Effects of hot-water extract of Toona sinensis on immune response and resistance to Aeromonas hydrophila in Oreochromis mossambicus

Abstract: Respiratory burst, lysozyme and phagocytic activities, and immunoglobulin levels in response to the pathogen Aeromonas hydrophila were examined in tilapia (Oreochromis mossanbicus, 10.65 ± 2.5 g) injected individually with hot-water extract of Toona sinensis at 4 or 8 μg g−1. Tilapia receiving the hot-water extract of T. sinensis at either dose had significantly increased respiratory burst, phagocytic activity and lysozyme activity towards A. hydrophila by 1 and 2 days post injection. No significant differences in total immunoglobulin levels were observed among the tilapia that received the two different doses of hot-water extract of T. sinensis at 4 and 8 μg g−1. In another experiment, a Tilapia that had been injected with hot-water extract of T. sinensis was challenged with A. hydrophila at 5 × 107 colony-forming units (cfu) fish−1. The survival of tilapia that received the hot-water extract of T. sinensis at 8 μg g−1 was significantly higher than fish that received phosphate buffered saline and the control fish after 2 days, and at the termination of the experiment (7 days after the challenge). It was concluded that the hot-water extract of T. sinensis at 8 μg g−1 or less had increased the immune response and resistance to A. hydrophila infection in tilapia. [Copyright &y& Elsevier]