PCR-based molecular characterization and insilico analysis of food-borne trematode parasites Paragonimus westermani, Fasciolopsis buski and Fasciola gigantica from Northeast India using ITS2 rDNA

Food-borne fluke infections/trematodiases are emerging as a major public health problem worldwide with over 40 million people affected and over 10% of world population at risk of infection. The major concentration of these infections is in Southeast Asian and Western Pacific Regions, where the epidemiological factors (including the prevalent socio-cultural food habits) are conducive for transmission of these infections. The preponderance of these infections is usually in food deficit poor communities that lack access to proper sanitary infrastructure. While targeting health for all, especially the poor rural tribal communities, it is imperative to take these infections into account. Bayesian analysis phylogeny of food-borne trematode parasites under study showed that they are closely related phylogenetic groups. To focus the control strategies at the target populations, the aim of the present study was to establish molecular methods for accurate discrimination between common food-borne trematodes parasites Paragonimus (lung fluke), Fasciolopsis (giant intestinal fluke) and Fasciola (liver fluke), the infections of which commonly prevail in NE India. In the first step, we amplified and sequenced the second internal transcribed spacer (ITS2) region of ribosomal DNA, utilizing nucleotide differences between the multiple sequence alignments of the parasites under study. Based upon the differences in nucleotide sequences of conserved regions, we designed species-specific primers that can unequivocally discriminate one species from another. ITS2 sequence motifs allowed an accurate in-silico distinction of the trematodes. The data indicate that ITS2 motifs (≤ 50 bp in size) can be considered promising tool for trematode species identification. Using molecular morphometrics that is based on ITS2 secondary structure homologies, phylogenetic relationships with various isolates of several trematode species have been discussed. The present results suggest that the ITS2 specific primers can be used for epidemiological investigations of the prevalence of trematodiasis.