Nobody knows where the disease came from, or if it has existed forever, confined to the lodgepole forests, shortgrass prairies and alfalfa fields of north-central Colorado and southeast Wyoming. It is not known how it passes among its victims. What is certain is that the whitetails, mule deer and elk that contract it inevitably die after a prolonged period of suffering - staggering, listlessness, progressive emaciation. Researchers call it chronic wasting disease, or CWD (HCN, 3/16/98).
first appeared in captive mule deer at a Colorado Department of
Wildlife research lab near Fort Collins in 1967, it has been an
ugly regional phenomenon, killing a small percentage of the wild
elk and deer within its range. Only about 100 cases of chronic
wasting disease have been documented in wild mule deer since 1981.
The disease is still rare, but it is spreading
In the past two years, CWD has spread to
a new niche - the expanding game-farm industry, where elk and deer
are ranched for meat, velvet antlers and captive trophy shoots. The
brisk interstate commerce in elk breeding stock and bull elk sold
for the trophy shoots has brought the disease to game farms in
Nebraska, South Dakota, Oklahoma and Saskatchewan,
Chronic wasting disease is a
transmissible spongiform encephalopathy, or TSE, similar both to
scrapie, a disease that for centuries has periodically devastated
domestic sheep herds, and to the "mad cow" disease that wreaked
havoc on the British beef industry in the early 1990s. It is also
linked to an extremely rare disease that affects humans, a variant
known as Creutzfeldt-Jacob disease. Under a microscope, brain
tissue from TSE-infected animals shows the sponge-like degeneration
that gives the disease its name, but the infection attacks no other
organs and triggers no response from the animal's immune system.
Scientists have no way to test living animals for the disease -
it's diagnosed by analyzing the brain tissue in dead
"Without a live test, we have no way of
knowing what our rate of infection is," says Tom Cline, a vet with
the South Dakota Animal Husbandry Board. "Could be zero, could be
100 percent. We're not even sure how long it takes to show up." In
South Dakota, 300 of the state's 2,000 captive elk are under
quarantine for chronic wasting disease.
chronic wasting disease more prevalent among confined animals than
in the wild? Cline explains, "Let's face it, captives stay around
longer, they have much more contact, and they have a much greater
chance to pass the disease around. If a mule deer is staggering
around in the wild, a predator will just take it down, probably
before it has a chance to pass the disease on."
In May of 1999, two elk that died on a
newly established Oklahoma game farm were diagnosed with chronic
wasting disease, and the farm was placed under a five-year
quarantine. The infected herd had been purchased almost two years
before from the Kesler Game Farm of Philipsburg, Mont. Neither
Oklahoma nor Montana will admit that the elk were exposed to the
disease in their state. Until this incident, both states were
considered free of the disease.
Gene Eskew, a vet
for the Oklahoma Department of Agriculture, says, "Based on the
known incubation periods for this disease, we believe those elk
were exposed before they got to our state. Exactly where is hard to
say. That Montana herd was from a wide, wide variety of sources."
The possibility that game farm animals could
pass chronic wasting disease on to wild animals outside the fences
has long worried researchers, game managers and wildlife advocates.
Mike Miller, veterinarian for the Colorado Division of Wildlife,
has researched the disease since its
"The area where CWD is found in the
wild has low numbers of elk and mule deer," he says, "and the
disease has been slow to spread for that reason. If infected
animals were brought into the western part of Colorado, where our
game herds are much larger, it would be a disaster."
Miller says that when it comes to trying to
manage CWD in wild herds, the alternatives are "hell if you do,
hell if you don't. This is not like the bison/brucellosis problem
in Montana, where you have vaccines and tests to help you. About
the only way we know to manage CWD is to do a density reduction on
the animals that may be carrying it, which basically means
clobbering the native wildlife."
Division of Wildlife asked for a moratorium on new game farms in
the part of the state where the disease is found in wild herds, but
its request has gone unheeded. The Department of Livestock
continues to license elk farms there.
veterinary pathologist Beth Williams, one of the pioneers in
chronic wasting disease research, says, "I have always been worried
that this disease would eventually get into the game farms and be
moved around that way."
Chris Marchion of the
Montana Wildlife Federation puts it more bluntly: "You can document
every single instance of CWD travel and trace it back to a game
farm," he says. "We need a legitimate moratorium on transporting
game-farm animals until we get a live test, or some kind of
effective monitoring. All we have done so far is provide this
disease with the best possible means of transportation."
"In one sense, we pose a bigger risk because we
move animals," says Paonia, Colo.-based Steve Wolcott of the Elk
Research Council, a game-farm trade group. "But wherever they go,
they're behind a fence."
He adds that
quarantines and close monitoring should control the spread of the
disease. In Colorado, for instance, state regulators record the
deaths and sales of all captive elk, and all deaths are examined
for chronic wasting disease. The Elk Research Council has
contributed more than $180,000 to researchers studying the disease,
"The critics of the elk industry
are not asking the state wildlife agencies to commit to eliminating
the disease in the wild herds," says Wolcott. "Yet, the game
farmers are being asked to bear responsibility for the spread of
"We will bear some cost and pain to
get rid of the disease," he says. "At the same time, we're not
going to put ourselves out of business."
fought a lengthy and costly court battle to outlaw the practice of
game farming altogether, as did California. Washington, Oregon,
Nevada, Arizona and Alaska have outlawed captive trophy shooting.
Colorado leads the West in the number of licensed game farms
operating, with 155 scattered throughout the
Wildlife concerns aside, the possibility
that chronic wasting disease can be transmitted to traditional
livestock, or even humans, worries many researchers. Experimental
attempts at infecting cattle with the disease at several research
facilities have so far failed or proved inconclusive, but it is
still too early to tell. Bruce Chesebro, of Rocky Mountain
Laboratories in Hamilton, Mont., is an expert on TSE diseases and
has followed chronic wasting disease with growing
"Somebody at the Montana Department of
Livestock needs to be very worried about the spread of this disease
to the cattle industry," Chesebro says. "Elk and deer are closely
related to cattle, and CWD has already made at least one shift,
from mule deer to elk. Scrapie moves from sheep to goats with no
problem. Who is to say that CWD cannot make the shift to cattle?"
Chesebro was in England during the mad cow
epidemic, and witnessed firsthand the collapse of the beef industry
there. "Because TSE did affect human beings there, the emotional
reaction was tremendous. If we get even one case of CWD in Montana
cattle, the industry will be in deep trouble."
Mike Miller points out that scrapie has never
passed to humans or cattle, despite a long history of close
contact. "All our data so far say CWD cannot pass to cattle. That
is not to say that it cannot happen. I just believe that this is a
serious enough problem with respect to our wildlife resources
without raising the issues of transmission to humans or cattle."
Hal Herring writes and
hunts from Corvallis,
You can contact
* Steve Wolcott, Elk Research Council,
* Mike Miller, c/o Colorado
Division of Wildlife, 317 W. Prospect, Fort Collins, CO 80526
* Chris Marchion, Montana
Wildlife Federation, 2105 Garfield, Anaconda, MT 59711