Resistance of Libyostrongylus douglassi in ostriches to levamisole.

: While fenbendazole at 15 mg kg-1 either alone or in combination with resorantel reduced the total burden of Libyostrongylus douglassi by more than 98%, levamisole alone at 30 mg kg-1 was only 28% effective, and in combination with resorantel its efficacy was 67%. These results with levamisole do not correspond with the registered rate of efficacy which is given as at least 80% in South Africa. This is apparently the first reported case of anthelmintic resistance in ostriches.