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International journal for parasitology. Drugs and drug resistance2019; 10; 118-124; doi: 10.1016/j.ijpddr.2019.08.008

Managing anthelmintic resistance in cyathostomin parasites: Investigating the benefits of refugia-based strategies.

Abstract: Selective anthelmintic therapy has been recommended as a sustainable strategy for cyathostomin control in horse populations for several decades. The traditional approach has been to determine strongyle fecal egg counts (FEC) for all horses, with treatment only recommended for those exceeding a predetermined threshold. The aims are to achieve a reduction of overall egg shedding, while leaving a proportion of the herd untreated, which lowers anthelmintic treatment intensity and reduces selection pressure for development of anthelmintic resistance. This study made use of the cyathostomin model to evaluate the influence of treatment strategies with between 1 and 8 yearly treatment occasions, where either 1) all horses were treated, 2) a predetermined proportion of the herd remained untreated, or 3) horses were treated if their FEC exceeded thresholds between 100 and 600 strongyle eggs per gram. Weather data representing four different climatic zones was used and three different herd age structures were compared; 1) all yearlings, 2) all mature horses 10-20 years old, and 3) a mixed age structure of 1-20 years of age. Results indicated a consistent effect of age structure, with anthelmintic resistance developing quickest in the yearling group and slowest among the mature horses. Development of anthelmintic resistance was affected by treatment intensity and selective therapy generally delayed resistance. Importantly, the results suggest that the effects of selective therapy on resistance development are likely to vary between climatic zones and herd age structures. Overall, a substantial delaying of resistance development requires that the average number of treatments administered annually across a herd of horses needs to be about two or less. However, results also indicate that an age-structured prioritisation of treatment to younger horses should still be effective. It appears that a 'one-size-fits-all' approach to the management of anthelmintic resistance in cyathostomins is unlikely to be optimal.
Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.
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Publication Date: 2019-08-28 PubMed ID: 31491731PubMed Central: PMC6731328DOI: 10.1016/j.ijpddr.2019.08.008Google Scholar: Lookup
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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.

This research study assesses the impact of different treatment strategies on managing anthelmintic resistance in cyathostomin parasites. The study showed that factors such as climate, herd age, and treatment frequency influence resistance development, and no one method suits all situations.

Study Method

  • The researchers used a cyathostomin model to investigate the effects of various treatment strategies for horse populations affected by cyathostomin parasites. Commonly, anthelmintic therapy is administered to horses with strongyle fecal egg counts (FEC) above a certain threshold, leaving some of the population untreated, thereby reducing the likelihood of anthelmintic resistance.
  • The study assessed 1 to 8 yearly treatment strategies, where either all horses were treated, a part of the herd remained untreated, or horses were treated if their FEC exceeded thresholds between 100 and 600 eggs per gram.
  • Different climatic zones were accounted for by utilizing weather data from four distinct areas. The study also evaluated three age groups, including all yearlings, all mature horses aged 10-20, and a mixed age structure of horses aged 1-20 years.

Results and Findings

  • The study found that the development of anthelmintic resistance is influenced by the intensity of treatment and the age structure of the horse population. Resistance developed faster in the group of yearlings and slower among mature horses.
  • Across different climatic zones and herd age structures, selective therapy generally helped delay resistance, although the effect varies.
  • The results suggested, to significantly delay the development of resistance, the average number of treatments across a herd needs to be about two or fewer per year. An age-structured prioritisation of treatment, particularly focussing on younger horses, seems to be effective.
  • The study indicates that a ‘one-size-fits-all’ approach to managing anthelmintic resistance in cyathostomin parasites is unlikely to be the most effective strategy due to varying factors.

Study Implications

  • The findings highlight that multiple facets like climate, age structure of the herd, and treatment intensity must be considered when formulating strategies to manage anthelmintic resistance in cyathostomin-infected horse populations.
  • In conclusion, individualized plans based on the specific circumstances and conditions of each herd appear to be the key to successful and sustainable anthelmintic resistance management, rather than a singular, blanket approach.

Cite This Article

APA
Leathwick DM, Sauermann CW, Nielsen MK. (2019). Managing anthelmintic resistance in cyathostomin parasites: Investigating the benefits of refugia-based strategies. Int J Parasitol Drugs Drug Resist, 10, 118-124. https://doi.org/10.1016/j.ijpddr.2019.08.008

Publication

International journal for parasitology. Drugs and drug resistance
ISSN: 2211-3207
NlmUniqueID: 101576715
Country: Netherlands
Language: English
Volume: 10
Pages: 118-124

Researcher Affiliations

Leathwick, Dave M
  • AgResearch, Grasslands Research Centre, Private Bag 11008, Palmerston North, 4442, New Zealand. Electronic address: dave.leathwick@agresearch.co.nz.
Sauermann, Christian W
  • AgResearch, Grasslands Research Centre, Private Bag 11008, Palmerston North, 4442, New Zealand.
Nielsen, Martin K
  • M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA.

MeSH Terms

  • Age Factors
  • Animals
  • Anthelmintics / administration & dosage
  • Drug Resistance
  • Feces / parasitology
  • Female
  • Horses
  • Male
  • Parasite Egg Count
  • Refugium
  • Strongyle Infections, Equine / drug therapy
  • Strongyle Infections, Equine / parasitology
  • Strongylida / drug effects
  • Strongylida / physiology

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Citations

This article has been cited 10 times.
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