Immunopathological effects of pesticides on lymphoid organs in sheep

There has been indiscriminate use of pesticides in agriculture and animal husbandry resulting in contamination of environment. The residues present in the environment may affect the immune system of the body. Since lymphoid organs like lymph nodes and spleen regulate immune system, this work was planned to investigate the immunotoxic effect of insecticides on lymphoid organs of sheep by chronic feeding of low level of these insecticides for 6 months. For this, 20 lambs of about 6 months of age were procured and divided randomly into 5 groups of 4 lambs each. Keeping one group (1) as control, lambs of groups 2, 3, 4 and 5 were orally given commercial preparations of lindane (1.25 ppm), monocrotophos (0.025 ppm), carbofuran (2.5 ppm) and fenvalerate (1.25 ppm) respectively, daily in water for 6 months. After 6 months, lymphocyte stimulation test was performed on spleen and mesenteric lymph nodes. Sections of spleen and lymph nodes were collected in 10% formol sublimate and 2.5% glutaraldehyde for histopathology and electron microscopy, respectively. Significant reduction in mean delta OD values was seen in groups of lambs given lindane and monocrotophos in both Con-A and PHA stimulated cultures of both spleen and lymphocytes. On histopathological examination, spleen and lymph nodes showed depletion of lymphoid tissue in insecticide treated lambs. Electron microscopic examination of the spleen and lymph nodes revealed coagulative necrosis of the lymphoid cells, pyknotic nuclei, karyorrhexis and presence of toxic granules in granulocytes in pesticide fed groups.