Toxicology and ecotoxicology of para-aminopropiophenone (PAPP) – a new predator control tool for stoats and feral cats in New Zealand

Para-aminopropiophenone (PAPP) paste was approved as a stoat control agent in New Zealand by the Environmental Protection Authority in August 2011 and for feral cat control in November 2011. PAPP was originally researched in Europe and the USA as treatment for cyanide and radiation poisoning. Over the last 10 years, our research has focused on several factors, including determining its toxicity to predators, field effectiveness for controlling stoats and feral cats, animal welfare profile, toxicology, ecotoxicology, and understanding and reducing non-target risks. PAPP has been developed specifically for the control of stoats and feral cats because of the special sensitivity displayed by these species. Its toxicity is mediated by the induction of methaemoglobinaemia (the ferric state of haemoglobin). Normally, methaemoglobin levels in the blood are below 1%. Levels of methaemoglobin in the blood above 70% are usually fatal, creating a lethal deficit of oxygen in cardiac muscle and the brain. In stoats and feral cats, death after a lethal dose usually occurs within 2 h after eating bait, with clinical signs first appearing in 10 to 20 min for stoats and at around 35 min for cats. Animals become lethargic and sleepy before they die, hence PAPP is relatively humane. A simple antidote exists, namely methylene blue. Further, birds display a lack of toxicity to PAPP when compared with other vertebrate pesticides. A paste containing 40% PAPP has been developed for use in meat baits in New Zealand. A toxic dose for stoats and feral cats is achieved when pea-sized amounts of paste are delivered in 10–20 g meat baits. When meat baits containing PAPP are applied in bait stations in field settings, stoat and feral cat numbers can be rapidly reduced. However, there has been limited practical experience with PAPP to date, especially when compared with alternative tools such as traps or sodium monofluoroacetate (1080) baits. Additional practical experience should enable the effective use of PAPP as a tool to help protect native species from introduced predators. In the future, PAPP will be developed in long-life bait and in a resetting toxin delivery system

Integrating ecology and technology to create innovative pest control devices

Blackie, H., MacMorran, D., Shapiro, L., Woodhead, I., Diegel, O., Murphy, E., Eason, C.T

Diphacinone and coumatetralyl persistence in deer and implications for wildlife management

Eason, C.T., Murphy, E., Ross, J.G., Hix, S., Arthur, D., MacMorran, D., Broome, K., Fairweather, A

Retrieving and retaining older and advancing novel rodenticides-as alternatives to anticoagulants

Eason, C.T., Henderson, R., Murphy, E., Shapiro, L., MacMorran, D., Blackie, H., Brimble, M., Conole, D., Rennison, D., Gibson, T.J., Gregory N.G

Control and eradication of feral cats: field trials of a new toxin

Feral cats (Felis catus) have caused the decline and extinction of threatened species on islands worldwide. The eradication or long-term control of cats is therefore an essential part of restoring native communities on these islands. In most situations, a combination of lethal techniques is required to remove feral cats, including trapping, hunting and poisoning. Para-aminopropiophenone (PAPP) is being developed as a new, humane poison for feral cats. Mammalian carnivore species appear more susceptible to PAPP than birds, so it potentially has higher target selectivity than other available toxins. A proprietary formulation of PAPP (PredaSTOP) developed by Connovation NZ Ltd. has been shown to kill cats humanely when delivered in a meat bait in pen trials. Two field trials of the formulation were undertaken with radio-collared cats. Toxic baiting was carried out by placing meat baits containing 80 mg PAPP in bait stations. Five of eight radio-collared cats in the South Island study and 13 of 16 radio-collared cats in the North Island study were poisoned. In the latter study, an additional three cats without collars that were monitored using infra-red cameras were also poisoned. Our results indicate that PAPP is an effective toxin for cats in the field, with potential application for their eradication or control on islands

Susceptibility of four bird species to para-aminopropiophenone (PAPP)

The suitability of para-aminopropiophenone (PAPP) for the humane control of stoats (Mustela erminea) and feral cats (Felis catus) is being investigated in New Zealand. Birds are potential non-targets that may be affected by this toxin. Therefore, the objective of this study was to test the toxicity of a proprietary formulation of PAPP in four bird species: Australian magpies (Gymnorhina tibicen; n = 40), blackbirds (Turdus merula; n = 20), mallard ducks (Anas platyrhynchos Pekin breed; n = 20) and weka (Gallirallus australis; n = 21). Birds were orally dosed with PAPP in the form of a 40% paste that had been added to meat as a delivery vehicle. The lethal dose to kill 50% of the sample (LD₅₀) was 1387 mg/kg for magpies, 174 mg/kg for blackbirds, 32 mg/kg for mallard ducks and 568 mg/kg for weka. However, the LD₅₀ value for weka underestimates the risk to this species, as individuals were affected at the lowest dose tested (62 mg/kg), becoming subdued and losing their appetite until they were euthanized 30 h after dosing. Whilst birds are less susceptible to PAPP than stoats or feral cats (LD₅₀ for both of these species is < 10 mg/kg), some bird species are adversely affected, so it will be important to limit their exposure

Control of ferrets using 1080 and PAPP in baits and a resetting toxin delivery device

Ferrets (Mustela furo) are widespread in pastoral habitats and are considered a vertebrate pest because they prey on native birds. Also, ferrets are carriers of bovine tuberculosis (TB, Mycobacterium bovis), and TBfree New Zealand currently controls ferrets by labour-intensive and costly trapping. A Lincoln University research programme, 'Pest Control for the 21st Century', funded by the Ministry of Business, Innovation and Employment seeks to advance more humane and effective tools for vertebrate pest control. As a vital part of this programme the new toxin para-aminopropiophenone (PAPP) is being developed for multiple vertebrate pests. With our partners (Connovation Ltd), we have developed a self-resetting delivery device, the Spitfire, which sprays 800 mg of toxic paste onto a pest’s belly. Both PAPP and 1080 have been trialed in a Spitfire for ferrets. Ferrets were found to groom the paste from their bellies and consume a lethal dose. We have also trialed encapsulated PAPP delivered in minced beef to ferrets. Encapsulation prevented vomiting, allowing a lethal concentration of PAPP to be absorbed across the gut. We achieved mortality in 14/15 (93%) ferrets in laboratory trials and field trials are planned. The goal of this research is to provide information on the effectiveness of these new tools to enable registration, and to add to the toolbox of control methods currently used for ferret control

Technology advances for vertebrate pest eradication

In New Zealand and worldwide feral pigs are a serious threat to biodiversity and agriculture as well as being a known vector for disease. Control options are generally limited to hunting, trapping, fencing and the use of toxins in some countries. The use of the toxins 1080, warfarin and phosphorus to control feral pigs have come under fire due to concerns over welfare and residues and the need to develop more humane and safer toxins has been identified. Pilot trials, carried out by the Invasive Animals Cooperative Research Centre, on pigs in 2006 showed that sodium nitrite (SN) delivered by gavage and freely consumed in bait caused death through methaemoglobinanemia. SN appeared to be humane, with deaths following bait consumption occurring within two hours, with unremarkable poisoning signs. SN whilst effective is unpalatable due to its salty taste and encapsulation or taste masking is necessary to overcome this and ensure adequate bait is consumed. A method of encapsulation developed by researchers at Connovation Ltd in New Zealand enabled succesful free feeding cage and field trials on pigs to be completed. A bait containing this encapsulated SN was registered in New Zealand in 2013 for the control of feral pigs and brushtail possums. The results from these initial trials and learnings post registration are to be presented in this talk. Registration trials with this formulation of encapsulated SN are now underway in the USA and Australia

Trends in vertebrate pesticide use and new developments: NZ perspectives and international implications

Trends in vertebrate pesticide use and new developments

Pharmacokinetics of rodenticides, risk assessment and technology advances for vertebrate pest eradication

The risks to non-target animals that accompany the field use of rodenticides are determined in part by their tendency to bioaccummulate linked to pharmacokinetics, and comparisons are possible. We have identified a huge variation in the way that the different vertebrate pesticides are absorbed, distributed, metabolised and excreted by animals. “Low residue” compounds will be substantially excreted from mammals within 24 hours. Others will be largely cleared from the body within 2 to 8 weeks and more potent anticoagulant compounds like bromodiolone, brodifacoum and flocoumafen are most likely to persist for longer periods. Three new low residue compounds have been developed and registered with NZ EPA and MPI within NZ, namely para-aminopropiophenone (PAPP) in 2011 for stoats and feral cats, zinc phosphide for possums in 2012 and encapsulated sodium nitrite (ESN) in 2013 for possums and feral pigs. The development of PAPP and ESN, coined red blood cell toxins, developed for humaneness, represent the first new vertebrate pesticides registered for field control of mammalian pests anywhere in the world for > 25 years. Research on rodenticides continues, and more effective and selective killing systems are being developed. The first successful field trials of resetting toxin delivery devices for possum and stoat control have been completed in the last 2 years. Improved deployment strategies, integration of humane, low residue and selective toxins, lures of greater potency and improved killing devices will transform ground control for endangered species protection and reduce risk to non-target species