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A
new theory proposes that mad cow disease may have
come from feeding British cattle with meal
contaminated with human remains infected with a
permutation of the disease.The hypothesis,
outlined this week in The Lancet medical journal,
suggests that the infected cattle feed came from
the Indian subcontinent, where bodies sometimes
are ceremonially thrown into the Ganges
river.Indian experts not connected with the
research exposed weaknesses in the theory, but
agreed it should be investigated.
The
cause of the original case or cases of mad cow
disease, or bovine spongiform encephalopathy, is
unknown.It belongs to a class of illnesses called
transmissible spongiform encephalopathies, or TSEs.
They exist in several species. Scrapie is a TSE
that affects sheep and goats, while chronic
wasting disease is one that afflicts elk and
deer.A handful of TSEs are found in humans,
including Kuru, Alper's disease and
Creutzfeldt-Jakob disease, or CJD.All the TSEs are
fatal, untreatable and undiagnosable until after
death. They are called spongiform encephalopathies
because the diseases involve spongy degeneration
of the brain.
The
disease was not known to infect cows until 1986,
when the first cases were noticed in Britain.
About a decade later, a new permutation of CJD,
which scientists dubbed variant CJD, started
showing up in people there. Experts believe this
new variant comes from eating beef products
infected with mad cow disease.But where the cows
got their disease in the first place remains a
mystery.The most popular theory is that cattle,
which are vegetarian, were fed meal containing
sheep remains, passing scrapie from sheep to cows,
where it eventually evolved to become a
cow-specific disease. Another theory is that cows
just developed the disease spontaneously, without
catching it from another species.
However,
a pair of British scientists now propose the
origin may be the bones of people infected with
classical CJD, which they theorise ended up in
cattle feed imported from South Asia.Britain
imported hundreds of thousands of tons of whole
bones, crushed bones and carcass parts to be used
for fertiliser and animal feed during the 1960s
and 1970s. Nearly half of that came from
Bangladesh, India and Pakistan, said the
scientists, led by Alan Colchester, a professor of
neuroscience at the University of Kent in
England."In India and Pakistan, gathering
large bones and carcasses from the land and from
rivers has long been an important local trade for
peasants," the scientists wrote.
"Collectors encounter considerable quantities
of human as well as animal remains as a result of
religious customs."Hindus believe remains
should be disposed of in a river, preferably the
Ganges."The ideal is for the body to be
burned, but most people cannot afford enough wood
for a full cremation ... Many complete corpses are
thrown into the river," the scientists said,
adding that the inclusion of human remains in
animal bone material exported from the Indian
subcontinent has been documented.
Britain
was the main recipient of animal byproducts
exported from India and Pakistan during the
relevant period and was also a leader in feeding
meat and bonemeal to calves, they noted.Finally,
the similarities between the strains - mad cow
disease, classical CJD and variant CJD - are
sufficiently close to support the theory of a link
among them, the authors argue."We do not
claim that our theory is proved, but it
unquestionably warrants further
investigation," the scientists wrote.
Indian
neuroscientists Susarla Shankar and P.
Satishchandra of the National Institute of Mental
Health and Neurosciences in Bangalore, India, said
they agreed the theory needs to be followed up,
but urged caution.
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