The French scrapie eradication programme for the entire national sheep flock based on a genetic strategy

Abstract

Studies carried out since 1993 on scrapie infected flocks, have allowed to describe the frequency of susceptible alleles of the PrP gene in French dairy sheep breeds, to verify the greater risk of susceptible animals, and to test the selection feasibility and efficiency based on PrP genotyping. The idea of using a genetic strategy to eradicate scrapie in infected flocks was born as a result. Since 2002, the programme to eradicate scrapie in French sheep livestock, implemented by the Ministry of Agriculture, is rooted in a genetic strategy based on the genotyping of the PrP gene : its objective is aimed both at eradicating scrapie in infected flocks and reinforcing the resistance of the entire national flock. The fact that it was launched within the framework of the livestock selection organisation, defined in 1966 by a French law, is obviously a key point to explain its efficient and rapid implementation from the starting year. Moreover, it illustrates the mobilisation of all the people in charge of the sheep breeding programmes in France: the jointed evolutions observed for the ARR allelic frequency, the genetic merit for production traits and the maintenance of criteria describing the genetic variability are evidence of a good application of the objectives defined for the breeding programmes. The national supervision, carried out by INRA, the Institut de l’Elevage and France UPRa selection, will set out, in the next years, to reach all the objectives of this national programme, particularly by supplying scrapie infected flocks with resistant sheep, managing the genetic variability of the selection flocks and diffusing resistant germplasm towards the commercial flocks. This plan is based on the following crucial points: resistance of ARR/ARR is universal to natural infections and ARR/ARR sheep are not healthy carriers. It will be necessary to always check these crucial points and include any new scientific knowledge in the breeding programmes.