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Journal article
A national survey of anthelmintic resistance in ascarid and strongylid nematodes in Australian Thoroughbred horses
International journal for parasitology -- drugs and drug resistance, Vol.24, 100517
2023
PMID: 38064906
Abstract
This study quantified the extent of anthelmintic resistance (AR) in ascarid and strongylid nematodes against commonly used anthelmintics in Australian Thoroughbred horses. Faecal egg count reduction tests (FECRTs, n = 86) and egg reappearance period (ERP) tests were conducted on 22 farms across Australia. Faecal egg counts (FECs) were determined using the modified McMaster technique, and percent faecal egg count reduction (%FECR) was calculated using the Bayesian hierarchical model and hybrid Frequentist/Bayesian analysis method. The results were interpreted using old (published in 1992) and new (2023) research guidelines of the World Association for the Advancement of Veterinary Parasitology (WAAVP). The species composition of strongylid nematodes was detected utilising a DNA-metabarcoding method using pre- and post-treatment samples. Resistance was observed in strongylid nematodes to commonly used single-active and combination anthelmintics, including ivermectin (IVM %FECR range: 82%-92%; 95% lower credible interval (LCI) range: 80%-90%), abamectin (ABM: 73%-92%; 65%-88%), moxidectin (MOX: 89%-91%; 84%-89%), oxfendazole (OFZ: 0%-56%; 0%-31%) and its combination with pyrantel (OFZ + PYR: 0%-82%; 0%-78%). Resistance in Parascaris spp. was observed to IVM (10%-43%; 0%-36%), ABM (0%; 0%) and MOX (0%; 0%). When the new thresholds recommended by the WAAVP were used, AR was detected in six additional FECRTs for strongylids and three more tests for Parascaris spp., introducing resistance to OFZ and OFZ + PYR in the latter. Shortened ERPs (4-6 weeks) of strongylids were observed in 31 FECRTs in which AR was not detected at 2 weeks post-treatment for all the anthelmintics tested. Among cyathostomins, Cylicocyclus nassatus, Cylicostephanus longibursatus and Coronocyclus coronatus were the most prevalent species at 2 weeks post-treatment, whereas the main species appearing at five weeks following treatments with macrocyclic lactones were Cylicocyclus nassatus, Cylicostephanus longibursatus and Cylicocyclus ashworthi. After treatment with OFZ + PYR, the latter three, plus Coronocyclus coronatus and Cyathostomum catinatum, were detected at 5 weeks post-treatment. Overall, the study highlights the prevalence of AR in both ascarids and strongylid nematodes against commonly used anthelmintic products to control worms in Australian horses. The results indicate that ML combination products provided acceptable efficacy at 2 weeks. However, ERP calculations suggest that products work less effectively than previously measured. It is suggested to regularly monitor the efficacy of the anthelmintics and consider changing the worm control practices to better manage worms and AR in Australian horses.
Details
- Title
- A national survey of anthelmintic resistance in ascarid and strongylid nematodes in Australian Thoroughbred horses
- Authors/Creators
- Ghazanfar Abbas - The University of MelbourneAbdul Ghafar - The University of MelbourneEmma McConnell - Murdoch UniversityAnne Beasley - The University of QueenslandJenni Bauquier - The University of MelbourneEdwina J A Wilkes - Racing VictoriaCharles El-Hage - The University of MelbournePeter Carrigan - Scone Equine Hospital, Scone, New South Wales 2337, AustraliaLucy Cudmore - Scone Equine Hospital, Scone, New South Wales 2337, AustraliaJohn Hurley - Swettenham Stud, Nagambie, Victoria 3608, AustraliaCharles G Gauci - The University of MelbourneIan Beveridge - The University of MelbourneElysia Ling - The University of MelbourneCaroline Jacobson - Murdoch University, Centre for Animal Production and HealthMark A Stevenson - The University of MelbourneMartin K Nielsen - University of KentuckyKristopher J Hughes - Charles Sturt UniversityAbdul Jabbar - The University of Melbourne
- Publication Details
- International journal for parasitology -- drugs and drug resistance, Vol.24, 100517
- Publisher
- Elsevier Ltd on behalf of Australian Society for Parasitology
- Identifiers
- 991005623669207891
- Copyright
- © 2023 The Authors.
- Murdoch Affiliation
- Centre for Animal Production and Health
- Language
- English
- Resource Type
- Journal article
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