Protective mechanisms of baicalein against white spot syndrome virus in Procambarus clarkii: Insights from intestinal microbiota and hepatopancreatic antioxidant system

White spot syndrome virus (WSSV) severely threatens the sustainable cultivation of Procambarus clarkii and causes substantial economic losses. To develop safe strategies for controlling WSSV, the present study evaluated the protective effects and underlying mechanisms of baicalein in WSSV-infected P. clarkii. P. clarkii were randomly allocated into four experimental groups: Control (C), Baicalein immersion (B), WSSV infected (W), and WSSV infected plus Baicalein immersion (WB) for a 14-day experimental period. Intestinal microbiota, intestinal histopathology, and hepatopancreatic antioxidant enzyme activities were analyzed to evaluate baicalein's protective effects. WSSV infection exerted severe adverse effects on P. clarkii: the survival rate significantly decreased to 64.89%, intestinal microbiota composition was perturbed with decreased relative abundance of Proteobacteria and increased Bacteroidota, pathogenic taxa such as Bacteroides and Vibrio proliferated, intestinal epithelial exfoliation occurred, and hepatopancreatic antioxidant function was impaired with reduced GPX/CAT activities and elevated MDA content. Notably, 2.5 mg/L baicalein immersion mitigated these WSSV-induced adverse effects: the survival rate increased to 73.33%, intestinal microbiota composition was restored with increased Proteobacteria and decreased Bacteroidota, pathogenic taxa such as Bacteroides were inhibited, intestinal damage was alleviated, and hepatopancreatic antioxidant capacity was partially enhanced by targeting the T-SOD and GSH pathways, whereas GPX and CAT activities remained unaffected. Collectively, baicalein protects P. clarkii against WSSV through a "microbiota-immune-antioxidant axis" synergistic mechanism.