At least 65 dogs in a year poisoned by 1080 in New Zealand
At least 65 dogs in a year poisoned by 1080 in New Zealand
By Dr J Pollard (BSc (Hons),
November 15, 2011
Research by the National Poisons Centre and the Otago University’s Pharmacy School which was presented at an International Poisons Congress in 2008 found that dogs across New Zealand are at extreme risk of poisoning from 1080(1).
The researchers carried out a postal survey of 125 randomly-selected veterinarians. Fifty-two vets responded and within their practices over a one year period, 65 dogs poisoned by 1080 had been dealt with. Three of the 52 respondents had each treated 10 cases. Only 25% of the treated dogs survived (only those that had not shown clinical signs of poisoning before treatment).
The 65 dogs will be a fraction of actual cases dealt with because not all vets in the country were involved in the survey, and not all dogs poisoned with 1080 will get to the vet. The researchers told the conference that in New Zealand “Poisoning of dogs by 1080 is widespread with no defined management in place.”
This finding contrasts sharply with what our Environmental Risk Management Authority (ERMA) claimed in its reassessment of 1080 poison in 2007. According to ERMA "Controls in place to ensure dogs are not exposed are adequate" (2)
It also makes nonsense of the claim made this June by our Parliamentary Commissioner for the Environment (Dr Jan Wright) that only 8 dogs have been reported killed in New Zealand by 1080 poison since 2007. Dr Wright quoted only the number of dogs in incidents reported to ERMA about 1080 operations. The “8 dogs” figure is clearly a gross misrepresentation of the actual number of dogs killed. This is just one of a large number of misleading statements in her report on 1080, which is heavily biased towards its use, as was the ERMA reassessment. (2)
Unfortunately for dogs and their owners, it is likely that the real number of deaths has actually increased in recent years. This is because the area over which 1080 poison is being spread has been increasing; a significant increase in its use (proposed by the Department of Conservation (DoC) and the Animal Health Board (AHB)) was a major reason for ERMA’s re-assessment of 1080 (Committee Decision, page 15).
Furthermore, the controls outlined by ERMA in 2007 require that signs warning of 1080 poison must be removed, after remaining in place for a minimum of six months (or less if toxin removal or testing indicates the area is safe). This control was imposed without any knowledge of how long 1080 remains a risk in carcasses, although it was admitted that "1080 residues in the carcasses of poisoned possums may be very slow to break down".
ERMA stated in its assessment "There is limited information available on the degradation of 1080 in animal carcasses...It is clear that 1080 residues remain in the guts of dead animals for prolonged periods (at least 75 days under cool winter conditions...) and only degrade slowly". Furthermore the low rate of degradation “may be a function of low pH in the gut, absence of bacteria able to degrade 1080, toxicity to gut bacteria, low levels of...invertebrate activity, accompanied by cool temperatures at the time of 1080 bait distribution."
This possible effect of the toxin helping to preserve the carcass has not been taken into account by DoC when drawing up its operating procedures. For some years now DoC has monitored carcass breakdown at poisoned sites but these carcasses “can be sourced from anywhere” and are not required to be poisoned. According to ERMA, the AHB (the biggest user of 1080 in NZ) and other users merely assume that six months after the operation the signs can come down.
Carcasses of 1080-poisoned animals are a huge risk to dogs because of the persistence of the poison and because dogs are so susceptible to it. Just 1.75 mg of 1080 poison will kill a 25 kg dog, and enough poison is spread aerially per hectare to kill over 2,500 dogs (Table 1) (and 125 times more poison than required per possum). 1080 poison concentrations in possum gut contents were 30.6 mg/kg after 25 days and 4.9 mg/kg after 75 days in one study. In another study 1080-poisoned rabbit carcasses became more toxic as they aged, possibly because of dehydration.
Table 1: 1080 application rate and killing power per hectare by species
* for 0.15% 1080/kg applied at 3 kg/ha (4.5 gms/ha or one level teaspoon). For lower concentrations or application rates figures will be proportionately lower.
|Species||LD50 mg/kg body wt||Average species wt (kg)||LD50 (mg) for this weight||mg 1080 /ha*||LD50 doses/ha|
|LD50 = dose per kg body weight to have a 50% kill risk|
Source: Dr Hugh Barr, NZ Wildlands Biodiversity Management Society Inc.
Dogs exposed to less than lethal doses of 1080 are likely to suffer damage to the heart, other organs and reproductive tissues, and unborn puppies are likely to develop deformities, as these effects are seen in other mammals. Water supplies are a likely source of on-going exposure to 1080, wherever poisoned carcasses enter them.
Coupled with the risk of poisoned carcasses is the fact that the baits themselves can remain toxic for months, especially when carrot is used, and when baits fall in dry areas. An example of the on-going risk was 78 sheep that died after grazing an airstrip used to load 1080 poisoned carrot bait, 20 weeks after the operation. In Fiordland, some cereal baits “looked quite fresh” after seven weeks, according to a report from DoC field staff (Waitutu 1080 operation, 2010).
Another blow to dog owners from the ERMA re-assessment was its decision to remove the requirement to erect a sign warning of forthcoming poisoning. No prior warning sign at the site is required now.
Historically, concerned officials have attempted to prevent the use of 1080 because of its extreme risk and cruelty to dogs. For example a biologist working for the US Fish & Wildlife Service wrote in 1948: "the spasm period of victims, particularly the canines, seems unduly violent...The severe spasms associated with 1080...[is an] outstanding objection". Another example is a report from 1972 that stated that our own Rabbit Destruction Council had suggested arsenic as a substitute for 1080 due to the danger to farmers' dogs.
Dog owners are advised to read public notices carefully and to consider all 1080-treated areas as extremely hazardous.
(1) Hope, A., Smith
M., Temple, W., 2008. Clinical Toxicology Volume 46,
(2) See www.1080science.co.nz