Streptococcosis is a bacterial disease of worldwide relevance that significantly affects the zootechnical performance of tilapia. Infectious spleen and kidney necrosis virus (ISKNV) is globally gaining more attention, due to its highly significant economic impact on the tilapia aquaculture industry. Vaccination is commercially available for these two pathogens, and therefore can play an important tool in the prevention of these diseases.
This study describes a field trial conducted to confirm the safety and of the combined vaccination program using AQUAVAC® Irido V and AQUAVAC® Strep Sa-Si vaccine, under real-world culture conditions in tilapia. The trial was conducted during the autumn period in the Ilha Solteira reservoir, São Paulo, Brazil, a location with previous history of ISKNV and Streptococcus’s infections. The juvenile fish were reared in excavated ponds, free of infection. They were divided and immunized into two groups: the control group received exclusively AQUAVAC Strep Sa-Si vaccine (inactivated bivalent vaccine against Streptococcosis caused by Streptococcus agalactiae serotype Ib and Streptococcus iniae) and the treatment group received a combined treatment of AQUAVAC Strep Sa-Si and AQUAVAC Irido V (inactivated vaccine against ISKNV). The average weights at the time of vaccination for each group were 31 g for the control group and 17.5 g for the treatment group , the difference in average weight does not interfere with the evaluation and occurred due to farm management. After the recommended rest period, the animals were transferred to cages in a grow-out environment in the reservoir. Mortalities were individual ly counted during the whole production cycle to measure the survival rate.
At the time of harvesting, survival rates of 71.90% was observed in the control group and 95.29% in the treatment group. The survival rate difference (23.39%) can be attributed to the ISKNV protection, as the higher mortality rate of the control group was observed in response to environmental thermal variation throughout the cultivation, evidencing mortality peaks, while the treatment group maintained a stable cumulative curve.
These results demonstrate that the combination of AQUAVAC Strep Sa-Si and AQUAVAC Irido V vaccines are safe and efficacious when used in combination under field conditions.