Molecular Conformation of the Equine Redworm, in the large intestine (Strongylus equinus) in Iraq

Abstract

Background and amis: Large strongyles (large redworms) are the most important gastrointestinal parasites of equids, commonly inhabiting the large intestine and causing various clinical manifestations that may lead to severe disease and death. This study aimed to confirm the natural infection of Strongylus equinus in horses and donkeys in Baghdad, Iraq, through morphological and molecular characterization.

Materials and Methods: Samples were collected from necropsied animals during the study period from December 2024, to May, 2025. A total of 65 equids, including horses and donkeys, were examined. Adult parasitic worms were carefully recovered during post-mortem examination and initially identified by to morphological characteristics, particularly buccal capsule. Molecular identification was subsequently performed using (ITS-2) sequence analysis.

Results: The prevalence of Strongylus equinus represented 1% of the total Strongylinae infections. Recovered specimens were morphologically identified as S. equinus. Molecular characterization confirmed species was identity despite the limited availability of S. equinus sequence data in GenBank. Phylogenetic analysis showed that the study isolates clustered within the primary clade alongside S. equinus (X77808.1) from Australia, Strongylus asini, and Strongylus edentatus isolates from China. The obtained S. equinus sequences were submitted to GenBank under accession numbers PX442255, PX442256, PX442257, and PX442258.

Conclusion: The integration of morphological and molecular identification of adult worms provides reliable species-level diagnosis of S. equinus infection in equids, and facilitate possibility of detecting species by eggs and other larval stage.