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#607 - Mad Cow Disease, Part 2, 15-Jul-1998

Mad cow disease appeared for the first time in Britain in 1985. Since
that time it has killed roughly 170,000 cows in Britain, and it has
spread to humans.[1] In humans the disease is called "new variant
Creutzfeld-Jakob disease," or nvCJD for short. At this point nvCJD has
killed 24 people in Britain and one in France. More human deaths are
expected in Britain[2] because several million people ate diseased beef
before the British government (or the beef industry) acknowledged that
mad cow disease could infect people.

From a U.S. perspective, the obvious question is, How can an outbreak
of mad cow disease be prevented here?

Mad cow disease is a member of a family of rare diseases called
transmissible spongiform encephalopathies, or TSEs. TSEs have different
names in different animals (for example, scrapie in sheep, chronic
wasting syndrome in deer and elk, and bovine spongiform encephalopathy
or BSE in cows). However all TSEs share a few common features: they
attack the central nervous system, causing disintegration of the brain;
they have a long incubation period between the time when infection
first occurs and the appearance of symptoms; TSEs are always fatal; and
they are transmitted by the eating of animals or animal parts,
especially brains and spinal cords.

TSEs are now thought to be caused by a unique disease agent, called a
prion (pronounced PREE-on). A prion is simply a particular kind of
protein. All mammals have prions, and some non-mammalian species have
them as well. Prions are normal.

According to modern biology, a prion should not be able to reproduce
itself, and therefore should not be able to cause disease, because
prions contain no DNA. Without DNA, reproduction should not be
possible. However, it is now becoming widely accepted that prions do
reproduce themselves and do cause disease. Somehow a normal prion goes
bad --it gets folded into an abnormal shape and in its abnormal shape
it can destroy nerve cells in the central nervous system. The abnormal
prions also cause other nearby prions to become folded into the same
shape, thus creating more abnormal prions by a domino effect. After a
long period of time (months or years, or even decades) the symptoms of
disease appear, followed a few weeks or months later by death. Thus
animals and humans can be carrying an infectious prion disease for
months or years without showing any symptoms.

The prion theory of disease is still not accepted by 100% of the
scientific community, but the inventor of the theory, Stanley B.
Prusiner of the University of California at San Francisco, received the
Nobel Prize for his work in 1997.[3]

In this country, the government agency with primary responsibility for
preventing an outbreak of mad cow disease or its human variant, nvCJD,
is the U.S. Food and Drug Administration (FDA).

The FDA in 1997 issued a rule declaring it illegal for farmers to feed
animal protein from ruminants or mink to other ruminants --a preventive
step that had been taken by the British government in 1988. Ruminants
are animals that chew their cuds, including cattle, sheep, goats, deer
and elk. Mink are included in the FDA's ban because they can get a TSE
similar to mad cow disease.

When cows, pigs, and chickens are slaughtered, much of the animal
cannot be used for food and is sent to a rendering plant to be ground
up, boiled down, dried to the consistency of brown sugar and sold as
feed for cows, pigs, chickens, and pets. It is this rendered "animal
protein" derived from ruminants (and mink) that FDA has banned from
feeding to ruminants.

The FDA's ruminant-to-ruminant ban still allows animal protein of all
kinds to be fed to pigs and chickens, and it allows animal protein
derived from pigs and chickens to be fed to ruminants. The FDA ban also
allows blood and gelatin derived from ruminants to be fed to other
ruminants. In the U.S., many newborn calves are fed a high-protein diet
consisting mainly of dried blood. Blood cells carry prions just as
nerve cells do.[4]

A small group of scientists, led by Dr. Michael Hansen of Consumers
Union, has challenged the adequacy of FDA's ruminant-to-ruminant rule.
[5] They argue that the FDA ban does not go far enough, "does not
adequately protect human health, and is not scientifically
defensible."[6] Consumers Union is the publisher of CONSUMER REPORTS
magazine.

Scientists on both sides of the controversy agree that mad cow disease
probably developed in Britain in one of two ways. Possibly cows ate
parts of sheep that had been infected with the TSE called scrapie, and
the scrapie, once in cows, evolved into mad cow disease. Or,
alternatively, a prion spontaneously went bad (via genetic mutation of
the gene that produces normal prions) in a cow, and that cow was fed to
other cows, which were fed to other cows until the disease was
amplified into an epidemic. In either case, it was cows (which are
vegetarians by nature) being forced to eat animals that created the
problem.

FDA officials say they are confident that their ruminant-to-ruminant
ban has prevented, and will continue to prevent, an epidemic of mad cow
disease in this country because (a) mad cow has never been observed in
cows in the U.S., and (b) Creutzfeld-Jakob (CJD) disease is not
increasing in the U.S.[7] If mad cow were occurring in U.S. cows, some
form of CJD should be increasing, and it isn't, the FDA argues.

Michael Hansen of Consumers Union offers evidence that the government
may be wrong on both counts. Here are his arguments:

Mad cow may have already appeared in U.S. cows. Hansen offers evidence
from seven studies that some "downer" cows may have a form of mad cow
disease, though with symptoms somewhat different from those in British
cows. Downer cows are cows that cannot stand up, cows that collapse,
and cows that die mysteriously. About 100,000 cows die each year in the
U.S. with "downer" symptoms, and most of them end up in rendering
plants, turned into animal feed.

In 1961, an outbreak of transmissible mink encephalopathy (TME) --a
brain-destroying TSE of mink --occurred on six mink farms in Wisconsin.
Because all the farms used the same ready-mix feed which came from the
same feed plant, investigators assumed that the feed was the source of
the infectious agent.[8] Two years later, in 1963, an outbreak of TME
occurred on two more Wisconsin mink farms. Based on the 1961 outbreak,
scientists suspected feed and they examined the two farms' feed records
carefully. They learned that "downer" cows from farm A had been fed to
mink on Farm A and Farm B. The researchers wrote, "Since mink on both
farms developed the disease almost simultaneously, we believe this feed
component has to be incriminated."[9]

In 1985 an outbreak of TME occurred on a mink ranch in Stetsonville,
Wisconsin. Dr. Richard Marsh of the University of Wisconsin
investigated and found that the mink had been fed 95% downer cows and
5% horse meat.[10] When brains from infected mink were injected into
two calves, within 19 months both calves had a bovine TSE but they did
NOT exhibit the symptoms of Britain's mad cows. The Stetsonville cows
simply became lethargic and then fell over. In other words, they
exhibited typical "downer cow" symptoms. When brains from these cows
were injected into mink, the mink got TME, confirming the kind of
disease that had killed the cows. Marsh and his colleagues concluded,
"These results suggest the presence of a previously unrecognized
scrapie-like infection in cattle in the United States."[10]

Marsh's cattle inoculation experiments have been repeated and, again,
mink TME was transmitted to cows and back to mink and the cows
exhibited "downer" symptoms, nothing like British mad cow disease.[8]
Furthermore, in 1979 U.S. Department of Agriculture researchers in
Mission, Texas, inoculated 10 cows with sheep scrapie. Three of the 10
cows developed neurological symptoms, but they were more like "downer
cow" syndrome than British mad cow disease: "progressive difficulty in
rising, a stiff-legged gait, incoordination, abnormal tail position,
disorientation, and terminal recumbency [lying down]," according to Dr.
Clarence Gibbs, Acting Chief of the Laboratory of Central Nervous
System Studies at the National Institutes of Health.[11] Ten years
later, when a test for mad cow disease became available, Dr. Gibbs
confirmed a bovine TSE disease in the three cows, whose brains had been
preserved.[11] Dr. Gibbs concluded, "Susceptibility of cattle to
scrapie further suggests the possibility that sporadic cases of BSE
[mad cow disease] may have occurred in the United States under the
clinical picture of the downer cow syndrome...."[11]

After Gibbs confirmed that the Mission, Texas cows had indeed died of a
TSE, the U.S. Department of Agriculture repeated the experiments at
Ames, Iowa under the direction of Randall Cutlip.[12] Dr. Cutlip
described the results: "All calves kept longer than one year became
severely lethargic and demonstrated clinical signs of motor neuron
dysfunction that were manifest as progressive stiffness, posterior
paresis [partial paralysis], general weakness, and permanent recumbency
[lying down]." In other words, cows infected with a sheep TSE had all
the signs and symptoms of downer cows.

Thus Hansen argues, there is considerable evidence that a TSE has been
present in some U.S. cattle for several decades.

But if mad cow disease is already present in some number of cows in the
U.S., where are the human victims? People should be getting some form
of CJD [Creutzfeld-Jakob disease], and this disease is thought to be
vary rare and not increasing in the U.S. population. So where are the
victims?

Hansen argues that CJD may be more prevalent in the U.S. population
than is presently thought. The official figures say that CJD is
exceptionally rare --one case in every million people. In the U.S. this
would mean there are 250 CJD cases at any given time. Hansen points to
two studies in which people diagnosed with Alzheimer's were examined
after death. In one study, among 54 presumed Alzheimer's victims, 3 (or
5.5%) were found to actually have CJD.[13] A Yale University study of
46 victims of Alzheimer's found that 6 (or 13%) actually died of CJD,
not Alzheimer's.[14] There are 2 million people with Alzheimer's in the
U.S.[8] If 5.5% of them actually have CJD, there are 110,000 cases of
CJD in the U.S., not 250 cases. If 13% of the 2 million have CJD, then
there are 260,000 cases of CJD in the U.S., not 250. If even 1% of the
2 million had CJD, it would mean there was an epidemic of 20,000 cases
of CJD masquerading as Alzheimer's. Thus the FDA's argument that CJD is
very rare, and not increasing, needs to be re-examined. [To be
continued.]

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

=====

[1] John Collinge and others, "Molecular analysis of prion strain
variation and the aetiology of 'new variant' CJD," NATURE Vol. 383
(October 24, 1996), pgs. 685-690. See also Adriano Aguzzi and Charles
Weissmann, "A suspicious signature," NATURE Vol. 383 (October 24,
1996), pgs. 666-667.

[2] 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.

[3] Lawrence K. Altman, "U.S. Scientist Wins Nobel for Controversial
Work," NEW YORK TIMES October 7, 1998, pg. A1.

[4] Elias E. Manuelidis and others, "Transmission to Animals of
Creutzfeld-Jakob Disease from Human Blood," LANCET (October 19, 1985),
pgs. 896-897.

[5] Marian Burros, "U.S. Is Asked to Take New Steps to Prevent Mad Cow
Disease," NEW YORK TIMES March 28, 1997, pg. A17.

[6] [Michael K. Hansen], "Consumers Union's Comments on Docket No. 96N-
0135, Proposed Rule: Substances Prohibited for Use in Animal Food or
Feed; Animal Proteins Prohibited in Ruminant Feed," February 14, 1997.
Available from Michael Hansen, Consumer Policy Institute, Consumers
Union, 101 Truman Avenue, Yonkers, NY 10703-1057; telephone (914) 378-
2000.

[7] Lawrence K. Altman, "U.S. Officials Confident That Mad Cow Disease
of Britain Has Not Occurred Here," NEW YORK TIMES March 27, 1996, pg.
A12.

[8] Letter from Michael K. Hansen, Consumer Policy Institute, to Thomas
Billy, Food Safety Inspection Service, U.S. Department of Agriculture,
Washington, D.C. dated May 5, 1997. Available from Michael K. Hansen,
Consumer Policy Institute, Consumers Union, 101 Truman Avenue, Yonkers,
NY 10703-1057; telephone (914) 378-2000.

[9] G.R. Hartsough and Dieter Burger, "Encephalopathy of Mink. I.
Epizootiological and Clinical Observations," JOURNAL OF INFECTIOUS
DISEASES Vol. 115 (1966), pgs. 387-392.

[10] R.F. Marsh and others, "Epidemiological and experimental studies
on a new incident of transmissible mink encephalopathy," JOURNAL OF
GENERAL VIROLOGY Vol. 72, Part 3 (March 1991), pgs. 589-594.

[11] C.J. Gibbs, Jr., "Experimental transmission of scrapie to cattle,"
LANCET Vol. 335, No. 8700 (May 26, 1990), pg. 1275.

[12] R.C. Cutlip and others, "Intracerebral transmission of scrapie to
cattle," JOURNAL OF INFECTIOUS DISEASES Vol. 169, No. 4 (April 1994),
pgs. 814-820.

[13] Francois Boller and others, "Diagnosis of dementia:
Clinicopathologic correlations," NEUROLOGY Vol. 39, No. 1 (January
1989), pgs. 76-79.

[14] E.E. Manuelidis and L. Manuelidis, "Suggested links between
different types of dementias: Creutzfeld-Jakob disease, Alzheimer
disease, and retroviral CNS infections," ALZHEIMER DISEASE AND
ASSOCIATED DISORDERS Vol. 3, Nos. 1-2 (1989), pgs. 100-109.

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; scrapie; britain; michael hansen; prions; prion
theory of disease; fda; stanley prusiner; bans; ruminants; pigs;
chickens; cows; consumers union; richard marsh; clarence gibbs; randall
cutlip; alzheimer's disease;