A Study of Immune Response in Nile Tilapia (Oreochromis niloticus) Fed Levamisole Incorporated Diet

This study was undertaken to evaluate the influence of levamisole on the immune enhancement of Nile tilapia (Oreochromis niloticus) against potential bacterial pathogens, Fish with weight of 98±5 g were randomly distributed into seven groups each at a rate of 20 fish per 300-L aquarium and fed on a diet containing 0.0, 250, 500, 750, 1000, 1250 or 1500 mg levamisole/kg diet for eight weeks. After the feeding trial, fish were challenged by pathogenic Aeromonas hydrophila, E.coli, Staphylococcus aureus and Salmonella, which was given by intraperitoneal (IP) injection and they were kept under observation for 10 days to record any abnormal clinical signs and the daily mortality rate. Levamisole fed fish groups showed significant activation of non-specific immunological measures together with a relative enhancement of resistance against challenged bacteria. Interestingly, the indices study indicated that the fed group showed significant (p<0.05) increment in all immune parameters like phagocytic activity, serum bactericidal activity and leukocrit. The challenge studies (RPS) also clearly indicated that fish supplemented diet containing 1500 mg levamisole/kg diet showed high protection (85%) over the control group. The lowest fish mortality and bacterial counts were obtained when fish fed diet containing 1.25-1.5g levamisole. These results indicate that levamisole supplementation is promising for disease prevention in tilapia culture.