Effects of diazinon on blood parameters in the African catfish (Clarias gariepinus)

The aim of this study was to assess the effect of diazinon [0,0-diethyl 0-(2-isopropyl-6-methylpyrimidin-4yl) phosphorothioate] on cultured and wild African catfish (Clarias gariepinus). The effect was assessed based on results of acute toxicity tests and on a comparison of results of haematological examination of a control and an experimental group exposed to Diazintol(R) pesticide preparation (active substance 162 mg.l(-1) of diazinon). The acute toxicity test lasting 96 h was performed semi-statically on the African catfish of mean weight 350 +/- 15 g, and mean total length of 35 +/- 2.0 cm. Examination of erythocyte and leucocyte profile was performed on 16 control and 20 experimental specimens of the catfish after 96 h of exposure to Diazintol(R) in concentration of 9.4 mgl(-1). The 96 h LC50 value of Diazintol(R) for the African catfish is 6.6 mgl(-1). The experimental group of the African catfish showed significantly lower values (p < 0.05) of erythocyte count (RBC), haemoglobin content (Hb) and haematocrit (PCV) compared to the control group. Values of MCV, MCH and MCHC were comparable in both groups during the study. On the contrary, there was a significant decrease in leucocyte count (p < 0.05), as well as in both the relative and absolute lymphocyte count (p < 0.05) and a significant increase in both the relative and absolute count of developmental forms of neutrophile granulocytes: myelocytes (p < 0.05) and metamyelocytes (p < 0.05) in the experimental group. Relative and absolute count of monocytes and both the band- and segmented neutrophile granulocytes was comparable in both groups during the study. Changes in values of both the erythocyte and leucocyte profile after exposure to diazinon-based preparation may be referred to disruption of haematopoiesis as well as to a decrease on non-specific immunity of the fish.