientists and wildlife managers have viewed the Mississippi River as an effective barrier limiting the disease to the deer populations spread out across the Western plains. Wisconsin, with its huge deer population -- nearly half a million were killed last year by hunters -- is a potent breeding ground for infection.

Prion diseases are so awful and the proteins so unpredictable that scientists take extraordinary precautions against infection when studying them in the lab. Patrick Bosque, a neurologist at the University of Colorado in Denver, studied prions in hamsters and mice, which do not appear to be transmissible to people. Yet he routinely wore disposable gloves, shoe covers and a gown, and avoided carrying his lab notebook or other potentially contaminated material out of the lab. Whenever he conducted a procedure that might spray or splash prions, he worked in a special hood to shield his face and upper arms. "Then you're going to tell me I'm going to eat deer?" Bosque asked. "I definitely would not eat deer I thought had been infected."

Bosque believes no one knows enough about CWD -- more commonly known as mad deer -- to say that eating venison is safe. "If it was very transmissible, we'd know it," he says. "But if it was somewhat transmissible, like BSE [bovine spongiform encephalopathy, or mad cow] in England, it would be hard to know."

Creutzfeldt-Jakob is a rare, fatal illness often described as "fast Alzheimer's" that occurs for no known reason in the population. It almost always occurs in the elderly.The first rash of cases in younger people was found in Britain and turned out to be a new variant of CJD, which was traced back to consumption of mad-cow beef. Variant CJD is similar to the "classic" illness, but often strikes younger people and tends to progress much more rapidly.

At least seven people age 66 or younger -- all hunters or venison eaters -- are known to have died of Creutzfeldt-Jakob in the U.S. in the last nine years. The total number will never be known because there's no federal requirement that all cases be reported. Preliminary studies suggest, and some neurologists suspect, that CJD is more common than generally believed -- it's simply misdiagnosed as Alzheimer's. That raises the obvious question: How many people would die of chronic wasting disease before a doctor called it?

In a highly publicized case, three Wisconsin hunters who attended wild-game feasts died of neurological diseases. Two had Creutzfeldt-Jakob, one turned out to have another rare neurological ailment, Pick's disease. Tests are ongoing.

Another victim from Oklahoma died with a freezer full of venison. A 50-year-old Montana elk hunter died last summer; his brain tissue is now being analyzed at one of the world's foremost prion labs, at the University of California in San Francisco. Test results are pending.

The Centers for Disease Control and Prevention did autopsies on three other deaths of people under the age of 31 -- from Utah, Oklahoma and Maine -- who died of CJD between 1997 and 2000. Two were hunters; a third was the daughter of a hunter. The agency concluded that there was "no strong evidence of a causal link" to mad deer because their brain tissue did not differ notably from carriers of standard CJD. Two did eat meat from animals killed in Wyoming and a third ate game processed at a plant that also butchered Colorado elk. Both states have infected deer, but the CDC could not find evidence of CWD infection in the specific areas linked to the victims. "According to our best evidence, their deaths were not linked to CWD," says Dr. Ermias Belay, a CDC epidemiologist who tracks Creutzfeldt-Jakob cases. "But our findings were limited to those three cases. We must continue to investigate."

The Medical Society of Milwaukee County, which is demanding strict new laws governing how deer are butchered in Wisconsin, did not find the CDC's conclusion reassuring. The CDC's determination was based, in part, "on the hypothesis that human CWD" here would look like the human cases linked to mad cow in Britain, said a statement by the medical society. Because a human version of CWD has not yet been identified, scientists don't know exactly what to look for should they find a case. "In England, it took over 20 cases for scientists to definitively determine that transmission had occurred," according to the society.

Given all that's known -- and still mysterious -- about the disease, the organization earlier this month called on Wisconsin officials to "consider taking the same public-health precautions that the English imposed on the British beef industry," on butchering and processing all deer carcasses. The organization called for a ban on any neurological deer tissue in sausage, and expressed concern about possible contamination of other meats by butchers carving deer. "Deer prions could survive standard cleaning procedures, imposing a potential risk to the beef, pork and chicken subsequently processed."

"It would seem reasonable to take some steps now to decrease the potential risk of transmitting this disease," said G. Richard Olds, chairman of medicine at the Medical College of Wisconsin and a member of the medical society's public-health committee. "We're only asking that instead of depending on the goodwill of people in a garage-and-basement industry, we have some assurances that they're following these guidelines."

Despite concerns, the CDC has not issued any warnings about consuming Wisconsin venison. "Why, and cause a panic?" Belay asked. "People have to make informed decisions for themselves," he said. "No one is forcing those people to go into those areas to hunt."

Chronic wasting disease was first identified in the 1960s in a mule deer at a wildlife research center in Ft. Collins, Colo. The illness was not recognized as a transmissible spongiform encephalopathy until the 1970s. For years, the disease remained confined to Colorado and Wyoming, first in research pens and zoological collections, then on the range.

Since 1996, the disease has moved relentlessly eastward: Montana, New Mexico, Nebraska, Kansas, Oklahoma, South Dakota, Saskatchewan, Alberta. In February, Wisconsin officials confirmed the first cases in that state, in three bucks shot near Mount Horeb, 25 miles west of Madison. Chronic wasting disease appears to be highly contagious among animals, much more than mad cow. A Nebraska ranch tested its herd after a deer fell ill and found half the animals had already been infected.

Besides mule deer, Rocky Mountain elk and white-tailed deer are susceptible. Sick animals typically waste away, stagger, behave erratically and drool excessively until they die. It's not known how long animals are infected before they become symptomatic. The epidemic is already an environmental disaster, threatening not only wildlife but also tourism.

Many observers believe game farms played a key role in spreading the illness quickly over vast areas of the U.S. There is almost no government oversight of the thousands of deer and elk raised in game farms across the country. Wisconsin alone has more than 900 farms where deer and elk are raised and hunted, up from a handful 15 years ago. Farmers and ranchers trade deer and elk aggressively across state lines, raising the odds that an infectious outbreak will become an epidemic. One Colorado game farm shipped 400 exposed elk to more than a dozen states, including Wisconsin. Many states with no mad deer have recently banned the importation of live deer and elk. In August, California went a step further, restricting the importation of deer and elk killed by hunters. The measures are intended to protect herds, not public health. Consumer safeguards have been slower to come.

"We're watching the total failure of any adequate preventive policy at the state or federal level," says John Stauber, executive director of the Madison-based Center for Media and Democracy and coauthor of the book "Mad Cow U.S.A." Stauber believes the government's response to CWD is disturbingly similar to Britain's failure to take quick action to stem mad cow. He believes officials' reluctance to sound the alarm is influenced in part by economic considerations, like the $1 billion hunters pump annually into the Wisconsin economy.

The Department of Agriculture does not extensively test deer to determine the prevalence of CWD, nor require meat producers to test game to certify it's infection free. This lack of controls doesn't just affect hunters or those who eat venison. Millions of people who would never touch a venison steak consume deer in processed meat, such as sausage, or pop "glandulars," nutritional supplements made from the adrenal glands of cows, deer and elk that purportedly do wonders for back and neck pain. And the soft antlers of young elk are marketed heavily and profitably to Asian communities as "velvet Viagra."

Unlike animals in Britain, deer and elk in the wild aren't feasting on each other's brains, where the prions are known to thrive. The disease may be spread through casual contact. Prions are shed in feces, saliva and urine. The fact is, no one knows exactly how the disease is transmitted.

A growing group of activists -- including old-line consumer advocates such as Consumers Union, disenchanted hunters, and a community of people who have lost loved ones to Creutzfeldt-Jakob -- blame in part the growing use of supplemental feeding by deer farmers who want to induce the growth of big antlers to increase game animals' value as trophies. Food supplements often contain rendered byproduct, or animal waste, the stuff that proved disastrous in England, where sheep with scrapie -- another prion disease -- were ground up and fed to cows.

There is a popular notion in the U.S. that feed is strictly regulated to prevent a mad cow-type epidemic. The Food and Drug Administration implemented regulations in 1997 but the rules are not as strict as the public assumes they are. They ban the use of feed containing proteins derived from mammalian tissue, and require that such feed be labeled: "Do Not Feed to Ruminants -- cattle, deer, elk and other animals with multiple stomach chambers." Legally, cows and deer can be ground up and fed to non-ruminants, such as pigs, horses or pet poodles. "You can feed cattle to pigs, then grind up the pigs and feed them to cattle," said Michael Hansen, research associate at Consumers Union. The regulations exempt plate waste and bovine blood products; spray-dried cow plasma is used widely as a milk substitute for weaned young cattle. The FDA called the new regulation a "firewall" against mad cow. "We called it a white picket fence," said Hansen. "We are still feeding mammal protein to food animals. If any of that protein is contaminated, the disease will spread."

"We frankly are astounded that the FDA would permit TSE-positive material to be used for any purpose," said a statement from Consumer's Union issued at the time. "The decision flies in the face of recommendations from the World Health Organization ... that "no part or product of any animal which has shown signs of a TSE should enter any food chain (human or animal)."

Enforcement also has gaps. A September 2000 report (#RCED-00-255) by the General Accounting Office found that 10 percent of rendering facilities weren't properly labeling the feed, and claimed not to know they were supposed to. The GAO investigated 9,000 renderers. A closer examination of 2,000 renderers handling ruminant bone meal found that 28 percent did not include the FDA warning on labels. Last January, a follow-up report (#GAO-02-183) by the GAO found that the FDA's data on inspections was "severely flawed." The agency "has not acted promptly to force firms to keep prohibited proteins out of cattle feed and to label feed that cannot be fed to cattle." The GAO also pointed out that the U.S. feed ban is "more permissive" than other countries'.

Because nobody knows how long it takes for an infected deer to become sick, nobody can say when Wisconsin's herds were exposed to chronic wasting disease, so pre-1997 feeding practices are also worrisome. Stauber, who lives in Wisconsin and has followed chronic wasting developments closely, says that in the 1980s through the mid-'90s, cattle, sheep and deer were rendered and fed by the tons as meat and bone meal to cattle, sheep and deer. In 1995, for instance, 26,488 deer were scraped off roads and delivered to renderers, according to a state Department of Natural Resources report on road kill.

While the laws remain lax, disturbing scientific evidence continues to build. Bosque's prion research, conducted at UCSF, calls into question the idea that eating possibly infected meat is safe as long as the brain, nerves and tonsils are avoided. Bosque and his colleagues detected prions at fairly high levels in the muscle of mice. "We recommended that other animals be looked at," he said.

The study was published in March in the prestigious Proceedings of the National Academy of Sciences. So far, wildlife officials in many states have ignored it. Pam Swift, a veterinarian at the California Department of Fish and Game, recently said eating Wisconsin deer was perfectly safe if it was butchered properly and the brain, spinal column and tonsils were discarded. "Prions are not known to be present in the muscle," she said.

There are other open questions. Can an animal that appears healthy be a "silent carrier" of the illness? A study published last November in the Journal of Virology suggests yes. The researchers, at the federal government's Rocky Mountain Laboratories in Hamilton, Mont., reported that infected but apparently healthy mice transmitted prions not only to other mice but also to hamsters, which then fell ill.

Strong evidence suggests that prions do not readily spread from one species to another. But it can happen. Scrapie never jumped to humans. But mad cow did. Researchers at the Rocky Mountain Labs found evidence that human (and cattle) proteins are slightly susceptible to deer prions. The work involved technical molecular experiments: Essentially, infectious prions from deer and elk were mixed with proteins from deer, cow, humans. The study, published in the EMBO (European Molecular Biology Organization) Journal in 2000, found that the exposure changed the human and cattle proteins in ways that suggested they'd been infected.

Earlier this month the Senate passed legislation introduced by Sens. Russ Feingold and Herb Kohl to require the U.S. Department of Agriculture to develop an efficient program for the inspection and certification of federal, state and private labs to conduct deer and elk tests for CWD. "The U.S. Department of Agriculture has really dropped the ball in providing the necessary resources and assistance to assure that Wisconsin hunters have the information they deserve," the senators said in a statement.

Wisconsin officials are still scrambling to contain the damage to wildlife and the state's reputation as a hunter's paradise. Wildlife authorities have mapped an eradication zone of roughly 400 square miles where as many as 25,000 deer will be killed and incinerated. But last summer a ranch-raised deer outside that zone, in central Wisconsin, tested positive, diminishing the likelihood that the slaughter will end the problem, Judd Aiken said. Authorities now plan to test 500 deer in every county beyond the zone to determine the prevalence of infection. To ease fears among hunters and consumers, the state has also launched a system of color-coded metal tags -- red for deer killed in the eradication zone, blue for deer killed just beyond, and silver for the rest -- so meat processors know where the deer come from.

In some communities, local officials urge worried hunters to get the meat tested before consumption, and several entrepreneurs are trying to market test kits. But although the current testing technology is valuable for measuring the prevalence of infection in a herd, it is not sensitive enough to reliably determine the safety of a single carcass. "It's possible for CWD to be present in levels that aren't detectable," Hauge said.

Meanwhile, hunters continue to sort through the often contradictory signals from officials, and health activists worry about the potential time bomb ticking in the herds of infected game. Says Stauber: "We should learn from mad cow in Britain. That was absolutely botched in the early 1990s by the public-health community. I believe we have a really dangerous situation here. And it's been botched from the beginning."

Fran Smith

Fran Smith is a freelance writer and editor who frequently covers health issues.

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