Presentation on theme: "Anticoagulants in the environment Balancing residue risks against effective pest control."— Presentation transcript:
Anticoagulants in the environment Balancing residue risks against effective pest control
Anticoagulant rodenticides Second generation First generation 1,3-indandiones Coumarins pindone diphacinone warfarin coumatetralyl brodifacoum bromadiolone flocoumafen Inhibit vitamin-K metabolism in liver until blood can’t clot properly - death through haemorrhage
Brodifacoum (e.g. Talon®, Pestoff20R®) Very effective for rodents & possums Most toxic of the anticoagulants BUT prolonged residual persistence in liver Relatively high secondary hazard to non-target predators and scavengers of rodents
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) Many ‘point sources’ for brodifacoum residues to enter environmental pathways…..
NZ dotterels & sandhoppers... Broadcast pellet baits Dragged under sand & consumed over time Contaminated invertebrates consumed by birds Mortality of dotterels after brodifacoum baiting Liver testing confirmed brodifacoum exposure Sandhoppers likely secondary exposure pathway
Brodifacoum makes the popular press… Sep 2009 – aerial application of brodifacoum, rodent eradication on Rangitoto/ Motutapu Marine wildlife carcasses later found on Hauraki beaches claimed as brodifacoum related (+ dog poisoning cases) Assumption of ‘cause & effect’ vs. ‘weight of evidence’ * Behavioural & necropsy signs of poisoning? * Expert veterinary opinion * Previous similar mortalities? * Activate the residue testing laboratory! ( not the EAV machine)
Dolphins, dog vomit, pilchards & penguins…. Pilchards & dolphins: no brodifacoum residues detected Dog: no brodifacoum residue in vomit but neurotoxin identified (from sea slugs) necropsy indicated starvation six liver samples, no brodifacoum detected three liver samples had detectable brodifacoum, in ‘likely sublethal’ range what was the exposure pathway?? Little blue penguins:
Questions – brodifacoum & penguins Source of brodifacoum residues in penguins? –not necessarily from Rangitoto application – long persistence in liver means they could have been exposed months before Exposure pathway for penguins? –primary exposure to bait, or secondary exposure through fish or invertebrates? Does this exposure contribute to penguin mortality? –Is there a ‘no harm’ threshold of liver residues? Test archived & newly-collected penguin carcasses for brodifacoum : is exposure limited to penguins in Hauraki? is exposure constant over time?
Diphacinone as alternative anticoagulant Multiple-feed bait formulations effective for rodents (but not possums) Far less toxic but also less persistent than brodifacoum >> indicates lower non-target & secondary risk Need to check role of invertebrates as environmental transfer vectors of residues…. Photo: Grant Norbury Recycled bait! Bait Very hungry caterpillar
Jan ’09, about 70 short-tailed bats found dead/ill at base of roost tree Necropsy revealed haemorrhage Diphacinone detected in livers How were they exposed? Diphacinone in NZ bats Diphacinone 0.005% paste bait in bags stapled to trees for rodent control ** Bags removed by rats & left open on forest floor ST bats feeding on forest floor find bait Invertebrates carry residues after feeding on bait ** This bait application now ceased in bat areas **
Anticoagulants are an important rodent control tool worldwide Especially in NZ for field management of possums & rodents Ongoing use should be accompanied by a clear understanding of environmental residues & associated exposure / risk in non-target wildlife Residue monitoring is your friend…… The overall message part……..