Efficacy of closantel against ivermectin- and fenbendazole-resistant Haemonchus sp. in sheep in Ontario, Canada.

摘要: In Ontario, Canada, widespread resistance to ivermectin and fenbendazole, the only readily available ovine anthelmintics, has been documented, primarily in Haemonchus sp. other parts of world, closantel used control such infections; however, drug was not currently licensed for use Canada USA. A randomized controlled trial conducted on six client-owned farms Ontario 2013 2014 determine efficacy (Flukiver® 5% Oral Suspension, Elanco Animal Health, 10mg/kg bodyweight) against ivermectin- fenbendazole-resistant infections periparturient ewes grazing lambs. Three were randomly assigned treat all ewes, three selectively individual at lambing, using predetermined criteria. Fecal samples collected from a minimum 15 selected 13 lambs per group each farm time treatment approximately 14days later. Trichostrongyle-type fecal egg counts (FEC) performed modified McMaster technique with lower detection limit 8.3 eggs gram feces (epg). Haemonchus-specific FECs determined by multiplying proportion identified coproculture farm; FEC reductions calculated farm. Twenty had monthly, when mean monthly surpassed 200 epg, allocated either closantel, positive (ivermectin, or levamisole) negative groups. Pre-treatment ranged 27 3359 epg 0-5698 Efficacy 99% (95% CI: 97%-99%) 100% recently lambed both years (total n=274 ewes), 98%-99%) but one n=171 lambs). On latter farm, whole flock treated 84% (95%CI: 81%-88%) first year, second year. Levamisole effective overall GIN two farms. Ivermectin fenbendazole continued be present, particularly Closantel excellent over year study period, regardless group, therefore should considered viable component sustainable integrated parasite programs documented anthelmintic problems haemonchosis.