Methanol extract of Nyctanthes arbortristis seeds enhances non-specific immune responses and protects Oreochromis mossambicus (Peters) against Aeromonas hydrophila infection

•Nyctanthes arbortristis seed methanol extract enhances non-specific immune response of Oreochromis mossambicus.•Serum non-specific immune parameters - lysozyme, myeloperoxidase, antiprotease increased significantly compared to control.•Antibody production and cellular ROS production were significantly higher in methanol extract treated groups.•The relative percent survival of treatment groups were higher.•N. arbortristis seed extract can be used as immunostimulant in aquaculture industry.

Immunostimulation using medicinal plant extracts is a promising approach for prevention and control of diseases with reference to sustainable fish farming. Oreochromis mossambicus, dubbed as aquatic chicken is a cultured fish worldwide and a laboratory model organism. Aeromonas hydrophila is one of the major bacterial pathogens in fish farming that causes huge loss to aquaculture industries. In this study, we investigated the efficacy of methanol extract of Nyctanthes arbortristis seeds on disease resistance of O. mossambicus against live virulent A. hydrophila. We also investigated its effect on the non-specific immune parameters such as serum lysozyme, myeloperoxidase, antiprotease and specific immune parameters in terms of specific serum antibody titres assayed by bacterial agglutination test. Our studies indicate that intra-peritoneal administration of 20 mg/kg methanol extract increases the Relative Percent Survival (RPS) of O. mossambicus challenged with LD80 of A. hydrophila. Further, both non-specific and specific immune parameters were enhanced by the methanol extract. Further experiments at molecular levels in the laboratory and also efficacy testing at field level are essential before applying this plant product in aquaculture industry.