Mapping of quantitative trait loci affecting classical scrapie incubation time in a population comprising several generations of scrapie-infected sheep.

Although susceptibility to scrapie is largely controlled by the PrP gene, the role of other genes that affect scrapie resistance in sheep is now confirmed. Following the detection of quantitative trait loci (QTL) on chromosomes 6 and 18 in a half-sib family with an ARQ/VRQ susceptible PrP genotype, the whole pedigree of a naturally infected flock was investigated to confirm these QTL regions in different PrP genotypes. The present study has allowed us to confirm the QTL on chromosome 18, and to demonstrate the QTL effects in several PrP genotypes.