Protective Efficacy of a Commercial β-hemolytic Streptococcus Vaccine for Japanese Flounder against Streptococcus iniae Infection of Threadsail Filefish

Abstract

A commercial β-hemolytic Streptococcus vaccine for Japanese flounder was examined for the protective efficacy against Streptococcus iniae infection of threadsail filefish Stephanolepis cirrhifer. In the artificial infection test a high mortality rate (90%) was obtained by intramuscular inoculation with S. iniae as low as 10² CFU/100 g body weight. In the vaccination test intraperitoneal inoculation with the vaccine at the usual and 1/10 dosages resulted in a high protective effect (RPS≥85%), and the high protective efficacy was kept for at least 7 months.