Establishment and pathogenicity of two strains of Ostertagia ostertagi and Cooperia oncophora in calves in different locations.

An experiment was carried out simultaneously in Glasgow and in Wageningen to investigate possible differences between the local strains of Ostertagia ostertagi and Cooperia oncophora. In each location calves of the local Friesian breed were infected with 100,000 larvae of either the Glasgow or Wageningen strain of O ostertagi or C oncophora. At both locations the calves received the same diet. The Glasgow strain of O ostertagi was more pathogenic than the Wageningen strain and a larger proportion of the worm burden was found in the abomasal mucosa. The number of ova per female was greater in the Wageningen strain. For C oncophora the Wageningen strain gave rise to higher worm burdens and longer worms. Differences were also present between locations. The British Friesians had higher worm burdens of C oncophora and the worms of this species were longer in this host. Compared with the Dutch Friesians the British calves had a higher proportion of O ostertagi in the mucosa. This experiment showed how difficult it is to compare data from the literature because of differences in parasite and host strains and laboratory techniques.