Genetics of susceptibility to scrapie in sheep : current research and prospect

Abstract

In several species (man, mouse, sheep), the susceptibility to transmissible subacute spongiform encephalopathies is highly regulated by the host genotype. A major part of the observed genetic variability depends on one gene. This gene is likely the Prn-p gene, which codes for the host prion protein PrP. According to an hypothesis supported by several authors, this protein could be the causal agent of these diseases or it could be associated with the causal agent. Molecular analysis of the structure of the Prn-p gene in sheep demonstrates segregating alleles that differ from each other by a single mutation. It could be interesting, therefore, to examine the possibility of controlling scrapie in sheep by selective breeding on the basis of laboratory analyses of the Prn-p gene polymorphism. Before selecting against this susceptibility, however, different questions need to be answered: Could resistant animals act as a source of infection? Could animals resistant to one scrapie strain be susceptible to another? How expensive would such a selection scheme be? How should the selection be organised in practice?