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

4.2 The establishment of the CJD Surveillance Unit (CJDSU) in 1990 in response to the Tyrrell recommendations is discussed in detail in vol. 8: Variant CJD. The main aim of the unit was to study the occurrence of CJD in the UK and to identify any change in the characteristics of the disease - clinical, pathological or epidemiological - that might be linked to the occurrence of BSE. ¹

4.3 From 1992 the CJDSU began to identify cases of CJD that could have been linked with BSE. Initially cases of CJD in farmers with a history of BSE on their farms were identified, though analysis did not support a link with BSE. In 1995 cases of CJD were reported in two young people. The occurrence of CJD in young people was an exceedingly rare event, and until this point only four such cases in teenagers had been recorded worldwide. ² By the end of 1995, the number of cases in young people reported to the CJDSU had increased to three, ³ and by March 1996 this number had risen to 10. An account of the emergence and investigation of CJD in farmers and in young people can be found in vol. 8: Variant CJD.

4.4 Neuropathological findings in the brains of these ten cases revealed a consistent but unusual pattern with large amyloid plaques as seen in kuru but atypical of sporadic CJD. All cases tested were found to have a similar methionine/methionine genotype in codon 129 at the prion gene locus and did not have familial prion mutations. The unusual clinical features and novel pathology suggested a new variant of the disease, which is now termed 'variant CJD' (vCJD). ⁴ BSE was considered to be the most likely origin of the new disease since exposure to the BSE agent in the UK would have been greatest in the mid-1980s, and the sudden emergence of cases in young people was consistent with an incubation period for the disease of 5 to 10 years.

4.5 The following paragraphs discuss experimental studies set up to investigate a link between the two diseases.