Parasite-host-environment approach to control anthelmintic resistance in sheep flocks

Abstract

The current situation of anthelmintic resistance in Brazil predicts low expectations for an increase in the number of small ruminants. However, studies indicate that the efficacy of Anthelmintics (AH) can be restored by replacing the parasitic population in sheep, here called Worm Replacement (WR). Thus, this proposal aims to evaluate and monitor the effect of partial and total replacement of the population of Haemonchus contortus on the status of anthelmintic resistance, in different sheep breeds, for the period of five years. This project will be carried out in the experimental farm of Embrapa Pecuária Sudeste - CPPSE, São Carlos - SP, involving its experimental herd. Fecal Egg Reduction Test (FECRT), in vitro tests (RESISTA-Test©) and molecular tests will help to verify and monitor the phenotypic and genotypic susceptibility of eggs and L3 obtained from the experimental animals before, during and after the WR process. The safety of the treatment will be verified by histological studies and induced inflammatory response. Molecular markers of resistance in H. contortus will be evaluated to monitor changes in allele and genotype frequencies and to trace the dilution of resistance genes in the evaluated population. In addition, it is expected to generate unprecedented information that makes possible to identify the most resistant Santa Inês, White Dorper and Texel individuals through identification of beta-globin haplotypes and other resistance-associated genomic markers, which will not only enable improvement of the selection process of animals resistant to haemonchosis, but also for leading farmers as regards the most suitable sheep breed for their farming conditions. Thus, it is expected to develop tools to be incorporated into a system of integrated parasite control, adding advantages such as: reduction in the number of applications of AH, reduction of the costs and of the environmental impacts of AH, increase in food security and longevity of AH, providing sustainability and growth potential for the small ruminant production chain. (AU)