Efficacy of Routinely Used Anticoccidials Against Eimeria tenella Field Isolates in Chicken: Bangladesh Perspective.

To evaluate anticoccidial drug efficacy against Eimeria tenella in chicken, seven different field isolates were experimented with in battery cages with five commonly used anticoccidials as manufacturer doses, like amprolium (1 g/L), maduramicin (5 ppm), sulphaclozine (2 g/L), toltrazuril (25 mg/L) and amprolium + sulphaquinoxaline (1 g/L). One hundred twelve birds of the Ross strain were raised on a rice husk-littered floor for the first 11 days with ad libitum water and anticoccidial-free feed, facilitating a standard environment. On Day 12, the birds were divided into seven experimental groups with 16 birds each, and the respective anticoccidials were started for Groups I-V and continued up to 7 days post-infection. Each bird was infected with 7.5 × 10⁴ sporulated oocysts of E. tenella field isolates on Day 14. Global index (GI) was calculated by weight gain, feed conversion ratio (FCR), lesion score, oocyst index and mortality, followed by calculation of %GI_NNC to determine the drug efficacy. Data obtained on various parameters were analysed using ANOVA, and the mean values were compared using the Duncan multiple range test through SPSS. The findings revealed that toltrazuril is the best among the experimental drugs, whereas amprolium and sulphaquinoxaline combination holds second place in terms of efficacy. However, the resistance of sulphaclozine was evident in all the isolates, whereas maduramicin showed limited efficacy to partial resistance against caecal coccidiosis. The study strongly recommends toltrazuril against chicken coccidiosis followed by amprolium but highly suggests avoiding long-term use to maintain drug efficacy.