| Popis: |
Bacterial infections have been associated with immune dysfunction and oxidative stress in cultured fish species while essential elements could boost immunity and exhibit antioxidant properties in fish. This study was therefore aimed at determining the effects of pre-exposure to waterborne selenium on humoral immunity and redox status of Clarias gariepinus experimentally challenged with Serratia marcescens. Juveniles C. gariepinus were pre-exposed to 50 µg/L selenium for 14 days after which they were challenged with 5 × 103 CFU/mL of S. marcescens via oral gavage for 24 or 48 h. The control fish were not exposed to selenium and not challenged with bacteria. Thereafter, fish were sacrificed, blood collected into EDTA bottles for the determination of plasma nitric oxide levels and respiratory burst, and the liver excised for the determination of reduced glutathione, lipid peroxidation, and activities of catalase, superoxide dismutase, and glutathione peroxidase. Fish that were challenged with bacteria without pre-exposure to selenium had elevated levels of nitric oxide, reduced glutathione, lipid peroxidation, and a higher activity of glutathione peroxidase and respiratory burst but a significant decrease in the activity of superoxide dismutase compared to the fish that were pre-exposed to selenium prior to bacterial challenge at both 24 and 48 h post-infection periods. The results from this study showed that infection with S. marcescens is capable of disrupting the immune system and redox homeostasis in C. gariepinus, while pre-exposure to selenium has the ability to improve the physiological status of fish that were challenged with bacteria probably through its antioxidant properties. |
