A review on the molecular characterization of digenean parasites using molecular markers with special reference to ITS region

The rDNA region of eukaryotes has the immense potential to resolve the evolutionary and phylogeny problems using molecular markers. As evident from the present review, ITS region data is considered for interpretation of inter and intra-specific variations of 136 studies of 33 families including 78 genus and 114 species affecting individuals worldwide. Along with ITS-1 and ITS-2 region in 29 studies 18S region, in 38 studies 28S region and in 43 studies mitochondrial genes (COI and NDI) were also analyzed. Three new genera (Allobilharzia gen. nov., Caulanus gen. nov., and Latuterus gen. nov.) and 49 new species were discovered. Only 47 studies expressed variations at intra-specific and inter-specific level in complete ITS region, ITS-1 and ITS-2 rDNA sequences due to differences in nucleotide positions. According to the findings ITS region is more reliable and precise marker for demarcation and identification of species in combination of other DNA markers. Major studies were involved around the parasites of families Fasciolidae, Schistosomatidae, Opisthorchidae, Paragonimidae and Paramphistomidae, Clinostomidae, Diplostomidae, Haploporidae, among others infecting humans, farm animals, birds, fishes, reptiles and amphibians on the clinical basis. In future, molecular and bioinformatics aspects based on genetic variations will lead to explore the untouched areas of trematodes.