Detection of antibody reaction of sea bass (Dicentrarchus labrax L.) against combined vaccine by serological methods

With this study, the protection level of a commercial bivalent vaccine which was developed to boost the resistance of cultured sea bass against bacterial diseases such as vibriosis and pasteurelllosis, was determined for a one year duration. The antibody level, an impotant specific immune system parameter which was developed in sea bass samples that were once vaccinated by injection against Vibrio (Listonella) anguillarum serotype O1 and Photobacterium damselae subspecies piscicida was determined by using various serologic methods. During the one-year field study period between 2015 and 2016, 5 sampling studies were performed in a commercial sea bass farm that is located in the Aegean Region of Turkey. In these sampling studies, blood samples were collected from a total of 60 vaccinated and 20 non-vaccinated fish samples weighing between 10-100 gr that were reared in floating cages. For bacterial investigation, inoculations were made from the internal organs of 2 fish samples in each sampling study. Later, blood samples were centrifuged and sera were used in serologic methods such as slide-agglutination, micro-well agglutination and enzyme linked immunosorbent assay (ELISA). Due to observation of an extremely high antibody level against V. anguillarum 4 months after the injection, a high protective level was determined in that period, but however, at the end of the one-year period after injection it was also determined that this level is still high in some samples but low in some other samples. Besides, during a one year period, a relatively low antibody level was developed against P. piscicida and so a low protective level against this bacterium was observed. It was determined that ELISA is a more sensitive method than slide and micro-well agglutination. Pathogen bacterial species that were included in the vaccine were not recovered in bacterial investigations and it is a proof of reliability of this bivalent vaccine. Depending on the results of this project, which was carried out as a MSc. thesis study, it was observed that the protective level of commercial vaccine used in sea bass cultured in Turkey is higher against V. anguillarum than P. piscicida. Besides, despite a lower antibody level against pasteurellosis was determined, this pathogen was not recovered in bacterial inoculations.