Delayed Scrapie Incubation Times for PRNP S127 Heterozygous Goats

Classical scrapie is a transmissible spongiform encephalopathy that affects domestic goats and sheep. Even if current scrapie eradication measures are successful in sheep, goats can act as a scrapie reservoir and transmit scrapie to sheep. Scrapie eradication in sheep is based in part on strong genetic resistance to classical scrapie. However, implications of differing genotypes have been less well explored in goats. In particular, one prion gene polymorphism at codon 127 (G/S127; G=glycine, S=serine) is significantly underrepresented in scrapie infected goats but the specific scrapie incubation period has not been defined for G/S127 heterozygous goats. Therefore, the aim of this study was to identify whether goats with the G/S127 genotype have extended incubation periods with classical caprine scrapie. Challenge experiments demonstrated control goats (G/G127 genotype) had scrapie incubation periods of 261-332 days while G/S127 heterozygous goats had incubation periods of 647-1333 days. These results suggest that scrapie eradication programs should include longer traceback history for G/S127 heterozygous goats compared to more common G/G127 genotype goats to accurately reflect potential exposures and sources of scrapie transmission.