Phenotypic and genotypic characterization of human-derived Strongyloides stercoralis based on cox 1 gene

Strongyloidiasis is a neglected tropical disease caused by the roundworm Strongyloides stercoralis. The prevalence of strongyloidiasis is higher in tropical and sub-tropical areas, there have been reports of infection in temperate regions. India is an endemic region for strongyloidiasis, however, there is extreme scarcity of molecular data related to S. stercoralis from this region.

A cross sectional study was conducted in Varanasi, Uttar Pradesh, from July 2023 to January 2025. A total of 800 stool samples from patients were screened based on microscopy and confirmed through culture and molecular aspects. Conventional PCR targeting 18S rRNA and mitochondrial cytochrome c oxidase subunit 1 (cox1) gene for S. stercoralis detection was performed and positive S. stercoralis isolates underwent sequencing, phylogenetic analysis and subsequent haplotype mapping.

This study identified S. stercoralis infection in 1.1% (9/800) in human stool samples via microscopy, culture and phylogenetic analysis. Clustering of Indian isolates with Asian lineages based on cox 1 sequencing revealed its potential role as biomarker. Haplotype mapping and codon-based analysis showed five novel haplotypes (Hd = 0.6667) including three novel haplotypes, under purifying selection and transition-biased substitutions.

This study inclusively underscores the importance of integrating molecular/genetic data into epidemiological frameworks to predictive public health action. By utilizing mitochondrial cox 1 gene for phylogenetic insights and haplotype mapping, the study revealed Indian isolates clustered strongly with Asian lineages.