Immunomodulatory effects of curcumin on Nile tilapia, Oreochromis niloticus and its antimicrobial properties against vibrio alginolyticus

Abstract

The effect of dietary curcumin on the non-specific immune defence mechanisms and resistance against challenge with pathogenic Vibrio alginolyticus in Nile tilapia, Oreochromis niloticus, was evaluated. Fish were divided into two groups before being fed for 30 days with commercial diets supplemented with 0% (control) and 2% curcumin (weight/weight) at the rate of 2% of body weight. Fish were challenged with virulent V. alginolyticus on the 30 days of feeding experiment. Immune parameters including; peroxidase, serum bactericidal activity and serum proteins were investigated to analyze fish immune defence mechanisms. All immune profiles were significantly enhanced in fish fed with curcumin supplemented diets (p<0.05) compared to the control group. Challenge study indicated highest survivability (100%) in the group of fish fed with curcumin whereas, others fed the basal diet showed a survival rate of 40%. The immunomodulatory and antimicrobial effects of curcumin were evaluated also in vitro by assaying Nitric Oxide (NO) production via macrophages and well diffusion method, respectively. A gradual significant increase in nitric oxide production in parallel with higher curcumin dose was demonstrated. The uppermost NO levels, were detected in 50 μg concentration. All curcumin concentrations showed varying degrees of inhibition against tested V. alginolyticus strains and the minimal inhibitory concentration was determined as 12.5 mg mL-1. Therefore, results confirmed substantial evidence to suggest that low concentrations of curcumin as food supplements are able to enhance the immune defence mechanisms of Nile tilapia and could be of value in protection against invading pathogens.