Prevalence of vCJD prions is higher than previously shown, but questions remain over risk of clinical disease.
The prion protein which causes variant Creutzfeldt–Jakob disease destroys neurons in the brain but more easily infects the lymphoid system. As a new study in the British Medical Journal reveals that 1 in 2000 people in the UK may harbour the infectious prion protein which causes variant Creutzfeldt–Jakob disease (vCJD).
The usually fatal condition is the human form of bovine spongiform encepalpoathy — dubbed 'mad cow disease' in the UK after an outbreak of the disease in the 1980s. Both diseases are caused by misfolded proteins called prions, which induce other proteins in the brain to clump, eventually destoying neurons. Humans are thought to contract the disease by consuming beef containing infected bovine brain or other central nervous system tissue. But it also spreads through blood transfusions, and some worry that the prion disease is transmitted via contaminated surgical instruments .
The BSE outbreak in the 1980s and 1990s led to a surge in British vCJD cases, and a total of 177 have been detected in the UK to date, with just one in the last two years. Cases of vCJD peaked in 2000, leading some scientists to speculate that the disease takes about a decade to develop. Yet other studies of different forms of CJD suggest its incubation time could be much longer — indicating that many Britons may be carrying the infection without symtoms.
Studies have come to varying conclusions as to just how many people harbour the abnormal prion protein (PrP) that causes vCJD. Surveys of tens of thousands of appendices and tonsil, discarded after surgery, have come up with prevalence rates ranging from 1 in 4,000 to 1 in 10,000 to 0.