Volume 2: Science
4. The link between BSE and vCJD
Summary

4.29 The evidence discussed above that vCJD is caused by BSE seems overwhelming. Uncertainties exist about the cause of CJD in farmers, their wives and in several abattoir workers. It seems that farmers at least might be at higher risk than others in the general population. ¹ Increased ascertainment (ie, increased identification of cases as a result of greater awareness of the condition) seems unlikely, as other groups exposed to risk, such as butchers and veterinarians, do not appear to have been affected. The CJD in farmers seems to be similar to other sporadic CJD in age of onset, in respect to glycosylation patterns, and in strain-typing in experimental mice. Some farmers are heterozygous for the methionine/valine variant at codon 129, and their lymphoreticular system (LRS) does not contain the high levels of PrP^Sc found in vCJD. It remains a remote possibility that when older people contract CJD from BSE the resulting phenotype is like sporadic CJD and is distinct from the vCJD phenotype in younger people.

4.30 Estimates of the likely scale of a possible epidemic of vCJD are wide-ranging and the subject of much debate. To know the likely number of cases is very important, not least to enable preparations to be made for the care of victims, as well as to be able to draw up guidelines to reduce the risk of transmission from infected but asymptomatic people. Preliminary results of the study examining tonsil and appendix material for signs of infection were not informative in this regard and full results are awaited. A blood test that would allow the widespread screening of the population by a simple method is still being sought.