Evaluating Oxidative Stress in Labeo rohita, Infected Asypmtomatically with Native and Invasive Aeromonads Using Biochemical Indices

Abstract

In view of the importance of disease management in aquaculture, the impacts of Aeromonas hydrophila and Aeromonas salmonicida infection at sublethal dose on Labeo rohita (Hamilton, 1822), were investigated by determining the changes in the levels of serum biochemical parameters (total protein, glucose, cholesterol, bilirubin and calcium); detoxifying enzyme concentration {glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione (GSH)} and rate of reactive oxygen species production in phagocytes. Fishes were inoculated (i.p.) with 3 × 107 cfu ml−1 of A. hydrophila and 2 × 107 cfu ml−1 of A. salmonicida to generate asymptomatic carrier state. After an exposure period of 3 days, the above parameters were studied. The levels of total protein, glucose, cholesterol, bilirubin and calcium concentration in serum were found to be significantly (p < 0.05) higher in infected fishes. Total protein level was not significantly different among the infected groups. However, glucose and cholesterol concentrations were higher in A. salmonicida infected fish while cholesterol and calcium levels were higher in A. hydrophila treated group. Concentrations of all the detoxifying enzymes in A. hydrophila treated fishes were higher than those measured in A. salmonicida treated group and control fishes. The rate of reactive oxygen production in phagocytes was determined by formazan deposition which indicated that A. salmonicida infection triggered more reactive oxygen as compared to A. hydrophila treatment. The findings indicated that these parameters could be analyzed as potential exposure biomarkers for clinical monitoring of fish health at field level against pathogenic Aeromonads.