Oxfendazole: anthelmintic activity in sheep artificially infected with nematodes. Results of trials against nine species including benzimidazole-resistant Haemonchus contortus.

In a series of 11 trials, in which 281 lambs were artificially infected with 9 species of nematodes, larval anthelmintic tests were carried out to assess the activity of a dose of 5 mg/kg oxfendazole against all 3 parasitic stages of each species. An efficacy of over 99,4% was obtained against all stages of Haemonchus contortus, Ostertagia circumcincta, Trichostrongylus colubriformis, Nematodirus spathiger, Gaigeria pachyscelis, Chabertia ovina and Oesophagostomum columbianum with the exception of the third larval stage of O. Columbianum for which an efficacy of 93,5% was recorded. Against Dictyocaulus filaria efficacies against the fifth stages and adults, fourth larval and third larval stages were 99,8%, 92,0% and 37,5% respectively, and in two additional tests against the combined third and fourth larval stages, efficacies of 86,4% and 85,3% were recorded. Efficacy against Strongyloides papillosus was poor. In 2 supplementary experiments oxfendazole exhibited a 92,2--94,8% efficacy against adults of the Boshof benzimidazole-resistant strain of H. contortus, the highest activity so far recorded against the strain of any benzimidazole tested.