ASSOCIATION BETWEEN NATURAL SCRAPIE AND PRP GENOTYPE IN A FLOCK OF SUFFOLK SHEEP IN SCOTLAND

The incidence of natural scrapie in sheep is associated with polymorph isms of the PrP gene, particularly those at codons 136, 154 and 171. I n many breeds, the PrP allele encoding valine at codon 136 confers an extremely high risk of scrapie, but in Suffolk sheep this allele is va nishingly rare. In this study of a single closed flock of Suffolk shee p in Scotland, scrapie occurred primarily in animals which were homozy gous for glutamine at codon 171, a genotype which was significantly le ss frequent in healthy flockmates. However, the apparent linkage betwe en glutamine at codon 171 and scrapie was not completely recessive bec ause two of 64 scrapie cases were heterozygous glutamine/arginine. The se results suggest that breeding for increased resistance to scrapie i n Suffolks by the selection of animals according to their PrP genotype is a feasible option.