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International journal for parasitology. Drugs and drug resistance2019; 12; 28-34; doi: 10.1016/j.ijpddr.2019.12.002

Dealing with double trouble: Combination deworming against double-drug resistant cyathostomins.

Abstract: An alternative control regimen for drug-resistant parasites is combination deworming, where two drugs with different modes of action are administered simultaneously to target the same parasite. Few studies have investigated this in equine cyathostomins. We previously reported that an oxibendazole (OBZ) and pyrantel pamoate (PYR) combination was not sustainable against a cyathostomin population with high levels of OBZ and PYR resistance. This study consisted of a field study and two computer simulations to evaluate the efficacy of a moxidectin-oxibendazole (MOX-OBZ) combination against the same cyathostomin population. In the field study, anthelmintic treatments occurred when ten horses exceeded 100 eggs per gram. Fecal egg counts and efficacy evaluations were performed every two weeks. The two simulations utilized weather data as well as equine and parasite population parameters from the field study. The first simulation repeated the treatment schedule used in the field study over a 40 year period. The second evaluated efficacies of combination treatments using selective therapy over 40 years. In the field study, efficacies of MOX and both combination treatments were 100%. The egg reappearance period for MOX was 16 weeks, and the two combination treatments were 12 and 18 weeks. The first (46.7%) and last (40.1%) OBZ efficacies were not significantly different from each other. In the simulation study, the combination treatment delayed MOX resistance development compared to when MOX was used as a single active. This occurred despite the low efficacy of OBZ. The second set of simulations identified combination treatments used with selective therapy to be the most effective at delaying MOX resistance. Overall, this study supports the use of combination treatment against drug-resistant cyathostomins, when one of the actives exhibits high efficacy, and demonstrates benefits of this approach despite substantially lowered efficacy of the other active ingredient.
Copyright © 2019. Published by Elsevier Ltd.
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Publication Date: 2019-12-16 PubMed ID: 31883485PubMed Central: PMC7139983DOI: 10.1016/j.ijpddr.2019.12.002Google 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 how drug-resistant parasites in horses are being tackled by combining two drugs simultaneously. A field study and computer simulations show a moxidectin-oxibendazole combination’s effectiveness on a specific parasite population. Despite the low efficacy of one component, the combination treatment was able to delay resistance development.

Introduction

  • The subject of this research is the efficacy of combination deworming against drug-resistant cyathostomins in horses. Cyathostomins, or small strongyles, are common gastrointestinal parasites in horses that are increasingly showing resistance to common anthelmintics or dewormers.
  • Combination deworming is an alternative control regimen for drug-resistant parasites. This involves the simultaneous administration of two drugs with different modes of action targeting the same parasite.

Study Design

  • The study is divided into a field study and two different computer simulations to evaluate the efficacy of a moxidectin-oxibendazole (MOX-OBZ) combination against a parasite population known to exhibit high levels of resistance.
  • The field study involved monitoring a group of horses, with anthelmintic treatments being administered when fecal egg counts exceeded a certain limit.
  • The two computer simulations utilized weather data as well as equine and parasite population parameters from the field study. They aimed to project the impact of the treatment schedule and evaluate the efficacy of combination treatments over a 40-year period.

Results

  • The field study found that the efficacy of MOX and the two combination treatments were 100%. The egg reappearance period, or the time before eggs are detected in the feces again after treatment, differed for MOX and the combinations.
  • The simulation study concluded that the combination treatment could delay the development of resistance to MOX as compared to when MOX was used as a standalone treatment. This was the case even when the efficacy of oxibendazole (OBZ), the other drug in the combination, was low.

Conclusions

  • The study supports the use of combination treatments against drug-resistant cyathostomins, even when one of the two drugs used has a significantly lower efficacy.
  • By combining drugs, there is a valuable delay in resistance development, providing more time for alternative treatment strategies to be devised.

Cite This Article

APA
Scare JA, Leathwick DM, Sauermann CW, Lyons ET, Steuer AE, Jones BA, Clark M, Nielsen MK. (2019). Dealing with double trouble: Combination deworming against double-drug resistant cyathostomins. Int J Parasitol Drugs Drug Resist, 12, 28-34. https://doi.org/10.1016/j.ijpddr.2019.12.002

Publication

International journal for parasitology. Drugs and drug resistance
ISSN: 2211-3207
NlmUniqueID: 101576715
Country: Netherlands
Language: English
Volume: 12
Pages: 28-34
PII: S2211-3207(19)30146-0

Researcher Affiliations

Scare, J A
  • M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA. Electronic address: jscare.kenealy@gmail.com.
Leathwick, D M
  • AgResearch, Grasslands Research Centre, Private Bag 11008, Palmerston North, 4442, New Zealand.
Sauermann, C W
  • AgResearch, Grasslands Research Centre, Private Bag 11008, Palmerston North, 4442, New Zealand.
Lyons, E T
  • M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA.
Steuer, A E
  • M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA.
Jones, B A
  • College of Veterinary Medicine, Lincoln Memorial University, Harrogate, TN, USA.
Clark, M
  • College of Veterinary Medicine, Lincoln Memorial University, Harrogate, TN, USA.
Nielsen, M K
  • M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA.

MeSH Terms

  • Animals
  • Anthelmintics / therapeutic use
  • Benzimidazoles / therapeutic use
  • Drug Resistance
  • Drug Therapy, Combination
  • Feces / parasitology
  • Female
  • Horse Diseases / drug therapy
  • Horse Diseases / parasitology
  • Horses
  • Macrolides / therapeutic use
  • Parasite Egg Count / veterinary
  • Strongyle Infections, Equine / drug therapy

Conflict of Interest Statement

Declaration of competing interest The authors declare no conflicts of interest.

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Citations

This article has been cited 7 times.
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