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Home / Equine Research Bank / Parasitol Res / Critical tests evaluating efficacy of moxidectin against sma...
Parasitology research2010; 107(6); 1495-1498; doi: 10.1007/s00436-010-2025-5

Critical tests evaluating efficacy of moxidectin against small strongyles in horses from a herd for which reduced activity had been found in field tests in Central Kentucky.

Abstract: Critical tests were performed in 2009 and 2010 in four 2-year-old horses naturally infected with internal parasites. The horses were from a herd (Farm MC) where reduced activity of ivermectin and moxidectin on small strongyles was demonstrated previously from EPG (eggs/gram of feces) data in field tests. Also, in critical tests in horses from the same herd, ivermectin was less effective on immature small strongyles in the lumen of the large intestine than when the drug was first marketed. The main interest in the present critical tests was to determine the efficacy of moxidectin (400 μg/kg) on small strongyles. This was done to try and find indications of why there has been a return of strongyle EPG counts sooner after treatment in field tests than when moxidectin was first commercially available. Removal of adult small strongyles for the four treated horses was >99% to 100%. Efficacy on immature (L(4)) small strongyles was 82%, 96%, 98%, and >99% for the individual horses. Identification of small strongyles recovered from two of the horses revealed that three genera and 11 species were present. Specimens of Cylicocyclus ashworthi are reported for the first time in horses in Kentucky although eggs of this species have been identified. Moxidectin, in the present study, was excellent on removing adult small strongyles but was less effective on immatures (L(4)) in the intestinal contents. The question as to why moxidectin efficacy on small strongyles has declined in field tests may have been answered at least to a certain extent. It seems that a significant factor is "quick development" of a few remaining immatures in the gut lumen of horses. Also, possible activity may have decreased on encysted stages in the large intestinal lining. In any event, after treatment of some horses with moxidectin, the life cycle of small strongyles is shorter now than at the onset of usage of this compound.
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Publication Date: 2010-08-17 PubMed ID: 20714749DOI: 10.1007/s00436-010-2025-5Google Scholar: Lookup
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  • Journal Article
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  • Non-U.S. Gov't

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 investigated the effectiveness of the drug moxidectin in treating internal parasites in horses, with focus on small strongyles. Interesting outcomes suggests while moxidectin efficiently gets rid of adult small strongyles, it’s less effective on the immature versions of the parasite, possibly leading to early recurrence of infection.

Background

  • The study took place over 2009 and 2010 on four 2-year-old horses naturally infected with internal parasites. The horses were part of a herd, identified as Farm MC, in which earlier studies had shown reduced effectiveness of anti-parasitic drugs ivermectin and moxidectin against small strongyles.

Objectives

  • The aim of this research was to assess the efficacy of moxidectin on small strongyles in horses from the same herd where the reduced activity of the medicine had been previously discovered.
  • Another goal was to understand why there’s a quicker return of strongyle EPG (eggs per gram of feces) counts following treatment in field tests than when moxidectin was initially released into the market.

Key Findings

  • The study revealed that moxidectin was successful in eliminating adult small strongyles in the tested horses, featuring a removal rate ranging between 99% and 100%.
  • However, for immature small strongyles, the efficacy was less ranging between 82% and 99% across the different individual horses subjected to the tests.
  • The study resulted in the identification of three genera and 11 species of small strongyles from two of the horses. This included the identification of Cylicocyclus ashworthi in horses in Kentucky for the first time.

Conclusion and Implications

  • The study findings hint at why the effectiveness of moxidectin against small strongyles may have decreased over time. A significant influence seems to be the ‘quick development’ of a few residual immature strongyles inside the gut of horses. This suggests that post treatment, the lifecycle of small strongyles is shorter now than in the onset of usage of the drug.
  • Additionally, the research suggests that the efficacy of moxidectin might have also reduced on encysted stages in the large intestine lining. The implication being that more research is necessary to fully understand the decreased effectiveness of the drug and develop solutions to this issue.

Cite This Article

APA
Lyons ET, Tolliver SC, Kuzmina TA, Collins SS. (2010). Critical tests evaluating efficacy of moxidectin against small strongyles in horses from a herd for which reduced activity had been found in field tests in Central Kentucky. Parasitol Res, 107(6), 1495-1498. https://doi.org/10.1007/s00436-010-2025-5

Publication

Parasitology research
ISSN: 1432-1955
NlmUniqueID: 8703571
Country: Germany
Language: English
Volume: 107
Issue: 6
Pages: 1495-1498

Researcher Affiliations

Lyons, Eugene T
  • Department of Veterinary Science, Gluck Equine Research Center, University of Kentucky, Lexington, KY 40546-0099, USA. elyons1@uky.edu
Tolliver, Sharon C
    Kuzmina, Tetiana A
      Collins, Sandra S

        MeSH Terms

        • Animals
        • Anthelmintics / administration & dosage
        • Feces / parasitology
        • Horse Diseases / drug therapy
        • Horses
        • Kentucky
        • Macrolides / administration & dosage
        • Parasite Egg Count
        • Strongylida / classification
        • Strongylida / isolation & purification
        • Strongylida Infections / drug therapy
        • Strongylida Infections / veterinary
        • Strongyloidea / drug effects
        • Treatment Outcome

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        Citations

        This article has been cited 10 times.
        1. Bull KE, Allen KJ, Hodgkinson JE, Peachey LE. The first report of macrocyclic lactone resistant cyathostomins in the UK.. Int J Parasitol Drugs Drug Resist 2023 Apr;21:125-130.
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        5. Leathwick DM, Sauermann CW, Nielsen MK. Managing anthelmintic resistance in cyathostomin parasites: Investigating the benefits of refugia-based strategies.. Int J Parasitol Drugs Drug Resist 2019 Aug;10:118-124.
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