First report of molecular characterization of Metastrongylus salmi in pigs from Karnataka, India using mitochondrial COX1 gene.

The microscopical examination revealed the typical features of Metastrongylus salmi, in the present study. The PCR amplification and sequencing of the COX1 gene confirmed 99.7-100% nucleotide identity with reference to M. salmi sequences and less identity with other Metastrongylus species. The phylogenetic analysis grouped the Indian isolates with Brazilian M. salmi sequences in a well-supported clade. Pairwise identity analysis demonstrated clear genetic divergence from M. apri and M. pudendotectus. Haplotype network analysis revealed 15 distinct haplotypes across Metastrongylus species, indicating substantial genetic differentiation. Mismatch distribution analysis suggested a stable population of M. salmi with potential sub-structuring. These findings enhance our understanding of the genetic diversity and evolutionary patterns of M. salmi, with implications for its epidemiology and control. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-025-04534-9.