Pathological evidence links white feces syndrome in farmed Penaeus vannamei to severe hepatopancreatic Ecytonucleospora hepatopenaei infection in China.

Authors

Yuan Wang, Juan Zhang, Jin-Yang Zhou, Ying Na, Shi-Ting Lin, Di Peng, Gan-Xiang Wang, Shou-Hu Li, Yan-Qing Huang, Jun-Fang Zhou, Xin-Cang Li, Wen-Hong Fang

Published in

Journal of invertebrate pathology. Pages 108770. Oct 19, 2026. Epub Oct 19, 2026.

Abstract

White feces syndrome (WFS) remains a major health problem in global Penaeus vannamei aquaculture, yet its etiology and pathogenesis remain debated. In this study, WFS outbreaks were investigated in 24 shrimp ponds across four provinces in China between 2013 and 2024, using light microscopy, histopathology, in situ hybridization, transmission electron microscopy, and molecular diagnostics. Ecytonucleospora hepatopenaei (EHP) was detected in all WFS-affected ponds examined. Microscopic and ultrastructural analyses showed that both fresh white feces from intestinal tract and pond-floating white feces were dominated by mature EHP spores, empty spore shells, and limited excretory debris, whereas bacteria were not a predominant structural component. Histopathology and in situ hybridization demonstrated that severe EHP infection was present in the hepatopancreas of WFS-shrimp, while the shrimp midgut and hind gut remain structurally intact. The observed hemocytic infiltration, encapsulation, and melanization suggest that host immune response contributes to the degradation of sloughed necrotic epithelial cells while leaving the resilient EHP spores within the hepatopancreatic tubule lumens. These massive, relatively pure spore loads were subsequently discharged into the midgut to form white feces. These findings indicate that WFS in the investigated field cases was strongly associated with severe hepatopancreatic EHP infection. The characteristic white coloration was most likely due to intense light scattering by dense spore aggregates, rather than to extensive intestinal epithelial injury or massive bacterial accumulation. WFS is recommended as a practical clinical indicator of high EHP burden in EHP-endemic shrimp farms.

PMID:
42896699
Bibliographic data and abstract were imported from PubMed on 20 Oct 2026.

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