AUSMECTIN® SHEEP DRENCH contains ivermectin, a member of the macrocyclic lactone class of chemicals, which has a unique mode of action. It acts selectively in invertebrate nerve and muscle cells resulting in paralysis and death of the parasite. Therefore, AUSMECTIN® SHEEP DRENCH has been used for the control and treatment of ivermectin-sensitive gastrointestinal roundworms in sheep, including benzimidazole, levamisole and morantel resistant strains of Haemonchus contortus, Ostertagia circumcincta and Trichostrongylus colubriformis. It is also effective against lungworm (Dictyocaulus filaria), itchmite (Psorergates ovis) and all parasitic larval stages of nasal bot (Oestrus ovis) in sheep. Ivermectin has a long intrinsic half-life, which provides excellent residual protection against parasitic reinfestation for a varying period depending on the target parasite.