NR ARVH
AU Ridley,R.M.; Baker,H.F.
TI Who gets Creutzfeldt-Jakob disease
QU British Medical Journal 1995 Nov 25; 311(7017): 1419
IA http://bmj.bmjjournals.com/cgi/content/full/311/7017/1419
PT Article
VT
Whenever an unusual case of Creutzfeldt-Jakob disease is reported in Britain someone asks: "Is this the beginning of the end - are we all going to die of BSE?" It is a commonly held view that the incubation period for spongiform encephalopathy in humans is at least one to two decades. This is a misconception. For kuru, when the dose of infectivity by the oral route was high the minimum incubation period was less than four years and the median ranged from less than five years to nine years (judged by the minimum ages at onset at the height of the epidemic)[i] However, the incubation period can be as long as 30 years (judged by the ages of the most recent cases).[ii]
While experimental transmission of spongiform encephalopathy across species generally results in increased incubation times, this is because the "species barrier" increases the dose required, so that fewer individuals are affected. It is now six to nine years since the general public was at greatest risk of consuming meat products containing brain tissue from cattle incubating bovine spongiform encephalopathy (that is, between the emergence of this disease in 1986 and the Specified Offals Ban of 1989), so it is already clear that a substantial proportion of the population will not be affected. Nonetheless, the occurrence of only a handful of cases of human spongiform encephalopathy resulting from exposure to bovine spongiform encephalopathy would be a tragedy, and any possible case warrants close examination. It is, however, another misconception to suppose that every case of Creutzfeldt-Jakob disease must have been caught from somewhere. About 15% of cases are wholly genetic in origin, and in nearly all of the remaining cases persistent and extensive epidemiological investigation has failed to find a contamination event, leading to the proposition that these cases are idiopathic. It is against this background that the occurrence of Creutzfeldt-Jakob disease in four farmers and two teenagers should be considered.
The four farmers had ages at onset and clinical pictures consistent with idiopathic Creutzfeldt-Jakob disease.[iii-v] During a similar period the number of farming employees with Creutzfeldt-Jakob disease in France was five, in Germany two, and in Italy three.[vi] Bovine spongiform encephalopathy has not been reported in these countries. This suggests that the number of cases in farmers in Britain is not surprising and need not be related to bovine spongiform encephalopathy. The only known cases of acquired spongiform encephalopathy in humans have involved ingestion, injection, or other internal contamination with material associated with human brain, and brain is the only tissue consistently infectious in bovine spongiform encephalopathy. If these farmers had been at risk from handling cattle feed one would expect feed producers to have been at greater risk, and if the farmers had been at risk from handling affected cattle one would expect abattoir workers to have been at greater risk. There is no evidence that these occupational groups are at higher risk of contracting Creutzfeldt-Jakob disease.
Four cases of apparently idiopathic Creutzfeldt-Jakob disease have been reported in teenagers in continental Europe and the United States.[vii-x] Since these cases cannot be related to bovine spongiform encephalopathy, the occurrence of Creutzfeldt-Jakob disease in two teenagers in Britain[xi,xii] does not make a link with bovine spongiform encephalopathy obligatory. However, these two cases are extremely unusual both in the ages at onset and in the reported neuropathology. A greater appreciation of the variety of clinical presentations, neuropathology, and age at onset of Creutzfeldt-Jakob disease in recent years - together with the heroic attempts of the National CJD Surveillance Unit to identify all cases - should lead to greater ascertainment, particularly of those cases which are unusual. We hope that this explains the detection of these two cases in young people.
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ZR 12
AD
0ES R M Ridley head of team H F Baker senior scientific officer
Molecular Neuropathology SmithKline Beecham Pharmaceuticals New Frontiers Science Park-North Harlow CM19 5AW
SP englisch
OR Prion-Krankheiten 7