Pathogenicity of Yersinia ruckeri bacterium in Persian sturgeon (Acipenser persicus) fingerlings

In the present study, we evaluated the pathogenicity of Yersinia ruckeri on Persian sturgeon (Acipenser persicus) fingerlings. We divided the sturgeon into one treatment group, one positive control group and one negative control group (with three replicates for each group). The treatment group juvenile Persian sturgeon received 0.1 ml of bacterial suspension (2.8 × 106 cells/fish) via an intraperitoneal injection. Positive control fish received 0.1 ml intraperitoneal injection of sterile normal saline. The negative control group received no injection. According to the results, first mortality was observed 48 h post-challenge in the treatment group. Mortality rates in the treatment group post-challenge were 6.7% (48 h), 26.6% (72 h), 60% (96 h), and 70% (7 days). Haemorrhage in terminal part of intestine and accumulation of bloody fluid in the  intestinal lumen were observed in the majority of sick fish. Intestinal histopathology was characterized by spread necrosis in the epithelium of the villi and lymphocytic infiltration to the connective tissues. In the haematological study, we observed significant differences in RBC, WBC, MCH, MCHC, hemoglobin, and hematocrit counts between fish from the treatment and control groups.