Streptococcus agalactiae (Group B Lancefield) has emerged as a significant pathogen affecting both humans and animals, including aquatic species. Infections caused by S. agalactiae 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 (Oreochromis niloticus), a member of the Cichlid family, is one of the severely affected fish species by S. agalactiae. The current study aims to focus on S. agalactiae infection in cultured O. niloticus with reference to its transmission and sources of infection; risk factors influencing GBS infection, disease clinical signs, lesions, and pathogenesis; S. agalactiae virulence factors; and how to diagnose, treat, control, and prevent infection including vaccination and herbal extract medication.
Keywords: Gram-positive cocci; biofilm formation; immunization; plant extracts; teleost.