Introduction
Global shrimp aquaculture has expanded rapidly over the past decades, driven by increasing demand and the widespread adoption of intensive and super-intensive farming systems. Production of Penaeus vannamei now dominates global shrimp output, particularly in Asia. However, high stocking densities and suboptimal environmental control have increased disease outbreaks, significantly affecting productivity.
White Faeces Disease (WFD) has emerged as a major challenge, characterized by floating white fecal strings and reduced growth performance. It is widely considered a multifactorial disease, with the microsporidian Ecytonucleospora hepatopenaei (EHP) identified as a primary pathogen causing hepatopancreatic dysfunction. Opportunistic Vibrio spp., including V. parahaemolyticus and V. alginolyticus, are thought to act as secondary agents that exacerbate disease severity. Despite its impact, the lack of a reproducible challenge models limit understanding of WFD pathogenesis and the development of effective treatments. This study aims to develop a standardised co-infection model to better understand WFD and support disease management strategies. This approach provides, for the first time, a controlled framework to reproduce WFD under experimentally defined multifactorial conditions.
Approach
To ensure the acquisition of high-quality biological materials, a collaborative effort was established between IMAQUA B.V. (Belgium), Ghent University (Belgium), and Can Tho University (Vietnam). Field surveys and targeted sampling campaigns were conducted in shrimp farming regions affected by WFD and confirmed EHP presence. Diseased shrimp specimens were collected for pathogen isolation and characterization.
Bacterial isolates were obtained from hepatopancreatic and intestinal tissues using selective culture techniques. Approximately 20 Vibrio strains representing multiple species, including V. parahaemolyticus, V. alginolyticus, and V. vulnificus were successfully isolated. At the Laboratory of Aquaculture and Artemia Reference Center (ARC), these strains underwent comprehensive characterization, including molecular identification via 16S rRNA gene sequencing. Functional assays were conducted to assess virulence-related traits, such as quorum sensing activity and bacterial motility.
In parallel, EHP spores were isolated from infected shrimp at Can Tho University (Vietnam) and propagated under controlled laboratory conditions at IMAQUA. Successful experimental transmission of EHP was achieved, confirming the viability of the spores and enabling their use in subsequent co-infection trials.
This integrated pipeline from field sampling to laboratory validation ensures that both primary and secondary pathogens used in this study reflect real-world disease dynamics while maintaining experimental reproducibility.
Discussion
This initial phase successfully established a high-quality pathogen collection representing both primary (EHP) and secondary (Vibrio spp.) agents of WFD. These results provide a critical foundation for developing a controlled co-infection model.
Future work will focus on optimizing challenge protocols by varying pathogen concentrations and exposure timing to reliably reproduce WFD symptoms. Such a model will enable deeper investigation of pathogen interactions and provide a robust platform for evaluating therapeutics and management strategies.
Developing a reproducible WFD model represents an essential step toward transforming a complex field syndrome into a predictable and manageable disease, ultimately supporting the sustainability of shrimp aquaculture.
Overall, this study establishes the foundation for a co-infection model of White Faeces Disease by integrating field-derived EHP and Vibrio isolates with laboratory infection systems. The upcoming optimization of this model is expected to enhance understanding of disease mechanisms and facilitate the development of effective control strategies in shrimp farming.
Acknowledgment
This research was supported by Flanders Innovation & Entrepreneurship (Belgium) under the Baekeland mandates program (HBC.2024.0281).