Evaluation of the efficacy of four fasciolicides in naturally infected cattle in Beni-Suef governorate, Egypt: First report of therapeutic failure of triclabendazole.

The emergence of anthelmintic resistance presents a major threat to the health and productivity of grazing livestock. This study aimed to evaluate the efficacy of commonly used fasciolicides against Fasciola spp. in naturally infected cattle from Beni-Suef, Egypt-an area where fasciolosis is endemic. Twenty adult female cattle, confirmed by microscopic examination to be infected with Fasciola spp., were selected and divided into three experimental trials to evaluate the efficacy of four commercial fasciolicides: triclabendazole (TCBZ), rafoxanide (RAF), nitroxynil (NIT), and oxyclozanide (OCZ). Experiment I evaluated possible resistance to TCBZ, RAF, and NIT by administering two consecutive doses of each drug. Experiment II investigated potential multidrug resistance by treating animals resistant to RAF and NIT with a single dose of TCBZ. Experiment III examined the efficacy of OCZ as an alternative treatment. The fecal egg count reduction test (FECRT) was used as the primary assessment method in all trials. In Experiment I, cattle treated with RAF or NIT showed no reduction in egg counts, even after the second dose. TCBZ treatment resulted in a marked decrease in egg counts at day 7 post-treatment, but counts gradually increased from day 14 onwards, returning to pre-treatment levels by day 56. In Experiment II, animals treated with TCBZ again showed a significant drop in egg counts at day 7, followed by a steady rise to baseline values by day 28. In Experiment III, OCZ achieved complete elimination of eggs by day 7, with 100 % efficacy. This study provides the first documented evidence of triclabendazole (TCBZ) treatment failure in animals in Egypt, highlighting the urgent need for large-scale investigations across the country. In contrast, oxyclozanide (OCZ) showed high efficacy in eliminating Fasciola infections in cattle, emphasizing its potential as a valuable alternative for improving fasciolosis control and management strategies in Egypt.