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Anticoagulants in the environment : FRST research update 2010/11

Anticoagulants in the environment : FRST research update 2010/11. Balancing residue risks against effective pest control. Brodifacoum use patterns in NZ. ‘Over-the-counter’ household rodent baits. Field application in bait stations for possums (no user licence needed).

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Anticoagulants in the environment : FRST research update 2010/11

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  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) Envirolink review (2010) : Environmental fate & persistence of brodifacoum in wildlife http://www.envirolink.govt.nz/PageFiles/606/884-HBRC131%20Environmental%20fate%20of%20brodifacoum%20in%20wildlife.pdf

  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. 2000-2010) • 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 Australasian harrier hawk (Circus approximans) - common, widespread predator/scavenger in NZ - adult weight 600-900 g (liver up to ~2.5 g) Roadkilled hawks opportinstically collected Oct-Dec 2010 from Selwyn & Hurunui • 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. NO detectable brodifacoum Case study : aerial brodifacoum 24th 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

  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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