Flow cytometric analysis of fish leukocytes as a model for toxicity produced by azadirachtin-based bioagrocontaminant

Azadirachtin is one of the most promising natural biopesticide used to overcome the hazardous effects of different organic pesticides and believed to be more environmentally friendly due to the unique nature of biodegradability. In the present study, the impact of no-observed-effect level (NOEL) dose of an azadirachtin-based bioagrocontaminant, Neemsheild, on the blood profile of Indian major carp, Labeo rohita, was examined. The 96-hr LC₅₀ value of Neemsheild was found to be 44.61 ppm. The total erythrocyte count (TEC), hematocrit (Hcrt), and Hb (hemoglobin) values showed a gradual decrease throughout the experimental period, whereas total leukocyte count (TLC) showed an initial increase followed by decline. Flow cytometric analysis subdivided the entire leukocyte population into four separate groups: thrombocytes together with small lymphocytes, monocytes, neutrophils, and basophils. The fluctuation in leukocyte subpopulation indicated an immunotoxicological effect due to azadirachtin. Clustering of different cell types and similarity percentage values were found to differ greatly from control. It was evident from the study that the cell population comprising small lymphocytes and thrombocytes indicated predominant changes as physiological response of fish to different doses of azadirachtin. Thus, flow cytometric analysis of leukocyte populations may be considered as a biomarker to assess fish toxicity.