POTENTIAL OF BACTERIOPHAGE PUB36 TO ENHANCE NONSPECIFIC IMMUNE RESPONSE AND DISEASE RESISTANCE OF TILAPIA (OREOCHROMIS NILOTICUS)PARICHAT PHUMKHACHORN AND PONGSAK RATTANACHAIKUNSOPON
Diets supplemented with live and heat inactivated bacteriophage PUB36, specific to Streptococcus agalactiae PUB36, were tested for their effects on nonspecific immunity of tilapia (Oreochromis niloticus). No significant difference (P > 0.05) between the effects of both diets on plasma lysozyme activity and phagocytic activity. Elevated levels of plasma lysozyme activity and phagocytic activity of leukocytes were first observed at week 3 after feeding. After increase, both activities remained constant till the end of 4 week observation period. The diet supplemented with inactivated bacteriophage was also found to reduce cumulative mortality of tilapia caused by S. agalactiae PUB36 and Aeromona hydrophila from 52.5% to 15% and from 50% to 10%, respectively. These results indicated that the disease resistance resulted from the improved nonspecific immunity of fish, not from the phage lysis of the bacterial pathogens. This study is the first report presenting the effect of a bacteriophage on nonspecific immunity and disease resistance of fish.
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