The immunomodulatory and antioxidative effects of curcumin-supplemented diets against the isolated Aeromonas hydrophila in Oreochromis niloticus

Abstract

Worldwide, Aeromonas hydrophila (A. hydrophila) has become a significant foodborne pathogen, causing gastrointestinal and extra-intestinal infections in humans as well as severe economic losses in fish farms. Thus, we conducted this research in two experiments. The experiment 1 investigated the prevalence of A. hydrophila among Nile tilapia in different farms in Kafrelsheikh province and its pathogenicity by detecting some of its virulence genes before being used in the in vivo experiment. The experiment 2 was done to investigate the effect of dietary curcumin on growth performance, humoral immunity, antioxidants, and histopathology of Nile tilapia through a sixty-day feeding trial. Nile tilapia was divided into 3 groups, each in 3 replicates. Fish were given diets that included 0.0 (C, control), 1 % (10 g curcumin/kg diet; G1), and 2 % curcumin/kg diet (20 g curcumin/kg diet; G2). Moreover, the antibacterial effect of dietary curcumin against isolated bacteria in experiment 1 was investigated through experimental infection. The study's findings of experiment 1 indicated that the incidence of isolated A. hydrophila was 28 %. Moreover, the virulence aerolysin (aerA) and haemolysin (hlyA) genes were found in 100 % and 50 % of the isolates, respectively. The experiment 2 outcomes demonstrated that the growth-modulating impacts of dietary curcumin were notably noticed in final weight, feed intake, weight gain%, and specific growth rate without pathological lesions in the different organs. In addition, the white blood cell and lymphocyte counts significantly (P < 0.05) increased in Nile tilapia fed dietary curcumin. Similar improvements in humoral immunity (lysozyme and phagocytic activity) and antioxidants (catalase and superoxide dismutase) were seen in the 1 % curcumin group (G1). The experimental infection with a virulent strain of A. hydrophila that was previously isolated in experiment 1 showed a significant decrease in the morbidity and mortality rates in the 1 % curcumin treatment group (G1), followed by the 2 % group (G2). The present study concluded that under current experimental conditions, dietary curcumin at a dose of 10 g/kg diet proves effective, but the dose of 1 % may not be optimal for tilapia.