Goat Scrapie Susceptibility

Scrapie is a fatal, infectious neurodegenerative disease that affects sheep and goats. The disease results from infection with pathogenic agents known as “prions” which change the normal prion protein (PrP^C) to the improperly folded, disease-associated form (PrP^Sc). The abnormal PrP^Sc is resistant to the protein turnover process and forms deposits in the central nervous system and some peripheral tissues that lead to progressive neurodegeneration. Goat scrapie is similar to a group of prion diseases that includes Creutzfeldt-Jakob disease in humans, bovine spongiform encephalopathy (BSE) in cattle, sheep scrapie and chronic wasting disease in cervids. The disease impacts animal health and welfare, animal movement, and trade.

Natural mutations (also called variants or alleles) in the prion protein gene (PRNP) of sheep and goats have been identified which confer susceptibility or resistance to scrapie. In the goat, S146 and K222 variants have been confirmed, experimentally and in the field, to confer genetic resistance against classical scrapie. These variants are named for the amino acid changes in the PRNP protein. S146 indicates serine (S) at position 146 instead of normal asparagine (N) and K222 indicates lysine (K) instead of normal glutamine (Q) at position 222. Serine-146 or Lysine-222 forms of PrP^C are more resistant to conversion to the abnormal PrP^Sc.

This test for classical scrapie in goats screens for presence/absence of the protective alleles S146 and K222. Information from the test can be used by breeders to select breeding stock to increase frequency of beneficial alleles in their herds. The latest research shows that even a single copy of S146 or K222 alleles confers resistance to classical scrapie beyond the productive lifetimes of goats. Breeding for resistance is an effective means to control classical scrapie at the herd and population levels. This test is applicable to goats of all types and breeds, including those raised in the U.S.