Morphological and molecular identification of Euclinostomum heterostomum in the spotted snakehead (Channa punctata) in Narayanganj, Bangladesh

Abstract

Parasites of the Clinostomidae family are widely distributed worldwide. Freshwater fish of Bangladesh frequently serve as hosts for various Clinostomidae species. The metacercariae stage of Euclinostomum heterostomum, a prevalent digenetic trematode, exhibits a distinct affinity for infecting Channidae species and becomes encysted within the liver, kidneys, and muscles of these species. This study focused on identifying E. heterostomum in Channa punctata using a combination of morphological and molecular approaches. The morphological characteristics of the species were examined using both light and scanning electron microscope. Encysted flukes, inflammatory infiltrates of leukocytes, along with degeneration and loosening of hepatic tissue were observed in the histopathological examination of the infected liver tissue. Molecular analysis of the partial nuclear ribosomal internal transcribed spacer (ITS rDNA) sequence confirmed the presence of Euclinostomum heterostomum. A comparison of the collected metacercariae sequence (Accession no. OR591452) with the NCBI GeneBank databases found similarity to other species within the same genus in India and Thailand. The phylogenetic reconstruction provided compelling evidence of genetic similarity among different strains of the genus Euclinostomum, indicating their shared genetic heritage.