Effects of diazinon on some innate resistance parameters in the Caspian pond turtle (Mauremys caspica caspica)

Several experimental studies have been conducted to determine whether environmental stressors, including chemical pollutants, may have immunosuppressive effects and therefore, trigger disease emergence in exposed organisms. The present study aimed to evaluate the effect of diazinon (DZN), a worldwide used organophosphate pesticide, on some immune parameters of Caspian pond turtle (Mauremys caspica caspica). Twenty-four turtles (with a mean body weight of 182.6±10.8 g and mean age of 2 years) were randomly distributed in four groups. Three groups were intraperitoneally injected once with three different doses of DZN (1, 10, or 100 ng/g body mass), while one was main-tained as control (1 mL olive oil injected). Blood samples were taken 1 and 2 weeks post-treatment. A positive correlation was found between diazinon (high dose) concentration and immunosuppressive effects at the 2nd week post exposure as evidenced by lowered serum complement maximum haemolysis (MH%) (from 57.0% to 31.5%), diminished lysozyme activities (from 6.6 mg/L to 4.8 mg/L), increased heterophil/lymphocyte ratio (from 1.62 to 2.97), reduced leukcocyte counts (from 4.46×109/L to 2.85×109/L) as well as phagocytic activity (from 28.16% to 19.0%). The data demonstrated that turtles with high-dose diazinon exposure exhibited immunomodulation