Study On The Vaccination Against V.anguillarum In Farmed Marine Turbot

Culture of turbot, Scophthalmus maximus ,a species of high commercial value,has grown rapidly since it was introduced into China several years ago. Infectious diseases, specially the vibriosis caused by V.anguillarum ,commonly occur where the fish is farmed in intensive conditions and contribute to the severe losses of the turbot cultural industry. Control of fish diseases using therapeutics such as antibiotics has problems including potential development of resistant bacteria ,consumer concern over drug residues and environmental impacts.Moreover, the presence of antibiotic residues in fish products is a major obstacle to international trade. Immunoprphyllaxis is the alternative and vaccination has become one of the most desirable and effective methods to protect farmed fish from infectious diseases.The vaccination against V.anguillarum(W-1)was performed in two tests to determine the specific immune response of the turbot for the inactivated vaccine.In the first test,turbot fries were vaccinated with formalin-killed vaccine of V.anguillarum (W-l)via intraperitoneal injection and immersion . Specific antibody titres were determined at 1.2.4.6 weeks post-vaccination.. A dosage of 0.2 ml of V.anguillarum(W-1) (3.7xl08cfu/ml) was intraperitoneally injected to the vaccinated fish and control groups 4 weeks after immunisation to evaluate the protective efficiency of the f vaccine . The results showed that specific immune response could be stimulated with the vaccine by the either administration methods. Specific antibody could be detected in a week after injection immunization and increased continuously over 6 weeks period, with the highest of 1228.8 , the relative percentage survival (RPS) was 91.70%. While the specific antibody could not be detected until 3 weeks after immersion immunization, with the highest of 36, and the RPS was 33.3%.In the second test, another group of bigger turbot fries were vaccinated with formalin-killed vaccine of V.anguillarum(W-l) via intraperineal injection. And the booster vaccination was performed two months later. The level of the specific antibody was determined and the booster effect was investigated during the following 15 weeks. The results show that the turbot fry had the function of immunological memory andthe immunological reaction of turbot fry can be lasted for more than 3-6 months.A rod-shaped bacterium(TMOl) was isolated from the diseased Turbot (Scophthalmus maximus), the bacterium was re-injected to the healthy turbot to study its pathogenicity. The same bacterium was isolated from the infected fish. The morphological, physiology and biochemical characteristics of isolated bacteria were studied. They were identified as Vibrio anguillarum. The formalin-killed vaccine of the bacterium was prepared and vaccinated turbot fries and brood-turbots by intraperitoneal injection . Specific antibody of the turbot fries could be detected in a week after injection immunization and maintained high level for at least 6 weeks, with the highest of 1382,the relative percentage survival (RPS) was 50%;The level of the specific antibody of the vaccinated brood turbots was low but maintained stable and kept long time.