Objective: Scrapie of sheep and Creutzfeldt-Jakob disease (CJD) are both classified as prion diseases. The infectious agents of both diseases are closely related. The objectives of the study was to explore, whether sheep scrapie could be transmitted to humans and cause CJD.
Material and methods: The occurrence of CJD was studied in a period of 40 years, 1960 to 2000. The first part of the study, which was started in 1980, was retrospective. Hospital records from the Department of Neurology of the National Hospital from the years 1960-1980 were scrutinised and paraffin blocks from the collection of the Department of Pathology from cases with the diagnosis CJD and some suspect cases were obtained and analysed. The latter part of the study was prospective, which gave the possibility to study codon 129 of PRNP gene and characterise the strain of the infectious agent. Information on the epidemiology of scrapie in Iceland and of the diet of Icelanders was collected.
Results: Four cases of CJD were detected in the 40 years studied, which corresponds to an incidence of 0.44 per million inhabitants, which is less than half the average incidence in 18 other European countries in the years 1997-2004.
Conclusion: The low incidence of CJD in Iceland does not indicate that sheep scrapie can be transmitted to humans and cause CJD. If this were the case, we would have expected an higher incidence of CJD and possibly atypical cases, as the Icelandic population has been exposed to scrapie for 130 years.