The use of antibiotics in aquaculture can have adverse effects on fish organs. While the impact of florfenicol (FFC) on the organ histology of Oreochromis niloticus has been studied, a comprehensive report summarizing these effects is lacking. This study aimed to evaluate the histological effects of FFC on O. niloticus juveniles by administering a dose of 15 mg/kg biomass/day for 10 consecutive days, which was in line with approved therapeutic guidelines. Significant alterations were observed in key organs such as the kidney, liver, intestine, and gills, while the impact on the spleen, heart, and eyes was minimal. Specifically, the kidneys exhibited renal tubular degeneration at the therapeutic dose and liver tissues documented glycogen-type vacuolation. The swollen intestinal lamina propria indicated impaired feed intake and increased biomass. Gill tissues showed epithelial hyperplasia, probably a protective response to FFC toxicity. Although minor alterations were noted in the spleen, they were considered insignificant. No abnormalities were detected in the heart or ocular tissues. This study highlighted the use of histological analysis as a valuable tool for assessing the safety of FFC in aquaculture. The findings suggested that histological alterations could serve as a preliminary assessment method for evaluating antibiotic safety in piscine research, offering insights into the organ-specific effects of FFC in O. niloticus.

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