Efficacy of a commercial vaccine PISCIVAC™ Irido Si against iridoviral disease and streptococcosis in Asian seabass (Lates calcarifer)

Asian seabass (Lates calcarifer) is an economically important fish species in Southeast Asia. Iridoviral disease and streptococcosis are two of the major diseases in farmed Asian seabass. Here, we studied the efficacy of PISCIVAC™ Irido Si, a commercially available inactivated vaccine containing red seabream iridovirus (RSIV genotype II) and Streptococcus iniae antigens, against infectious spleen and kidney necrosis virus (ISKNV) genotype I and S. iniae infections in Asian seabass. In laboratory settings, the challenge of vaccinated fish with Vietnamese ISKNV genotype I strain showed 70–83% relative percent survival (RPS) at 21 days post-vaccination (dpv) and S. iniae challenge showed 75% or higher RPS at 7, 14, and 32 dpv. Also, the vaccine efficacy was confirmed at early vaccination stages (3 and 7 dpv) with an RPS of 85–97% against both pathogens and lasted for at least 74 and 348 dpv against ISKNV genotype I and S. iniae challenges, respectively. Furthermore, the vaccine was highly effective against challenges of ISKNV genotype I and S. iniae strains isolated in Thailand and Indonesia. These results suggest that the PISCIVAC™ Irido Si is useful for the prevention of iridoviral disease and streptococcosis in aquaculture of Asian seabass in ASEAN countries.