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International journal for parasitology. Drugs and drug resistance2023; 24; 100517; doi: 10.1016/j.ijpddr.2023.11.006

A national survey of anthelmintic resistance in ascarid and strongylid nematodes in Australian Thoroughbred horses.

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.
Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.
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Publication Date: 2023-11-29 PubMed ID: 38064906PubMed Central: PMC10757041DOI: 10.1016/j.ijpddr.2023.11.006Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research article discusses the toxicity of certain plants to horses, particularly when these plants are ingested by horses through contaminated feed. It highlights common plants in North America that potentially cause poisoning in these animals.

Introduction

The paper kicks off by emphasizing that many toxic plants are generally not appetizing to horses. These animals will avoid eating them as long as there are other forage options available. However, the key concern is when these plants inadvertently make their way into horse feeds, thus resulting in toxicity.

Feed Contamination and Equine Poisoning

  • The study explains how feed contamination happens and why it leads to equine plant poisonings. This is usually due to fierce competition within a herd and the improved taste of toxic plants once they have been processed into feeds. As a result, horses may unknowingly consume hazardous plant substances.

Toxic Plants

The researchers detail several plants known for their toxicity to horses:

  • Dehydropyrrolizidine alkaloid-containing plants: These are naturally occurring plant toxins that, when ingested, can cause liver disease and other serious health issues in horses.
  • Cocklebur plants: These contain a toxic principle, carboxyatractyloside, which can cause glucose deprivation in the brain and liver toxicity in horses.
  • Salvia reflexa: Also known as Mintweed, these contain tansy and camphor that are potentially toxic to horses.
  • Various saponin-containing grasses, such as kleingrass and switchgrass: Saponins in these grasses can cause bloat and other digestive issues in horses.
  • Tropane alkaloid-containing plants like jimson weed and black henbane: The toxic alkaloids found in these plants can affect the central nervous system of horses, leading to hallucinations and abnormal behavior.

Other Toxic Sources

  • Other dangerous substances for horses highlighted in the research include toxic components found in lantana, Cassia species, castor bean, cyanogenic glycoside-containing plants, thiaminase-containing plants, and hoary alyssum. All these plant varieties pose significant health threats to equines if ingested, especially in areas of North America where they are common.

Overall, the paper underscores the importance of careful feed and forage selection and proper pasture management to minimize the risks of equine plant poisonings. It underlines the need for collaborative efforts in research, monitoring, and public awareness to protect the health and wellbeing of horses.

Cite This Article

APA
Abbas G, Ghafar A, McConnell E, Beasley A, Bauquier J, Wilkes EJA, El-Hage C, Carrigan P, Cudmore L, Hurley J, Gauci CG, Beveridge I, Ling E, Jacobson C, Stevenson MA, Nielsen MK, Hughes KJ, Jabbar A. (2023). A national survey of anthelmintic resistance in ascarid and strongylid nematodes in Australian Thoroughbred horses. Int J Parasitol Drugs Drug Resist, 24, 100517. https://doi.org/10.1016/j.ijpddr.2023.11.006

Publication

International journal for parasitology. Drugs and drug resistance
ISSN: 2211-3207
NlmUniqueID: 101576715
Country: Netherlands
Language: English
Volume: 24
Pages: 100517

Researcher Affiliations

Abbas, Ghazanfar
  • Melbourne Veterinary School, The University of Melbourne, Werribee, Victoria 3030, Australia.
Ghafar, Abdul
  • Melbourne Veterinary School, The University of Melbourne, Werribee, Victoria 3030, Australia.
McConnell, Emma
  • Centre for Animal Production and Health, Murdoch University, Murdoch, Western Australia, Australia.
Beasley, Anne
  • School of Agriculture and Food Sustainability, University of Queensland, Gatton, Queensland 4343, Australia.
Bauquier, Jenni
  • Melbourne Veterinary School, The University of Melbourne, Werribee, Victoria 3030, Australia.
Wilkes, Edwina J A
  • Racing Victoria, Flemington, Victoria 3031, Australia.
El-Hage, Charles
  • Melbourne Veterinary School, The University of Melbourne, Werribee, Victoria 3030, Australia.
Carrigan, Peter
  • Scone Equine Hospital, Scone, New South Wales 2337, Australia.
Cudmore, Lucy
  • Scone Equine Hospital, Scone, New South Wales 2337, Australia.
Hurley, John
  • Swettenham Stud, Nagambie, Victoria 3608, Australia.
Gauci, Charles G
  • Melbourne Veterinary School, The University of Melbourne, Werribee, Victoria 3030, Australia.
Beveridge, Ian
  • Melbourne Veterinary School, The University of Melbourne, Werribee, Victoria 3030, Australia.
Ling, Elysia
  • Melbourne Veterinary School, The University of Melbourne, Werribee, Victoria 3030, Australia.
Jacobson, Caroline
  • Centre for Animal Production and Health, Murdoch University, Murdoch, Western Australia, Australia.
Stevenson, Mark A
  • Melbourne Veterinary School, The University of Melbourne, Werribee, Victoria 3030, Australia.
Nielsen, Martin K
  • M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA.
Hughes, Kristopher J
  • School of Agricultural, Environmental and Veterinary Sciences, Charles Sturt University, Wagga Wagga, New South Wales 2650, Australia.
Jabbar, Abdul
  • Melbourne Veterinary School, The University of Melbourne, Werribee, Victoria 3030, Australia. Electronic address: jabbara@unimelb.edu.au.

MeSH Terms

  • Animals
  • Anthelmintics / pharmacology
  • Australia / epidemiology
  • Bayes Theorem
  • Drug Resistance
  • Feces / parasitology
  • Horse Diseases / drug therapy
  • Horse Diseases / parasitology
  • Horses
  • Parasite Egg Count / veterinary
  • Strongyloidea / genetics

Conflict of Interest Statement

Declaration of competing interest The authors of this manuscript are members of the Australian Equine Parasitology Advisory Panel (AEPAP), including Abdul Jabbar, Ghazanfar Abbas, Jenni Bauquier, Charles El-Hage, Abdul Ghafar and Ian Beveridge (The University of Melbourne), Anne Beasley (University of Queensland), Kristopher Hughes (Charles Sturt University), Caroline Jacobson and Emma McConnell (Murdoch University), Edwina Wilkes (Racing Victoria), Peter Carrigan and Lucy Cudmore (Scone Equine Hospital) and John Hurley (Swettenham Stud). Boehringer Ingelheim supported the panel. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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