Comparison of the therapeutic efficacy of five anthelmintics against natural Fasciola hepatica infections in dairy cattle from the Mantaro Valley, Peru.

The intensive use of anthelmintic drugs to control Fasciola hepatica infections in dairy cattle has resulted in the emergence of anthelmintic resistance. Cases of resistance to triclabendazole (TCBZ) have been reported worldwide. The main goal of this research was to evaluate the main five fasciolicides to control fasciolosis in dairy cattle in the Mantaro Valley, Peru. Two fecal egg count reduction tests were performed. In a first study, 24 naturally F. hepatica infected cattle were randomly grouped into three experimental groups (n = 8). Groups were treated with either TCBZ, nitroxynil (NTX) or closantel (CLOS). In a second experiment, 55 naturally infected cows were grouped into three experimental groups and treated with either TCBZ (n = 18), rafoxanide (RFX) + albendazole (ABZ) (n = 19) or clorsulon (CLN) + ivermectin (IVM) (n = 18). Therapeutic efficacy was determined following the WAAVP guidelines by measuring reduction in fluke egg output at days 15 and 30 post-treatment. Bootstrapping method was used to obtain the 95% confidence intervals. The efficacy of TCBZ was inadequate in both studies (≤80.8%). Closantel showed high efficacy (≥ 90%) at both days, while NTX showed 92.9% (83-100) and 82.1% (53.6-100), efficacy, at days 15 and 30, respectively. Efficacy for RFX were 92.1% (79.6-98.9) and 97.4% (94.1-99.4); and for CLN, 98.8% (97.6-100) and 80.1% (44.7-99.4), at days 15 and 30, respectively. The outcome of this study indicates reduced therapeutic efficacy of TCBZ against F. hepatica in an important dairy area of the Peruvian central highlands but also demonstrates the validity of four alternatives.