PrP genotype contributes to determining survival times of sheep with natural scrapie

Abstract

Several allelic variants of the sheep PrP gene are associated with scrapie susceptibility. However, it is not known whether, and to what extent, the PrP genotype contributes to determining survival times of scrapie sheep. We therefore determined the PrP genotype and life spans of over 50 Flemish and Swifter sheep within a single scrapie-affected flock. Eighty-three per cent of the scrapie sheep were homozygous for the PrPVQ allele (polymorphic amino acids at codons 136 and 171 are indicated) and these sheep died from scrapie at a mean age of 25 months. In sheep heterozygous for PrPVQ, development of scrapie was delayed or did not occur. Sheep with at least one PrPAR allele, including PrPVQ/PrPAR sheep, did not develop scrapie. No scrapie sheep were found without a PrPVQ allele. We conclude that the PrP genotype contributes to determining survival times of sheep with natural scrapie. Additionally, we describe two novel sheep PrP allelic variants.