title: The efficacy of fenbendazole and albendazole against immature and adult stages of benzimidazole-resistant sheep trichostrongylids.
abstract: The efficacy of two recently introduced benzimidazole anthelmintics, albendazole and fenbendazole, was determined for six-day, 10-day and adult stages of resistant strains of Haemonchus contortus and Trichostrongylus colubriformis. Albendazole, at 3.8 mg/kg reduced H contortus worm counts by 92.4, 70.8 and 67.1 per cent while fenbendazole, at 5.0 mg/kg, reduced worm burdens by 51.7, 95.5 and 93.4 per cent against six-, 10- and 25-day-old parasites respectively. For T colubriformis, the corresponding reductions with albendazole were 97.7, 95.8 and 64.9 per cent and for fenbendazole 29.0, 66.3 and 33.4 per cent. Compared with susceptible strains of H contortus and T colubriformis, for which therapeutic doses of benzimidazole anthelmintics are generally highly active against all stages of development, the present results show that these drugs do not have a uniform level of activity against all developmental stages of resistant strains.
mesh_terms: D000818:Animals; D001562:Benzimidazoles / Q000494:pharmacology*; D004351:Drug Resistance; D005260:Female; D005273:Fenbendazole / Q000494:pharmacology* / Q000627:therapeutic use; D006188:Haemonchiasis / Q000188:drug therapy / Q000662:veterinary; D008297:Male; D012756:Sheep / Q000469:parasitology; D012757:Sheep Diseases / Q000188:drug therapy*; D014251:Trichostrongyloidea / Q000187:drug effects*; D014252:Trichostrongyloidiasis / Q000662:veterinary*; D014253:Trichostrongylosis / Q000188:drug therapy / Q000662:veterinary
chemical_list: D001562:Benzimidazoles; D005273:Fenbendazole