Figure 1. Pathologic changes in artificially bred Chinese sturgeon offspring infected with Yersinia ruckeri, China, 2022. A) Intestinal tissue showing mass intestinal villus necrosis and disordered structure; a large amount of mucosal epithelial cell necrosis and shedding (black arrow); extensive intestinal gland necrosis and connective tissue hyperplasia, with multiple lymphocyte infiltration (blue arrow); thick muscularis propria layer with small amount of connective tissue hyperplasia and small amount of lymphocyte infiltration (green arrow). B) Spleen tissue showing no obvious white pulp and unclear boundary between red pulp and white pulp; large area of red pulp congestion (black arrow); excessive lymphocyte necrosis and nuclear fragmentation (blue arrow); large number of lymphocytes with ballooning degeneration and vacuolization of the cytoplasm (green arrow); excessive infiltration of neutrophils (yellow arrows). C) Liver tissue showing diffuse balloon-like cell degeneration with vacuolization of cytoplasm (black arrow), dilation of liver sinuses, and irregular cell arrangement; multiple necrotic foci with a small amount of liver cell necrosis, nuclear lysis, and enhanced eosinophilia (blue arrow); small amount of focal infiltration of lymphocytes around the central vein (green arrow). D) Renal tissue showing diffuse watery degeneration of renal tubular epithelial cells with loose cytoplasm and light staining (black arrow) and loose arrangement of renal tubules; renal tubular epithelial cell necrosis, nuclear fragmentation (blue arrow), renal tubular structure disorder, accompanied by a small amount of lymphocyte infiltration (yellow arrow); excessive glomerular dilation with eosinophilic substances visible in the renal capsule (green arrow), cell necrosis and dissolution in the lumen, and disappearance of capillary loop structure (red arrow). E) Gill tissue showing small necrotic and detached pieces (black arrow) accompanied by a small amount of lymphocyte infiltration (blue arrow).