Praziquantel residue profile and integrated biomarker response-based risk assessment for Nile tilapia Oreochromis niloticus.

As aquaculture intensifies, Nile tilapia Oreochromis niloticus is increasingly susceptible to parasitic infections. This study evaluated the safety and physiological effects of praziquantel (PQ) in tilapia. PQ was administered orally at 50 mg/kg (recommended dose) and 125 mg/kg biomass/day (supratherapeutic dose) for 3 days, and the effects were compared with a control group. Mortality in PQ-treated groups ranged from 0.67% to 4%. Plasma glucose increased dose-dependently on day 3 and returned to baseline in the recommended dose group by day 28 post-treatment. Calcium, chloride, and acetylcholinesterase levels decreased during dosing, with partial recovery observed subsequently. On day 3, reductions in erythrocyte, hemoglobin, and hematocrit levels were accompanied by increases in leucocyte and thrombocyte counts. The supratherapeutic dose group exhibited more pronounced cellular and nuclear alterations in erythrocytes. Oxidative stress biomarkers in liver and kidney tissues indicated organ-specific stress. Integrated Biomarker Response analysis revealed that a supratherapeutic dose induced greater biological disturbances. At the recommended dose, PQ residues in muscle and skin reached below detectable levels within 2 days, supporting a 2-day withdrawal period for consumer safety. However, some biological instabilities persisted beyond this period, suggesting incomplete physiological recovery and therefore, residue clearance alone does not confirm complete biological safety.