[Benzimidazole resistant Ostertagia circumcincta in Angora goats]

Angora goat kids from the eastern Cape Province with natural infestations of Ostertagia circumcincta, Nematodirus spathiger, and Trichostrongylus rugatus were treated with albendazole, fenbendazole or morantel citrate, while a fourth group remained an untreated control group. The benzimidazoles were less than or equal to 50% effective against O. circumcincta, and approximately 50% effective against possibly resistant fourth larval stage N. spathiger. To confirm the diagnosis of anthelmintic resistance in the O. circumcincta, infective larvae (L3) were cultured from the faeces of the kids prior to treatment, and passaged through a donor sheep. Thereafter 2 groups each of sheep and goats were infested artificially with these parasites, and one group of each animal species was drenched with albendazole at 4.75 mg kg-1 in a second trial. The remaining groups were kept as untreated controls. This treatment was less than 5% effective in both sheep and goats, confirming the resistance of this isolate of O. circumcincta to benzimidazoles in both host species.