Bacteriological, Metabolic and Immunological Evaluation of European sea Bass Reared in Ponds with Heated Water under a Natural Vibriosis-Like Outbreak

Abstract

Received: Revised: Accepted: Published online: July 04, 2017 November 06, 2017 January 24, 2018 June 19, 2019 Fish culture in ponds with heated water offers better fish growth compared to farms in natural sea water temperature, but the increase in temperature favors the development of bacteria and fish disease. In this study, in European sea bass (Dicentrarchus labrax) specimens reared in ponds with heated water from a power plant showing symptoms of a vibriosis-like disease we aimed to characterize the bacterial community as well as some serum metabolic and immune parameters. Bacteriological analysis revealed an important contamination with fecal coliforms, Pseudomonas aeruginosa, Vibrio alginolyticus, yeasts and molds whilst fish tissues from both healthy and diseased specimens were positive for total aerobic flora and several potential pathogenic bacteria such as V. alginolyticus, Aeromonas hydrophila, Pasteurella multocida, P. aeruginosa, Proteus vulgaris and P. mirabilis. Additionally, Grimontia hollisae was only present in diseased fish tissues. Serum metabolic parameters such as aspartate aminotransferase, bile acids, creatine kinase, uric acid, glucose, globulin and potassium were generally increased in diseased fish though only the levels of phosphorous reached a significant level compared to the healthy specimens. Regarding fish innate immunity, our results showed no statistical differences between healthy and diseased fish on peroxidase, protease or antiprotease activity while the bactericidal activity against V. anguillarum was significantly decreased in diseased fish. Lastly, the gene expression of il1b, c3, dic and mpx was down-regulated in the blood of diseased fish while ighm was up-regulated. ©2018 PVJ. All rights reserved