Number Of vCJD Cases Is Low
Latest estimates of the number of people asymptomatic for variant Creutzfeldt-Jakob disease (vCJD) in the population remain very low, according to results from a large scale study of tonsil tissue by the Health Protection Agency, published in today's BMJ.
No evidence of the abnormal prion protein associated with vCJD was found in any of the 63,000 samples analysed.
In 2004, the Health Protection Agency launched the National Anonymous Tissue Archive (NATA) to determine prevalence of asymptomatic vCJD in the population, by looking for the prion protein associated with vCJD in extracted tonsils. The tonsils are one of the sites in the body where, once infected, vCJD prions can accumulate (other sites include the spleen, appendix, lymph nodes, spinal cord and brain).
Awareness of the prevalence of vCJD in the population is important to determine the level of risk to the population and to limit the impact of infection or plan healthcare interventions for people who may develop the disease.
The survey has already involved collection and analysis of 63,000 discarded tonsils, and will continue on until a total of 100,000 samples of leftover tonsil tissue have been examined.
When the archive was established it was estimated that up to 50 of the 100,000 samples could contain the abnormal prion protein, however so far none of the samples are positive.
The findings suggest there may be fewer undetected asymptomatic cases of vCJD in the population than were previously expected. However, only by testing a larger number of tonsils and continuing and expanding on the current survey, will scientists be confident that the prevalence is lower than earlier estimates.
Dr Jonathan Clewley, an expert on vCJD at the Health Protection Agency, said: "It may be that we have seen the worst of vCJD already, although we need to keep vigilant and implement appropriate public health measures to prevent any possible secondary spread of disease.
"Estimating the prevalence of people who are carrying vCJD unknowingly is important in guiding our public health response to this disease and ensuring all necessary precautions are taken to reduce this risk of further transmission of the agent through surgical operations and other healthcare settings.
"Further studies are planned to strengthen prevalence estimates, these will involve large scale anonymous tissue surveys, and continuation with the testing of tonsil specimens especially in the older age groups."