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Helminthologia2025; 62(2); 87-94; doi: 10.2478/helm-2025-0018

A pilot study on the potency of injectable vs. oral moxidectin formulation to suppress strongyle egg excretion in horses at twice lower dose.

Abstract: The aim of present study was to examine the potency of moxidectin solution (Cydectin 1 %; Zoetis) and commercially available oral moxidectin gel (Equest®; Zoetis) to suppress the excretion of strongyle eggs in horses over a 6-week period. The horses naturally infected with strongyle nematodes (>500 eggs/g of feces) were divided into two comparable groups according age, sex and weight. On day 0 of the study, horses in Group OT (oral treatment; N=5) were dewormed with moxidectin gel (Equest®; Zoetis; 0.4 mg/kg of b.w.) according to the manufacturer's instructions, and horses in Group IT (intramuscular treatment; N=4) were dewormed with moxidectin injectable solution (Cydectin 1 %; Zoetis; 0.2 mg/kg of b.w.). Stool samples were collected rectally, on day 0, 17, 28, 35, and 42 of the study and examined using a modifi ed McMaster technique (Roepstorff ., 1998) with modifi cations. The mean strongyle egg excretion has signifi cantly decreased in Group IT (P<0.01) and Group OT (P<0.001) on day 17 post treatment as compared to those on day 0. The effi cacy of oral gel (99.43 %) and injectable moxidectin (99.32 %) formulations was therefore high and comparable and no resistance of strongylids to moxidectin was recorded. On day 35 (P<0.001) and 42 (P<0.05) post treatment, the mean effi cacy was signifi cantly higher in Group IT as compared to Group OT. The present study contributes to the existing knowledge and providing more information on the use of injectable MOX solution for the treatment of strongylid infection in horses.
© 2025 M. Šarkūnas et al.
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Publication Date: 2025-09-30 PubMed ID: 41058774PubMed Central: PMC12498210DOI: 10.2478/helm-2025-0018Google 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.

Overview

  • This study compared the effectiveness of injectable versus oral moxidectin formulations in reducing strongyle egg excretion in horses.
  • The research aimed to determine whether a lower dose of injectable moxidectin could be as effective as the standard oral dose over a six-week period.

Introduction and Objective

  • The study focused on strongyle nematode infections in horses, which are diagnosed by counting eggs per gram (EPG) of feces.
  • Moxidectin is an anthelmintic drug commonly used to treat such infections; it is available as an oral gel (Equest®) and as an injectable solution (Cydectin 1%).
  • The objective was to compare the potency and efficacy of these two formulations: oral moxidectin gel administered at 0.4 mg/kg body weight (b.w.) and injectable moxidectin solution at half that dose (0.2 mg/kg b.w.).

Study Design and Methodology

  • Subjects: Naturally infected horses (with strongyle egg counts >500 EPG) were selected and separated into two groups balanced by age, sex, and weight.
  • Treatment groups:
    • Group OT (Oral Treatment): 5 horses treated with oral moxidectin gel at 0.4 mg/kg b.w.
    • Group IT (Injectable Treatment): 4 horses treated with injectable moxidectin solution at 0.2 mg/kg b.w.
  • Sample collection occurred at multiple timepoints: day 0 (before treatment), day 17, 28, 35, and 42 post-treatment.
  • Egg counts were measured using a modified McMaster technique, a standard parasitology method for quantifying intestinal parasite eggs in feces.

Results

  • Both treatment groups showed a significant reduction in strongyle egg excretion by day 17 compared to baseline:
    • Group IT (Injectable): Significant decrease (P<0.01).
    • Group OT (Oral): Highly significant decrease (P<0.001).
  • Egg reduction efficacy was very high and comparable between groups shortly after treatment:
    • Oral gel efficacy: 99.43%
    • Injectable solution efficacy: 99.32%
  • No evidence of resistance to moxidectin was observed in either group.
  • At later timepoints (days 35 and 42):
    • The injectable group maintained significantly higher efficacy compared to the oral group (day 35 P<0.001; day 42 P<0.05).
    • This suggests longer suppression of egg excretion after injectable moxidectin, even at a lower dose.

Conclusions and Implications

  • Injectable moxidectin administered at half the oral dose was nearly as effective initially and maintained superior efficacy at later time points.
  • The injectable formulation may provide a longer duration of strongyle egg suppression in horses.
  • This study supports the use of injectable moxidectin as an effective treatment option for strongylid infections and provides data encouraging dose optimization.
  • Results contribute to better understanding of dosing strategies to potentially reduce drug usage while maintaining efficacy, supporting parasite control and resistance management efforts.

Limitations and Future Research

  • The study was a pilot with a small sample size (9 horses total); larger studies are needed to confirm findings.
  • Only naturally infected horses were included; controlled infection models might provide additional insights.
  • Longer follow-up beyond 42 days could better evaluate duration of efficacy and resistance development.
  • Further research should explore pharmacokinetics and safety profiles for the injectable formulation at reduced doses.

Cite This Article

APA
Šarkūnas M, Schwahn A, Suleimanova K. (2025). A pilot study on the potency of injectable vs. oral moxidectin formulation to suppress strongyle egg excretion in horses at twice lower dose. Helminthologia, 62(2), 87-94. https://doi.org/10.2478/helm-2025-0018

Publication

Helminthologia
ISSN: 0440-6605
NlmUniqueID: 0043764
Country: Germany
Language: English
Volume: 62
Issue: 2
Pages: 87-94

Researcher Affiliations

Šarkūnas, M
  • Department of Veterinary Pathobiology, Veterinary Academy, Lithuanian University of Health Sciences, LT-47181, Kaunas, Lithuania.
Schwahn, A
  • Department of Veterinary Pathobiology, Veterinary Academy, Lithuanian University of Health Sciences, LT-47181, Kaunas, Lithuania.
Suleimanova, K
  • Department of Natural Sciences, Z. Aldamzhar Kostanay Socio-Technical University, Kostanay, Kazakhstan.

Conflict of Interest Statement

Conflict of Interests The authors declare that the study was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest pertaining to this submission.

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