LAUSR

Objective The objective of the present study was to identify Trichostrongylus species by molecular analysis and also phylogenetic relationships of Trichostrongylus species by mitochondrial Cytochrome c oxidase subunit 1 (Cox1) gene in Guilan province, northern Iran. Methods Abomasum and duodenum contents of 144 livestock were collected from sheep, goats, and cattle in Guilan province. Morphological survey was performed for initial screening. Total DNA was extracted, and the partial region of Cox1 gene was amplified and sequenced. Genetic diversity was calculated and phylogenetic analysis of the data on nucleotide sequence was conducted by MEGA7 software. Results Three species of Trichostrongylus including T. colubriformis, T. vitrinus, and T. axei were identified by morphological characteristics. The genetic divergence within the species in the present study was observed for T. axei (0-2.5%), T. colubriformis (0.77%), and T. vitrinus (0%). The mean inter-species difference between the three species of Trichostrongylus obtained in this study was 14.4-15.4%. Conclusion The Cox1 sequences of the members of Trichostrongylus spp. were highly variable and this could be used as a valuable measure to achieve a proper assessment on biodiversity. Sequence data generation from other species of Trichostrongylus will be needed to reconstruct the phylogenetic relationships of this genus of nematodes.