Characteristics and Pathogenicity of SWS Causing High Mortality in Mud Crab () Aquaculture in Hong Kong

Introduction: is a Gram-negative, rod-shaped bacterium belonging to the family of , a common pathogen in aquaculture animals, However, studies on its impact on (mud crabs) are limited. In this study, we isolated SWS from dead mud crab during a disease outbreak in a Hong Kong aquaculture farm, which caused up to 70% mortality during summer.

Methods: Experimental infection and histopathology were used to investigate the pathogenicity of SWS in and validate Koch's postulates. Comprehensive whole-genome analysis and phylogenetic analysis antimicrobial susceptibility testing, and biochemical characterization were also performed.

Results: Our findings showed that SWS caused high mortality (75%) in with infected individuals exhibiting inactivity, loss of appetite, decolored and darkened hepatopancreas, gills, and opaque muscle in the claw. Histopathological analysis revealed tissue damage and degeneration in the hepatopancreas, gills, and claw muscle suggesting direct and indirect impacts of SWS infection.

Conclusions: This study provides a comprehensive characterization of SWS as an emerging pathogen in aquaculture. Our findings underscore the importance of ongoing surveillance, early detection, and the development of targeted disease management strategies to mitigate the economic impact of vibriosis outbreaks in mud crab aquaculture.