Effects of <i>Astragalus</i> polysaccharides on erysipelas and intestinal microbiota of <i>Whitmania pigra</i>

Whitmania pigra (Whitman leech) is an aquatic annelid with extensive pharmacological activities. Erysipelas has severely affected the development of its artificial aquaculture industry. Astragalus polysaccharide (APS), as an immunopotentiator, is often used in aquaculture to enhance disease resistance of aquatic animals. However, the effect of APS on the intestinal microbiota of W. pigra remains unclear. In this study, 16S rDNA amplicon sequencing was used to explore the effects of APS on the prevention and control of “erysipelas” and the intestinal microbial community of W. pigra . The results showed that after injection with APS, the abundances of Bacteroidota and Firmicutes in the leech intestinal tract increased, while those of Proteobacteria decreased. At the genus level, the relative abundance of Bacteroides increased significantly. The results indicate that APS can optimize the intestinal microbial community structure of W. pigra , correct the imbalance in flora composition, thereby enhancing the body’s immunity and effectively preventing and controlling erysipelas, providing a theoretical reference for green prevention and control of disease in the aquaculture of this species.