Just stumbled upon a really interesting mad cow disease article.
(Bold print added by me, to aid "skimmers").
February 23, 1999
Weighing 'Mad Cow' Risks in American Deer and
Elk
By SANDRA BLAKESLEE
As a 30-year-old deer hunter lies dying at his home near Salt Lake City,
consumer advocates and Government regulators are squabbling over a
terrifying question that cannot be answered to anyone's satisfaction: Is
it possible to contract a version of mad cow disease from eating deer or elk?
Mad cow disease appeared in British cattle in the mid-1980's and caused an
epidemic that left the brains of infected animals spongy and riddled with
gum-like strings. Eventually, the British Government ordered the destruction
of more than four million animals.
At least 34 young people in Britain contracted a human form of the fatal
disease, possibly from eating infected beef or from coming into contact with
products made from sick cows.
Nothing similar has turned up in American beef, although experts believe one
in a million cows will develop the disease spontaneously.
Animal feeding practices have been revised to reduce chances of
transmission. But a similar disease has been seen in sheep and mink, and
people are now worried about a version of mad cow disease endemic in deer
and elk in parts of Colorado and Wyoming, raising the possibility that hunters
who eat infected animals may similarly develop a human form of the deer and
elk malady, called chronic wasting disease.
The cow, elk, deer and human diseases belong to a family of disorders called
transmissible spongiform encephalopathies, or T.S.E. The human form,
Creutzfeldt-Jakob disease or C.J.D., occurs in three varieties. Most cases are
spontaneous with no known cause. About 10 percent of cases run in families,
linked to inherited gene defects.
The British cases are called new variant C.J.D.
In all three varieties, the disease agent is believed to be not a virus or
bacterium but a mysterious particle called a prion -- a kind of renegade protein
that transforms normal proteins into abnormal, indestructible substances that
create spongy holes in the brain.
Prion diseases have been found in 85 species, passing easily between some
animals and not others.
When a prion "jumps" species, new T.S.E. diseases are created that can be
more or less virulent for reasons no one can explain.
This is the question raised by the deer hunter's case: Does he have a new
variant of Creutzfeldt-Jakob disease contracted from deer and elk, and if so,
what does it look like?
Health and wildlife officials point out there is no proof that mad deer or elk
disease has "jumped" to humans. At the same time, consumer advocates point
to the dying hunter, Doug McEwen, whose illness is uncannily similar to that
seen in the young victims of mad cow.
According to his wife, Tracie, Mr. McEwen hunted in season, and often ate
deer and elk that he bagged. But he never hunted in Colorado or Wyoming,
where chronic wasting disease is found. So no one knows if he contracted his
brain disease from animals or spontaneously developed the illness destroying
his brain.
Moreover, Mr. McEwen was a frequent donor of blood plasma and his
plasma was pooled with many blood products and shipped to 21 countries.
Blood safety officials here and abroad at first quarantined the blood products
but have since let some of them be used.
In part because of the mad cow outbreak in Britain, the United States Food
and Drug Administration barred blood banks from accepting donations from
people with family members with C.J.D. But given that it is not known if
blood or plasma can transmit the disease, and the fact that almost all
Americans with the disease have the sporadic form, which tends not to
involve the blood, the Public Health Service and food and drug agency
changed the nation's blood policy in August.
Now only those people with familial or genetic versions of C.J.D. are
prohibited from donating blood, said Dr. Jay Epstein of the Center for
Biologics Evaluation and Research at the drug agency.
American public health officials say that chronic wasting disease in deer and
elk and Mr. McEwen's plasma donations pose no threat to people. Careful
epidemiological surveys have not shown any increase in the type of brain
disease afflicting Mr. McEwen and no indication that frequent users of blood
products, like hemophiliacs, have a higher incidence of any kind of C.J.D.,
said Dr. Lawrence Schonberger, an epidemiologist who coordinates
surveillance activities for Creutzfeldt-Jakob disease at the Centers for Disease
Control and Prevention in Atlanta.
Many people are unconvinced. "The fact that we have a disease in elk and
deer at levels equivalent to mad cow disease at the height of the British
epidemic is truly alarming," said John Stauber, director of the Center for
Media and Democracy, a group that reports on government and industry
public relations, and the author of "Mad Cow U.S.A.," a book critical of
American health officials. In both cases, an estimated 6 percent of animals
carry the infection.
Mr. Stauber and others interested in the disease say they distrust Government
estimates, citing, among other things, published reports estimating that 6 to 8
percent of people who are told they have Alzheimer's disease may actually
have a form of C.J.D., said Dr. Thomas Pringle, a scientific consultant for the
Sperling Foundation, a charitable public health organization.
"Was nothing learned from the British experience?" asked Dr. Pringle, who
maintains an encyclopedic Web page on the subject (http://www.mad-cow.org).
"Why are we repeating the gamble they took?"
British officials for years adamantly denied the cow disease was any threat to
humans, he said.
Mr. McEwen, a territory manager of a groceries firm who lives in Kaysville,
Utah, first showed symptoms in June when he forgot how to spell his wife's
name and could no longer do simple arithmetic. His condition worsened
rapidly; by the end of the summer he was forced to quit his job.
Neurologists carried out scores of tests, including brain scans and spinal taps,
to no avail, until Nov. 24, when they finally took a brain biopsy. The next day,
Mr. McEwen was given a diagnosis of C.J.D.
Creutzfeldt-Jakob disease strikes one in a million people over age 50, said Dr.
Michael Hansen, a scientist who closely follows the issue for Consumer's
Union. The disease strikes fewer than one in a billion people worldwide at Mr.
McEwen's age, 30. Moreover, in Mr. McEwen's case, the disease has moved
with astounding rapidity, leaving him near death, unable to recognize his two
young daughters or his wife.
Alarmed by Mr. McEwen's age and the speed of his illness, state health
officials sent a brain tissue sample to Dr. Pierluigi Gambetti, an expert on
prion diseases at Case Western Reserve University in Cleveland. Dr. Gambetti
ruled out most known causes of C.J.D. Mr. McEwen never received
transplanted tissues that might have been infected with abnormal prions.
His disease was not inherited and it definitely did not come from cattle.
The diagnosis: sporadic C.J.D., meaning no known cause.
Cases like that are rare but not unknown, Dr. Gambetti said.
But Dr. Pringle and others do not accept this diagnosis as final.
They point out that no one knows what chronic wasting disease would look
like in a human, and tests to determine the nature of such a disease have not
been done.
All mammals have prion proteins whose structures vary by just a few building
blocks called amino acids, Dr. Pringle said.
The difference between a cow and a human prion might be eight of these
building blocks out of hundreds.
But when the abnormal cow prion co-opts the normal human prion, a new
abnormal human prion -- and a new disease -- is formed.
It looks exactly like a C.J.D.-related human prion but it can be more insidious.
If the new variety of human prion is injected into a cat, yet another disease
can be created. It may be more infectious or less infectious in the cat.
Such experiments in which the infectious prion of one species is "passaged"
into another species is a standard test for sorting out various T.S.E.'s.
"There are many imponderables in these experiments," said Dr. Byron
Caughey, a prion expert at the National Institute of Health Rocky Mountain
Laboratory in Hamilton, Mont.
"One prion is an infectious unit large enough to give you the disease. But it
can be terribly inefficient going across species.
A person could take in a billion infectious units from a deer or elk and never
get sick in his lifetime," he said.
Dr. Schonberger said that there were no plans to carry out interspecies tests
on Mr. McEwen's brain tissue because it is clear that he has a natural human
form of the disease and because there is no increase of C.J.D. where deer and
elk hunting occurs.
According to wildlife officials, chronic wasting disease affects about 5
percent of the deer and 1 percent of the elk found in a small area in
northeastern Colorado and southern Wyoming.
Sick animals drool excessively, stagger around and lose weight before dying.
Hunters in several states are required to turn in deer and elk heads so that the
brain tissue can be tested. So far, the disease in the wild has not spread
beyond Colorado and Wyoming.
Game farms are another story. The disease is found in captive deer and elk
herds in three states -- South Dakota, Nebraska and Oklahoma -- and in the
Canadian province of Saskatchewan, said Dr. Beth Williams, the nation's
leading expert on chronic wasting disease, at the University of Wyoming in
Laramie.
The disease was reported in the mid-1960's at the Wildlife Research Station in
Fort Collins, Colo., where it eventually wiped out 90 percent of the animals.
But before people knew what was happening, many infected animals were
sold to game farms or zoos elsewhere for breeding, thus spreading the
infection.
Ranchers made large profits selling antlers to Asia, where they are used in
making herbal remedies and aphrodisiacs.
The disease was first observed in the wild in 1981, Dr. Williams said. No one
knows how it spreads. The infectious prion may be shed in saliva, feces or
placenta and if wild animals come across downed fences, they might step on
contaminated ground. There is new evidence that the prion may be
concentrated in inflamed skin cells, suggesting that the disease could be
spread by scratching posts or trees in the wild.
But Dr. Mike Miller, a veterinarian with the Colorado Department of Wildlife
who is familiar with the problem, said thousands of people had consumed
deer and elk meat and field dressed hundreds of infected animals in the Fort
Collins area over the last 25 years. "We make no secret of where the disease
occurs," and leave it up to hunters to decide the risks for themselves, he said,
although hunters are advised to wear gloves when cutting up animals and to
avoid brain and spinal cord tissue.
But a deeper reason to worry is the diabolical nature of the infectious prion
particle. It seemingly cannot be destroyed.
When medical instruments contaminated with prions are boiled at high
temperatures for 30 minutes, the prions remain infectious -- and have passed
the infection from person to person.
When infected materials are incinerated, the ash contains prions, which
remain infectious.
This problem is highly relevant to Mrs. McEwen, who has learned that a local
funeral home will not embalm her husband if an autopsy, exposing brain
tissue, is performed. Several prion laboratories want her to donate her
husband's brain to them exclusively, said Mel Steiger, also from Salt Lake
City, whose wife died last spring from C.J.D. and who is now helping Mrs.
McEwen. "She has not decided what to do," he said.
Meanwhile, Federal officials are in a regulatory bind, weighing risks and
benefits.
The risks of spreading C.J.D. contracted from deer and elk seem minuscule
compared with threatening jobs (Colorado's Department of Wildlife gets half
its income from selling deer and elk tags), frightening hunters needlessly and
shaking confidence in the nation's blood supply.
Dr. Schonberger is confident that the best decisions have been made on the
available evidence.
"If something happens down the road people will come and chop our heads
off," he said. "But I don't think that's going to happen."
Copyright 1999 The New York Times Company |
