Is sodium fluoroacetate (1080) a humane poison
Sodium fluoroacetate (1080) is widely used for the control of vertebrate pests in Australia. While the ecological impact of 1080 baiting on non-target species has been the subject of ongoing research, the animal welfare implications of this practice have received little attention. Literature relevant to the humaneness of 1080 as a vertebrate pest control agent is reviewed in this paper. Previous authors have largely concentrated on the perception of pain during 1080 toxicosis, giving limited attention to other forms of distress in their assessments. Authors who suggest that 1080 is a humane poison largely base their conclusions on the argument that convulsive seizures seen in the final stages of 1080 toxicosis indicate that affected animals are in an unconscious state and unable to perceive pain. Other authors describe awareness during seizures or periodic lucidity that suggests central nervous system (CNS) disruption cannot be assumed to produce a constant pain-free state. Some literature report that 1080 poisoning in humans is painless and free of distress, but this is contradicted by other clinical studies. Using available data an attempt is made to reassess the humane-ness of 1080 using the following criteria: speed and mode of action, appearance and behaviour of affected animals, experiences of human victims, long-term effect on survivors, and welfare risk to non-target animals. It is concluded that sodium fluoroacetate should not be considered a humane poison, and there is an urgent need for research into improving the humaneness of vertebrate control methods in Australia.
Previous assessments of the humaneness of 1080 have failed to adequately address welfare issues such as distress. They focus on the difficulties surrounding the interpretation of pain states in the late stages of poisoning, with little regard for earlier stages of toxicosis. The extensive CNS disruption in the late stages of 1080 poisoning poses a dilemma as abnormal electrical activity in the brain makes judgements regarding consciousness and perception difficult to make, and CNS involvement in the toxicosis may alter behavioural indicators of pain and distress. As the involvement of the CNS is progressive, an assessment of humaneness thus becomes more difficult to make as poisoning progresses.
In the initial stages of 1080 poisoning, animals display a range of signs that potentially cause them distress, or are indicative of distress. Conscious human patients who have ingested 1080 frequently report pain and anxiety at this time. A majority of species develop nervous involvement including inco-ordination, partial paralysis, and tetanic convulsions (rigid contractions of the muscles). The potential for suffering is probably greatest during this period of toxicosis. In some species neurological involvement may further progress to generalised convulsions that are typically cyclic with periods of awareness between fits. The degree of awareness during fits is difficult to assess but at least one author indicates that some animals remain conscious during fitting (Foss 1948). Overall, the period from ingestion of 1080 to death can range from less than an hour to several days, with a similarly wide-ranging symptomatic period. Survivors may suffer from partial paralysis or other nervous conditions for a period of several days before they fully recover and permanent neurological damage is a possible outcome. The extent of sub-lethal debilitation that results from 1080 baiting programmes is unknown. Apart from the possibility of pain and distress occurring in the initial stages of poisoning, or convulsive episodes, there are important welfare concerns associated with prolonged periods of repeated convulsions. Animals may experience confusion and distress during the onset of generalised convulsions before the entire cortex has become involved (Chenoweth & St John 1947b; Ward 1947) and in periods of lucidity between convulsions. Given the severity of convulsions and potential for movement during convulsions that has been observed (Egekeze & Oehme 1979a,b; McIlroy 1981; Marks et al 2000; Potter et al 2006), there is a potential for injury to occur during fitting, and affected animals experiencing periods of conscious awareness between convulsions or eventually recovering from a sub-lethal dose of 1080 may be capable of suffering as a result of any injuries sustained. A poison that caused death more rapidly, or with less opportunity for injury, would clearly be more desirable from a welfare perspective. Para-aminopropiophenone (PAPP) has been shown to produce a much more rapid death in red foxes that is not associated with many of the signs that may be indicative of distress during 1080 toxicosis (Marks et al 2004). There is some scope for reducing the severity of signs and symptoms associated with 1080 toxicosis by combination with other pharmacologic agents that could be co-administered in a bait and mitigate distress experienced by poisoned animals (Marks et al 2000).
Mason and Littin (2003) argue that the most desirable poisons have a minimum number of symptoms before rapid loss of consciousness and death, with no lasting illeffects on the survivors. Sodium fluoroacetate does not clearly meet these criteria and it is inappropriate to claim that 1080 is a humane poison based upon prior reviews that fail to consider wider welfare impacts and do not use a consistent framework for assessing humaneness. Given the widespread use of this poison in countries such as Australia and New Zealand, research into alternative control methods and/or improving the humaneness of 1080 baits should be made a priority.