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Equine veterinary journal2025; 58(2); 508-522; doi: 10.1111/evj.70120

Enhanced detection of equine strongyles: Insights from morphological and nemabiome metabarcoding approaches in northern Iran.

Abstract: Strongyles pose significant health concerns for equids globally. Strongyles, comprising over 60 species, can lead to severe morbidity and mortality, with Strongylus vulgaris posing higher risks due to its migratory behaviour. Routine diagnostic methods, such as faecal egg counts, lack species-level resolution, while traditional morphological techniques require advanced expertise. DNA metabarcoding offers a high-throughput alternative. Objective: To characterise the diversity of strongyles infecting horses in northern Iran and evaluate how age, sex, diagnostic methods and host population influence community composition. Methods: Cross-sectional. Methods: Strongyle communities were studied across four locations. At two farms, subsets of horses were analysed either by morphological identification of adult worms or by ITS2 metabarcoding of larval cultures. Morphological identification was performed on 1476 adult worms recovered from 23 horses at two farms (Rezvanshahr and Gisum). In parallel, ITS2 nemabiome metabarcoding was applied to pools of ~2500 L3 larvae from faeces of 25 untreated horses. Community composition was analysed using dissimilarity indices (Jaccard, Bray-Curtis), PERMANOVA and generalised linear models to assess the effects of farm, method, age and sex. Results: Thirty-three species were detected across both methods. DNA metabarcoding identified more species and 11 species were recorded in Iran for the first time. Strongyle community composition varied significantly among locations, including between resident and non-resident horses at the riding club, and between diagnostic methods. Neither horse age nor sex explained variation. S. vulgaris was prevalent across the majority of locations, potentially due to inconsistent treatment. Conclusions: Morphological and nemabiome identifications were conducted on different subsets of horses in the same location, precluding direct within-individual comparisons. The study relied on owner-reported information about horse characteristics and management practices. Conclusions: These findings provide new insights into strongyle diversity in northern Iran and highlight the value of molecular diagnostics for equine parasite surveillance and control.
© 2025 The Author(s). Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2025-11-29 PubMed ID: 41316832PubMed Central: PMC12892384DOI: 10.1111/evj.70120Google Scholar: Lookup
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Summary

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Overview

  • This study investigates the diversity of equine strongyle parasites in northern Iran by comparing traditional morphological identification with modern DNA metabarcoding methods.
  • The research evaluates how factors such as location, diagnostic method, age, and sex of horses influence strongyle community composition, aiming to improve diagnostic accuracy and parasite control strategies.

Background

  • Strongyles are a group of parasitic nematodes infecting horses, consisting of more than 60 species, many of which can cause serious health issues.
  • Strongylus vulgaris is particularly dangerous due to its migratory behaviour within the horse’s body, leading to increased morbidity and mortality.
  • Routine diagnostic methods like faecal egg counts provide limited resolution, failing to identify parasites at the species level.
  • Traditional morphological identification of adult worms requires significant expertise and is limited by the need for adult specimens.
  • DNA metabarcoding, particularly targeting the ITS2 region, offers a high-throughput, sensitive method to identify multiple parasite species simultaneously from larval stages.

Objectives

  • To characterize the diversity of strongyle parasite species infecting horses in northern Iran.
  • To assess how horse age, sex, diagnostic methods, and the specific host population influence the composition of strongyle communities.
  • To compare the effectiveness and species detection capabilities of morphological identification versus DNA metabarcoding.

Methods

  • Study Design: Cross-sectional study across four distinct locations in northern Iran.
  • Sampling:
    • Morphological identification was performed on 1476 adult worms collected from 23 horses at two farms (Rezvanshahr and Gisum).
    • DNA metabarcoding (ITS2 region) was applied to pools of approximately 2500 third-stage larvae (L3) from faeces of 25 untreated horses, including both resident and non-resident animals.
  • Diagnostic Comparison:
    • Two main methods compared: morphological identification of adult worms versus ITS2 nemabiome metabarcoding of larval cultures.
    • Methods were applied on different samples of horses, precluding direct individual-level comparisons.
  • Data Analysis:
    • Community composition analyzed using dissimilarity indices such as Jaccard and Bray-Curtis.
    • Statistical tests including PERMANOVA and generalized linear models were used to evaluate the effects of location, diagnostic method, age, and sex on parasite community structure.

Results

  • A total of 33 different strongyle species were detected across both diagnostic methods.
  • DNA metabarcoding identified a greater number of species than morphological methods.
  • Eleven strongyle species were recorded in Iran for the first time using the metabarcoding approach, indicating previously undocumented parasite diversity.
  • Strongyle community composition significantly varied by geographic location, including differences between resident and non-resident horses within the same riding club.
  • Diagnostic method influenced detected community composition, with metabarcoding revealing more species richness.
  • Neither horse age nor sex significantly explained variations in strongyle community composition.
  • Strongylus vulgaris, the highly pathogenic species, was present across most locations, which might relate to inconsistent parasite treatment practices.

Limitations

  • Morphological and metabarcoding analyses were conducted on different subsets of horses, preventing direct within-individual comparison of diagnostic methods.
  • Owner-reported data on horse characteristics and management could introduce inaccuracies or bias.

Conclusions and Implications

  • This study provides valuable new information on the diversity and distribution of strongyle species infecting horses in northern Iran.
  • DNA metabarcoding proved a powerful tool to detect a broader range of parasite species compared to traditional morphological methods.
  • The presence of Strongylus vulgaris underscores the ongoing risk to equine health in the region due to potentially inadequate parasite control.
  • Molecular diagnostics such as metabarcoding can enhance parasite surveillance and contribute to more effective equine parasite control strategies by providing species-level information.
  • Future studies could benefit from concurrent sampling and individual-level comparisons of diagnostic methods to better validate DNA-based approaches against morphology.

Cite This Article

APA
Mohtasebi S, Ahn S, Karimi M, Saberi M, Gilleard JS, Poissant J. (2025). Enhanced detection of equine strongyles: Insights from morphological and nemabiome metabarcoding approaches in northern Iran. Equine Vet J, 58(2), 508-522. https://doi.org/10.1111/evj.70120

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 58
Issue: 2
Pages: 508-522

Researcher Affiliations

Mohtasebi, Sina
  • Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada.
Ahn, Sangwook
  • Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada.
Karimi, Mahan
  • Department of Medical Parasitology and Mycology, School of Medicine, Guilan University of Medical Sciences, Rasht, Iran.
Saberi, Mohammad
  • Department of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
Gilleard, John S
  • Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada.
Poissant, Jocelyn
  • Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada.

MeSH Terms

  • Animals
  • Horses
  • Iran / epidemiology
  • DNA Barcoding, Taxonomic / veterinary
  • Male
  • Female
  • Cross-Sectional Studies
  • Strongyle Infections, Equine / parasitology
  • Strongyle Infections, Equine / epidemiology
  • Strongyle Infections, Equine / diagnosis
  • Feces / parasitology
  • Strongylus / genetics
  • Strongylus / classification

Grant Funding

  • Margaret Gunn Endowment for Animal Health Research
  • University of Calgary Faculty of Veterinary Medicine Clinical Research Fund
  • Zoetis Investment in Innovation Fund
  • Alberta Graduate Excellence Scholarship
  • University of Calgary Provost's Doctoral Scholarship

Conflict of Interest Statement

The authors declare no conflicts of interest.

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