Study of histopathology and changes of some hematology indicators of indigenous and French Rainbow trout fish due to Aeromonas hydrophila

This research was carried in order to study of pathology and changes of some hematology indicators of indigenousand French Rainbow trout fish after following with Aeromonas hydrophila. For this research, treatments were performed in eight treatments and each treatment with three replications (each replicate containing 10 rainbow trout fish with an average weight 16±0.36 g). two treatments as a negative control (including of indigenous and French fish without bacterial injection), Two treatments as a positive control (including of indigenous and French fish with serum physiology injection), two treatments including indigenous fish with 10⁶ and 10⁸ CFU/ml Aeromonas hydrophila bacteria and two treatments including French fish, which were injected with 10⁶ and 10⁸ CFU/ml of Aeromonas hydrophila by intra-peritoneal method. After 20 days, to determine the values of some hemotology parameters including counts of white blood cells (WBC), red blood cells (RBC), hemoglobin, hematocrit, and MCV, MCH and MCHC indices, blood samples were taken from 6 fish of each treatment, and then, in order to study of pathology of the tissues of the kidney, liver and spleen, fishes were fixed in 10% formalin solution. The present study, the results showed that the hematocrit, hemoglobin and counts of red blood cells decreased significantly in the treatments of infected with bacterial infection of Aeromonas hydrophila compared with the control groups, and the number of white blood cells and neutrophils increased significantly. Lesions such as mild degeneration lesions in liver cells and tissue texture and severe cytoplasmic vacuating of liver cells and complications such as degeneration and necrosis of renal tubules and hyperemia, edema and lose of spleen pulmonary defence cells, the most important changes in tissue pathology were in experimental treatments compared to control. The highest survival rate was observed in indigenous Rainbow trout control group without bacterial injection and with serum physiology injection. Due to the greater capability of internal race resistance along with management measures that have been able to increase survival rates, improvement of environmental conditions and elimination of stressors can be effective in reducing Aeromonas lesions.