Use of 1080 for Pest Control

NZVA recognises that, in the absence of effective alternatives, the continued use of 1080 as a means of pest control (possums and some other introduced species) is necessary to assist the eradication of bovine tuberculosis and the conservation of New Zealand’s unique native flora and fauna.

Use of 1080 must be carefully managed to reduce the potential for accidental or secondary poisoning of non-target species especially dogs, which are extremely susceptible, and food-producing animals that may enter the food chain (including wild animals hunted for food).

Background

The major user of the Vertebrate Toxic Agent* 1080 is the Animal Health Board (AHB), for the control of vectors of bovine tuberculosis (Tb), usually possums, followed by the Department of Conservation (DoC), for the protection of native plants and animals from a number of pests. Some regional councils also use 1080 for pest control.

1080 is registered for use on the following target species in New Zealand: wallabies (carrot, cereal pellets and gel); possums (paste, gel blocks, carrots, apple and cereal pellets); rabbits (paste, oats, carrots and cereal pellets); deer (carrots and gel); rodents (cereal pellets); wasps (paste) and cats (fish meal pellet). Its use is tightly controlled and includes requirement for public notification in the areas in which it is laid.

New Zealand’s economy is heavily dependent on the export of products derived from animals. Trading partners demand product of increasingly high animal health standards, and their own livestock are mostly free from bovine tuberculosis. Therefore eradication of Tb from New Zealand domestic livestock is important for market access. Despite more than 30 years of a compulsory national Tb eradication campaign, the disease is still a significant problem because it is present in possums in large and often inaccessible parts of the country, from which it can spread to livestock in farms that border on to forest areas. Possum control is therefore central to Tb control.

Control of possums and introduced mammalian species (rats, ferrets and stoats in particular) is also essential to the preservation of much of New Zealand’s natural forest habitat and endangered bird, reptile and invertebrate populations. DoC uses 1080 also for wasp control in beech forests and for wallaby control.

The detrimental effects of possums on the environment are many and various: damage to native forests from browsing on leaves, flowers, fruit; predation on birds and their eggs; predation on invertebrates. Rats, stoats and ferrets are also predators of birds, reptiles and invertebrates. Browsing by wild goats and deer can interfere with forest regeneration.

1080

Sodium monofluoroacetate, commonly known as 1080, is manufactured as a fine white powder. The active ingredient, fluoroacetate, is chemically identical to the fluoroacetate that occurs naturally in some poisonous plants found in Brazil, Africa and Australia. Plants with high concentrations can be toxic if eaten, but do not occur in New Zealand.

1080 is used in the form of a paste, cereal pellets, carrot baits, gels and fish-based pellets, depending on the species targeted and the terrain. It is applied by aerial spreading, or by ground operations that use bait stations; as a paste spread on upturned earth spits, small bait stations or retrievable cardboard squares or tin lids; or spread by hand in small areas.

The toxic effects of 1080 result from disruption of the Krebs cycle. Possums usually die in 6-18 hours from heart failure. Herbivores also suffer heart failure. In carnivores 1080 causes central nervous system disturbance resulting in convulsions and death from respiratory failure. Sublethal doses are metabolised and excreted without accumulation in the body, with the dose likely to be eliminated within a week. However, long-term damage can occur, e.g. myocardial necrosis in sheep (Eason & Wickstrom)

Under favourable conditions, 1080 undergoes defluorination within 1 -2 weeks, but in extremes of cold, rain or drought, this process can be delayed. Public notification is required for areas where 1080 has been laid.

Advantages and disadvantages

1080 has been the vertebrate toxic agent of choice for possum control. It has the advantages of being the only one registered for aerial application[1], which allows control operations in areas otherwise inaccessible or difficult to access, and of being relatively cheap. It is highly effective for killing possums, giving rapid reduction in possum numbers. It is rapidly biodegradable, quickly diluted in waterways, and is broken down in both soil and water by microorganisms so does not build up in the environment, except under the unfavourable conditions mentioned previously.

Its disadvantages lie in the risks it poses to non-target species. It can have direct effects, especially in dogs, which are extremely sensitive, or through the ingestion of poisoned carcasses. Buffer zones and caution periods are used to manage the risks to food safety. A buffer zone of 2 km is imposed around treated zones to prevent removal of wild animals for food from around poisoned areas. Caution periods (defined by time and rainfall) are imposed to restrict the removal of wild animals for food during risk periods.

There is currently no antidote for poisoning with 1080, and treatment is difficult and depends on early presentation (McLaren 1999, Parton et al 2001, Williams 2009).

Public concerns

Some New Zealanders have expressed their opposition to the widespread use of 1080. Concerns expressed include the risks to non-target species, possible appearance of 1080 in the food chain, and contamination of environment and waterways from aerial application over wide areas. Evidence suggests that much of the publicly voiced concern is unfounded and that risks can be managed by selection of application method. Aerial application rates of 1080 bait are now much lower than were used in the past. Additionally, other aspects of methodology, such as toxin loading of the baits, bait quality and size, and bait characteristics, have changed markedly to reduce risks to non-target animals. Scientists conclude that on present evidence, the ecological costs of using vertebrate toxic agents such as 1080 is much less than the damage resulting if they are not used.

Poisoning of non-target species

Non-target species can be poisoned by direct ingestion of 1080 or by secondary poisoning through eating carcasses of poisoned possums or other animals.

Species vary in their sensitivity. In general, dogs are particularly sensitive, herbivores and birds are less sensitive, and reptiles and amphibians less sensitive again. Body size is important, and although the LD50 for birds is relatively high, very small insectivorous birds are particularly at risk. Fish and aquatic species have low sensitivity.

Predatory and scavenging birds such as harriers and moreporks are at risk of secondary poisoning from eating dead possums, rodents, small birds or invertebrates.

Secondary poisoning is common in dogs because of their scavenging habits, and particularly when the dog consumes the whole carcase including the gastrointestinal tract. Dogs should be muzzled in areas where 1080 has been laid. Secondary poisoning can also occur in cats.

Effective control of dogs by dog owners will reduce the opportunity for dogs to be poisoned with 1080.

In cases of suspected 1080 poisoning, samples for diagnosis include vomitus, rumen or stomach contents, fresh liver and muscle.

Alternative control methods

Currently the other options for control of pest animals are trapping, hunting and the use of other vertebrate toxic agents. The NZVA recognises that, despite concerns about its humaneness (Sherley 2007), 1080 has numerous advantages over the other toxic agents available at present, but looks forward to research into pest-specific toxins and other means of control (including fertility control) yielding alternatives in the future.

References

Eason CT, Wickstrom M.Vertebrate pesticide toxicology manual (poisons): Information on poisons used in New Zealand as vertebrate pesticides. Department of Conservation Technical Series 23. http://www.doc.govt.nz/upload/documents/science-and-technical/docts23a.pdf (accessed 16/03/09)

McLaren J. Treatment of 1080 poisoning in dogs. Vetscript, March 1999

Parton K, Bruere AN, Chambers JP.Fluoroacetate – 1080 in Veterinary Clinical Toxicology, Veterinary Continuing Education 208, 141-53, Massey University, 2001

Sherley M.Is sodium fluoroacetate (1080) a humane poison? Animal Welfare 16, 449-458, 2007

Williams V.You can save dogs poisoned with 1080. Vetscript, February 2009

Policy Files: 

13b - Use of 1080 - Mar09.pdf