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