Triclabendazole resistance involving Fasciola hepatica in sheep and goats during an outbreak in Almirante Tamandare, Paraná, Brazil.

Fasciolosis is a disease of extreme importance, occurring throughout Brazil, with great economic losses to the animal industry. This study aims to determine the effectiveness of treatment against Fasciola hepatica on a sheep and goat farm during an outbreak of fasciolosis, in which a high proportion of deaths occurred. The farm harbored 33 sheep and 60 goats of mixed breeds with varying weights and ages. Parasite control was based on suppressive, monthly treatments with moxidectin. Over the course of the study, assessments with Famacha method, body condition score, faecal exam (EPG), coproculture and the egg sedimentation technique were made on seven occasions. At the time of the first visit 81% of the goats and 100% of the sheep were positive for F. hepatica. Salvage treatment with triclabendazole failed to relieve the heavy infection due to resistance, with an efficacy of only 66.3% being obtained against the F. hepatica population consensual in sheep and 57.3% in goats. There was no record of triclabendazole having been administered previously on the farm. A low level of correlation was found between the Famacha values and the incidence of anemia due to clinical fasciolosis (C<0.5). There is an urgent need to investigate the correct use of available drugs against F. hepatica and the implementation of alternative control strategies in endemic areas in order to ensure optimum sustainability of the efficacy of available fasciolicides.