Citrullus colocynthis extract and synthesized Selenium nanoparticles enhance non-specific response and resistance against Aeromonas sobria in Nile tilapia (Oreochromis niloticus )

The effects of Citrullus colocynthis extract (CCE) and synthesized Se nanoparticles (Nano-Se) on non-specific immune response and resistance to Aeromonas sobria in Nile tilapia (Oreochromis niloticus) were investigated. Treatments included three levels of Nano-Se (0.5, 1 and 2 mg/kg of feed), three levels of CCE (0.1%, 0.3% and 0.5%) and control group (no additives). The diets were fed for 4 weeks, and biochemical indices, serum lysozyme, respiratory burst activities and antioxidant enzymes were measured on weeks 1, 2 and 4. After 4 weeks of feeding, fish were infected with A. sobria and mortalities were recorded for 14 days. Results of this study showed that feeding tilapia with CCE and Nano-Se supplements significantly enhanced biochemical indices, serum lysozymes and respiratory burst. CCE treatments had a moderate effect on superoxide dismutase and no effect on the other antioxidant enzymes. Nano-Se treatments had significantly positive effects on antioxidant enzymes. Both CCE and Nano-Se supplements reduced mortality following A. sobria infection. The lowest mortality (13%) was observed in the group fed with 2 mg/kg Nano-Se, and the highest mortality of 90% was observed in the control group. It can be concluded that C. colocynthis extract and synthesized Nano-Se supplementation added to fish feed can act as immunostimulants and enhance the immune functionality, antioxidant status and disease resistance in cultured Nile tilapia (O. niloticus).