Correlation analysis of white feces syndrome (WFS) of Litopenaeus vannamei with host immunity, environment factors and microbial community

Shrimp white feces syndrome (WFS) was highly infectious and causes huge economic losses in shrimp aquaculture industry worldwide. In this study, the relationship between the occurrence of WFS in pond culture Litopenaeus vannamei and environmental factors, microbial factors, host immunity and water microbial community composition were analyzed. Measures including water environment factors, culturable bacteria in shrimp hepatopancreas and water, immune activity in shrimp muscle and microbial community structure in water were detected. Compared with the healthy group, the fluctuation trend of water temperature, dissolved oxygen (DO), pH, salinity and other physical and chemical factors in the diseased pond was similar, they were 26.1-29.0 °C, 4.26-6.08 mg/L, 8.39-8.73, 40-49, and DO and salinity were higher than those in the healthy group. The number of culturable bacteria and Vibrio spp. in hepatopancreas of the healthy shrimp were 1.19×10⁵-7.70×10⁵ CFU/g and 8.80×10³-1.96×10⁴ CFU/g, and the proportion of Vibrio spp. was 2%-16%. Furthermore, the number of culturable bacteria and Vibrio spp. in hepatopancreas of the diseased shrimp were 3.80×10⁵-2.51×10⁶ CFU/g and 2.02×10⁵-1.49×10⁶ CFU/g, the proportion of Vibrio spp. was 55%-70%, the number of Vibrio spp. was 15-113 times higher than that of healthy group. The activities of AKP, ACP, LZM, SOD and PO were 1.21-5.64, 9.17-15.25, 3.56-7.43, 4.83-6.70 and 3.10-4.55 U/mg in healthy shrimp muscles, and 2.12-5.39, 19.22-26.96, 19.73-26.85, 3.00-4.14 and 7.76-9.21 U/mg in diseased shrimp muscles. Comparative analysis showed that the occurrence of WFS was correlated with culturable bacteria, the proportion of Vibrio spp., ACP, LZM, and PO. Microbial community structure analysis showed that the Ace and Chao indices of water bacteria structure in the diseased group showed a certain degree of downward trend, and the PCoA index was high. The relative abundance of Actinomycetota and Proteobacteria decreased, and the relative abundance of Bacteroidetes and Cyanobacteria increased significantly in diseased group. RDA analysis showed that salinity, DO, culturable bacteria in shrimp hepatopancreas and water and culturable Vibrio spp. in shrimp hepatopancreas were the main factors influencing the microbial community structure in the water. The results indicated that the occurrence of WFS is affected by pathogen, body immunity and water microbial community composition, which provides data support for further pathogenic analysis of shrimp WFS, and establishes the theoretical basis for the prevention and control of WFS. The occurrence of aquatic diseases is the result of the comprehensive action of environmental factors, pathogenic microorganisms and host autoimmune ability. Comprehensive analysis of the pathogen of WFS, host immunity and changes in the structure of bacteria in water environment from the production practice is of great significance to explore the related factors of WFS occurrence and comprehensive control. It not only deepens the thinking of studying the occurrence of WFS from multiple perspectives, but also provides valuable information for strengthening the healthy cultivation of L. vannamei.