Development, application, efficacy, and future directions of vaccination against Streptococcus infections in tilapia: a systematic review and meta-analysis

This systematic literature review and meta-analysis synthesizes empirical findings regarding the application of vaccines against Streptococcus infections in tilapia culture. Beyond systematically assessing advances and future directions in anti-Streptococcus vaccination, we examined vaccine effects on prechallenge immunomodulation and postchallenge protection in tilapia. Injectable vaccines remain the standard but present logistical and technological challenges, while oral and immersion vaccines require formulation improvements. Innovations in delivery systems show promise in boosting vaccine coverage. However, challenges persist, including variability in study methodologies, limited field trials, and the need for cross-protective vaccines. Prechallenge vaccine administration generally led to a significant (p < 0.05) increase in antibody titer, lysozyme activities, and immune gene regulation, while postchallenge survival based on meta-analysis indicated significantly (p < 0.05) higher survival in vaccinated fish compared to the control nonvaccinated. A comparison of the relative percentage survival (RPS) of the main vaccine types indicated that the attenuated vaccine had the highest mean RPS, followed by the ghost vaccine, while the DNA vaccine had a significantly (p < 0.05) lower RPS. There were no significant (p > 0.05) differences observed among the inactivated, subunit, attenuated, and ghost vaccine groups, indicating comparable survival rates. These findings support vaccination as a viable strategy for Streptococcus management in tilapia culture. Further research should focus on optimizing vaccine formulations, enhancing long-term field efficacy, and analyzing the cost-effectiveness of vaccine application in fish culture.