Protective Efficacy of a Formalin-Killed Vaccine against Atypical Edwardsiella tarda Infection in Red Sea Bream Pagrus major

Edwardsiella tarda causes high mortality infections in fish. To determine the efficacy of a vaccine against E. tarda, a formalin-killed preparation of atypical E. tarda FPC503 was intraperitoneally injected into red sea bream Pagrus major with or without the oil adjuvant, Montanide ISA 763 A VG. Both vaccine regimens showed protective efficacy against experimental infection with E. tarda FPC503 at 28 and 56 days post-vaccination. An enzyme-linked immunosorbent assay (ELISA) revealed the specific antibody production in vaccinated fish but the relationship between protective efficacy and antibody titer was not clear. The present results indicate that the formalin-killed vaccine is useful for the prevention of atypical E. tarda infection in red sea bream.