Nematodirus of domestic sheep, Ovis aries, in the United States with a key to the species.
D000818:Animals; D009348:Nematoda / Q000033:anatomy & histology / Q000145:classification*; D009349:Nematode Infections / Q000453:epidemiology / Q000662:veterinary*; D012756:Sheep; D012757:Sheep Diseases / Q000453:epidemiology*; D014481:United States