Retained efficacy of ivermectin against cyathostomins in Swedish horse establishments practicing selective anthelmintic treatment.
Abstract: Cyathostominae are ubiquitous to grazing horses and regarded the most prevalent internal parasite in the horse. Unfortunately, decades of indiscriminate use of anthelmintic drugs have resulted in the development of resistance in cyathostomins to all currently available drug groups, the most recent being a documented lack of efficacy to the macrocyclic lactones (ML). In vivo determination of anthelmintic resistance in horses most often utilises the faecal egg count reduction test (FECRT). Further, a shortened egg reappearance period (ERP) can indicate a change in response to the applied treatment and suggest an upcoming reduction of efficacy. Although both true resistance as demonstrated by the FECRT and shorter ERPs after ML treatment have now been shown in cyathostomins worldwide, the efficacy of ML as regards to cyathostomins in Sweden is currently unknown. The aim of the present study was therefore to determine FECRTs and ERPs after ivermectin (IVM) treatment in Swedish horses. Sixteen equestrian establishments with a minimum of six horses excreting at least 150 eggs per gram faeces (EPG) at screening were selected. For each establishment, FECRTs and ERPs were determined by collecting faecal samples prior to and 14 days after IVM treatment (200 µg/kg), and thereafter at weekly intervals for a total of eight weeks. All participants responded to a questionnaire detailing pasture management methods and anthelmintic routines.Questionnaire results showed that the majority of establishments (69%) only treated horses with anthelmintic drugs if indicated by faecal diagnostics and all of the establishments had a mean FECRT exceeding 99.0% and ERPs ranging from six to over eight weeks. The ERP was shown to increase with age as young individuals were shown to excrete cyathostomin eggs earlier after treatment compared with older horses (R = 0.21, p = 0.015). Riding schools, stud farms and those declaring not to use separate summer and winter paddocks had significantly shorter ERPs (p <0.01).In conclusion, retained ERPs and no confirmed resistance to IVM were found in Swedish equine establishments practising selective anthelmintic treatment, and supports the use of selective deworming regimens as a means of reducing the risk of anthelmintic resistance development.
Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.
Publication Date: 2023-08-14 PubMed ID: 37639919DOI: 10.1016/j.vetpar.2023.110007Google Scholar: Lookup
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- Journal Article
Summary
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The research article investigates the effectiveness of ivermectin, a commonly used antiparasitic drug, on cyathostomins (a type of horse parasite) in Swedish equine institutions practicing selective antiparasitic treatment. Findings indicate ivermectin still efficiently combats these parasites, supporting the continued use of selective deworming tactics, which may reduce the possibility of antiparasitic drug resistance.
Background and Objectives
- The study aims to evaluate the potency and impact of ivermectin, an anthelmintic drug, on cyathostomins within the horse population in Sweden. These internal parasites are highly prevalent among grazing horses.
- The widespread and uncontrolled use of anthelmintic medications has resulted in the parasites developing resistance to them. This includes macrocyclic lactones (a drug group to which ivermectin belongs), thereby framing the importance of evaluating its effectiveness.
- Specific measurement tools such as the faecal egg count reduction test (FECRT) and the egg reappearance period (ERP) test were utilized to identify antiparasitic resistance and assess the efficiency of the deworming process.
Methodology
- The research was conducted at 16 equestrian establishments that housed at least six horses excreting a minimum of 150 eggs per gram faeces at the screening stage.
- FECRTs and ERPs were ascertained by collecting faecal samples before and two weeks after horses were treated with ivermectin. The collection continued at weekly intervals for eight weeks.
- Additionally, a questionnaire detailing pasture management methods and anthelmintic routines was answered by participants to draw more detailed conclusions.
Results and Discussion
- The survey results pointed out that most establishments (69%) provided anthelmintic drugs to the horses only if faecal diagnostics indicated the necessity.
- All examined establishments had an average FECRT exceeding 99.0% and ERPs varying from six to over eight weeks. This points towards the effectiveness of selective deworming regimens and the efficiency of ivermectin.
- The study also found that the ERP increased with age, with younger horses starting to excrete cyathostomin eggs earlier post-treatment than their older counterparts.
- Establishments like riding schools, stud farms, and those not using distinct summer and winter paddocks confirmed shorter ERPs.
Conclusion
- In conclusion, the study affirms that selective anthelmintic treatment practices, including the use of ivermectin, remain effective and as such should be continued. This might also help in mitigating the risk related to the development of anthelmintic resistance.
Cite This Article
APA
Alm YH, Osterman-Lind E, Martin F, Lindfors R, Roepstorff N, Hedenström U, Fredriksson I, Halvarsson P, Tydén E.
(2023).
Retained efficacy of ivermectin against cyathostomins in Swedish horse establishments practicing selective anthelmintic treatment.
Vet Parasitol, 322, 110007.
https://doi.org/10.1016/j.vetpar.2023.110007 Publication
Researcher Affiliations
- Department of Biomedical Science and Veterinary Public Health, Parasitology Unit, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden. Electronic address: ylva.hedberg.alm@slu.se.
- Department of Microbiology, Section for Parasitology, National Veterinary Institute (SVA), SE-751 89 Uppsala, Sweden.
- Department of Biomedical Science and Veterinary Public Health, Parasitology Unit, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden.
- Ambulatory Clinic, University Animal Hospital, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden.
- Ridskolan Strömsholm AB, Stallbacken 6, Knytpunkten, SE-734 94 Strömsholm, Sweden.
- WångenAB, Vången 110, SE-835 93 Alsen, Sweden.
- Flyinge AB, Kungsgården, SE-247 93 Flyinge, Sweden.
- Department of Biomedical Science and Veterinary Public Health, Parasitology Unit, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden.
- Department of Biomedical Science and Veterinary Public Health, Parasitology Unit, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden.
Conflict of Interest Statement
Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Eva Tyden reports financial support was provided by The Swedish-Norwegian Foundation for Equine Research.
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