A survey of macrocyclic lactone efficacy in Australian cyathostomin populations.
Abstract: The macrocyclic lactone (ML) drugs are central to the control of equine strongyles but recent international reports raise concerns about reduced efficacy of these drugs against cyathostomins. The objectives of the present study were firstly, to evaluate the efficacy of ML drugs against cyathostomins on a cross-section of Australian horse farms, and secondly, to determine the egg reappearance period (ERP) following treatment of horses with MLs. A total of 419 horses on 43 properties were treated orally with ivermectin, abamectin or moxidectin, at recommended dose rates and drug efficacy was determined using the faecal egg count reduction test. Efficacy of 100% at 14days post-treatment was reported on all of the 43 farms. ERP following ivermectin treatment was 6weeks on two properties and ERP following moxidectin treatment was 12weeks on a third property. These ERPs are shorter than those reported at the time of commercial release of these drugs which likely reflects changing drug susceptibility of the cyathostomin populations tested. Ongoing surveillance of drug efficacy and ERPs should be part of an integrated management approach to equine worm control that prioritises the preservation of anthelmintic efficacy.
Copyright © 2017 Elsevier B.V. All rights reserved.
Publication Date: 2017-03-21 PubMed ID: 31014629DOI: 10.1016/j.vprsr.2017.03.009Google Scholar: Lookup
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- Journal Article
Summary
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This study investigates the efficiency of macrocyclic lactone (ML) drugs in controlling horse roundworms in Australia, as well as the time it takes for worm eggs to reappear after treatment. The study shows high initial drug efficacy but shortest egg reappearance times, indicating possible drug resistance development in these worm populations.
Objective and Methodology
The study aims to:
- Determine the efficacy of ML drugs against horse roundworms or cyathostomins across various horse farms in Australia.
- Establish the egg reappearance period (ERP) after treatment with ML drugs.
The researchers treated a total of 419 horses on 43 properties with ivermectin, abamectin, or moxidectin, all of which are common ML drugs. They gauged drug efficiency using the faecal egg count reduction test, a standard test for assessing anthelminthic (worm drug) effectiveness.
Results
- All 43 farms reported 100% drug efficacy 14 days after treatment.
- ERP following ivermectin treatment was six weeks on two properties.
- ERP after treatment with moxidectin was 12 weeks on another property.
These ERP times are shorter compared to when the drugs were initially launched, indicating the possible development of drug resistance among the worm populations tested.
Implications
- The study highlights the potential problem of increasing drug resistance among worm populations, as indicated by the shorter ERPs.
- In order to maintain the effectiveness of these worm drugs, ongoing drug efficacy and ERP monitoring should be integrated into a broader horse worm control programme.
- Such a program would focus on preserving the efficacy of anti-worm drugs, ensuring the optimal health of horses, and reducing the chance of drug-resistant worm populations developing.
Cite This Article
APA
Beasley AM, Kotze AC, Allen K, Coleman GT.
(2017).
A survey of macrocyclic lactone efficacy in Australian cyathostomin populations.
Vet Parasitol Reg Stud Reports, 8, 127-132.
https://doi.org/10.1016/j.vprsr.2017.03.009 Publication
Researcher Affiliations
- School of Veterinary Science, The University of Queensland, Gatton, QLD 4343, Australia. Electronic address: a.beasley@uq.edu.au.
- CSIRO Agriculture and Food, Queensland Bioscience Precinct, St Lucia, QLD, Australia.
- School of Veterinary Science, The University of Queensland, Gatton, QLD 4343, Australia.
- School of Veterinary Science, The University of Queensland, Gatton, QLD 4343, Australia.
Citations
This article has been cited 4 times.- Macdonald SL, Abbas G, Ghafar A, Gauci CG, Bauquier J, El-Hage C, Tennent-Brown B, Wilkes EJA, Beasley A, Jacobson C, Cudmore L, Carrigan P, Hurley J, Beveridge I, Hughes KJ, Nielsen MK, Jabbar A. Egg reappearance periods of anthelmintics against equine cyathostomins: The state of play revisited.. Int J Parasitol Drugs Drug Resist 2023 Apr;21:28-39.
- Ghafar A, Abbas G, King J, Jacobson C, Hughes KJ, El-Hage C, Beasley A, Bauquier J, Wilkes EJA, Hurley J, Cudmore L, Carrigan P, Tennent-Brown B, Nielsen MK, Gauci CG, Beveridge I, Jabbar A. Comparative studies on faecal egg counting techniques used for the detection of gastrointestinal parasites of equines: A systematic review.. Curr Res Parasitol Vector Borne Dis 2021;1:100046.
- Abbas G, Ghafar A, Hurley J, Bauquier J, Beasley A, Wilkes EJA, Jacobson C, El-Hage C, Cudmore L, Carrigan P, Tennent-Brown B, Gauci CG, Nielsen MK, Hughes KJ, Beveridge I, Jabbar A. Cyathostomin resistance to moxidectin and combinations of anthelmintics in Australian horses.. Parasit Vectors 2021 Dec 4;14(1):597.
- Saeed MA, Beveridge I, Abbas G, Beasley A, Bauquier J, Wilkes E, Jacobson C, Hughes KJ, El-Hage C, O'Handley R, Hurley J, Cudmore L, Carrigan P, Walter L, Tennent-Brown B, Nielsen MK, Jabbar A. Systematic review of gastrointestinal nematodes of horses from Australia.. Parasit Vectors 2019 Apr 29;12(1):188.
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