Determination of Brain Cholinesterase Activity in Normal and Pesticide Exposed Wild Birds in Israel

Whole brain cholinesterase activity was measured in 26 species of wild birds in Israel, and compared to depressed cholinesterase activities of birds known to having been exposed to certain organophosphorus and carbamate insecticides. The purpose of the study was to establish a reference range of normal whole brain cholinesterase activities, which will enable ecotoxicologists to evaluate suspected cases of organophosphorus and carbamate exposure in wild birds in Israel. Normal whole brain cholinesterase activity in birds of prey ranged from 7.4-12.5 mu mol/min/g tissue, and the remaining avian species exhibited a wider range of 7.4-19.8 mu mol/min/g. Birds' carcasses with residual pesticides in their proventriculus and gizzard, revealed a significant decrease of more than 50% of their normal whole brain cholinesterase activity, thereby confirming the cause of the death due to cholinesterase inhibition. The most prominent pesticides detected in the stomach content of wild birds were the carbamates, aldicarb and methomyl. The reference values presented in this study could facilitate routine diagnosis and monitoring of exposure to anticholinesterase agents in wild birds in Israel.