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Veterinary parasitology2013; 204(1-2); 44-54; doi: 10.1016/j.vetpar.2013.12.022

The management of anthelmintic resistance in grazing ruminants in Australasia–strategies and experiences.

Abstract: In many countries the presence of anthelmintic resistance in nematodes of small ruminants, and in some cases also in those infecting cattle and horses, has become the status quo rather than the exception. It is clear that consideration of anthelmintic resistance, and its management, should be an integral component of anthelmintic use regardless of country or host species. Many years of research into understanding the development and management of anthelmintic resistance in nematodes of small ruminants has resulted in an array of strategies for minimising selection for resistance and for dealing with it once it has developed. Importantly, many of these strategies are now supported by empirical science and some have been assessed and evaluated on commercial farms. In sheep the cost of resistance has been measured at about 10% of the value of the lamb at sale which means that losses due to undetected resistance far outweigh the cost of testing anthelmintic efficacy. Despite this many farmers still do not test for anthelmintic resistance on their farm. Many resistance management strategies have been developed and some of these have been tailored for specific environments and/or nematode species. However, in general, most strategies can be categorised as either; identify and mitigate high risk management practices, maintain an anthelmintic-susceptible population in refugia, choose the optimal anthelmintic (combinations and formulations), or prevent the introduction of resistant nematodes. Experiences with sheep farmers in both New Zealand and Australia indicate that acceptance and implementation of resistance management practices is relatively easy as long as the need to do so is clear and the recommended practices meet the farmer's criteria for practicality. A major difference between Australasia and many other countries is the availability and widespread acceptance of combination anthelmintics as a resistance management tool. The current situation in cattle and horses in many countries indicates a failure to learn the lessons from resistance development in small ruminants. The cattle and equine industries have, until quite recently, remained generally oblivious to the issue of anthelmintic resistance and the need to take pre-emptive action. In Australasia, as in other countries, a perception was held that resistance in cattle parasites would develop very slowly, if it developed at all. Such preconceptions are clearly incorrect and the challenge ahead for the cattle and equine industries will be to maximise the advantages for resistance management from the extensive body of research and experience gained in small ruminants.
Copyright © 2014 Elsevier B.V. All rights reserved.
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Publication Date: 2013-12-31 PubMed ID: 24439840DOI: 10.1016/j.vetpar.2013.12.022Google 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.

This research paper addresses the growing problem of anthelmintic resistance in nematodes of small ruminants, and also in those infecting cattle and horses. Various strategies for controlling and managing the resistance, which are often supported by empirical science, have been discussed and evaluated.

Understanding Anthelmintic Resistance

An integral part of using anthelmintics, irrespective of the country or host species, is considering and managing anthelmintic resistance. The research provides insights into the development and management of anthelmintic resistance in nematodes that infect small ruminants.

  • Anthelmintic resistance occurs when parasites no longer respond effectively to a class of drugs (anthelmintics) designed to eliminate them.
  • The study reveals the grim reality that in many countries, the existence of anthelmintic resistance has now become a norm rather than an exception.

Cost of Resistance and Testing

The cost associated with anthelmintic resistance has been quantified in the study.

  • In sheep farming, it is estimated that resistance costs close to 10% of the value at the time of sale of the lamb. Consequently, losses incurred due to undetected resistance outweigh the expenditure of testing anthelmintic efficacy.
  • Despite the apparent financial benefits of testing, many farmers are not doing so on their farms.

Resistance Management Strategies

The research presents a set of strategies formulated over the years for mitigating the selection for resistance and for addressing it once it is detected.

  • While some strategies are specifically designed for distinct environments or nematode species, most can be grouped under the following categories: identifying and mitigating high-risk management practices, maintaining an anthelmintic-susceptible population in refugia, selecting the optimal anthelmintic (formulations and combinations), and preventing the introduction of resistant nematodes.
  • The adoption of these resistance management strategies is considered to be fairly straightforward for sheep farmers in both New Zealand and Australia, particularly when the necessity is evident and the suggested strategies are practical.
  • In Australasia, a distinguishing factor from most other countries is the extensive acceptance and availability of anthelmintic combinations as a tool for managing resistance.

Lessons for Cattle and Equine Industries

Insights from the observation of resistance development in small ruminants provide a cautionary tale for the cattle and equine industries.

  • The research indicates that these industries have largely been ignorant about the issue of anthelmintic resistance, hence the pressing need for preventive measures.
  • A misconception existed in Australasia and other countries that resistance in cattle parasites would evolve slowly, if at all. This assumption has been proven incorrect by the study.
  • The challenge moving forward is for these industries to maximize the benefits for resistance management based on the wealth of research and experience gained in managing resistance in small ruminants.

Cite This Article

APA
Leathwick DM, Besier RB. (2013). The management of anthelmintic resistance in grazing ruminants in Australasia–strategies and experiences. Vet Parasitol, 204(1-2), 44-54. https://doi.org/10.1016/j.vetpar.2013.12.022

Publication

Veterinary parasitology
ISSN: 1873-2550
NlmUniqueID: 7602745
Country: Netherlands
Language: English
Volume: 204
Issue: 1-2
Pages: 44-54

Researcher Affiliations

Leathwick, D M
  • AgResearch, Grasslands Research Centre, Private Bag 11008, Palmerston North 4442, New Zealand. Electronic address: dave.leathwick@agresearch.co.nz.
Besier, R B
  • Department of Agriculture and Food Western Australia, 444 Albany Highway, Albany, WA 6330, Australia.

MeSH Terms

  • Animal Husbandry
  • Animals
  • Anthelmintics / therapeutic use
  • Australasia
  • Drug Resistance
  • Helminthiasis, Animal / drug therapy
  • Nematode Infections / drug therapy
  • Nematode Infections / veterinary
  • Ruminants / parasitology

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