Prevalencia y factores asociados a la resistencia a antihelmínticos en ganaderías ovinas de Aragón

Abstract

A survey to determine the level of flock resistance to benzimidazoles (BZ) was performed under field conditions in 107 commercial sheep farms from Aragon region (NE Spain). Resistance was measured using the in vitro egg hatch assay (EHA) in the simplified form of discriminant dose. Management and environmental variables were compiled from each flock and their relationships with resistance levels analyzed in a multivariate approach Estimated prevalence of resistant flocks was 11% although presence of BZ resistant parasite strains was suspected in 98% of samples. Frequency of deworming, grazing in private pastures and subdosification were management variables positively related to resistance levels whereas using benzimidazoles only was negatively, probably because they were substituted by other anthelmintic groups in flocks where reduced BZ efficacy was suspected. Different uses of soil in addition to climatic conditions and seasonality were environmental variables associated with observed resistance levels.