Immunosuppressive action of nuvan (dichlorovos) in the banded pearl spot, Etroplus suratensis - evaluation of effect on haematology and humoral immune response

Abstract

Experiments were conducted to elucidate the effect of the organophosphorus pesticide, nuvan (dichlorvos) on some of the haematological parameters and humoral immune response in the pearl spot, Etroplus .suratmsis. The 96 hour LC, of nuvan for juveniles of this fish, was determined as 0.09 mg I-'. Juveniles were exposed to a sub-lethal dose of nuvan i.e., 0.01 mg I-' (a value close to 1/10' of the 96 hour LC,, value) for a period of 4 weeks by bath exposure. Blood samples were analyzed for hematological parameters such as total erythrocyte count (TEC), total leucocyte count (TLC), hemoglobin content (Hb), packed cel! volume (PCV), erythrocyte sedimentation rate (ESR) and serum protein content at fortnightly intervals. There was significant (P< 0.05) reduction in hemoglobin content and total serum protein in the test groups compared to the control fish. The TEC, PCV and ESR values were lower in the test groups compared to the controls but the differences were not statistically significant (P< 0.05). The total leucocyte counts were significantly higher (PC 0.05) in nuvan treated groups compared to control fish. There was also significant (P< 0.05) reduction in serum agglutinating antibody production to sheep red blood cells (SRBC) in the fish exposed to nuvan, as compared to the control group.