Florfenicol Therapy Reduces Brain Histoarchitectural Anomalies in Streptococcus agalactiae-Infected Nile Tilapia Oreochromis niloticus

Streptococcus agalactiae (Sa) infection can result in severe economic losses in tilapia aquaculture. This study offered insights into the therapeutic potential of florfenicol (FFC) and the histopathological changes in the forebrain and midbrain of Sa-infected Oreochromis niloticus. Healthy tilapia (n=225) were divided into three groups: control, Sa-challenged and untreated, and Sa-challenged and FFC-treated. The Sa-infection was induced by intramuscular injection of 1.32×10⁷ cells/fish, and the infected fish received FFC orally at 15 mg/kg biomass/day for 10 consecutive days. Sa exerted serious pathological effects on the forebrain and midbrain of O. niloticus. These effects include focal hemorrhage, mononuclear cell infiltration, lifting of the superficial layer, spongiform encephalopathy, intracellular edema, edematous optic tectum, connective tissue damage, and meningitis. Compared with the untreated group, the treated group demonstrated that FFC is a potential therapeutic agent for mitigating Sa-induced infections by reducing mortality and improving the overall brain histoarchitecture of O. niloticus.