- A killer is on the loose.
-
- As "mad cow" disease, it has taken more than
120 lives and devastated cattle farmers in England, Europe and Japan.
-
- Now as chronic wasting disease in deer and elk, it threatens
to cripple Colorado's hunting economy -- and possibly much more.
-
- How concerned should we be?
-
- Recent research points to an unsettling possibility.
This family of diseases -- called transmissible spongiform encephalopathies
(TSEs) -- may be more sinister than even pessimistic scientists first envisioned.
-
- Once symptoms develop, each TSE is fatal, caused by a
mutant protein called a prion. Spongiform vividly describes the diseased
brain tissue: It is spongelike, filled with microscopic holes.
-
- In laboratory tests, the National Institutes of Health
found that a TSE can rest undetected in one animal before attacking another
in a more virulent form.
-
- There is no proof that chronic wasting disease can infect
humans, but there is some evidence that it might be possible.
-
- Test tube experiments show that human proteins are as
susceptible to chronic wasting disease as to mad cow disease. Three young
venison eaters have come down with a TSE, but federal investigators were
unable to prove any linkage.
-
- It is now clear that British authorities stumbled in
responding to the mad cow threat. Seeking to ease public fear and protect
economic interests, government officials said for 10 years that there was
no danger to humans from the disease that was attacking cattle.
-
- Then people started dying. And the world witnessed grim,
almost medieval scenes of pyres of burning cattle in the English countryside.
-
- During its decade of denial, Great Britain banned feeding
cattle a protein supplement called meat and bone meal (MBM), which was
determined to be at the root of mad cow disease.
-
- Yet, during the same period, Great Britain exported millions
of tons of the same protein meal throughout the world. The full impact
of that mistake is still not known, but it's feared that mad cow may break
out in 10 to 15 additional countries.
-
- How have we responded in America and Colorado?
-
- Without a sense of urgency.
-
- The United States stalled for 10 years before banning
the feeding of MBM to cattle in this country. Then, after Britain and the
European Union halted all exports of MBM for public health concerns, the
U.S. saw a trade opportunity, becoming the world's leading exporter.
-
- One result is that cattle in other countries that may
have eaten American meat and bone meal are being exported back to the United
States, as are meat products. Mexico, for example, only implemented a ban
on feeding MBM to cattle this year, and it exports one million cattle annually
to the U.S. Even though there are questions about Mexico's enforcement
of the ban, to date no case of mad cow disease has been reported in either
country.
-
- A study by a Harvard University-based group said that
the ban on feeding MBM to American cattle should insulate the U.S. from
a major mad cow outbreak. However, the General Accounting Office, the congressional
watchdog agency, has been sharply critical of the ban's enforcement in
the U.S.
-
- Scientists didn't know chronic wasting disease was a
TSE until Beth Williams, a young Fort Collins researcher, reached that
conclusion in 1977. The disease was first noticed almost 10 years earlier,
but was believed to be a digestive tract illness.
-
- But from the 1977 discovery on, it was apparent that
chronic wasting was highly infectious among penned animals. Unlike mad
cow, in which animals became sick after being fed infected meal, chronic
wasting spreads from animal to animal, perhaps through nose-to-nose contact,
feces or urine.
-
- For the better part of two-and-a-half decades, the state
mostly monitored CWD as a curiosity in its wildlife.
-
- CWD PIONEER
-
- As a graduate student at Colorado State University in
1977, Beth Williams peered into a microscope at a section of a deer's brain
and noticed the telltale holes of spongiform encephalopathy. Her discovery
showed that the wasting disease that had been killing deer in CSU's research
pens was related to scrapie in sheep. Williams, currently a professor of
veterinary science at the University of Wyoming, is considered one of the
leading authorities on CWD. All photography »
-
- During the decade between the onset of the disease and
its classification as a TSE -- and for at least a few years afterward --
some deer and elk were released from infected pens back into the wild and
were shipped between facilities.
-
- It is not known whether these practices led to CWD in
wild deer and elk.
-
- In a 1992 paper, Williams warned that the advent of elk
game ranching posed a significant threat for the spread of the disease.
Even so, during the decade of the '90s, the state permitted wholesale expansion
of elk ranches.
-
- The game ranch risk is threefold. Regardless of which
way the disease might pass through the fence, free-ranging elk and deer
have nose-to-nose contact with captive animals. Animals escape from, or
break into, the ranches. Captive animals are transported in commerce around
the state, across state lines and to other countries.
-
- The disease is now found in the wild in five states,
on the east side of the Mississippi and the Western Slope of the Rocky
Mountains. It's found in captive animals in six states and two provinces
of Canada.
-
- Colorado's response to the disease has been complicated
by the fact that two agencies, with sometimes conflicting agendas, share
responsibility. The Division of Wildlife manages the wild animals and the
Department of Agriculture oversees game ranches.
-
- The DOW walks a tightrope. Its very existence is based
on funding from hunting licenses, monies that would be threatened should
hunting become restricted by the disease.
-
- The Department of Agriculture has permitted the threefold
expansion of elk ranching and is now faced with destroying some of those
very herds.
-
- The agencies are incinerating herds of deer and elk where
infected animals have been found, a process carefully shielded from a sensitive
public. Images of burning Bambi are a public relations nightmare.
-
- In the past year and a half, the state has clearly stepped
up its response.
-
- "The danger of not being aggressive enough is far
greater than the danger of overreacting," said Gov. Bill Owens in
a recent interview with the News.
-
- Division of Wildlife chief Russell George, in a separate
discussion, asked, "Will we stop hunting altogether? I don't see that
in the cards right away. If our other efforts don't work and the disease
is still out there, we may have to do that. We don't want to infect anybody."
-
- Another critical question in this livestock-rich state
is whether CWD might cross the species barrier and infect cattle. The consequences
would be horrific. This has occurred under experimental conditions, but
there is no proof that it can happen outside a laboratory.
-
- "This is an extraordinarily contagious disease,"
Dr. Paul Brown, former head of the federal Food and Drug Administration's
TSE committee, said last year of CWD.
-
- "This is explosive."
-
- "The prime danger of CWD is a cross-contamination
of species -- jumping to an animal species, a livestock species, rather
than a human species," he said.
-
- Here, in Colorado, with our huge cattle operations and
feedlots, our bountiful deer and elk populations and the most intense concentration
of CWD in the United States, we are at the epicenter of an emerging epidemic.
-
- This is that story, as we know it today.
-
- http://cfapp.rockymountainnews.com/cwd/killer/
|
