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Iranian journal of parasitology2025; 20(3); 389-399; doi: 10.18502/ijpa.v20i3.19614

Evaluation of Benzimidazole Resistance in Equine Cyathostomins in the Kermanshah Province of Iran Using Coprological Analysis and Allele-Specific PCR.

Abstract: Resistance to benzimidazole (BZ) by cyathostomin nematodes has become a major threat to equine health around the world. We aimed to evaluate the efficacy of BZ drugs against small strongyle nematodes in horses of western Iran using coprological and molecular examination. Unassigned: Faecal egg count reduction tests were performed on 398 horses kept in 16 stables in western Iran (Kermanshah Province), to detect benzimidazole resistance in small strongyle nematodes. Allele-specific PCR was used to identify the F200Y (TAC/TTC) SNP in the beta-tubulin gene codon in cyathostomin larvae. Unassigned: There was a 96.1%-98.3% (90% CI) reduction in faecal egg counts following mebendazole treatment and a 96.6% - 98.7% (90% CI) reduction in faecal egg counts following fenbendazole treatment. The allele-specific PCR showed BZ-susceptible homozygote genotypes in all examined samples (Two pools of 10 to 50 L of cyathostomin nematodes from each of the 18 selected horses). Unassigned: Benzimidazole resistance in equine small strongyles has been reported globally, and the results of the present study were unexpected. The probable reasons for the slow development of BZ-resistance are climatic conditions in the country that have significant negative effects on the ability of free stages of the resistant strongyle nematode to survive and develop.
© 2025 Jamshidpour et al. Published by Tehran University of Medical Sciences.
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Publication Date: 2025-11-03 PubMed ID: 41181201PubMed Central: PMC12579469DOI: 10.18502/ijpa.v20i3.19614Google 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.

Evaluation of benzimidazole resistance in equine cyathostomin nematodes in western Iran shows that these parasites currently remain susceptible to benzimidazole drugs based on fecal egg count reduction and molecular testing, contrasting with global trends of increasing resistance.

Background and Purpose of the Study

  • Cycling nematode parasites called cyathostomins infect horses worldwide posing significant health issues.
  • Benzimidazole (BZ) class anthelmintics are commonly used to control these small strongyle nematodes.
  • Resistance to BZ drugs has increasingly been documented globally, threatening effective equine parasite management.
  • This study aimed to evaluate the current status of BZ resistance in cyathostomin populations infecting horses in the Kermanshah Province of Iran.
  • The researchers sought to assess drug efficacy using traditional coprological (fecal egg count reduction) and molecular (allele-specific PCR) methods.

Methods

  • 398 horses from 16 different stables in western Iran were included in the study to capture a representative sample.
  • Fecal Egg Count Reduction Tests (FECRT) were conducted after treatment with two common benzimidazole drugs: mebendazole and fenbendazole.
  • FECRT involved measuring parasite egg counts in feces before and after treatment to quantify drug efficacy.
  • Allele-specific PCR focused on detecting the F200Y single nucleotide polymorphism (SNP) in the beta-tubulin gene linked to benzimidazole resistance.
  • Samples for PCR were grouped larvae pools from cyathostomin nematodes isolated from 18 selected horses.

Key Findings

  • Both mebendazole and fenbendazole treatments resulted in over 96% reduction in fecal egg counts, indicating high efficacy of these drugs against cyathostomins in this region.
  • Allele-specific PCR detected only benzimidazole-susceptible genotypes (homozygous susceptible) in all tested larvae pools.
  • No molecular evidence was found for the specific mutation (F200Y) commonly associated with resistance despite thorough testing.
  • The combination of coprological and molecular data confirmed the absence of benzimidazole resistance in this population.

Interpretation and Implications

  • The findings contrast with reports from many other countries where BZ resistance in equine small strongyles is well documented.
  • One hypothesis provided for this unexpected susceptibility is the specific climatic conditions in Iran.
  • Iran’s environment may negatively impact survival and development of resistant free-living nematode stages, slowing resistance selection and spread.
  • Maintenance of BZ susceptibility is beneficial as it preserves an effective, affordable treatment option for horse owners in the region.
  • The study highlights the importance of regional surveillance and indicates that resistance dynamics can vary significantly based on ecology and management.

Conclusion

  • This research demonstrates that benzimidazole drugs are still effective against equine cyathostomins in the Kermanshah Province of Iran.
  • The absence of the F200Y resistance mutation and high fecal egg count reduction suggest low or no resistance currently.
  • Ongoing monitoring is recommended to detect emerging resistance and to aid informed parasite control strategies adapting to local conditions.
  • Understanding environmental influences on resistance evolution may guide sustainable anthelmintic use worldwide.

Cite This Article

APA
Jamshidpour R, Nabavi R, Moadab H, Rezaie F, Chale AC, Sargison N. (2025). Evaluation of Benzimidazole Resistance in Equine Cyathostomins in the Kermanshah Province of Iran Using Coprological Analysis and Allele-Specific PCR. Iran J Parasitol, 20(3), 389-399. https://doi.org/10.18502/ijpa.v20i3.19614

Publication

Iranian journal of parasitology
ISSN: 1735-7020
NlmUniqueID: 101464309
Country: Iran
Language: English
Volume: 20
Issue: 3
Pages: 389-399

Researcher Affiliations

Jamshidpour, Rezvan
  • Department of Clinical Science, Faculty of Veterinary Medicine, Razi University, Kermanshah, Iran.
Nabavi, Reza
  • Department of Pathobiology, Faculty of Veterinary Medicine, Bu-Ali Sina University, 6517658978, Hamedan, Iran.
Moadab, Hossein
  • Department of Clinical Science, Faculty of Veterinary Medicine, Razi University, Kermanshah, Iran.
Rezaie, Farid
  • Department of Pathobiology, Faculty of Veterinary Medicine, Razi University, Kermanshah, Iran.
Chale, Abdolali Chale
  • Department of Pathobiology, Faculty of Veterinary Medicine, Razi University, Kermanshah, Iran.
Sargison, Neil
  • Royal (Dick) School of Veterinary Studies and RoslinInstitute, Easter Bush Veterinary Centre, University of Edinburgh, Midlothian EH25 9RG, UK.

Conflict of Interest Statement

Conflict of Interest The authors declare that there is no conflict of interests.

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