Effects of Levamisole on the Immune Function and Disease Resistance of Macrobrachium rosenbergii

In order to determine the immunomodulatory effect of the dietary intake of levamisole in the giant freshwater prawn(Macrobrachium rosenbergii),the prawn were fed diets containing 0(control),50,100 and 150 mg/kg dry diet for 14 days.The phagocytic activity,phenoloxidase(PO)activity,lysozyme(LSZ)activity and superoxide dismutase(SOD)activity were examined at once after administration of levamisole.Prawn were challenged with a virulent strain of Aeromonas hydrophila of M.rosenbergii at a concentration of 6 × 105 cells /mL 20 μL/prawn)at once after administration of levamisole,and mortalities were recorded over a 7 d period.The results demonstrated that prawn treated with levamisole showed significantly higher phagocytic percentage(PP)and phagocytic index(PI)of haemocyte,the PO activity,LSZ activity and SOD activity than those of the control group(P0.05).Furthermore,M.rosenbergii treated with levamisole had significantly stronger resistance to Aeromonas hydrophila.It was concluded that M.rosenbergii that were fed with diets at 50,100 or 150 mg/ kg dry diet showed increased immune ability as well as resistance to A.hydrophila infection.Under the experimental condition,the optimum dose of dietary intake of levamisole should be 100 mg levamisole/kg dry diet.