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- Half the tools used to remove tonsils in the UK could
be infected with the human form of mad cow disease.
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- Half of the kits used to remove tonsils in British hospitals
could transmit the human form of mad cow disease, a senior government adviser
on BSE warned on Wednesday.
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- In a doom-laden speech, he also warned that the worst
of the variant Creutzfeldt-Jakob Disease (vCJD) epidemic might yet be to
come, with waves of people affected for decades ahead.
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- "We work out that if there are 10,000 people in
Britain incubating [vCJD], then half the tonsilectomy sets are already
contaminated," says John Collinge, at the Medical Research Council's
Prion Unit at Imperial College School of Medicine in London.
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- He was speaking in London at the "Millennium Festival
of Medicine" organised by the British Medical Association and others.
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- Virtually indestructible
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- The problem for surgeons is that the misshapen protein
which causes vCJD - the PrPSC prion - is not destroyed by conventional
methods of cleaning surgical instruments. These include steam sterilisation,
exposure to disinfectants and even autoclaving (see New Scientist, 13 February,
p18).
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- Research presented earlier this year suggests that the
stainless steel in instruments might even amplify the infectiousness of
prions, (see New Scientist conference report here).
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- "These things are all rather scary," says Collinge,
who sits on the British government's Spongiform Encephalopathy Advisory
Committee. "We've known since 1997 that tonsils contain lots of PrPSC,
around 10 per cent of what you might find in the brain," he says.
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- Collinge suspects that thousands of people may not know
they are infected. If so, the tools that surgeons use to remove tonsils
could become irreversibly contaminated. The prions on the instruments then
infect all subsequent patients operated on. "These instrument kits
are re-used several times a year," he says.
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- To assess how many people might be infected, Collinge
is screening anonymous tonsil samples. He says that all samples are taken
using disposable kits, so infected volunteers can't pass on the prion.
The results won't be known until next year, he says.
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- An earlier programme of screening on appendixes drew
a blank, but Collinge thinks that this provides little reassurance.
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- Fatal forecast
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- Collinge also revealed disturbing new evidence that the
worst of the vCJD epidemic in Britain could be yet to come.
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- He explained that all the patients so far diagnosed with
vCJD have a particular "MM" variant of the gene that makes their
"normal" prion protein. This variant is present in 40 per cent
of the population.
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- Collinge's new research from islanders in New Guinea
suggests that the 60 per cent with other variants can't relax, however.
They could be equally susceptible, but might have to wait until old age
for the disease to strike.
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- Collinge examined genes from "late onset" sufferers
of Kuru, a form of CJD in found in New Guinea. Kuru used to spread from
person to person through a cannibalistic funeral rite that obliged relatives
and guests to eat parts of the deceased.
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- Alarmingly, genes from the 11 sufferers all have the
"MV" variant thought to be the most protective. "We're saying
there might be lifelong incubation periods," says Collinge.
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- Correspondence about this story should be directed to
latestnews@newscientist.com
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