Efficacy of a vaccine against Streptococcus parauberis infection in starry flounder Platichthys stellatus Pallas

Starry flounder, which are recently increasingly cultured in Korea, are known to highly vulnerable to Streptococcus parauberis infection. Five groups of starry flounder (n=30 for each group) were vaccinated with S. parauberis formalin-killed whole cells by intraperitoneal injection at a final concentration of 0, 0.01, 0.1, 1 and 10 mg fish -1 . Specific antibody production of 1 and 10 mg fish -1 administered groups significantly increased at four weeks post immunization. All vaccinated groups showed higher survival rates than a control group when five groups of fish were challenged with S. parauberis at a dose of 1.14×10 4 cfu fish -1 and 1.14×10 2 cfu fish -1 , respectively. In particular, 0.1 or higher concentrations of formalin killed bacterial cells are able to confer the fish high protection against S. parauberis infection.