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From: rachel@rachel.org
MAD COW DISEASE AND HUMANS
When a new form of an old human disease appeared in England in
1995, some medical specialists immediately suspected that it
might be a human version of "mad cow disease," but they had no
proof.[1] Mad cow disease had appeared in British dairy cattle
for the first time in 1985 and during the subsequent decade
175,000 British cows had died from it. British health authorities
spent that decade reassuring the public that there was no danger
from eating the meat of infected cows. They said a "species
barrier" prevented mad cows from infecting humans. A "species
barrier" does prevent many diseases from crossing from one
species to another -- for example, measles and canine distemper
are closely related diseases, but dogs don't get measles and
humans don't get distemper.
While the British government was placing its faith in the species
barrier, British citizens began to die of a new disease, called
"new variant Creutzfeldt-Jakob disease" or nvCJD. A similar
disease, CJD (Creutzfeldt-Jakob disease) had been recognized for a
long time but it almost never occurs in people younger than 30;
nvCJD, on the other hand, strikes people as young as 13. There
are several other differences between CJD and nvCJD, so nvCJD
represents something new. To date, nvCJD has killed 48 people in
England and one or two others elsewhere in Europe. The main
feature of both mad cow disease and nvCJD is the progressive
destruction of brain cells, inevitably leading to total
disability and death.
New research published late in 1999 showed that nvCJD is, in
fact, a human form of mad cow disease, [2] dashing all hope that a
species barrier can protect humans from this deadly bovine
affliction.
Mad cow disease is formally known as "bovine spongiform
encephalopathy" or BSE. BSE is the cow version of a larger class
of diseases called "transmissible spongiform encephalopathies,"
or TSEs. TSEs can afflict sheep, deer, elk, cows, mink, cats,
squirrels, monkeys, humans and other species. In all species the
symptoms of TSEs are the same -- progressive destruction of brain
cells leading to dementia and death.
Traditional Creutzfeldt-Jakob disease (CJD) is a rare human
affliction. The visible symptoms are similar to Alzheimer's
disease; in fact, CJD is sometimes diagnosed as Alzheimer's and
therefore may go unrecognized. CJD strikes one in a million
people almost all of whom are older than 55. In people younger
than age 30, CJD is extremely rare, striking an average of 5
people per billion each year, worldwide (not counting the recent
outbreak in England).
In cows, the latency (or incubation) period for mad cow disease
is about 5 years, meaning that cows have the disease for five
years before symptoms begin to appear. No one knows the latency
period for nvCJD in humans, but it is thought to be around 10
years. Because of this uncertainty, no one is sure how many
people in England already have the disease but are not yet
showing symptoms. The British government's chief medical officer,
Professor Liam Donaldson, said December 21, 1999, "We're not
going to know for several years whether the size of the epidemic
will be a small one, in other words in the hundreds, or a very
large one, in the hundreds of thousands."
The epidemic of mad cow disease was caused by an agricultural
innovation -- feeding dead cows to live cows. Cows are, by
nature, vegetarians. But modern agricultural techniques changed
that. Cows that died mysteriously were sent to rendering plants
where they were boiled down and ground up into the consistency of
brown sugar, and eventually added to cattle feed. It was later
determined that mad cow disease was being transmitted through
such feed, and especially through certain specific tissues --
brain, spinal cord, eyes, spleen and perhaps other nerve tissues.
Ten new cases of nvCJD were reported in England in 1999, bringing
the total to 48. It has been more than 10 years since government
authorities banned the use of the particular parts of cows
thought to transmit mad cow disease. The appearance of new cases
of nvCJD in 1999 implies either that the latency period for the
disease is longer than 10 years, or that infected meat was not
effectively eliminated from the food chain when government
authorities said it was, or both.
The SUNDAY TIMES of London reported in late December that some
meat banned for human consumption is still being marketed in
England. After the mad cow scandal erupted, the British
government attempted to eradicate the disease by requiring that
all cows older than 30 months be slaughtered. As a result, by
last September more than 2.5 million British cows had been
killed. But the TIMES reported that British investigators have
documented at least 50 cases of farmers and cattle dealers using
bogus identity documents to falsify the ages of cows in order to
sell them for human consumption. Furthermore, the Agriculture
Ministry acknowledged that as many as 90,000 cattle could not be
accounted for. About 1600 new cases of mad cow disease are still
being reported each year in England.
In December, French health authorities announced finding a second
case of nvCJD, a 36-year-old woman in Paris. France has continued
to refuse to import British beef, even though the European Union
on August 1, 1999, formally declared British beef as safe as any
in the European Union. The European Union said in December it
will take France to the European Court of Justice to force it to
import British beef. Germany is also refusing to import British
beef.
The U.S. government says mad cow disease has never been observed
in any U.S. cows. However, a closely-related TSE disease, called
chronic wasting disease (CWD), has been increasing for almost 20
years among wild deer and elk in northern Colorado and southern
Wyoming. Since 1981, CWD has been spreading slowly among wild
deer and elk herds in the Rocky Mountains and now afflicts
between 4% and 8% of 62,000 deer in the region between Fort
Collins, Colorado and Cheyenne, Wyoming.
During 1999, CWD erupted among a herd of elk on the David Kesler
Game Farm near Philipsburg, Montana, which raised elk
commercially. A few of Mr. Kesler's elk had been shipped to
Oklahoma and Idaho, and perhaps elsewhere, and CWD was discovered
in some of those animals, too. In early December, Montana health
authorities slaughtered 81 elk on Mr. Kesler's farm. They
initially announced plans to incinerate the carcasses, but later
decided that incineration would be too expensive. The animals
were finally buried at the High Plains Sanitary Landfill north of
Great Falls. Equipment used to feed, water and care for the
animals was also buried in the landfill. Montana authorities
announced that the fenceline at the elk farm would be
decontaminated, but they did not say what procedure they would
use. Nor did they announce what would become of Mr. Kesler's
contaminated land. The disease agent that causes CWD -- a prion
protein -- is very hardy and resists destruction by traditional
sterilization techniques like alcohol and heat.
The diseased elk carcasses in the High Plains landfill have been
buried under a mound of garbage but will still be accessible to
rainwater and perhaps to scavenging animals. continued
Previous page
In northeastern Colorado and southeastern Wyoming, state
officials are urging hunters to protect themselves when dressing
wild deer and elk they have shot. Hunters should wear rubber
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