Plasma cholinesterase inhibition in the clay-colored robin (Turdus grayi) exposed to diazinon in maradol papaya crops in Yucatan, Mexico

The use of organophosphorous pesticides in agriculture can result in intoxication of birds foraging in sprayed crops. Effects on birds resulting from pesticide intoxication are varied and include behavioral and reproductive effects, including death. One widely used insecticide in Maradol papaya crops is diazinon which has been associated with various incidents of intoxication and death of wild birds. The objective of this study was to evaluate the impact of diazinon application to papaya crops on plasma cholinesterase activity of the clay-colored robin (Turdus grayi). We captured clay-colored robins foraging in a papaya crop the following day after the field had been sprayed with diazinon at a dose of 1.5 kg/ha during March and May, respectively. We took a blood sample from the brachialis vein of the birds captured and measured plasma enzymatic activity. The plasma samples from birds used as controls were taken during the same time period and were analyzed in a similar way. Enzymatic activity of males was greater than that of females (53,52%) and mean cholinesterase inhibition was 49.43%. Cholinesterase inhibition was greater during May than in March probably due to more continuous exposure and ingestion of the insecticide through food and possible absorption through the skin. This degree of enzymatic inhibition is possibly affecting the behavior of the clay-colored robin and could result in death in severe cases.