The effectiveness of a -1,3-glucan (derived from Schizophyllum commune) containing diet to enhance the resistance of the prawn to a white spot syndrome virus (WSSV) was investigated. Juvenile grass prawn, Penaeus monodon, was fed either a -1,3-glucan 2g kg-1 diet, or a glucan-free diet for 20 days, and was then challenged by injection of WSSV solution either blank, WSSV only, or a mixture of WSSV and glucan. The haemolymph total haemocyte counts (THC), phagocytosis (PI), phenoloxidase (PO), superoxide anion (O2-) and superoxide dismutase (SOD) production were measured at days 0, 1, 2, 3, 4, 5, 6 and 7 after challenge, and prawn survival rates also recorded. The results showed that all of the prawn fed with glucan-free diet and injected either WSSV or a mixture solution died at day 4 and 5, respectively. Conversely, the survival rate of prawn fed with -1,3-glucan contained diet was significantly high (P<0.001) at day 4. As the prawn were infected with WSSV, THC, phagocytic activity, PO, O2- production and SOD activity significantly reduced (P<0.001) in the first three days. After five days, they, however, rebounded for the glucan fed group. Therefore, oral administration of -1,3-glucan 2 g kg-1 diet for 20 days effectively enhanced the immune system and improved the survival of WSSV-infected grass prawn.
Key words: Penaeus monodon, -1,3-glucan, White spot syndrome virus, Superoxide anion, Superoxide dismutase.