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Veterinary parasitology2011; 185(1); 9-15; doi: 10.1016/j.vetpar.2011.10.009

Anthelmintic resistance in non-strongylid parasites of horses.

Abstract: Since 2002, selected populations of Parascaris equorum in several countries have been reported to survive treatment with macrocyclic lactone (M/L) anthelmintics. Clinical treatment failures are characterized by negligible fecal egg count reduction, but M/L resistance has been confirmed in ascarids by controlled efficacy testing. Resistance was selected by current parasite control practices for foals, which often include exclusive and excessively frequent use of M/L dewormers, thereby minimizing refugia within the host and in the environment. Chemical control of M/L-resistant isolates can be accomplished with pyrimidine and/or benzimidazole anthelmintics, but a few M/L-resistant populations have recently exhibited resistance to pyrantel pamoate as well. Some specimens of Oxyuris equi regularly survive treatment with macrocyclic lactones, but it is uncertain whether this constitutes resistance or merely confirms the incomplete oxyuricidal efficacy of virtually all broad spectrum equine anthelmintics. Variations in other biological parameters of Oxyuris and Parascaris, specifically atypical infection of older hosts and shorter prepatent periods, have been reported anecdotally. These changes may represent genetic modifications that have evolved in parallel with resistance as a result of anthelmintic selection pressure.
Copyright © 2011 Elsevier B.V. All rights reserved.
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Publication Date: 2011-10-18 PubMed ID: 22078748DOI: 10.1016/j.vetpar.2011.10.009Google 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 discusses the emerging treatment resistance to some deworming drugs within specific horse parasite populations, specifically the Parascaris equorum and Oxyuris equi. Solutions to the resistance related issues and probable causes are also examined in the study.

Study Objective and Methodology

  • The study aimed to examine and report the growing resistance of certain horse parasitic species (Parascaris equorum and Oxyuris equi) towards macrocyclic lactone anthelmintics.
  • By evaluating selected populations of these parasites from different countries since 2002, the researchers gathered evidence and data on resistance development in these species.
  • The explicit signs of resistance were identified as a virtually unchanged fecal egg count reduction post-treatment.
  • Effects of current parasite control practices, notably the overuse of M/L dewormers, on the development of resistance were also investigated.

Key Findings

  • Confirmed macrocyclic lactone resistance was found in Parascaris equorum. This resistance stems from the frequent use of macrocyclic lactone dewormers, reducing refugia in both the host and its environment.
  • While other classes of anthelmintics like pyrimidines and benzimidazoles were found effective against M/L-resistant isolates, isolated populations exhibited resistance to these and other drugs like pyrantel pamoate.
  • Oxyuris equi were sometimes found to survive post macrocyclic lactone treatment, although the researchers could not confirm if it constituted resistance or merely showed the incomplete efficacy of broad-spectrum anthelmintics on this particular parasite.

Implications

  • There could be genetic modifications happening in these parasites in synchronization with resistance development given the observed anomalies like infection in older hosts and shorter prepatent periods. These could be a result of the significant pressures applied to these parasites in the form of anthelmintics.
  • The overuse of certain dewormers may contribute to the development of treatment resistance by these parasites.
  • While alternative drug treatments are found effective, there is a concern about the parasites developing resistance to these over time if not used properly.

Cite This Article

APA
Reinemeyer CR. (2011). Anthelmintic resistance in non-strongylid parasites of horses. Vet Parasitol, 185(1), 9-15. https://doi.org/10.1016/j.vetpar.2011.10.009

Publication

Veterinary parasitology
ISSN: 1873-2550
NlmUniqueID: 7602745
Country: Netherlands
Language: English
Volume: 185
Issue: 1
Pages: 9-15

Researcher Affiliations

Reinemeyer, Craig R
  • East Tennessee Clinical Research, Inc., Rockwood, TN 37854, USA. crr@easttenncr.com

MeSH Terms

  • Animals
  • Anthelmintics / pharmacology
  • Anthelmintics / therapeutic use
  • Ascaridida / drug effects
  • Ascaridida Infections / drug therapy
  • Ascaridida Infections / prevention & control
  • Ascaridida Infections / veterinary
  • Drug Resistance, Multiple
  • Horse Diseases / drug therapy
  • Horse Diseases / parasitology
  • Horse Diseases / prevention & control
  • Horses

Citations

This article has been cited 15 times.
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