Stability of residues and brain cholinesterase activity in carcasses of northern bobwhite exposed to three organophosphate insecticides

Abstract

AbstractPresence of pesticide residues in animal tissues and inhibition of brain cholinesterase (ChE) activity are often used to document exposure of animals to organophosphorus and carbamate insecticides and determine if the animal's death resulted from exposure. Carcasses found during field studies can be several days old; therefore, it is important to determine how residue and ChE levels change over time after death. Objectives of this study were to determine pesticide residues in tissues and/or brain acetylcholinesterase (AChE) activity of northern bobwhite (Colinus virginianus) exposed to either sulprofos, methamidophos, or azinphos‐methyl, and the extent to which residue and AChE levels change with decomposition of carcasses under field conditions. Test compounds were administered orally by gavage and/or in the diet to northern bobwhite at previously determined sublethal and lethal exposure levels. Birds surviving the dose were sacrificed and placed in crop fields. Carcasses were recovered following 0‐, 24‐, 48‐, and in some cases 96‐h intervals and analyzed for residues. Brain AChE activity was also determined for birds exposed to sulprofos. Residues were detected in all exposed birds and varied with dose. Results indicate that pesticide residues and brain AChE levels were stable under field conditions at least up to 48 to 96 h following death.