title: Nematode parasitism in sheep in north-east England: the epidemiology of Ostertagia species.
mesh_terms: D000818:Animals; D004739:England; D007814:Larva; D010029:Ostertagiasis / Q000453:epidemiology / Q000469:parasitology / Q000662:veterinary*; D012621:Seasons; D012756:Sheep; D012757:Sheep Diseases / Q000453:epidemiology* / Q000469:parasitology; D014251:Trichostrongyloidea / Q000254:growth & development; D014252:Trichostrongyloidiasis / Q000662:veterinary*