Blood esterase inhibition in birds as an index of organophosphorus contamination: field and laboratory studies.

: With the aim of developing a nondestructive biomarker (serum 'B' esterases) for monitoring bird populations exposed to azamethiphos S((6-chloro-2-oxooxazolo(4,5-b)pyridin-3(2H)-yl)methyl) 0,0-dimethyl phosphorothioate (9Cl), parallel laboratory and field studies were performed. In japanese quail (Coturnix coturnix japonica) treated with azamethiphos at 10 mg kg(-1), serum butyrylcholinesterase (BChE) and carboxylesterase (CE) activities were inhibited by 88% and 35%, respectively, after 24 h. A gradual recovery was observed after 48 and 72 h. With a higher dose (50 mg kg(-1)), the birds died, or were killed 3 h after dosing. Serum BChE and brain acetylcholinesterase (AChE), in birds that were sampled at 3 h, were inhibited by 98% and 92%, respectively. Hepatic microsomal and serum CEs were also inhibited. There was a statistically significant correlation (r=0.9808, p<0.001) between the activities of serum BChE and brain AChE. Swallows (Hirundo rustica) nesting in a stable treated with azamethiphos showed a drastic reduction in BChE (56%) and CE (36%) 24 h after treatment of the stable.