PARENT SESSION
PS1 - Wildlife Toxicology
Sunday, 17 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P009) Fenitrothion exposure and effects in native arid zone Australian bird species during locust control.
Fildes, Karen1, Bain, David1, Szabo, Judit1,2, Story, Paul3, Hooper, Michael2, Buttemer, William1, Astheimer, Lee*,1, 1 Institute for Conservation Biology, University of Wollongong, Wollongong, NSW Australia, Australia2 The Institute of Environmental and Human Health, Texas Tech University, Lubbock, Texas, USA3 Australian Plague Locust Commission, Canberra, ACT, Australia, Australia
ABSTRACT- Outbreaks of the Australian plague locust (Chortoicetes terminifera) are unpredictable, occurring in response to rainfall and other local conditions. In arid and semi-arid regions of Australia the conditions promoting locust buildups, and the abundance of locusts themselves, attract aggregations of nomadic and opportunistic birds, making them vulnerable to pesticide exposure. The Australian Plague Locust Commission (APLC), responsible for locust control across 2 million km2 of eastern Australia, routinely spray the OP fenitrothion (210-300 ml/hectare, ULV) to limit locust bands or swarms. During a recent spray event in southwestern Queensland we observed avian diversity and abundance and captured birds to determine fenitrothion exposure using cholinesterase (ChE) inhibition as a biomarker. Active locust bands attracted an unusual assemblage of birds. Both locusts and granivorous birds (e.g. Zebra Finch) fed heavily on ripe grass seeds. Many insectivorous species consumed locusts (e.g. Australian Bustard, Raven, Brown Songlark), with flocks of Black Kites gorge feeding. Further, an unusual abundance of Brown Falcons preyed on smaller birds. Birds were caught in mist nets and plasma samples collected prior to the spray event and 24 and 72 hours post-spray. Plasma ChE activities were measured using the Ellman method (1961) modified by Gard and Hooper (1993). Mean acetylcholinesterase (AChE) activity in Zebra Finch plasma was significantly reduced 24 h after spraying, with post-spray AChE activity only 25% of pre-spray values. ChE reactivation was performed on plasma from 18 birds to identify the presence of OP-inhibited ChEs. Plasma ChE, treated with 2-PAM, will increase activity if previously OP- inhibited. Significant reactivation (increase in activity of at least 5 percent after 2-PAM) was apparent in samples from 8 birds of 5 species (a raptor, 3 insectivores, and a granivore), demonstrating the potential for sub-lethal impacts on birds via varied routes of fenitrothion exposure during locust control activities.
Key words: locust control, fenitrothion, avian exposure, cholinesterase inhibition