Para-aminopropiophenone (PAPP) in canid pest ejectors (CPEs) kills wild dogs and European red foxes quickly and humanely

Para-aminopropiophenone toxicity in domestic dogs: a description of non-target toxicosis in Victoria, Australia: 13 dogs (2016-2023)

BACKGROUND

PAPP is widely used in Australia as a potent vertebrate bait, with potential for off-target ingestion and poisoning in domestic dogs. Whilst toxicosis and resulting methaemoglobinaemia is anecdotally known to occur, this is the first description in the literature. This study reports thirteen clinical cases of suspected Para-aminopropiophenone (PAPP) toxicity in dogs, with the aim of describing clinical presentation and current management of toxicosis in this species.

CASE REPORT

Three veterinary clinics in Victoria provided records of dogs where PAPP toxicity was the likely diagnosis (considering regional exposure, historical information and clinicopathological findings). Pertinent case data was described, and inferences made, based on commonalities and differences. Acute collapse, vomiting and cyanotic or brown mucous membranes were the most common presenting complaints. Marker beads associated with bait were identified in stomach contents from two dogs. All dogs received intravenous methylene blue (MB) with a mean initial dose of 3.8 mg/kg. A higher initial dose of MB (5mg/kg) was associated with a more rapid decline in methaemoglobin concentration. The mean hospitalisation time was 1.6 days with a 77% survival to discharge.

CONCLUSIONS

This case series enhances our understanding of the clinical presentation of PAPP toxicity in dogs, and response to treatment with MB. It highlights the consideration of PAPP toxicosis based on clinicopathological findings, even when definitive ingestion (i.e. presence of marker beads) cannot be established. Furthermore, it contributes to our knowledge of MB administration and suggests a fair prognosis for survival of PAPP toxicosis with prompt recognition and treatment.

Are canid pest ejectors an effective control tool for wild dogs in an arid rangeland environment?

Abstract Context Wild dogs are a significant pest species of livestock production and native wildlife in Australia. A suite of control tools is used to mitigate predation impacts. Baiting with sodium fluoroacetate is the most commonly used control tool in Australia; however, its effectiveness can be reduced by interference by non-target species, and in some contexts by microbial degradation of the toxin. Canid pest ejectors (CPEs) are a mechanical device with an attractant ‘lure head’ designed to eject a lethal toxin into the mouth of canids pulling on the lure head. A range of lure heads can be used to attract canids to pull, and trigger CPEs. Aims We aimed to determine whether uptake of CPEs by wild dogs in an arid rangeland environment could cause a decline in a wild dog population. We also aimed to determine whether there are particular lure heads that increase the rate of CPEs being triggered by wild dogs. Methods We deployed one hundred CPEs over four sessions of control across three properties in the southern rangelands of Western Australia from 2018 to 2020. Each session consisted of 2 months of CPE deployment with two different lure heads, totalling eight lure head types over the entire study. All CPEs were monitored using camera traps. Key results Wild dog density varied over the study period. In all four control sessions, a decrease in wild dog density was recorded (–46%, –5%, –13%, –38%). Wild dog activity events on camera and their interest in CPEs differed between sessions and lures (i.e. higher with scent-based lures). Non-target species did not interfere with CPEs significantly, despite a higher number of activity events by non-target species than wild dogs. Conclusions CPEs caused a reduction of 5–46% of wild dog density when deployed in the southern rangelands of Western Australia. Non-target interference was minimal when using CPEs for wild dog control. Implications Use of scent-based lures on felt lure heads is recommended for successful use of CPEs for wild dog control in arid rangeland environments. Future on-ground wild dog control should include CPEs as a complementary tool for the reduction of wild dog density.

The canid pest ejector challenge: controlling urban foxes while keeping domestic dogs safe

Abstract ContextIt is widely recognised that red foxes (Vulpes vulpes) are abundant within urban areas; however, it is difficult to apply lethal control measures using poison baits in cities because of concerns about the safety of domestic pets, particularly dogs (Canis familiaris). AimsWe tested canid pest ejectors (CPEs) as a potential method of fox control by measuring visitation and activation behaviour of foxes and other wildlife while assessing non-target risk to domestic dogs. MethodsWe compared eight urban and eight peri-urban sites in Sydney, with half of the sites having restricted access for domestic dogs. We allocated five camera traps and ejectors per site. Through generalised linear mixed models, we compared the probability of ejector activation between foxes and dogs. We also assessed the relationship between dog visitation and distance to habitation and dog restrictions as measures of dog safety. Key resultsBoth species of canids were equally likely to pull the ejector (P=0.26). As expected, dog visitation was significantly lower in sites with dog restrictions (P<0.001). However, it was not related to distance from habitation. Only two non-canid species were recorded pulling the ejector, suggesting high target-specificity for canids. ConclusionsIn sites with dog restrictions, the risk of dog casualties from CPEs is minimal. However, distance from habitation does not increase dog safety, at least within 250m. The ejector is highly specific for canids. ImplicationsWe provide specific recommendations for the design of a potential fox control program using CPEs in urban and peri-urban areas. The ejector may be a safe method for fox control in cities when deployed at places without domestic dogs.

Minimizing animal welfare harms associated with predation management in agro-ecosystems

The impacts of wild predators on livestock are a common source of human-wildlife conflict globally, and predators are subject to population control for this reason in many situations. Animal welfare is one of many important considerations affecting decisions about predation management. Recent studies discussing animal welfare in this context have presented arguments emphasizing the importance of avoiding intentional harm to predators, but they have not usually considered harms imposed by predators on livestock and other animals. Efforts to mitigate predation impacts (including 'no control' approaches) cause a variety of harms to predators, livestock and other wildlife. Successfully minimizing the overall frequency and magnitude of harms requires consideration of the direct, indirect, intentional and unintentional harms imposed on all animals inhabiting agricultural landscapes. We review the harms resulting from the management of dingoes and other wild dogs in the extensive beef cattle grazing systems of Australia to illustrate how these negative impacts can be minimized across both wild and domestic species present on a farm or in a free-ranging livestock grazing context. Similar to many other predator-livestock conflicts, wild dogs impose intermittent harms on beef cattle (especially calves) including fatal predation, non-fatal attack (mauling and biting), pathogen transmission, and fear- or stress-related effects. Wild dog control tools and strategies impose harms on dingoes and other wildlife including stress, pain and death as a consequence of both lethal and non-lethal control approaches. To balance these various sources of harm, we argue that the tactical use of lethal predator control approaches can result in harming the least number of individual animals, given certain conditions. This conclusion conflicts with both traditional (e.g. continuous or ongoing lethal control) and contemporary (e.g. predator-friendly or no-control) predation management approaches. The general and transferable issues, approaches and principles we describe have broad applicability to many other human-wildlife conflicts around the world.

Lethal methemoglobinemia in the invasive brown treesnake after acetaminophen ingestion

The invasive brown treesnake (Boiga irregularis) has extirpated much of Guam's native birdlife and poses significant threats to other parts of the western Pacific. Acetaminophen (APAP) is a proven lethal oral toxicant in reptiles but the physiological mechanism is unknown. The effects of a lethal APAP oral dose on methemoglobin (MetHb, non-oxygen carrying form) levels and other blood parameters were examined in brown treesnakes. Co-oximetry was used to measure MetHb (%) and other hemoglobin species. Assessment of red blood cell integrity, white blood cell differential counts, and plasma biochemical analyses were conducted to evaluate tissue damage, stress, and liver function. Changes in oxygen carrying capacity were noted in APAP-treated snakes indicated by a 50-60% increase in methemoglobin levels and a 40% decrease in oxyhemoglobin (oxygen-carrying form) levels compared to controls. APAP-treated snakes had decreased lymphocyte and increased monocyte counts while also having increased levels of blood analytes associate with impaired liver function and muscle damage. The proximate cause of death in APAP-treated snakes was likely acute methemoglobinemia and respiratory failure due to severe hypoxia with no observed signs of distress or pain. An orally-ingested lethal dose of APAP appears to be a humane method for lethal control of this species.