White Feces Disease In Liptopenaeus Vannamei Caused By Various Pathogen Agents: A Case Study Reported In Vietnam

Abstract

White Feces Disease (WFD) presents a persistent challenge in the aquaculture of Litopenaeus vannamei and Penaeus monodon throughout Southeast Asia, manifesting as white fecal strings, diminished feeding, and stunted growth. This study examined outbreaks in Bac Lieu, Soc Trang, and Ben Tre provinces in Vietnam to elucidate the causative agents and their interactions. Bacterial cultures and molecular analyses consistently identified Vibrio parahaemolyticus, confirmed through 16S rRNA sequencing and the detection of virulence genes (toxR, tlh). All tested shrimp were also positive for the microsporidian Enterocytozoon hepatopenaei (EHP). Histopathological examinations revealed hepatopancreatic degeneration, sloughing of enterocytes, and the presence of intracytoplasmic EHP spores, while the white fecal casts consisted of shed epithelial cells heavily colonized by bacteria. Assessments of pond phytoplankton indicated a diverse algal community, with no harmful species detected, suggesting that algae are not direct causative agents of the disease. These findings indicate that WFD is a multifactorial syndrome primarily driven by EHP and V. parahaemolyticus, with pond conditions likely exacerbating the disease's manifestation. In contrast to acute hepatopancreatic necrosis disease (AHPND), the pathology associated with WFD arises from the synergistic interaction of microsporidian infection and opportunistic Vibrio overgrowth. These results underscore the necessity for integrated management strategies that combine biosecurity measures to control EHP, interventions to limit Vibrio proliferation, and ecological practices to sustain stable pond environments. Such measures are essential to reduce disease risk and promote sustainable shrimp aquaculture in Vietnam.