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.
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.
鈥淲e work out that if there are 10,000 people in Britain incubating [vCJD], then half the tonsilectomy sets are already contaminated,鈥� says John Collinge, at the Medical Research Council鈥檚 Prion Unit at Imperial College School of Medicine in London.
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He was speaking in London at the 鈥淢illennium Festival of Medicine鈥� organised by the British Medical Association and others.
Virtually indestructible
The problem for surgeons is that the misshapen protein which causes vCJD 鈥� the PrPSC prion 鈥� is not destroyed by conventional methods of cleaning surgical instruments. These include steam sterilisation, exposure to disinfectants and even autoclaving (see New 杏吧原创, 13 February, p18).
Research presented earlier this year suggests that the stainless steel in instruments might even amplify the infectiousness of prions, (see New 杏吧原创 conference report here).
鈥淭hese things are all rather scary,鈥� says Collinge, who sits on the British government鈥檚 Spongiform Encephalopathy Advisory Committee. 鈥淲e鈥檝e known since 1997 that tonsils contain lots of PrPSC, around 10 per cent of what you might find in the brain,鈥� he says.
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. 鈥淭hese instrument kits are re-used several times a year,鈥� he says.
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鈥檛 pass on the prion. The results won鈥檛 be known until next year, he says.
An earlier programme of screening on appendixes drew a blank, but Collinge thinks that this provides little reassurance.
Fatal forecast
Collinge also revealed disturbing new evidence that the worst of the vCJD epidemic in Britain could be yet to come.
He explained that all the patients so far diagnosed with vCJD have a particular 鈥淢M鈥� variant of the gene that makes their 鈥渘ormal鈥� prion protein. This variant is present in 40 per cent of the population.
Collinge鈥檚 new research from islanders in New Guinea suggests that the 60 per cent with other variants can鈥檛 relax, however. They could be equally susceptible, but might have to wait until old age for the disease to strike.
Collinge examined genes from 鈥渓ate onset鈥� 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.
Alarmingly, genes from the 11 sufferers all have the 鈥淢V鈥� variant thought to be the most protective. 鈥淲e鈥檙e saying there might be lifelong incubation periods,鈥� says Collinge.
