Growing plague in deer baffles, worries scientists

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Posted May 25, 2002

Growing plague in deer baffles, worries scientists

By Regalado

The Wall Street Journal

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 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, including Wisconsin, and parts of Canada. The U.S. Department of

Agriculture has called the disease 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.

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.

Fears that chronic wasting disease 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.

McCallum pleaded for financial assistance and declared that the

disease " 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.

One western case being investigated 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 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 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

chronic wasting disease.

Meanwhile, scientists in Fort 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 chronic wasting disease

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.

In 1981, 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 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 chronic wasting disease 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

8-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

' findings about chronic wasting disease, 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 pens and Sybille

Canyon had become deadly reservoirs of sickness. Whatever was causing

chronic wasting disease was somehow loose in the dirt enclosures. That led

to what Hobbs calls a " grisly " cleanup effort at the Foothills facility. The

deer, big horn sheep and other animals being studied on site were all

destroyed, and 6 inches of topsoil hauled away. The out buildings were

washed with bleach, then left vacant for more than a year. But when new deer

were brought to the Foothills pens, the disease came back too.

Today, both Fort 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 chronic wasting

disease, he hauls the carcass in his pickup truck to ' laboratory

near Laramie. The corpse is dissected and incinerated, but few other

precautions are taken. 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, chronic wasting disease had been spreading slowly, since wildlife

in the main infection area of about 20,000 square miles between Fort

and Laramie were contained by natural barriers, such as the slopes of the

Rocky Mountains. But the disease'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, chronic wasting disease 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 pens,

, 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 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 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 , says some hunters haven't waited for test

results before eating their kills. 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 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. "