Studies on Haemonchus contortus. IV. The effect of Trichostrongylus axei and Ostertagia circumcincta on challenge with H. contortus.

Worm-free Merino yearlings were dosed with either a mixture of infective larvae of Trichostrongylus axei and Ostertagia circumcincta or with O. circumcincta only, and challenged 90-93 days later with infective larvae of Haemonchus contortus. Neither of these methods protected sheep against challenged and slight protection was afforded sheep predosed with T. axei and O. circumcincta and challenged with a trickle dose of H. contortus.