Streptococcus agalactiae Infection in Nile Tilapia (Oreochromis niloticus): A Review

Abstract

<i>Streptococcus agalactiae</i> (Group B Lancefield) has emerged as a significant pathogen affecting both humans and animals, including aquatic species. Infections caused by <i>S. agalactiae</i> are becoming a growing concern in aquaculture and have been reported globally in various freshwater and marine fish species, particularly those inhabiting warm water environments. This has led to numerous outbreaks with high morbidity and mortality in fish. Nile tilapia (<i>Oreochromis niloticus</i>), a member of the Cichlid family, is one of the severely affected fish species by <i>S. agalactiae.</i> The current study aims to focus on <i>S. agalactiae</i> infection in cultured <i>O. niloticus</i> with reference to its transmission and sources of infection; risk factors influencing GBS infection, disease clinical signs, lesions, and pathogenesis; <i>S. agalactiae</i> virulence factors; and how to diagnose, treat, control, and prevent infection including vaccination and herbal extract medication.