Anthelmintic resistance against gastrointestinal nematodes: an emerging threat in cattle farms in Bangladesh.

Anthelmintic resistance (AR) is a major problem in the profitable production of livestock. Therefore, this study evaluated AR status in cattle farms at Mymensingh Sadar using in vivo, fecal egg count reduction test (FECRT) and in vitro, egg hatch assay (EHA) techniques. For this, ten cattle farms and forty animals from individual farms with more than 200 eggs per gram (EPG) of feces were selected by employing the McMaster technique. For FECRT, four groups having ten animals in each group were designed and animals of group I were treated with albendazole (ABZ), group II with levamisole (LEV), group III with ivermectin (IVM) according to the bodyweight and group IV was served as control (untreated). Fecal samples were collected at day 0 (pre-treatment) and day 14 of post-treatment (p. t) from animals of all treated and untreated groups directly from the rectum to calculate EPG and subsequently considered for copro-culture to detect resistant parasitic larvae. For EHA, following the collection of pooled fecal samples from ten farms, eggs were isolated and incubated with different concentrations of albendazole such as 0.05, 0.1, 0.2, 0.3 and 0.5 µg/ml. In FECRT, the result revealed that all three drugs such as ABZ, LEV and IVM were resistant in all farms except one where IVM was suspected resistance (SR). The identified resistant larvae from copro-culture were Haemonchus, Trichostrongylus and Oesophagostomum. In EHA, the EC₅₀ value of ABZ ranged from 0.14 to 0.29 µg ABZ/ml (> 0.1 µg/ml designated as resistance) with the coefficient of correlation (R2) > 0.97 confirming ABZ resistance in all cattle farms. The present study suggests that AR is increasing and creates an alarming condition in controlling GI nematodes in Bangladesh.