Pathological characteristics of Chinese soft-shelled turtle (Pelodiscus sinensis) with white abdominal disease

White abdominal disease is one of the major diseases in Chinese soft-shelled turtle (Pelodiscus sinensis, SST) aquaculture. To clarify the pathological characteristics of white abdominal disease, 24 SSTs with typical white abdominal symptoms were collected from a farm in Hubei Province, China. First, the pathogens of the SSTs were detected, including viruses and bacteria. No virus was detected. A variety of bacteria have been isolated. The pathological characteristics of the diseased SSTs were then studied using hematological analysis, histopathological observation, intestinal microbial analysis, and immunity-related gene expression. Compared with the healthy SST, the number of red blood cells reduced from 1.2 & PLUSMN; 0.5 x 1013 /L to 1.5 & PLUSMN; 0.2 x 1012 /L in the diseased SSTs. Meanwhile, the number of white blood cells increased by nearly four-fold (from 1.8 & PLUSMN; 0.5 x 1010 /L to 7.1 & PLUSMN; 3.5 x 1010 /L). In the diseased SSTs, the liver displayed several abnormalities, such as hepatocyte vacuolation and changes in nonparenchymal tissue. Some glomeruli of the kidney showed necrosis and disintegration. Cavities and loose muscles were observed in the gastric muscle layer. The blurred boundary between the red pulp and white pulp of the spleen was accompanied by massive invasion of inflammatory cells. Significant differences were detected in the relative abundances of Proteobacteria (from 29% to 7%) and Fusobacteria (from 12% to 28%) between the diseased and healthy SSTs. Compared with those in the healthy SSTs, the gene expression levels of toll-like receptor 2(TLR), TLR3, and myeloid differentiation primary response 88 (MyD88) were increased, by more than 4-fold, 7-fold, and 5-fold, respectively (P < 0.01) in the diseased SST liver. The TLR2, TLR4, and MyD88 expression levels increased significantly in the diseased SST kidney. These results indicated that the diseased SSTs experienced anemia, visceral tissue lesions, reduction of intestinal microbial species, and innate immune activation.