Insights into the histopathology and microbiome of Pacific white shrimp, Penaeus vannamei, suffering from white feces syndrome

Abstract White feces syndrome (WFS) is an emerging digestive system disease of intensively cultured penaeid shrimp in Asian countries. In this study, Penaeus vannamei suffering from WFS were collected from a pond with water salinity of 2 g/l. Histopathology and comparative analysis of dominant bacterial populations (DBPs) and their interactions through high-throughput sequencing bacterial 16S rRNA genes were conducted, using the digestive tracts of shrimp at different infection stages. Although Enterocytozoon hepatopenaei and acute hepatopancreatic necrosis disease-causing Vibrio (VAHPND) were detected using PCR in WFS-affected shrimp, the histopathology did not support their pathogenicity for WFS. Histopathology of WFS was characterized by collapsed epithelia and enlarged lumens in hepatopancreatic tubules. Vibrio predominated in the digestive tracts of diseased shrimp and served as a major hub to interact with the co-occurring DBPs in the networks. The purified opportunistic Vibrio isolates (V. sinaloensis and V. parahaemolyticus) could cause experimental shrimp to develop a similar histopathology to the naturally WFS-affected. By contrast, Acinetobacter and Candidatus Bacilloplasma dominated in the bacterial communities of hepatopancreas and gut from grossly healthy shrimp, respectively, and they were major hubs in the networks. Contributions of bacterial commensalism and amensalism were highlighted to shift the major hubs in the interaction networks and to change the DBPs of microbial communities from healthy to diseased. Taking together, these findings provide insights into the histopathology and microbiome dynamics in the shrimp digestive system during WFS infection, and provide a histopathology-based support for that Vibrio species are the major bacterial species responsible for WFS and the consequent mortality of infected shrimp, which are valuable for controlling WFS in shrimp farming ponds.