Progress and limits of PrP gene selection policy.

Area of Science:

• Veterinary Medicine
• Animal Genetics
• Disease Control

Background:

• Classical scrapie control is challenging due to limited understanding of its natural history.
• Prion protein (PrP) genotype linkage to disease risk offers a novel control strategy: selective breeding.
• Concerns exist regarding potential unintended consequences on performance traits, inbreeding, and genetic diversity.

Purpose of the Study:

• To evaluate the effectiveness of a national selective breeding program for classical scrapie control in Great Britain.
• To assess the impact of PrP genotype selection on disease risk, performance traits, and genetic diversity in sheep.

Main Methods:

• Implementation of the National Scrapie Plan (2001) in Great Britain, focusing on voluntary genotyping and selective breeding.
• Genotyping of 700,000 rams across 90 breeds.
• Comparison of PrP genotype frequencies in ram lambs born in 2002 and 2006 to assess changes and potential impacts.

Main Results:

• Significant changes in PrP genotype frequencies observed between 2002 and 2006, predicted to reduce classical scrapie risk.
• No consistent associations found between PrP genotype selection and negative impacts on performance traits.
• Unlikely to be detectable impacts on inbreeding levels in mainstream sheep breeds.

Conclusions:

• Selective breeding based on PrP genotype is an effective strategy for controlling classical scrapie in sheep.
• The implemented National Scrapie Plan has successfully altered PrP genotype frequencies without adverse effects on genetic diversity or performance.
• Semen banks are established to preserve genetic material for all common PrP genotypes, ensuring future options for disease management.