Investigation of trace elements in soil as risk factors in the epidemiology of scrapie.

Scrapie is a fatal transmissible spongiform encephalopathy (TSE) of sheep and goats which is thought to be caused by a conformational change of the normal prion protein to its pathological isoform. It has been speculated that this change may be mediated by an interaction between the prion protein and various trace elements, in particular manganese and copper, and that the levels of trace elements in soils may therefore be risk factors for TSEs. This hypothesis was tested by comparing the level of trace elements in the soils on farms with and without scrapie and on those with a higher and lower incidence of the disease. The levels of trace elements were obtained from the UK's National Soil Inventory and deficiencies reported by farmers. The results provide no evidence that trace elements are risk factors for scrapie on farms, and the variations in the levels of trace elements in soils at regional scales do not account for the regional differences in the prevalence of scrapie.