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#606 - Mad Cow Disease, Part 1, 08-Jul-1998

In 1985, cows in Britain began to die of a mysterious ailment that no
one had ever seen before. The symptoms were strange. At first the cows
staggered and drooled, their ears twitching. Then they began to show
signs of fear, grinding their teeth, acting aggressively toward other
animals. Soon they died. Farmers named the condition "mad cow disease"
and the name stuck.

The disease is now known formally as "bovine spongiform encephalopathy"
or BSE for short. BSE is one of a small family of diseases called
transmissible spongiform encephalopathies, or TSEs. TSEs destroy
neurons, the main nerve cells in the brain, creating holes that leave
the brain resembling a sponge (thus "spongiform"). BSE, like the other
TSEs, is an infectious disease, meaning that it can be transmitted from
one cow to another.

During the 13 years since it first appeared, mad cow disease has killed
more than 167,000 cows in Britain[1] and many more became infected but
were slaughtered for food before symptoms appeared. Symptoms take an
average of 5 years to show up after a cow is infected. Until the late
1990s, there was no test that could detect whether a cow was infected -
- only the appearance of symptoms and microscopic examination of the
brain could provide a definitive diagnosis. (Even today, tests require
brain tissue, so they cannot be conducted on live animals.) British-
type BSE has now been observed in cows in Switzerland, the Netherlands,
Ireland, Portugal, France, Oman and the Falkland Islands. To date, the
disease has not been observed in cows in the U.S.

When the disease first struck in Britain in 1985, health authorities
insisted that British beef was safe to eat. For 10 years they defended
that position aggressively, despite mounting evidence to the contrary.
Then in 1996, the official story changed suddenly and the public was
stunned. A panel of government scientists told Parliament in 1996 that
the "most likely explanation" for 10 cases of a new TSE disease in
humans was that BSE had moved from cows into people. That explanation
is now widely accepted by most scientists, though airtight evidence
remains elusive.

By the time of the stunning announcement in 1996, some British experts
calculated that more than a million infected cows had already been
consumed in Britain.[2]

In humans, the BSE-like disease is called "new variant Creutzfeld-Jacob
disease," or nvCJD for short. Creutzfeld-Jacob disease (CJD) is a
member of the TSE family, a brain-destroyer. CJD has been recognized
for a long time as a rare disease of the elderly -- very similar to
Alzheimer's disease -- but nvCJD is different. It has somewhat
different symptoms, a different pattern of disintegration in the brain,
and it strikes young people, even teenagers. Between 1995 and early
1998, at least 23 people died of nvCJD in Britain and at least one in
France,[3] the oldest of them age 42 and the youngest 15.

In January 1997, British epidemiologists tried to estimate how large
the outbreak of nvCJD might become. They concluded that the data were
not sufficient to allow a precise estimate: somewhere between 75 people
and 80,000 people would eventually die of the new disease, they
estimated.[4] Only time will tell. More precise estimates of the size
of the problem are not possible because no one knows for sure how long
nvCJD "incubates," how much time elapses between infection and the
appearance of symptoms.

An excellent recent book by Sheldon Rampton and John Stauber, MAD COW
U.S.A.--CAN THE NIGHTMARE HAPPEN HERE? tells the story of the emergence
of mad cow disease in Britain, and the scientific and political battles
that have ensued.[5] Despite the evocative title, the book is
thoroughly-documented and carefully-written. Without oversimplifying
the details, the book recounts a complicated story of medical
discoveries, strongarm tactics by the beef industry, and waffling and
coverup by governments on both sides of the Atlantic -- yet it reads as
easily as a detective story. As a piece of science writing -- a
description of science as it plays out in the real world -- the book is
an impressive accomplishment. By the end, the reader has absorbed
several important lessons about public health policies distorted by big
money, and about very serious threats to our first amendment right of
free speech. Rampton and Stauber show that the U.S. beef industry will
go to almost any lengths to try to prevent a public discussion of "mad
cow" and the steps that the U.S. government still needs to take to
prevent this disease from becoming an American problem.

In a nutshell: Mad cow disease developed because of a little-known but
very-widespread modern agricultural practice -- farmers feeding dead
cows to their cows, thus turning a vegetarian species into meat-eaters.

In Britain and the U.S., when a cow is slaughtered, about half of the
animal cannot be sold for human uses -- the hide, bones, entrails,
hooves, horns, fat, gristle and tough membranes are, by law, not
permitted to be used in food. Obviously something else has to be done
with these parts, to avoid creating a public health hazard.

Then there are "downer cows" that must be dealt with. Cows that cannot
stand up, cows that collapse, and cows that die mysteriously are called
"downers." Every year in the U.S. about 100,000 cows die of unknown
causes. One day they are alive and the next day they are dead, and no
one knows why. Something must be done with their carcasses.

In addition to downer cows there are thousands of pigs, horses,
chickens, and sheep that die of unknown causes each year. To prevent
public health problems, they must be disposed of. Then there is road
kill -- deer, elk and other large mammals killed by motor vehicles.

In the U.S. all of these animals and animal parts end up at 280
"rendering" plants where they are ground up and boiled down. (The
British call such plants "abbatoirs.") Up until the 1960s, the fat from
rendering plants was generally used to make soap. But the invention of
detergents, derived from petroleum, greatly reduced the demand for
soap. As a result, the rendering industry had to develop new markets
for its products. They hit on animal feed, and it became a great
commercial success.

From the 1960s through the mid-1990s, rendering plants dried their
rendered products, ground them into the consistency of brown sugar, and
sold them for animal feed. Feed mills then mixed these animal by-
products into various feed formulations -- about one-third for cattle,
one-third for pigs and chickens, and one-third for pets.

Unfortunately, some of the animals sent to rendering plants (or
abbatoirs) are sheep killed by a disease called "scrapie." Scrapie is
another TSE, a member of the same family as BSE, CJD, and nvCJD -- one
of those diseases that eats holes in the brain and invariably kills its
victims. Scrapie takes its name from the way sheep act once they get
the disease -- they rub up against a fence or a barn until they scrape
away their wool, leaving raw wounds. Then they die.

Scrapie has been a well-known, though mysterious, disease of sheep for
at least 200 years, but only recently have scrapie-infected sheep been
fed to cows. Scientists who study mad cow disease believe that the
illness crossed the species barrier from sheep to cows through
contaminated feed. Indeed, the British in 1988 banned the practice of
feeding animal carcasses to other animals and within seven years new
cases of mad cow disease diminished quite dramatically from 900 to 1000
per week to 280 to 300 per week.[6]

The U.S., however, has been slow to act. Scrapie is well-established
among sheep in this country. From October, 1988, to June, 1989, scrapie
was diagnosed in 52 flocks of sheep in 20 states.[5,pg.104] Clearly,
there was ample reason to ban the feeding of animal carcasses to
animals in this country when the British took that action in 1988.
However, the beef industry, and the rendering and feed industries, have
generally opposed such precautionary measures.

TSEs have a very long incubation period. In cows, BSE takes three to
eight years (average, five years) from the time of first infection to
the appearance of symptoms shortly before death. CJD in humans has an
incubation period of 10 to 40 years. Thus, by the time symptoms of BSE
appear, many cows are likely to be carrying the infection silently.
This was confirmed earlier this year in Switzerland when tests of brain
tissues from 1761 cows revealed 8 infected animals without any
symptoms, for a "silent" infection rate of 4.5 per 1000. This is 100
times as high as the rate of Swiss cows showing symptoms.[7] If this
rate holds for Britain, it means that today there are about 460,000
British cows infected -- but symptom-free -- in a total herd of roughly
11 million.

TSE diseases are characterized by a long incubation period, and they
are always fatal. Furthermore, the infectious agent is incredibly
resistant to deactivation. Cooking infected meat, or even rendering it
at high temperature, does not completely eliminate its infectivity.
Animals get TSEs by eating infected animals or parts of infected
animals, especially nerve tissues.

TSE diseases have now been identified in sheep, pigs, goats, cattle,
deer, elk, mink, mice, hamsters, guinea pigs, domestic cats, puma,
cheetah, eland, kudu, Arabian oryx, myland, marmosets, macaques,
chimpanzees and humans. In addition, a TSE has been reported in
ostriches in a German zoo.[8]

Thus one might think the U.S. Food and Drug Administration (FDA) would
prohibit the feeding of any animals to any other animals, as the
British did in 1988. But that is not what the FDA has done. Under
pressure from the beef, rendering, and feed industries, in 1997 FDA
only prohibited the feeding of ruminants and mink to ruminants.[1,8]
Ruminants are animals that chew their cuds, including cattle, sheep,
goats, deer and elk. Mink are included in the ban because they can get
a TSE similar to mad cow disease.

FDA is still allowing the feeding of pigs to other animals, and the
feeding of blood and gelatin from rendering plants to all animals. For
example, many calves in the U.S. are being raised on a diet of dried
blood taken straight from rendering plants. Pigs and chickens are still
being fed rendered animal products. There are sound scientific
arguments why this policy represents a form of Russian roulette being
played with the health of the American public. Given that we are
dealing with infectious diseases that invariably kill, the
precautionary principle (see REHW #586) seems the only appropriate

More next week.

--Peter Montague (National Writers Union, UAW Local 1981/AFL-CIO)


[1] Michael Hansen, "The Reasons Why FDA's Feed Rule Won't Protect Us
from BSE," GENETIC ENGINEERING NEWS (July, 1997), pgs. 4, 40. See also
Lawrence K. Altman, "F.D.A. Proposal Would Ban Using Animal Tissue in
Feed," NEW YORK TIMES January 3, 1997, pg. A14, which says BSE has
affected 165,000 British cows.

[2] John Darnton, "Britain Ties Deadly Brain Disease to Cow Ailment,"
NEW YORK TIMES March 21, 1996, pgs. A1, A7.

[3] Associated Press, "Clues Found in Brain-Killing Process," NEW YORK
TIMES February 10, 1998, pg. F7.

[4] S.N. Cousens and others, "Predicting the CJD Epidemic in Humans,"
NATURE Vol. 385 (January 16, 1997), pgs. 197-198. See also, David C.G.
Skegg, "Epidemic or false alarm?" NATURE Vol. 385 (January 16, 1997),
pg. 200.

[5] Sheldon Rampton and John Stauber, MAD COW U.S.A. COULD THE
NIGHTMARE HAPPEN HERE? (Monroe, Maine: Common Courage Press, 1997).
ISBN 1-56751-111-2. Available from Common Courage Press, Box 702
Monroe, Maine 04951. Telephone (207) 525-0900; fax: (207) 525-3068.

[6] John Darnton, "Fear of Mad-Cow Disease Spoils Britain's Appetite,"
NEW YORK TIMES January 12, 1996, pgs. A1, A8.

[7] Debora MacKenzie, "BSE's hidden horror," NEW SCIENTIST (June 13,
1998), pg. 4.

[8] [Michael Hansen], "Consumers Union's Comments on Docket No. 96N-
0135, Sustances Prohibited for Use in Animal Food or Feed; Animal
Proteins Prohibited from Ruminant Feed, Draft Rule," April 28, 1997.
Available from Michael Hansen, Consumer Policy Institute, Consumers
Union, 101 Truman Avenue, Yonkers, NY 10703-1057; telephone (914) 378-

Descriptor terms: mad cow disease; emerging diseases; creutzfeld-jacob
disease; new variant creutzfeld-jacob disease; nvcjd; cjd; great
britain; consumers union; bse; tse; transmissible spongiform
encephalopathies; sheldon rampton; john stauber; scrapie; britain;
michael hansen;