Anthelmintic resistance in ovine gastrointestinal nematodes in inland southern Queensland

OBJECTIVE: To establish the prevalence of anthelmintic resistance in ovine gastrointestinal nematodes in southern Queensland. DESIGN: An observational parasitological study using the faecal egg count reduction test. METHODS: Sheep farms (n = 20) enrolled in this study met the twin criteria of using worm testing for drench decisions and having concerns about anthelmintic efficacy. On each farm, 105 sheep were randomly allocated to one of six treatment groups or an untreated control group. Faecal samples were collected on day 0 and days 10–14 for worm egg counts and larval differentiation. Single‐ and multi‐combination anthelmintics, persistent and non‐persistent, oral liquid or capsule, pour‐on and injectable formulations were tested. Monepantel was not tested. Farmers also responded to a questionnaire on drenching practices. RESULTS: Haemonchus contortus was the predominant species. Efficacy