The effects of ivermectin and moxidectin on egg viability and larval development of ivermectin-resistant Haemonchus contortus

K.L. Tyrrell; R.J. Dobson; P.A. Stein; S.W. Walkden-Brown

doi:10.1016/S0304-4017(02)00092-4

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The effects of ivermectin and moxidectin on egg viability and larval development of ivermectin-resistant Haemonchus contortus

Journal article

Peer reviewed

The effects of ivermectin and moxidectin on egg viability and larval development of ivermectin-resistant Haemonchus contortus

K.L. Tyrrell, R.J. Dobson, P.A. Stein and S.W. Walkden-Brown

Veterinary Parasitology, Vol.107(1-2), pp.85-93

2002

DOI: https://doi.org/10.1016/S0304-4017(02)00092-4

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Abstract

The in vivo effects of ivermectin and moxidectin on egg viability and larval development of ivermectin-resistant Haemonchus contortus were examined over time after anthelmintic treatment of sheep. Twenty merino sheep, (12 months old) were allocated to five treatment groups and infected with ivermectin-resistant H. contortus. Thirty one days later, the sheep were treated with intraruminal ivermectin capsules, oral ivermectin, oral moxidectin or injectable moxidectin at the manufacturer's recommended dosages, or left untreated. At various times up to 112 days after treatment, faecal egg counts (FEC) were determined and development rates of infective larvae (L3) cultured in faeces or on agar were measured. Eggs in faecal cultures from ivermectin capsule treated sheep showed reduced L3 development percentages in comparison to faecal cultures from untreated sheep. Eggs from ivermectin capsule treated sheep, isolated from faeces, and cultured on agar showed similar L3 development to eggs from control sheep. These results demonstrate an inhibitory effect of excreted ivermectin in faeces on larval development of ivermectin-resistant H. contortus. L3 development in faecal culture from animals receiving oral ivermectin were reduced for only 3 days after treatment. Faecal egg counts and development of L3 larvae in both culture systems from moxidectin treated sheep were low, due to the high efficacy of the drug. Egg counts in moxidectin treated sheep were reduced by approximately 90% 24h after treatment, before decreasing to almost 100% at 48h, suggesting that the current quarantine recommendation of holding sheep off pasture for 24h after treatment may still lead to some subsequent pasture contamination with worm eggs.

Details

Title: The effects of ivermectin and moxidectin on egg viability and larval development of ivermectin-resistant Haemonchus contortus
Authors/Creators: K.L. Tyrrell (Author/Creator) - Commonwealth Scientific and Industrial Research Organisation
R.J. Dobson (Author/Creator) - Commonwealth Scientific and Industrial Research Organisation
P.A. Stein (Author/Creator) - Commonwealth Scientific and Industrial Research Organisation
S.W. Walkden-Brown (Author/Creator) - University of New England
Publication Details: Veterinary Parasitology, Vol.107(1-2), pp.85-93
Publisher: Elsevier BV
Identifiers: 991005544593007891
Copyright: © 2002 Elsevier Science B.V.
Murdoch Affiliation: School of Veterinary and Biomedical Sciences
Language: English
Resource Type: Journal article

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Collaboration types: Domestic collaboration
Citation topics: 1 Clinical & Life Sciences; 1.163 Parasitology - General; 1.163.1022 Anthelmintic Resistance
Web Of Science research areas: Parasitology; Veterinary Sciences
ESI research areas: Plant & Animal Science