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[SANET-MG] the Dahmer Cow theory of Mad Cow
Published online: 1 September 2005; | doi:10.1038/news050829-17
British duo probes origin of mad cow disease
Did human remains in food spawn the infection in cattle?
Did British cows eat remains of humans with brain disease?
Human remains in cattle feed could have caused the first case of mad cow
disease, two UK researchers propose. The hypothesis seeks to answer
lingering questions about the fatal infection, which has affected
180,000 cows in Britain alone since the mid-1980s, and has gone on to
cause more than 100 deaths in humans.
Alan Colchester of the University of Kent and his daughter Nancy
Colchester, of the University of Edinburgh, point out that during the
1960s and 1970s Britain imported hundreds of thousands of tonnes of
whole and crushed bones and animal carcasses. These were used for
fertilizer and to feed livestock.
Nearly 50% of these imports came from Bangladesh, where peasants
gathering animal materials may have also picked up human remains, the
Other experts in the field view the idea with scepticism, saying that
proof remains circumstantial. "The argument isn't very compelling
because there's no smoking gun evidence," says Surachai Supattapone, an
expert in infectious diseases at Dartmouth Medical School in Hanover,
Transmissible spongiform encephalopathies (TSEs) are a group of fatal
neurodegenerative diseases that affect mammals. Yet until 1986 no such
illness had been spotted in cattle.
Once recognized, bovine spongiform encephalopathy (BSE) became widely
known as 'mad cow disease'. The incidence of the disease then rocketed,
peaking in late 1992.
Tests indicated misshapen prion proteins in the brains of the cows as
the source of the problem. And when authorities banned the practice of
recycling animal remains into cattle feed the number of sick livestock
began to drop.
But experts continue to puzzle over how BSE arose in the first place.
One of the most widely believed theories is that prions responsible for
sheep scrapie got incorporated into cattle feed. Scientists argue that
ingested scrapie prions radically altered the normal, analogous proteins
in one cow, which then developed the first case of BSE.
But the Colchesters point out that cows have been exposed to scrapie for
70 years, so it is hard to explain why BSE emerged only recently.
They propose that a more likely source is recent exposure to human
remains carrying sporadic Creutzfeldt-Jakob Disease (CJD), a TSE thought
to arise spontaneously in people.
Religious customs in Bangladesh and surrounding areas mean that many
corpses are disposed of in rivers. People may have collected remnants
from such bodies when foraging for animal carcasses, the Colchesters
argue in The Lancet1. Any prions in these corpses might then have caused
mad cow disease.
Experts agree that the theory needs to be checked. More information
needs to be collected, they say, about the number of deaths from CJD in
the Indian subcontinent, what happened to the bodies, and whether prions
could have been transmitted in the way proposed. When human sporadic CJD
prions were injected into mice in previous studies, the mice did not
Colchester A. & Colchester N. et al. Lancet, 366. 856 - 861 (2005).
Scott M . R., Peretz D., Nguyen H. O., Dearmond S. J. & Prusiner S. B.
J. Virol., 79. 5259 - 5271 (2005). | ChemPort |
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