Study of microsporidians in white faecal syndrome affected farmed shrimp (Penaeus vannamei) Boone, 1931 of West Bengal, India

Enterocytozoon hepatopenaei (EHP), an intracellular microsporidian parasite, has been reported in cultivated Penaeus vannamei infected with white faecal syndrome (WFS) in south-east Asian shrimp producing countries. The appearance of white faecal strings floating on the surface of the ponds indicates a severe microsporidian infection. In the present study suspected shrimps and floating faecal strings were collected from culture ponds of study area located in Purba Medinipur district of West Bengal. This study aims to unveil the presence of microsporidians in hepatopancreas and associated histopathological changes in it using light and scanning electron microscopy, and microsporidian identification by nested PCR. Microscopic study revealed the presence of oval-shaped microsporidian spores in the hepatopancreas and nested PCR study confirmed that these spores belong to E. hepatopenaei. The spores isolated from the floating faecal strings exhibited similar morphology with those found in hepatopancreas. Histopathology of the hepatopancreas of WFS-affected shrimp exhibited alterations in hepatopancreatic tissues along with haemocytic infiltration into the inter-tubular spaces and evidence of necrosis, vacuolation and degeneration. The findings from the nested PCR analysis indicated a total of 18 positive results (69.23%) out of 26 samples studied. WFS infection can be considered a gastrointestinal disorder caused by severe EHP infection, which is significant in the grow-out ponds in the regions under study.