The latest surveillance report on the incidence of Creutzfeldt-Jakob disease (CJD) situation, including variant-CJD (vCJD), in the United Kingdom (UK) was published last week (1) and is available from the National CJD Surveillance Unit (http://www.cjd.ed.ac.uk
). The report provides a detailed overview of the situation for all forms of CJD.
By the end of 2000, there had been 84 deaths from definite or probable vCJD in the UK (in addition two probable cases died in January 2001 and a further seven probable cases remained alive as at 31 January 2001). The estimated annual increase in incidence of vCJD is 1.35 (95% confidence interval 1.13 to 1.61). The predicted total number of deaths for 2001, assuming this trend continues, is 36 (21 to 58). By the end of June 2001 the total number of definite and probable cases of vCJD reported in the UK had reached 102 (2).
Of the 84 deaths to end 2000, 75 were confirmed neuropathologically, with a further two awaiting neuropathological confirmation. The clinical, neuropathological and epidemiological features of all these cases of vCJD are remarkably uniform and consistent with previous descriptions. A case of neuropathologically confirmed vCJD in an individual who died aged 74 years in October 1999 significantly extends the known age range for vCJD.
Analysis by standard region suggests that the incidence of vCJD in the "North" of Great Britain may be higher than in the "South"; rate ratio (north v south) based on place of residence in 1991 was 1.81 (1.20 to 2.74). The mean Carstairs' deprivation score for areas of residence of people with vCJD was –0.41 (–1.02 to 0.19), which is close to the national average of zero. Regional rates of vCJD were correlated with consumption of other meat or meat products as classified and recorded by the Household Food Consumption and Expenditure Survey (r=0.73), but not with similar data from the Dietary and Nutritional Survey of British Adults. Investigators of the five cases of vCJD in Leicestershire that formed a cluster concluded that the purchase and consumption of beef in the early 1980s from butcher’s shops where the meat could have been contaminated with brain tissue from cattle affected with bovine spongiform encephalopathy (BSE) provided a plausible explanation for the cluster (3,4).
Risk factors for the development of vCJD include age, residence in the UK, and methionine homozygosity at codon 129 of the prion protein gene – 87 cases of vCJD with available genetic analysis have all been methionine homozygotes. The analyses in the ninth annual report do not provide conclusive evidence of an increased risk of vCJD associated with past surgery, previous blood transfusion, occupation, or a range of dietary factors. The power of the case-control study from which these results are derived is, however, limited by the comparatively small number of cases and controls. For some putative risk factors, such as blood transfusion or surgery, it may be many years before an accurate assessment of risk can be made because of the likely prolonged incubation periods.
From 1990 to 2000 death rates from sporadic CJD in England, Scotland, Wales and Northern Ireland were 0.75 per million per year, 0.86/1000 000/year, 1.00/1000 000/year, and 0.46/million/year, respectively; these rate differences were not significant (P=0.3). The rates are similar to those observed in other countries in Europe and elsewhere in the world, including countries that are free of BSE. The variation seen in the observed death rates between different parts of the UK was not significant (P=0.5). There was no convincing evidence of space-time clustering. Since 1990 the average annual incidence of sporadic CJD has been higher than earlier. Whether this increase in incidence is due to improved case ascertainment or is a real reflection of an underlying incidence rise is impossible to say with certainty.
Between 1970 and 2000, 42 cases of iatrogenic CJD have been ascertained, six in recipients of dura mater implants, 35 in recipients of human derived growth hormone (hGH), and one in a recipient of human gonadotrophin (hGN). The mean age at death of the hGH/hGN group was 29 years (range 20-45 years) and for the dura mater recipients 43 years (27-59 years). The first recognised case in a dura mater recipient died in 1979, and the first hGH related death was in 1985.