Experimental cross-infections with gastrointestinal nematodes of sheep and cattle.

Five parasite-free lambs and five parasite-free calves were infected experimentally with 20,000 third stage gastrointestinal nematode larvae cultured from faeces of sheep from five different farms. In the same way five lambs and five calves were infected with larvae cultured from faeces of calves from five different farms. Host specificity of the nematodes was determined using the following parameters: infection rate; number, size, and stage of the worms; their distribution within the gastrointestinal tract; and the onset, duration, and level of egg production. The conclusions with regard to the different species are: Almost exclusively in cattle Skrjabinagia lyrata Strongly adapted to cattle Ostertagia ostertagi More adapted to cattle than to sheep Cooperia oncophora, C. surnabada, C. punctata, Trichostrongylus longispicularis No special host preference T. axei, O. leptospicularis, S. kolchida More adapted to sheep than to cattle C. curticei, T. vitrinus, T. colubriformis, O. trifurcata, Teladorsagia davtiani, Haemonchus contortus, Strongyloides papillosus Strongly adapted to sheep O. circumcincta, Oesophagostomum venulosum, Almost exclusively in sheep Chabertia ovina.