Toxicological and Food Safety Implications of Ethanolic Extract of Avocado (Persea americana) Leaves on the Liver and Gills of Clarias gariepinus (Burchell, 1822) Fingerlings

This study investigated the effects of ethanolic leaf extract of avocado (Persea americana) on the behavior and histopathology of Clarias gariepinus fingerlings. One hundred fish specimens were exposed to graded concentrations of the plant leaf extract (0.0, 2.0, 4.0, 6.0, and 8.0 mg/l) over a period of 96 h, Time-dependent (24 h, 48 h, 72 h, and 96 h). Responses were monitored, with particular attention to behavioral alterations and histopathological changes in the gills and liver. The 96-hour LC₅₀ was determined to be 2.8 mg/L, corresponding to a log-transformed concentration of 0.45 mg/L indicating the concentration at which 50 % of the test organisms were lethally affected. The study revealed that P. americana extract influenced water quality parameters in a concentration-dependent manner over time. Exposed fish exhibited prominent behavioral abnormalities, including excessive mucus secretion, air gulping, respiratory distress, erratic swimming, and vertical orientation. Histopathological analysis showed dose-dependent lesions in the gills, such as hyperplasia, epithelial erosion, lamellar fusion, disorganization of secondary lamellae, and cellular degeneration and in the liver, including hepatic coagulative necrosis, vacuolation of the parenchyma, hepatocellular hyperplasia, necrosis, and hepatopancreatic tissue lysis. These alterations suggest that bioactive phytochemicals present in avocado leafs, such as saponins, tannins, flavonoids and persin may disrupt oxidative balance, impair protein and lipid metabolism, and compromise detoxification pathways. While avocado leaves contain compounds with reported antioxidant and antimicrobial benefits at low doses, their indiscriminate use in aquaculture poses risks to fish growth, nutrient utilization, and food safety. The findings underscore the need to define safe exposure limits for P. americana extracts in fish nutrition and to integrate biochemical biomarkers of oxidative stress in future risk assessments.