Veterinary parasitology, regional studies and reports2017; 8; 70-74; doi: 10.1016/j.vprsr.2017.02.001

The efficacy of Ivermectin against strongyles in yearlings on Thoroughbred breeding farms in New Zealand.

Abstract: Against a global background of increasing anthelmintic resistance in parasites and a domestic over-reliance on anthelmintics to control gastrointestinal parasites, little is currently known about the resistance status of equine parasites in New Zealand. The objective of the study was to investigate the efficacy of ivermectin in yearling Thoroughbreds. Data were collected from six stud farms from November 2014 to January 2015. Yearlings were selected based on not being treated with anthelmintics for a minimum of six weeks previously and on having a preliminary screening strongyle faecal egg count (FEC) of 25 eggs per gram (EPG) of faeces or greater. On Day 0, faeces were collected and yearlings were treated with ivermectin (a minimum of 200μg/kg). On Days 7, 14 and 21 faeces were again collected from the yearlings, with follow-up samples take on either Day 28, 35 or 42 depending on the stud farm. In total, six stud farms and 117 yearlings (median 23 yearlings; range 5 to 27 yearlings per stud) were eligible for the study. The mean FEC on Day 0 was 609.6 EPG (range 100 to 2000). The majority of horses (113/117) had zero egg counts 7-days after treatment. One and five horses had positive FEC 14 and 21days' post-treatment, respectively. The efficacy of ivermectin ranged from 99.8% to 100% on Day 7 to between 98.5% and 100% on Day 21. On one stud, the efficacy on day 14 was 94.4%. There was reduced efficacy (<90%) on three studs 28 to 42days' post-treatment suggesting shortened egg reappearance period (ERP). On one stud farm (n=7), egg counts remained zero up to 42days' post-treatment. The FECRT observed could be interpreted as consistent with the continued efficacy of ivermectin in the egg-laying adult stages. However, shortened ERP after ivermectin treatment is a concern and current practices for parasite control in horses in New Zealand are arguably not sustainable.
Publication Date: 2017-02-04 PubMed ID: 31014641DOI: 10.1016/j.vprsr.2017.02.001Google Scholar: Lookup
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  • Journal Article

Summary

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The study focused on investigating the effectiveness of the drug Ivermectin in controlling gastrointestinal worms, specifically strongyles, in yearling Thoroughbreds in New Zealand, against the backdrop of increasing global anthelmintic resistance.

Objectives and Methods of the Study

  • The research was conducted in response to increased worldwide resistance to anthelmintics, drugs used to treat parasitic worm infections, and the overreliance on these drugs in New Zealand.
  • The research aimed to investigate the efficacy of Ivermectin, a commonly used anthelmintic, against strongyles in yearling Thoroughbreds.
  • Data was collected from six stud farms in New Zealand between November 2014 and January 2015.
  • Yearlings used in the study had not been treated with anthelmintics for at least six weeks prior to the study. They were also selected based on their preliminary screening strongyle fecal egg count (FEC), which had to be 25 eggs per gram (EPG) of feces or more.
  • Fecal samples were collected from the yearlings before treatment (Day 0), and then on Days 7, 14, and 21 after treatment. Follow-up samples were collected on either Day 28, 35, or 42, depending on the stud farm.

Findings of the Study

  • A total of 117 yearlings, divided into groups of 5 to 27 per stud farm, were involved in the study.
  • The mean FEC on Day 0 was 609.6 EPG, ranging from 100 to 2000. It indicates a substantial presence of strongyles in the yearlings before treatment.
  • Seven days after treatment with Ivermectin, the majority of the horses (113 out of 117) had zero egg counts, indicating that Ivermectin was highly effective in eliminating strongyles.
  • On Day 14 and Day 21, a small number of horses (1 and 5, respectively) showed positive FEC. However, Ivermectin’s efficacy remained high, ranging from 99.8% to 100% on Day 7 to 98.5% to 100% on Day 21.

Conclusions and Concerns

  • On some farms, Ivermectin’s efficacy reduced to less than 90% 28 to 42 days after treatment, suggesting a shortened egg reappearance period (ERP). It could indicate the beginning of drug resistance.
  • One farm showed zero egg counts up to 42 days after treatment, suggesting full efficacy of Ivermectin.
  • The shortening of the ERP after Ivermectin treatment raises concerns about the future sustainability of current practices for parasite control in horses in New Zealand.

Cite This Article

APA
Rosanowski SM, Bolwell CF, Scott I, Sells PD, Rogers CW. (2017). The efficacy of Ivermectin against strongyles in yearlings on Thoroughbred breeding farms in New Zealand. Vet Parasitol Reg Stud Reports, 8, 70-74. https://doi.org/10.1016/j.vprsr.2017.02.001

Publication

ISSN: 2405-9390
NlmUniqueID: 101680410
Country: Netherlands
Language: English
Volume: 8
Pages: 70-74
PII: S2405-9390(16)30128-9

Researcher Affiliations

Rosanowski, Sarah M
  • Equine Research Centre, Institute of Veterinary Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand.
Bolwell, Charlotte F
  • Equine Research Centre, Institute of Veterinary Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand. Electronic address: srosanowski@rvc.ac.uk.
Scott, Ian
  • Institute of Veterinary Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand.
Sells, Patrick D
  • Kaipaki Veterinary Services, Windsor Park Stud, PO Box 51, Cambridge 3450, New Zealand.
Rogers, Chris W
  • Equine Research Centre, Institute of Veterinary Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand.

Citations

This article has been cited 1 times.
  1. Macdonald SL, Abbas G, Ghafar A, Gauci CG, Bauquier J, El-Hage C, Tennent-Brown B, Wilkes EJA, Beasley A, Jacobson C, Cudmore L, Carrigan P, Hurley J, Beveridge I, Hughes KJ, Nielsen MK, Jabbar A. Egg reappearance periods of anthelmintics against equine cyathostomins: The state of play revisited.. Int J Parasitol Drugs Drug Resist 2023 Apr;21:28-39.
    doi: 10.1016/j.ijpddr.2022.12.002pubmed: 36543048google scholar: lookup