Genotoxicity and gene expression modulation associated with the use of DDVP antiparasitic drugs in aquaculture on Danio rerio

Introduction Parasites are a significant threat to aquaculture, and the application of various antiparasitic chemicals by aquafarmers is a widely practiced strategy to control them. Few antiparasitic drugs are toxic to hosts at higher concentrations and may be genotoxic to them. Genotoxicity tests have been successfully used as indicators of the toxicity of several drugs and environmental pollutants, including heavy metals. The current study was aimed to assess the toxicity of antiparasitic chemicals or drugs at various levels, with special emphasis on genotoxicity in a Zebrafish model. Methods Adult zebrafish were acclimatized under laboratory conditions and exposed to graded concentrations of dichlorvos to determine acute toxicity (LC25 and LC50) through a 96 h semi-static bioassay. Based on these values, fish were further subjected to sublethal and lethal concentrations for in vivo assessment at 24, 48, 72, and 96 h intervals. Genotoxicity was evaluated using micronucleus and alkaline comet assays on blood and gill tissues. Gene expression analysis of p53, Cyp1a, and Bcl-2 was performed in gill, liver, and kidney tissues using qRT-PCR after RNA isolation and cDNA synthesis. Data were statistically analyzed by one-way ANOVA followed by Tukey's post-hoc test at p < 0.05. Results This study investigated the genotoxic potential of dichlorvos in zebrafish using micronucleus and comet assays, along with gene expression analysis of key biomarkers (p53, Cyp1a, and Bcl-2). The 96-hour LC50 and LC25 values of DDVP were determined as 10.6 ppm and 6.78 ppm, respectively. Based on sublethal toxicity, zebrafish ( Danio rerio ) were exposed to four concentrations (2.5, 5, 7.5, and 10 mg/L) for in vivo analysis. A significant, concentration- and time-dependent increase in micronucleus frequency was observed, with a 5.5-fold rise between the lowest and highest concentrations after 24 h (h). DNA damage, assessed through comet assay, was minimal at 24 h but increased non-linearly, reaching maximum levels at 96 h, particularly in the highest exposure group. Gene expression analysis revealed marked upregulation of p53, Cyp1a, and Bcl-2 in gill tissues, especially at higher concentrations. Bcl-2 showed the highest induction (19.1-fold), followed by p53 and Cyp1a, indicating activation of cellular stress, detoxification, and apoptosis-related pathways in response to DNA damage. Conclusion Overall, dichlorvos exposure induced significant genotoxic effects in zebrafish in a dose- and duration dependent manner. The findings suggest that concentrations below LC25 may be relatively safer for therapeutic use. Further studies are required to check the efficacy of DDVP against different parasites to formulate more specific treatment strategies for sustainable aquaculture practices.