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)
• Aerial application for rodent eradication (islands, fenced reserves)
http://www.envirolink.govt.nz/PageFiles/606/884-HBRC131%20Environmental%20fate%20of%20brodifacoum%20in%20wildlife.pdf
Envirolink review (2010) : Environmental fate & persistence of brodifacoum in wildlife
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
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 600-900 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
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)
Liver residues in hawks – so what?
0
0.05
0.1
0.15
0.2
0.25
0.3
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Hawk No,
Live
r co
ncen
trat
ion
(ug/
g)
Brodifacoum Flocoumafen
Bromadiolone CoumatetralylIncreasing probability of poisoning
Supplement with necropsy & histopath
data
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
NO detectable
brodifacoum
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
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……..
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
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)
0 5 10 15 20 250
1
2
3
4
5
6
7
8
9
Liver Muscle Fat
Residual concentration of pindone in rabbit tissue (mg/kg)
Pin
do
ne
ing
est
ed
ove
r fiv
e d
ays
(m
g/k
g)
Non-lethal expo-sure
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