Exploring the toxicity of thiamethoxam on aquatic ecosystems: an overarching assessment of biochemical parameters, genotoxicity, fish flesh residues and histological alterations in Nile tilapia

Abstract

This study assessed the effect of thiamethoxam on the Nile tilapia (Oreochromis niloticus) under subacute and chronic exposure. The study focused on biochemical markers, genetic damage, pesticide residue levels in fish flesh, and histopathological changes in fish exposed to different concentrations of thiamethoxam (25, 50) for 30 days and (100, 250 mg/L) for 4 days. The study found that prolonged exposure to high doses of thiamethoxam (50 mg/L for 30 days) had significant negative effects on fish health. This exposure led to increased levels of urea and ALT in the blood, indicating potential damage to the kidneys and liver. Additionally, thiamethoxam caused oxidative stress, as evidenced by elevated levels of MDA and upregulated TLR2 gene expression. Thiamethoxam also negatively impacted the fish’s antioxidant defense system. It significantly reduced the expression of key antioxidant genes like ghrelin and catalase, particularly at 250 mg/L for 4 days. The total antioxidant capacity (TAC) and superoxide dismutase (SOD) levels remained relatively stable, except for slight decreases at the highest dose. Thiamethoxam residues were detected in the muscle tissue of fish, with the highest levels found in the 250 mg/L for 4 days. Histological examination revealed severe degenerative changes in the gills and liver tissues of the fish exposed to thiamethoxam, with the severity of the damage increasing with the concentration of the pesticide. In conclusion, cautions must be taken when we use neonicotinoids due to its negative feedback impact on Nile Tilapia fish health and consequently affect humans as a final consumer.