Pathogenicity of Streptococcus iniae and Lactococcus garvieae in Farmed Thread-sail Filefish and Efficacy of the Formalin-killed Vaccines against These Bacteria

Abstract

The virulence of Streptococcus iniae and Lactococcus garvieae strains was evaluated in farmed thread-sail filefish Stephanolepis cirrhifer by intraperitoneally injecting live bacterial cells. These two pathogens were highly pathogenic to thread-sail filefish. The efficacy of each commercial vaccine, namely, S. iniae vaccine, L. garvieae vaccine, and a combined vaccine of S. iniae and L. garviae was evaluated in the fish. The mortality was significantly lowered in both S. iniae- and L. garvieae-vaccinated groups compared to the control group, and both vaccines showed strong protection against the respective pathogens. Moreover, the combined vaccine showed strong protection against these two pathogens. These results suggest that these commercial vaccines are applicable in filefish aquaculture.