ABSTRACT
Acephate (Ace) is an organophosphate foliar spray insecticide of moderate persistence with residual systemic activity of about 10–15 days. This study was designed to evaluate the immunotoxic effect of oral subacute acephate exposure in 125-day old WLH Cockerel chicks for 28 days. The experimental birds were randomly divided into five groups (C1, C2, T1, T2 and T3), each comprising 25 birds. The birds of group C1 were given no treatment and served as control. Group C2 was administered groundnut oil (1ml/kg) and served as control (vehicle). Group T1 was given ALD50/40 (21.3 mg/kg), and Group T2 was put on ALD50/30 (28.4 mg/kg), while group T3 received ALD50/20 (42.6 mg/kg) of acephate suspended in groundnut oil. Experimental birds of all groups were vaccinated with New Castle disease vaccine at day 7. Blood was collected at two-week intervals for evaluation of humoral immune response. Parameters such as TLC, TP, antibody titre against ND vaccine, DNCB dye test, and histopathology of immune organs were studied to evaluate immunotoxicity. The results were statistically compared (p<0.05) with the control. Acephate produced decreased humoral immune response in terms of New Castle disease vaccine antibody titre, total protein, serum globulin, and serum albumin. Cell mediated immune response was checked with 1-chloro 2, 4 dinitrobenzene dye dermal sensitization test, and it did not reveal any significant differences. Lymphoid organs such as thymus, spleen, bursa, and liver were weighed during necropsy for calculation of organ weight: body weight ratio. After 28 days of acephate exposure, organ:body weight ratios of immune organs were significantly reduced except liver:body weight ratio on 14 days of exposure, which was increased in all treatment groups as compared to control groups. Histopathologically, bursa and spleen showed mild depletion of lymphocytes. To further identify the specific type of cell death as apoptotic or necrotic, DNA ladder assay was performed. DNA fragmentation assay detected ladder pattern (180bp) in DNA from hepatocytes and splenocytes of acephate-treated birds. It is concluded that acephate is immunotoxic, and exerts its immunotoxicity through induction of apoptosis and alteration of immunological parameters.