Evaluation of Different Benzimidazole Formulations Against Sheep Naturally Infected with Fasciola hepatica and Anthelmintic Resistance Analysis.

Fasciola infection, which is widely distributed and has a major impact on livestock production, is emerging as a significant zoonotic parasitic disease affecting both human and animal health worldwide. The main control strategy currently relies on a limited number of anthelmintic drugs, especially benzimidazoles such as albendazole and triclabendazole. The aim of this study was to evaluate the efficacy of albendazole and triclabendazole in a sheep flock in northwestern Spain naturally infected with F. hepatica and to test fenbendazole and oxfendazole as alternative formulations. For this purpose, a faecal egg count reduction test (FECRT) was conducted applying various statistical methods based on the guidelines used for gastrointestinal nematodes. This study represents the first application of the new classification framework for F. hepatica, emphasizing the urgent need for standardized resistance detection protocols for this parasite and underlining the growing challenge of anthelmintic resistance in the treatment of fasciolosis.