Pathology of deltamethrin toxicity in chick embryo

Abstract

The present study was taken up to investigate the embryotoxic and teratogenic effects of deltamethrin along with the effects on antioxidant mechanisms and on haematological parameters. The weight of the embryo, bursa and spleen, histopathology of liver, kidney, brain, heart, spleen, bursa and thymus, antioxidant assay which includes estimation of super oxide dismutase, lipid peroxidation , reduced glutathione, and haematological parameters such as total erythrocyte count, total leukocyte count, haemoglobin concentration, , heterophil percentage, lymphocyte percentage and heterophil lymphocyte ratio along with blood glucose level were the parameters analysed to study the effects. The study revealed a dose related increase in the embryo mortality in the treatment groups with a maximum of 18 percent in group VI inoculated with 1600ppm of deltamethrin. Deltamethrin was found to be teratogenic at the given dose levels. The anomalies observed were shorter lower beak (prognathism), curled toe, stumpy toes, syndactylism, shortened left limb, edema of the head and crossed beak and live sticky chicks. Deltamethrin did not cause any significant gross lesions in the developing embryos except mild haemorrhages. Deltamethrin did not result in any significant reduction in the weight of the embryos or the weight of lymphoid organs. On histopathological examination deltamethrin was found to be hepatotoxic and nephrotoxic which was evident by varying degrees of degeneration and necrosis in liver and kidney. Effect on lymphoid organs like spleen, thymus and bursa were mild to moderate with predominance of degenerative changes. Dose related changes were also observed in the heart which included vacuolar degeneration, thinning of fibres , myolysis and inter muscular haemorrhage. At the highest dose levels, deltamethrin caused significant brain lesions like gliosis, dark neurons, spongiform changes, neovascularisation and neuronal necrosis. Antioxidant assay on liver tissue at 200 and 400ppm dose levels revealed the potent hepatotoxic effects of deltamethrin mediated through free radicals as indicated by an increase in the lipid peroxidase and decrease in reduced glutathione and super oxide dismutase. Deltamethrin also resulted in significant increase in blood glucose level and reduction in haemoglobin concentration of exposed chicks maintatined for four weeks.