Multiple anthelmintic resistance in Haemonchus contortus of sheep

C P Swarnkar, D Singh, F A Khan, P S K Bhagwan


Faecal egg count reduction test (FECRT) and in vitro egg hatch assay (EHA) detected anthelmintic resistance in Haemonchus contortus in sheep. On FECRT, fenbendazole and tetramisole were, respectively, found 0 and 25% effective against H. contortus, while closantel showed 100% efficacy. Though rafoxanide was 96% effective against H. contortus, but lower 95% confidence limit of less than 90 suggested suspected resistance against the rafoxanide. The EHA showed LC₅₀ value of 0.265 ± 0.098 µg thiabendazole / ml against H. contortus. It was concluded that H. contortus developed resistance against benzimidazole, tetramisole and low level resistance against rafoxanide.


Anthelmintic resistance; Egg hatch assay; Faecal egg count reduction; Haemonchus contortus; Sheep

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