Study of the effect of parasite replacement on the anthelmintic resistance of Haemonchus contortus in sheep breeds

Abstract

Studies indicate that the efficacy of Anthelmintics (AH) can be restored by replacing the parasite population in sheep, here called Worm Replacement (WR). Thus, we intend to evaluate and monitor the effect of partial and total replacement of the population of Haemonchus contortus in different sheep breeds (White Dorper, Santa Inês e Texel) on the anthelmintic resistance status for five years, also clarifying the role of refugia in different WR situations. The differences inherent to each breed in terms of susceptibility to parasites, evaluated in genomic studies, in association with the partial and total replacement of parasites, will bring understanding about the ability to dilute resistance in different breeding conditions and the possible use of this strategy/tool/technology by producers. In addition, Fecal Egg Count 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 of H. contortus obtained from experimental animals before, during and after the WR process. The safety of the treatment will be verified by histological and induced inflammatory response studies in sheep. Molecular resistance marker to benzimidazoles in H. contortus will be evaluated to monitor changes in allelic and genotypic frequencies and to monitor the dilution of resistance genes in the population evaluated. Thus, it is expected to develop tools that can be incorporated into the integrated control of parasites, adding advantages such as: reduction in the number of AH applications, reduction of environmental impacts of AH, increase in food security and longevity of AH, providing sustainability and potential of growth for the small ruminant production chain. (AU)