Impacts of Oral Florfenicol Medication and Residues on the Kidney and Liver of Nile Tilapia Oreochromis niloticus (L.)

SIMPLE SUMMARY: Florfenicol, an approved aquacultural antibiotic, is extensively used in temperate countries as therapeutics against several fish bacterial pathogens. It has never been introduced or used in several tropical countries. In earlier safety studies in tropical conditions, several alterations in the biological responses of Nile tilapia were documented. Yet, its safety was proclaimed at the juvenile stage. Though histopathological changes in the kidney and liver tissues upon oral florfenicol medication were assessed, the residue accumulation and depletion in these tissues were not documented vividly. The current study was undertaken to look at the biological responses, residue deposition and developmental oxidative stress in Nile tilapia upon oral administration at 0–10 times the therapeutic dose (15 mg kg biomass(−1) day(−1)) for 10 consecutive days and observed for 43 days post dosing. The therapeutic dose group documented 100% survival. Alterations in serum biochemistry were noted, which recovered completely with the suspension of medication. Florfenicol residues peaked on day 10 of medication and were undetectable within 9 days of post-dosing. Oral medication even at the therapeutic dose caused reversible oxidative stress. The results provided an insight into how the florfenicol residues behave in the vital organs at higher temperatures under controlled use in tropical conditions. ABSTRACT: Florfenicol (FFC), an approved aquaculture antibiotic, is administered in feed at doses of 10–15 mg kg biomass(−1) day(−1) for 10 successive days. In this study, healthy Oreochromis niloticus were fed with 0–10 times the therapeutic dose of 15 mg kg biomass(−1) day(−1) for 10 days and tracked for 43 days post dosing. Assessments of residue accrual and depletion, oxidative stress, serum biochemistry, histopathology and extent of kidney and liver damages were made. FFC dosing reduced the feed intake significantly. The therapeutic dose produced no mortalities on day 10. Dose-dependent alterations in serum biochemistry were noted upon dosing. Several histopathological alterations were observed in the kidney and liver, which vindicated the toxic potentials of FFC. The residual FFC and florfenicol amine (FFA) accrual, depletion and oxidative stress responses, such as increased malondialdehyde, total nitric oxide, ferric reducing antioxidant power and reduced glutathione S-transferase activity, were documented. The dietary FFC persuaded the physiological state of O. niloticus, the effects of which normalized sparsely with time upon cessation of dosing at the higher doses. The study provided a brief outlook on the physiological responses upon oral FFC administration, which should be kept in mind during its application for fish health safety purposes.