Protective Efficacy of a Combined Vaccine against Edwardsiella tarda, Streptococcus iniae and Streptococcus parauberis in Farmed Olive Flounder Paralichthys olivaceus

We evaluated the protective efficacy of a combined vaccine containing formalin-inactivated Edwardsiella tarda, Streptococcus iniae, and S. parauberis using olive flounder Paralichthys olivaceus. The fish were injected intraperitoneally with 0.1 mL of the combined vaccine. The fish were then challenged by intraperitoneal injection of the three bacterial strains. Mortality was significantly lower in the vaccinated groups compared with the control groups 3 wk post vaccination. Furthermore, there was a significant increase in antibody titer up to 16 wk after vaccination. Our results suggest that the combined vaccine successfully induced humoral and protective immunity against the three pathogens in olive flounder.