Abstract
Scrapie is a transmissible spongiform encephalopathy (TSE) in sheep and goats. In recent years, atypical scrapie cases were identified that differed from classical scrapie in the molecular characteristics of the disease-associated pathological prion protein (PrPsc). In this study, we analyze the molecular and neuropathological phenotype of nine Swiss TSE cases in sheep and goats. One sheep was identified as classical scrapie, whereas six sheep, as well as two goats, were classified as atypical scrapie. The latter revealed a uniform electrophoretic mobility pattern of the proteinase K–resistant core fragment of PrPsc distinct from classical scrapie regardless of the genotype, the species, and the neuroanatomical structure. Remarkably different types of neuroanatomical PrPsc distribution were observed in atypical scrapie cases by both western immunoblotting and immunohistochemistry. Our findings indicate that the biodiversity in atypical scrapie is larger than expected and thus impacts on current sampling and testing strategies in small ruminant TSE surveillance.
Highlights
Transmissible spongiform encephalopathies (TSEs) are fatal neurodegenerative diseases that are caused by prions [1] and include, among others, Creutzfeldt-Jakob and Gerstmann-Straussler-Scheinker disease (GSS) in humans, bovine spongiform encephalopathy (BSE) in cattle, and scrapie in small ruminants (SRs), comprising sheep and goats
Previously unrecognized atypical scrapie cases were identified that to date represent the majority of detected small ruminant TSE cases in some countries
Our results show that the neuropathological presentation in atypical scrapie–affected small ruminants varies remarkably, and the results indicate a biodiversity of TSEs in sheep and goats larger than expected, with some similarities to known human TSEs
Summary
Transmissible spongiform encephalopathies (TSEs) are fatal neurodegenerative diseases that are caused by prions [1] and include, among others, Creutzfeldt-Jakob and Gerstmann-Straussler-Scheinker disease (GSS) in humans, bovine spongiform encephalopathy (BSE) in cattle, and scrapie in small ruminants (SRs), comprising sheep and goats. Numerous so-called atypical scrapie cases that differed in their neuropathological and molecular characteristics from classical scrapie and experimental SR BSE were first reported in Norway [5] and later in other countries (reviewed by [6]). Such cases occurred in sheep with genotypes considered to confer resistance to scrapie and were missed by some screening test formats while others readily detected them [7]. Three forms of SR TSE can be discriminated by molecular PrPres typing [8]: classical scrapie, atypical scrapie, and BSE
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