Prevalence, Molecular Identification, and Phylogenetic Analysis of Strongylus equinus in Horses in Al-Muthanna Province, Iraq

Document Type : Original Articles

Authors

1 Department of Microbiology and Parasitology, College of Veterinary Medicine, Al-Muthanna University, Al-Muthanna, Iraq.

2 Department of Parasitology, College of Medicine, University of Al-Muthanna, Al-Muthanna, Iraq.

10.32598/ijvm.20.2.1005901

Abstract

Background: Gastrointestinal parasites, particularly Strongylus spp., represent a critical challenge to equine health and productivity in developing nations.
Objectives: This study aims to provide the first molecular and phylogenetic characterization of Strongylus equinus in horses in Iraq, using the internal transcribed spacer (ITS-1) region of rDNA as a marker for species-level identification. It has not been reported previously in the Middle East. Additionally, it establishes baseline data on age, sex, and season-linked risk factors influencing Strongylus spp. prevalence in Al-Muthanna Province, Iraq, a previously unstudied region, thereby addressing critical gaps in the epidemiology of equine parasites.
Methods: The flotation technique was performed on 118 horse fecal samples, randomly collected from stables in Al-Muthanna Governorate, Southern Iraq, from January to the end of October 2023. Then, polymerase chain reaction (PCR) was performed using species-specific primers (StrongF/StrongR) for 50 samples. Three high-quality PCR products with strong band intensity from local S. equinus isolates were sent for sequencing.
Results: The epidemiological analysis discovered that 50(42.3%) out of 118 horses were positive for Strongylus spp. infection via the flotation technique. Infection rates were significantly higher in horses under 4 years of age (57.1%); this difference was not statistically significant (P>0.05). Also, the highest prevalence rate was recorded during March (83.3%), and in females (56.2%) (P≤0.05). Moreover, PCR confirmed the presence of S. equinus in 22(44%) out of 50 morphologically positive samples. Partial ITS-1 sequence analysis of the local isolates (PQ900954.1, PQ900955.1, and PQ900956.1) revealed a high degree of similarity to strains from Australia (97%–100%) and to a Chinese isolate (94%).
Conclusion: Strongylosis is an important veterinary disease in local horses, with a 42.3% prevalence and significant association with the month and sex. Phylogenetic analysis revealed significant genetic similarity between strains from Iraq and Australia, highlighting the importance of molecular diagnostics to improve parasite management, prevent the spread of zoonotic diseases, and enhance livestock health. 

Keywords

Iranian Journal of Veterinary Medicine
Volume 20, Issue 2
March and April 2026
Pages 311-320

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