Abstract
Aim: The present study was aimed to determine the resistance against albendazole, fenbendazole, levamisole and closantel in gastrointestinal (GI) nematodes of sheep. Introduction: Anthelmintics are used traditionally as an integral part of helminthic control strategies for grazing livestock to prevent production losses from parasitic infections. The continuous and indiscriminate use of the same anthelmintics over years together as the sole means of control are now failing due to the emergence of resistance strains of helminths. Resistance to the commonly used anthelmintics in GI nematodes of sheep has become an increasingly widespread problem throughout the world. Materials and Methods: Fifty-five naturally infected Madras Red lambs of 6-12 months of age were selected and distributed randomly into five treatment groups of 11 animals each. Four groups were treated orally with albendazole (5 mg/kg), fenbendazole (7 mg/kg), levamisole (7.5 mg/kg) and closantel (10 mg/kg) respectively, whereas the fifth group served as untreated control. Fecal samples were collected per rectum of each lamb just prior to treatment (pre-treatment) and on 7, 14, 21 and 28 days post-treatment. The anthelmintic resistance was evaluated by in vivo fecal egg count reduction test (FECRT), post-treatment larval culture and in vitro egg hatch assay. Results: In the FECRT, albendazole reduced the faecal egg count by 86.50%, 84.81%, 85.28% and 84.47% respectively for 4 weeks after treatment. Fecal egg count reduction using fenbendazole was 92.64, 93.04, 90.80 and 90.06% respectively for 4 weeks after treatment. The percent efficacy for levamisole and closantel was more than 95%. The post-treatment larval culture contained only Haemonchus contortus. In the in vitro egg hatch assay, the ED50 value for benzimidazole was 0.299 μg albendazole/ml and levamisole showed an ED50 value of 0.283 μg/ml. Conclusion: Our study confirmed the resistance of H. contortus to benzimidazole in sheep.
Highlights
Anthelmintics are used traditionally as an integral part of helminthic control strategies for grazing livestock to prevent production losses from parasitic infections
Our study confirmed the resistance of H. contortus to benzimidazole in sheep
A recent study performed on anthelmintic worm control practices in Norwegian sheep and goat flocks has indicated the occurrence of under dosing, a lack of anthelmintic class rotation and, in some breeding areas, a high drench frequency, which alone or in combination, are likely to increase the risk for anthelmintic resistance [2]
Summary
Anthelmintics are used traditionally as an integral part of helminthic control strategies for grazing livestock to prevent production losses from parasitic infections. The continuous and indiscriminate use of the same anthelmintics over years together as the sole means of control are failing due to the emergence of resistance strains of helminths. Resistance to the commonly used anthelmintics in GI nematodes of sheep has become an increasingly widespread problem throughout the world. The extensive use of anthelmintics for control of gastrointestinal (GI) nematodes has resulted in the development of resistance to one or more of the widely used anthelmintics in many countries [1]. Resistance to anthelmintics by GI nematodes of sheep and goat is a widespread problem. Mixed grazing of sheep and goats has been evoked as a possible risk factor for the spread and emergence of anthelmintic resistance. A number of reports on anthelmintic resistance were documented in many countries [3,4]. Multiple resistances to most of the anthelmintics against
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