Efficacy of ivermectin against five genera of swine nematodes and the hog louse, Haematopinus suis.

Twenty pigs sequentially infected with Oesophagostomum spp, Metastrongylus spp, and Trichuris suis, and maintained on lots contaminated with Ascaris suum and Strongyloides ransomi, were assigned to 1 of 4 groups on the basis of weight, sex, and litter. Each group of pigs was given ivermectin subcutaneously at the rate of 0, 20, 100, or 500 microgram/kg of body weight. Lice on pigs were counted before treatment, on posttreatment day 1, and just before necropsy. Pigs were necropsied on posttreatment day 6 or 7, and worms were recovered and counted. Efficacies were: 0% to 100% against A suum; 66% to 100% against S ransomi; 99.4% to 99.9% against Metastrongylus spp; 0% against T suis; 3.2% to 635 against adult Oesophagostomum spp; 61.7% to 87.9% against immature Oesophagostomum spp; and 99% to 100% against Haematopinus suis.