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Veterinary parasitology2013; 197(1-2); 189-196; doi: 10.1016/j.vetpar.2013.06.009

Anthelmintic efficacy against cyathostomins in horses in Southern England.

Abstract: Cyathostomins are considered to be the most important group of helminths to affect equids due to their high prevalence, potential pathogenicity and ability to develop anthelmintic resistance. Their control relies almost exclusively on frequent anthelmintic use. Currently, fenbendazole (FBZ), pyrantel embonate (PYR), ivermectin (IVM) and moxidectin (MOX) are licensed for use in horses in the UK. With no new anthelmintics likely to be licensed in the near future, it is essential that investigations into the efficacy of current anthelmintics in different locations are performed to help inform control programmes. Here, efficacy of FBZ, PYR, IVM and MOX in horse populations in the South of England was investigated. Horses with a strongyle faecal egg count (FEC) of ≥50 eggs per gram (EPG) were enrolled onto a faecal egg count reduction test (FECRT) study. Efficacy was determined by calculating the percentage reduction in FEC between the group mean at Day 0 and 14 days post-treatment. Efficacy was indicated when a group arithmetic faecal egg count reduction (FECR) of ≥90% was recorded for FBZ and PYR, and ≥95% for IVM and MOX. Between March and December 2012, 404 FECRT were performed on 12 yards examining 101, 110, 93 and 100 equids for FBZ, PYR, IVM, and MOX, respectively. FBZ resistance was identified on all yards (mean FECR range 0-65.8%). On 10 of 12 yards, PYR efficacy was >90% (91.0-99.4%) and on two yards, PYR resistance was suspected (86.8-87.2%). IVM (96.4-100%) and MOX (99.9-100%) were >95% efficacious on all yards. As the prevalence of FBZ resistance was 100%, the future use of this anthelmintic for the control of strongyles should be questioned. PYR should be used strategically to reduce reliance on the macrocyclic lactone class products. Over-dispersion of FEC between horses was observed (average k=0.21) with 80% of the strongyle eggs counted measured in 15% of horses tested, strongly supporting the application of targeted helminth control programmes in this host species.
Copyright © 2013 Elsevier B.V. All rights reserved.
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Publication Date: 2013-06-10 PubMed ID: 23830687DOI: 10.1016/j.vetpar.2013.06.009Google 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 study investigated the effectiveness of four currently licensed medicines in the UK, aimed at controlling cyathostomins, a prevalent and potentially harmful type of horse worm. It found 100% of tested horse facilities exhibited resistance to the drug fenbendazole, ivermectin and moxidectin maintained good effectiveness, while pyrantel exhibited occasional resistance.

Background

  • Cyathostomins are a common and dangerous group of horse-infecting worms that are capable of developing resistance to anti-worm medicines or anthelmintics.
  • The research focuses on the efficacy of four anthelmintics currently licensed for use in the UK: fenbendazole (FBZ), pyrantel embonate (PYR), ivermectin (IVM), and moxidectin (MOX).
  • Given the absence of new anthelmintics in the near future, understanding the effectiveness of available medicines under various conditions helps in planning control strategies.

Methodology

  • The researchers conducted a faecal egg count reduction test (FECRT) study, enrolling horses with a strongyle faecal egg count (FEC) of ≥50 eggs per gram (EPG).
  • The efficacy of the anthelmintics was determined by calculating the percentage reduction in FEC between the group mean at day 0 and 14 days post-treatment.
  • For FBZ and PYR, a group arithmetic faecal egg count reduction (FECR) of ≥90% was considered effective; for IVM and MOX, the threshold was ≥95%.

Findings

  • The researchers performed 404 FECRT on 12 horse facilities between March and December 2012 examining 101, 110, 93, and 100 horses for FBZ, PYR, IVM, and MOX, respectively.
  • All facilities demonstrated resistance to FBZ, with a mean FECR range of 0-65.8%.
  • For PYR, 10 of the 12 facilities demonstrated efficacy greater than 90%, but two facilities exhibited possible resistance with lower efficacy.
  • Both IVM and MOX were more than 95% effective in all facilities.

Implications

  • Given the universal resistance to FBZ observed in the study, the continued use of this medication against strongyles in horses might need to be reconsidered.
  • PYR, given its occasional resistance, could be used strategically to minimize overreliance on the highly effective macrocyclic lactone class products (IVM and MOX).
  • The researchers also observed strong variation in FEC among individual horses, with 80% of the strongyle eggs counted present in just 15% of the horses tested. This suggests horse-specific helminth control programmes could be needed.

Cite This Article

APA
Lester HE, Spanton J, Stratford CH, Bartley DJ, Morgan ER, Hodgkinson JE, Coumbe K, Mair T, Swan B, Lemon G, Cookson R, Matthews JB. (2013). Anthelmintic efficacy against cyathostomins in horses in Southern England. Vet Parasitol, 197(1-2), 189-196. https://doi.org/10.1016/j.vetpar.2013.06.009

Publication

Veterinary parasitology
ISSN: 1873-2550
NlmUniqueID: 7602745
Country: Netherlands
Language: English
Volume: 197
Issue: 1-2
Pages: 189-196
PII: S0304-4017(13)00360-9

Researcher Affiliations

Lester, H E
  • Moredun Research Institute, EH26 0PZ, UK. hannah.lester@moredun.ac.uk.
Spanton, J
    Stratford, C H
      Bartley, D J
        Morgan, E R
          Hodgkinson, J E
            Coumbe, K
              Mair, T
                Swan, B
                  Lemon, G
                    Cookson, R
                      Matthews, J B

                        MeSH Terms

                        • Animals
                        • Anthelmintics / pharmacology
                        • Drug Resistance
                        • England / epidemiology
                        • Helminthiasis, Animal / drug therapy
                        • Helminthiasis, Animal / epidemiology
                        • Helminthiasis, Animal / parasitology
                        • Helminths / classification
                        • Helminths / drug effects
                        • Horse Diseases / drug therapy
                        • Horse Diseases / epidemiology
                        • Horse Diseases / parasitology
                        • Horses

                        Citations

                        This article has been cited 20 times.
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