Studies on haemonchus contortus. VII. The effect of treatment of Trichostrongylus axei prior to challenge with H. contortus.

Four-month-old worm-free Merino lambs were dosed with 20 000 infective larvae of Trichostrongylus axei on Day 0 and again on Day +14. On Day +83 they were treated with mebendazole at 15 mg/kg. All lambs in this group and a further group of 11 worm-free Merino control lambs were challenged with 50 000 infective larvae of Haemonchus contortus dosed from Day +90-Day +92. At necropsy 27 and 28 days later there was no significant difference between the worm burdens of the 2 groups. T. axei must be present in the abomasum to protect sheep from challenge with H. contortus.