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Anticoagulants in the environment : FRST research update 2010/11 Balancing residue risks against effective pest control.

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Presentation on theme: "Anticoagulants in the environment : FRST research update 2010/11 Balancing residue risks against effective pest control."— Presentation transcript:

1 Anticoagulants in the environment : FRST research update 2010/11 Balancing residue risks against effective pest control

2 Brodifacoum use patterns in NZ ‘Over-the-counter’ household rodent baits Field application in bait stations for possums (no user licence needed) Aerial application for rodent eradication (islands, fenced reserves) HBRC131%20Environmental%20fate%20of%20brodifacoum%20in%20wildlife.pdf Envirolink review (2010) : Environmental fate & persistence of brodifacoum in wildlife

3 Raptors: wildlife sentinels Hunters / scavengers of pest mammals targeted with anticoagulants Surveys for anticoagulant residues in birds of prey; USA (Stone et al. 2003, Hosea 2000) UK/Ireland (Eadsforth et al. 1996, Newton, Shore, Walker et al ) France (Poulinquen et al 2006,Lambert et al 2007) Canada (Albert, Mineau et al. 2009) In general, 30-60% of some hawk species with detectable coumarin residue in liver Secondary exposure of some raptors widespread as the result of commensal rodent control

4 Roadkill survey, NZ Roadkilled hawks opportinstically collected Oct-Dec 2010 from Selwyn & Hurunui Australasian harrier hawk (Circus approximans) - common, widespread predator/scavenger in NZ - adult weight g (liver up to ~2.5 g) Livers tested for multiple anticoagulants:  brodifacoum, flocoumafen, bromadiolone  coumatetralyl MDL 0.01 μg/g  warfarin MDL 0.1 μg/g

5 Results: residues in hawk liver Of 18 hawk livers tested to date 4 nothing detected i.e ~78% with residues 3 had just one coumarin present (brod, coum, or floc) 7 had two coumarins (all brodifacoum + another) 3 had three coumarins (mixed combinations) 1 had four coumarins (brod, floc, coum & warf)

6 Liver residues in hawks – so what? Increasing probability of poisoning Supplement with necropsy & histopath data

7 Case study : aerial brodifacoum 24 th June 2010 – bags of brodifacoum pellet bait spilled from helicopter into Lake Kirirua, Fiordland 700 kg bait entered lake (14 g brodifacoum into c. 30 ha lake) Environmental monitoring over 2 days – 4 weeks after spill: Water Sediment Benthic invertebrates Eels Birds NO detectable brodifacoum

8 Snails & anticoagulant baits Snails offered baits over 2 weeks: brodifacoum (Talon®, Pestoff®) or diphacinone (Ditrac®, Ratabate®) Baits weighed to determine uptake Snail poo collected for analysis to determine excretion Snail weight & survival recorded Snails sacrificed in groups/intervals to determine residue profile in gut & muscle tissue & elimination rate of residues

9 Snails & anticoagulant baits Snails fed more often on the two solid wax block baits (Ditrac and Talon WB) than either the paste (Ratabate) or pellet (Pestoff 20R) baits Coloured snail poo provides evidence of continued feeding No mortality attributed to feeding on bait over 2 weeks Residue results from snail tissues pending……..

10 Pindone residues in rabbits – lab trials Anticipated increase in pindone baiting for rabbit management Little known about residues of pindone in poisoned rabbits Anecdotal reports of secondary kills of hawks and gulls Lab trials of rabbits fed pindone cereal pellet bait (0.25 g/kg pindone) * lethal dose offered over five days * tissues sampled after death & tested for residues

11 Pindone residues in rabbits – lab trials Variability in what is a lethal intake Residues higher in liver than in muscle (expected) Residues in fat similar at concentrations to those in liver (not expected)


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