Preparation Of Streptococcus Iniae Vaccine And It's Immunological Efficacy On Tilapia

Streptococcus iniae is a significant pathogen of aquatic that has been associated with outbreaks of disease in freshwater and marine fish species in various parts of the world. The diseases caused by S.iniae results in huge harm in fishery,eatable safty,human health. At present chemotherapeutics was the mian means to prevent and cure diseases of S.iniae ,but chemotherapeutics could cause much problem. Vaccination is regarded as an ideal strategy. The S. iniae vaccine was recently reported in oversea,but that was not reported in china.In this study we had isolated 9 strains of Streptococcus from the samples of sickness tilapia in Guang Xi. After identifying 8 strains of them had confirmed to be S.iniae. By using the identified strains of S.iniae we prepared the formalin-killed S. iniae vaccine in our laboratory .The vaccine were used as immunogen to immunize healthy tilapia (Oreochromis niloticus ) by different methods (intraperitioneal, immersional and oral routes) and doses . The immunity mechanism of vaccine was studied by detecting the white blood cell count (WBC),differential leucocyte count (DLC), phagocytes activities, bacteriolytic activities,lysozyme activities,superoxide dismutase (SOD) activities and antibody activity (OD₄₅₀). The fishes immunized by vaccine showed increased resistance to S. iniae infection and high relative percent survival (RPS) .The IP groups showed the highest RPS reaching at 90%. The results indicated that the tilapia immunized with vaccine showed significantly higher WBC, the amount of lymphocyte,Granulocyte and monocyte showed significantly higher than those of the control group (P<0.05),the bacteriolytic activities,lysozyme activities and antibody activity (OD450) in the blood serum showed significantly higher than those of the control group (P<0.05). Among the three immune routes, the immune abilities of tilapia treated by IP route were higher than those treated by BI and oral routes. The enhance immunization resulted in higher immune ability of fish. The study results indicated the prepared vaccine are effect. It is possible to control the disease of S. iniae by this vaccine with proper immune route.In present study, we purified and analysised serum immunoglobulin from Oreochromis niloticus. The results have provided the foundation to further reseach in immunoglobulin of Oreochromis niloticus.