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Anthelmintic resistance in ovine gastrointestinal nematodes in inland southern Q ueensland
Author(s) -
LyndalMurphy M,
Ehrlich WK,
Mayer DG
Publication year - 2014
Publication title -
australian veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.382
H-Index - 59
eISSN - 1751-0813
pISSN - 0005-0423
DOI - 10.1111/avj.12250
Subject(s) - moxidectin , anthelmintic , levamisole , veterinary medicine , biology , abamectin , haemonchus contortus , drug resistance , helminths , zoology , medicine , agronomy , pesticide , immunology , microbiology and biotechnology
Objective To establish the prevalence of anthelmintic resistance in ovine gastrointestinal nematodes in southern Q ueensland. 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 H aemonchus contortus was the predominant species. Efficacy <95% was recorded on 85% of farms for one or more anthelmintics and on 10% of farms for six anthelmintics. No resistance was identified on three farms. The 4‐way combination product was efficacious (n = 4 farms). Napthalophos resistance was detected on one farm only. Resistance to levamisole (42% of farms), moxidectin injection (50% of farms) and the closantel/abamectin combination (67% of farms) was identified. Moxidectin oral was efficacious against T richostrongylus colubriformis , which was predominant on only one farm. Of the farms tested, 55% ran meat breeds, 60% dosed more than the recommended dose rate and 70% always, mostly or when possible practised a ‘drench and move’ strategy. Conclusion This level of anthelmintic resistance in southern Q ueensland will severely compromise worm control and force increased use of monepantel.