Effects of Chitosan on some immune response of rainbow trout (Oncorhynchus mykiss) and enhance resistance against a pathogenic Aeromonas hydrophila fallowing experimental infection

The aim of this study was to evaluate the effects of Chitosan as an immune stimulator on rainbow trout immune response and enhanced resistance against Aeromonas hydrophila fallowing experimental infection. 900 rainbow trout (25.62±0.10 g initial mean weigh) were obtained and acclimatized with experimental conditions for 10 days. Then the fish were divided into four groups, the first one (control) just fed with normal diet (GFT-1) and other three groups served different doses of Chitosan (0.25, 0.5 and 1 percent) with their feed. The trial continued for eight weeks and every two weeks blood samples were taken for measuring plasma lysozyme activity and glutathione peroxidase. After that, an experimental infection conducted with a pathogenic Aeromonas hydrophila by intra peritoneal injection (107 CFU/ml). The fish were monitored daily and the mortality recorded during one weeks after infection. The plasma lysozyme activity and glutathione peroxidase were increased significantly in the group that was fed with 0.25 percent Chitosan in comparison the untreated control fish. Further more the fish resistance against Aeromonas hydrophila enhanced in this group. Base on this result, 0.25 percent Chitosan could enhance some immune response and resistance of rainbow trout against Aeromonas hydrophila.