Investigation of pathologic findings infected with Aeromonas salmonicida in rainbow trout (Oncorhynchus mykiss Walbaum, 1792)

44 SUMMARY This research was carried out to constitute experimental furunculosis with Aeromonas salmonicida using intraperitoneal route and immersion method, as well as to investigate macroscopic and microscopic findings. For this reason, a total of 65 (50 experimental and 15 control) rainbow trout {Oncorhynchus mykiss Walbaum, 1792) (weight 155 ± 15 g and 20-25 cm in size) were used. Aeromonas salmonicida at a concentration of 3xl03 cfii/ml (0,1 ml per fish) was intraperitoneal^ injected to twenty five fish (first group). Another group (second group) were immersed into 30 1 water inoculated with 3 ml of bacterial inoculum (3x1 0J cfii/ml) for one hour. The same application was repeated after three days. Sterile saline solution (0,1 ml/fish) was intraperitoneally injected to control group. The first deaths were observed on the 6th day of application in the first group and on the 7th day of the second group. The remaining alive fish were killed on the 31s1 day of application (7 fish- 3 fish first group, 4 fish second group). The death and euthanasied fish were necropsied, macroscopic and microscopic findings were evaluated. The chronic form of disease was observed in both groups. Anorexie, darkening in the skin, irregular swimming, hemorrhage at the dorsal, ventral and pectoral base of fins were the main clinic and macroscopic findings. However, in some fish, diffused or focal scale eruption on the dermis from operculum to caudal fin were observed. Microscopically, foci of bacteria with no inflammatory response were observed especially in the muscles, gills, heart, stomach, pyloric caeca, intestines, kidney and spleen, in both of experimental groups. In addition, liquefactive necrosis in the muscles, reduction in the lymphoid cells of hematopoietic tissue of kidney, oedema, hyperplasia and telangiectasi in the gills were determined.