Pathogenicity of experimental Yersinia ruckeri infection in Caspian roach, Rutilus caspicus

Abstract

The present study investigated the susceptibility of Caspian roach, Rutilus caspicus to experimental exposure of Yersinia ruckeri. In this regard, 144 Caspian roach fingerlings with average weight of 9.3 ± 2.1 were assigned to 12 aquaria (12 fish per aquarium). Fish were acclimated for 4 weeks before challenge. Five experimental treatments and one control group (each with two replicates) were considered. After preparation of bacterial suspension, fish were challenged via intra peritoneal injection with different dosages of bacteria including 5.4×108, 5.4×107, 5.4 ×106, 5.4 ×105 and 5.4 ×104 cells/fish. Fish in control group received sterile normal saline. After 21 days, the median lethal concentration (LC50) of this bacterium calculated as 4.4×107. The most gill histopathology signs in sick fish included epithelial lifting and inflammatory cell infiltration in secondary lamella and hyperplasia in base of secondary lamella. Kidney histopathology was characterized by congestion in vessels and interstitial tissue, focal necrosis and inflammatory cell infiltration. In liver tissue, vacuolization of hepatocytes was observed in most specimens and focal hepatocyte necrosis was recorded in some individuals.

Keywords

• caspian roach
• histopathology
• yersiniosis
• clinical signs