Monitoring Wading Bird Exposure to Agricultural Chemicals Using Serum Cholinesterase Activity

Abstract

Abstract-Organophosphorus (OP) and carbamate (CB) insecticides are widely used and have a variety of lethal and sublethal effects on nontarget wildlife, primarily through cholinesterase (ChE) inhibition. To assess possible exposure to anti-ChE compounds in wading birds, we monitored breeding colonies in northeast U.S. estuaries (Boston Harbor, MA; New York Harbor, NY; Nantucket Sound, MA; Delaware Bay, DE; and Rehoboth Bay, DE) from 1991 to 1996. We documented serum ChE activities in black-crowned night-heron (Nycticorax nyticorax), cattle egret (Bubulcus ibis), snowy egret (Egretta thula), little blue heron (E. caerulea), and glossy ibis (Plegadis falcinellus), and we investigated factors known to affect ChE, including age, nutritional and immune status, location of the colony (estuary), and exposure to ChE-inhibiting compounds. Exposure to anti-ChE compounds in all species was supported by at least one of the following: positive pyridine-2-aldoxime methochloride (2-PAM; OP) and/or spontaneous (CB) ChE reactivations, negative or nonsignificant age correlations in most species, or regional land-use patterns. We observed negative or nonsignificant relationships between ChE and age in most species. Only glossy ibis showed the age-related patterns of ChE activity observed in other altricial species. Of the remaining potential explanatory factors, location (estuary) but not nutritional or immune status was the only one having a significant relationship with ChE activity (p Ͻ 0.024). Significant differences among colonies were consistent with surrounding land uses, specifically active agriculture. We conclude that extensive monitoring of serum ChE in wildlife can identify locations of exposure and provide reference data for wildlife pesticide-risk assessment.

Acute Toxicity and Cholinesterase Inhibition in Chicks Dosed Orally with Organophosphate Insecticides

“…Thirty minutes after dosing, diazinon at 10 mg kg -1 orally decreased brain and plasma ChE in chicks by 20 % and 79 %, respectively (40). A similar trend has been observed with brain and blood ChE activities following OP poisoning in rats (41,42) and wild birds (9,10). However, there are a number of exceptions to this generalisation (3,6,25,43).…”

“…Reduced ChE activity is still a reliable indicator of OP poisoning and a biomarker of absorption of OP insecticides (3,4,(6)(7)(8)(9)(10). In the avian species, ChE activities in the brain and plasma are frequently measured to assess the condition of exposure or poisoning (9, 10, 12-14, 18, 19, 22, 24).…”

“…The most important diagnostic or biomarker endpoint of OP exposure and poisoning is decreased ChE activity in the blood (erythrocytes, plasma or serum) and other tissues, brain in particular (3)(4)(5)(6)(7)(8). Birds have no ChE activity in erythrocytes; therefore, the extent of their exposure to and/or OP poisoning is based on ChE activity in plasma and nervous tissue (3,(9)(10)(11).…”

Ecological Risk Assessment for Chlorpyrifos in Terrestrial and Aquatic Systems in the United States

“…The resulting accumulation of acetylcholine causes overstimulation of cholinergic synapses (Testai et al 2010 ). Exposure to CPY in birds can be detected biochemically as reduced activity of AChE in blood plasma or brain (Parsons et al 2000 ;Testai et al 2010 ). Other symptoms of toxicity include loss of mass, ruffl ed appearance, loss of coordination, reduced reaction to sound and movement, wing droop, prostrate posture, weakness of lower limbs, lethargy, gaping, salivation, muscle fasciculation, convulsions, and death (Gallagher et al 1996 ).…”

“…Chlorpyrifos inhibits acetylcholinesterase activity causing acetylcholine to accumulate at nerve terminals and neuromuscular junctions, which leads to cholinergic overstimulation (Testai et al 2010 ). In birds, CPY poisoning can be detected biochemically as reduced cholinesterase activity in plasma and brain tissues (Cairns et al 1991 ;Parsons et al 2000 ;Timchalk 2010 ). A gavage study with northern bobwhite ( C. virginianus ) found reduced brain cholinesterase activity at concentrations of 47 mg ai kg −1 bwt of CPY and greater (Cairns et al 1991 ).…”