NZ533342A - Use of an anticoagulant and compounds that elevate serum calcium for control of possums - Google Patents

Abstract

A synergistic bait composition to kill possums containing cholecalciferol and at least one first generation anticoagulant, or calciferol and at least one first generation anticoagulant, is disclosed. The composition may also include a calcium source; this may be lucerne or calcium carbonate. The first generation anticoagulant may be coumatetralyl, diphacinone, pindone, warfarin or chlorphacinone. A method of poisoning a possum by administration of the described bait composition is also disclosed.

Description

533342 PATENTS FORM NO. 5 Fee No. 4: $250.00 PATENTS ACT 1953 COMPLETE SPECIFICATION After Provisional No: 533342 Dated: 8 June 2004 BAIT FOR CHRONIC POISONING OF POSSUMS I, Ray Henderson, of P.O. Box 40, Leeston, New Zealand, a New Zealand citizen, hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed to be particularly described in and by the following statement: ——» intellectual Property Office of N.Z. 0 9 SEP 2005 RECEIVED BAIT FOR CHRONIC POISONING OF POSSUMS Intellectual Property Office of N.Z. 0 9 SEP 2005 RECEIVED TECHNICAL FIELD The invention relates to a bait for chronic poisoning of possums. More specifically, the invention relates to compositions including cholecalciferol and/or calciferol as a 5 primary mechanism for poisoning and an anticoagulant as a synergist.

BACKGROUND ART A variety of anticoagulants have been considered to manufacture a chronic pesticide for control of possums. Chronic poisons for control of possums have 10 significant advantages over other types of pesticide, in so much as they are able to mitigate issues of low bait consumption associated with bait shyness and/or neophobia. Historically, chronic poisons for control of possums have contained an anticoagulant only, but these generally require possums to eat large amounts (i.e., >1.0 kg) of bait before possums ingest a lethal amount of poison. As possums 15 progressively consume existing baits containing brodifacoum, anticoagulant residues accumulate in the liver, muscle and other vital organs of animals. These residues cause secondary poisoning of non-target species and contaminate meat and by-products destined for human consumption.

The problem then becomes to develop a bait which when eaten in chronic doses 20 enables possums to progressively consume a lethal dose of poison, without the accumulation of toxic residues in possums that result in secondary poisoning of non-target species that feed on carcasses.

A variety of methods have previously been considered to potentiate the toxicity of poisons used to control of rodents. These include: a) The use of the anti-inflammatory drugs ibuprofen and phenylbutazone to potentiate the toxicity of brodifacoum to rats (Sridhara and Krisnamurthy 2 1992). However, this approach is likely to be an inhumane method of poisoning possums because it causes gastric ulceration and then haemorrhage. b) US patent No. 4,011,322 uses a variety of substances that induce haemorrhagic lesions to potentiate an anticoagulant, but this approach is unlikely to be a humane method of pest control. c) Although a combination of warfarin and calciferol (Bai et al. 1978) was effective for control of rats and mice, co-administering calciferol and warfarin did not potentiate the efficacy of either toxicant. d) Warfarin and cholecalciferol (Tanikawa and Kusano 1993) in the same bait were effective for rodent control, but high concentrations of cholecalciferol were required to potentiate the toxicity of warfarin. These high cholecalciferol concentrations would induce an immediate stop-feed effect in brushtail possums, because the possum is more susceptible to vitamin D induced calcinosis than rats. e) European patent EP0392934 uses cholecalciferol or calciferol in combination with acetylsalicylic acid for control of rodents. Although this approach was effective on rodents, it is unlikely to provide a humane means of controlling possums. f) Japanese patent JP62249905 uses warfarin in combination with cholecalciferol or ergocalciferol and a source of calcium for control of rodents. However, the combinations of cholecalciferol and calcium used in this patent would cause an immediate stop-feed effect in possums. g) Japanese patent JP3005406 uses calcium in combination with a vitamin D compound for control of rodents. This approach has since been used for possum control but results in an immediate stop-feed effect, and is therefore not suited as a chronic poison for possums.

Historically the control of many possum populations in New Zealand has used baits 3 containing an anticoagulant alone, or baits containing cholecalciferol with a synergist such as calcium or a stress inducing substance. Research has demonstrated that: a) Use of baits containing 0.8% cholecalciferol and calcium carbonate as a synergist is a means of controlling possums with minimal risks of secondary poisoning (Jolly et al. 1995; Eason etal. 2000). However, possums need to eat large amounts of this bait in a single feed, and it is not effective as a chronic poison for control of bait-shy possums. Consequently, this combination of substances has on average killed <80% of possums during control. b) Anticoagulant baits provide an effective means of controlling possums that are inherently neophobic or bait shy (Henderson et al. 1994). However, 1st generation anticoagulants kill <50% of possums unless administered in very high doses (i.e., >200 mg/kg). Brodifacoum (LD5o=0.26 mg/kg) is more effective than other 2nd generation anticoagulants such as bromadiolone (LD50 ~10 mg/kg) or flocoumafen (LD50~4 mg/kg). However, brodifacoum causes significant residues in the liver of possums, and results in secondary or tertiary poisoning of many non-target species (Eason et al. 1995, Eason etal 2002). c) New Zealand patent NZ 335579 uses stress inducing chemical agents to potentiate the toxicity of cholecalciferol to brushtail possums, but this method also produces a single feed poison that is not effective for control of bait shy or neophobic possums.

It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.

All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and Intellectual Prtpwty 4 Office ef N.Z. 09 SEP 2005 RECEIVED pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.

It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term 'comprised' or 'comprising' is used in relation to one or more steps in a method or process.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

DISCLOSURE OF INVENTION According to one aspect of the present invention there is provided a synergistic bait composition to kill possums containing cholecalciferol and at least one first generation anticoagulant.

According to a further aspect of the present invention there is provided a synergistic bait composition to kill possums containing calciferol and at least one first generation anticoagulant.

Preferably, the quantity of calciferol or cholecalciferol in the composition is from 0.005 to 0.8 % wt/wt.

The inventor has found that by administration of relatively small doses of 25 cholecalciferol or calciferol in combination with a first generation anticoagulant to a possum, an effective toxic bait and poisoning method is provided. The baits formed Intellectual Preeertv 5 Office ef N.z. 0 9 SEP 2005 RECEIVED using the composition are highly toxic to possums, particularly when administered over 7 or more days.

The inventor understands that the composition of the present invention exploits a physiological weakness in possums that predisposes them to calcinosis of pulmonary, cardiac, renal, and hepatic tissues when serum calcium levels are elevated. The use of a vitamin D complex (including cholecalciferol or calciferol) mobilises stored calcium in bones and tissue, and results in lesions particularly in the heart and lung that haemorrhage in the presence of an anticoagulant.

One advantage of the composition is that the bait is still effective even if only smaller amounts are eaten compared to bait that contains an anticoagulant only. This not only makes the bait more cost effective, but also reduces the amount of anticoagulant residue in carcasses which avoids secondary poisoning of other fauna.

It is the inventor's experience that on administration, low levels of toxic residue accumulate in a possum prior to its death, with most of this residue found in the liver. These low levels are unlikely to be lethal to scavengers feeding on possum carcasses, or predatory birds and carnivores that feed on sub-lethally poisoned animals.

Preferably, the composition also includes a calcium source. It is the inventor's experience that calcium may act as an additional synergistic poisoning substance. In one preferred embodiment, the calcium source is lucerne or low concentrations of calcium carbonate.

Preferably, the first generation anticoagulant or anticoagulants are selected from one or more of: coumatetralyl, diphacinone, pindone, warfarin and chlorophacinone.

In one preferred embodiment, the first generation anticoagulant or anticoagulants is included at a rate of 0.005 to 0.1% wt/wt.

Intellectual Property Office ef N.Z. 6 0 9 SEP 2005 RECEIVED According to a further aspect of the present invention there is provided a method of poisoning a possum by administration of a bait composition wherein the composition includes cholecalciferol and at least one first generation anticoagulant.

According to a further aspect of the present invention there is provided a method of 5 poisoning a possum by administration of a bait composition wherein the composition includes calciferol and at least one first generation anticoagulant.

In a preferred embodiment the bait composition substantially as described above is administered to a possum on a daily basis. Preferably, the composition is administered on a daily basis for a period of 5 or more days.

The inventor has found that preferred embodiments expose animals to a dose of cholecalciferol or calciferol in the bait at a concentration that does not impair the consumption of bait during the first 5 to 6 days that a possum feeds on it. For the purposes of this specification, this is referred to as a chronic dose. During and after this time period, the composition progressively induces a stop-feed effect after 15 possums have eaten bait, most preferably for between 5 and 12 days. This reduces the amount of bait that possums eat before the dose becomes lethal.

According to a further aspect of the present invention there is provided the use of cholecalciferol and at least one first generation anticoagulant in the manufacture of a bait to poison a possum.

According to a further aspect of the present invention there is provided the use of calciferol and at least one first generation anticoagulant in the manufacture of a bait to poison a possum.

It should be appreciated from the above description that the bait composition illustrated offers a number of advantages include but not limited to: a) the fact that the composition is significantly more toxic to possums than existing anticoagulant baits; Intellectual Property Office of N.Z. 0 9 SEP 2MB RECEi V E 6 b) the composition reduces the amount of bait that possums eat before it is lethal; c) the composition kills possums more quickly than existing anticoagulants; d) the composition is more humane than existing anticoagulants; e) the composition leaves fewer residues in carcasses; and, f) the composition is unlikely to cause secondary and/or XerWary poisoning of non-target species such as native birds, feral pigs and dogs.

BRIEF DESCRIPTION OF DRAWINGS Further aspects of the present invention will become apparent from the ensuing description which is given by way of example only and with reference to the accompanying drawings in which: Figure 1 shows a graph comparing the amount of bait consumed over time, and Figure 2 shows a graph of the amount of possums killed in time for varying bait treatments.

BEST MODES FOR CARRYING OUT THE INVENTION The composition is now described in terms of the product development process 20 showing various examples of formulations in use.

The development of the product is descried with respect to six examples as follows: 8 Intellectual Property Office of N.Z. 0 9 SEP 20*5 RECEIVED a) assessment of the toxicity of cholecalciferol in divided doses; b) use of appropriate concentrations of cholecalciferol to suppress appetite, c) optimising the toxicity of an anticoagulant synergist to possums, d) assessing secondary synergists, e) assessing the humaneness of the toxicants, f) measuring the field efficacy of bait, and g) measuring residues in carcasses.

Example 1: Chronic Toxicity of Cholecalciferol and Synergists Although haemorrhage was evident in the lungs of many possums given baits 10 containing cholecalciferol and an anticoagulant, it appeared that the primary cause of death was from calcification of tissue in the lung, heart, liver, and kidney. The percentage of possums that died (as measured by the LD50, LD90, and LD95) following calcinosis of vital organs was significantly enhanced by co-administering an anticoagulant with cholecalciferol (Table 1).

The chronic toxicity of cholecalciferol was determined by presenting bait containing a known concentration of poison to individually caged possums either in a single dose (i.e., acute toxicity) or in divided doses over a period of 7 nights (i.e., chronic toxicity). The amount of cholecalciferol ingested was calculated from the weight of bait eaten and concentration of cholecalciferol in that bait. The toxic dose ingested 20 (i.e., mg/kg) was calculated by dividing the amount of cholecalciferol ingested by the bodyweight of the possum, and this toxic dose was then regressed against the percentage of possums dying to determine the LD5o(i.e., the dose killing 50% of animals) and LD9o(i.e., the dose killing 90% of animals).

Research during 1993-95 demonstrated that the acute toxicity of cholecalciferol 25 was potentiated by adding calcium to the diet of possums (Jolly et al. 1995). However, the results presented here indicate that cholecalciferol is substantially more toxic to possums when co-administered with an anticoagulant in divided 9 Intellectual Property Office ef N.Z. 0 9 SEP 2005 doses over a period of 7 days.

Table 1. Enhanced toxicity (i.e., LD50, LDqo, LDas) of cholecalciferol to possums when it is co-administered with calcium, diphacinone, and coumatetralyl as synergists. Poisons were administered either as a single dose (i.e., acute) or in divided doses over 4-10 days (i.e., 5 chronic poisoning).

Synergist (used with cholecalciferol) Dosing Regime LD50 (95% CI) (mg/kg) LDgo (95% CI) (mg/kg) LD9S(95% CI) (mg/kg) Control (cholecalciferol alone) Acute 19.4(14-25) 56.3 (42-84) 68.2 Calcium Acute 9.8 (7-13) 43.5 (30-71) 55.0 (38-94) Coumatetralyl Chronic 12.5 (6-17) 1 1 Diphacinone Chronic 6.4 (2-11) 40.9 (22-276) 65.5 (34-1126) Brodifacoum Chronic =3.01 1 1 Coumatetralyl Chronic 2.8(1-4) 9.3 (7-14) 13.2(10-23) 1 sample sizes were too small to get precise estimates (n=21) Possums poisoned with low chronic doses of cholecalciferol and coumatetralyl were necropsied and tissue samples taken from the kidney, liver, lung and heart for histopathology. All showed extensive mineralization (i.e., calcification) of tissue. 10 Lungs were most severely affected, with all tissue sections showing extensive interstitial mineralisation. The heart of all possums was also affected by mineralization, with observed effects ranging from mild interstitial mineralization to extensive interstitial mineralization. Necrosis of the liver was evident in all possums, with effects varying from early centrilobular necrosis to acute centrilobular necrosis 15 and hepatocellular mineralization. Within the renal tubules of all possums there was moderate epithelial mineralization which is likely to obstruct normal renal function.

Example 2: Chronic Toxicity of Anticoagulants to Possums There were substantial differences in the chronic toxicity of anticoagulant poisons to possums (Table 2). The chronic toxicity of the 2nd generation anticoagulant 20 brodifacoum was determined during previous research, and found to be Intellectual Property Office ef N.Z. 0 9 SEP 2005 RECEIVED substantially higher than the toxicity of the 1st generation anticoagulants given to possums during product development. However, when diphacinone and coumatetralyl were enhanced with appropriate concentrations of cholecalciferol, the 1st generation anticoagulants were an order of magnitude more toxic than baits 5 containing the anticoagulant alone.

Table 2. The chronic toxicity (i.e., LD50, LD90) of anticoagulant poisons (brodifacoum, pindone, diphacinone, and coumatetralyl) when they were administered alone or with cholecalciferol as a synergist.

Anticoagulant Anticoagulant alone Anticoagulant + cholecalciferol LDso (mg/kg) LDgo (mg/kg) LD50 (mg/kg) LDgo (mg/kg) (95% CI) (95% CI) (95% CI) (95% CI) 2nd generation anticoagulant Brodifacoum3 0.26 (.18-.34) 1.01 (.76-1.62) 0.09 (.03-.19) 0.35 (.16-.77) 1st generation anticoagulant Pindoneb 277 (216-396) 527 (377-2197) Not tested Diphacinone >80 mg/kg1 1 11.1 (6-14) 39.3 (26-92) Coumatetralyl >40 mg/kg1 1 6.4 (3-9) .4(11-26) aFrom Henderson et al. 1999 10 b From Henderson et al. 1999 1 sample sizes were too small to get precise measurements The presence of an anticoagulant in all bait types reduced the palatability of baits. To mitigate the effects of reduced palatability with coumatetralyl, the toxicant was encapsulated with hydroxymethylcellulose (FIPMC) before it was included in bait.

Example 3: Chronic Toxicity of Cholecalciferol. an Anticoagulant, and Lucerne to Possums The use of aspirin, calcium carbonate and lucerne as secondary synergists in bait was evaluated (Table 3). There was no significant increase in bait toxicity following the addition of aspirin. Calcium carbonate (CaC03) at concentrations of 1% wt/wt 11 Intellectual Property Office of N.Z. 0 9 SEP 2005 induced an immediate stop-feed effect, which reduced bait efficacy. Although lower concentrations of CaC03did not result in a stop-feed, lucerne was a better alternative. The use of lucerne not only provided a natural source of calcium, but enhanced bait palatability. The use of lucerne meal in bait induced a slight, but significant increase in dose-related mortality without compromising consumption of bait over a 7-day period; presumably because the relatively high levels of calcium in lucerne complement the toxic effects of cholecalciferol.

Table 3. A pairwise comparison of the dose-response curves (estimated by probit analysis) for baits containing cholecalciferol and an anticoagulant when aspirin, calcium carbonate and lucerne were added to the bait and co-administered as a synergist. The toxicity of the anticoagulant was considered different when the P-value for either slope and intercept combined, or the slope on the probit curves were differently different (i.e., P<0.05). 2nd synergists used to enhance bait toxicity Anticoagulant used in bait Relative toxicity (c.f. bait containing an anticoagulant and cholecalciferol) Mortality in cage studies (%) P-value (intercept and slope) P-value (slope) CaC03 Coumatetralyl N/A (5/20) Aspirin Coumatetralyl 6.4 vs 3.9 90(18/20) 0.24 0.47 Aspirin Diphacinone 11.1 vs 10.0 70(14/20) 0.75 0.51 Lucerne Coumatetralyl 6.4 vs 3.5 100(37/37) 0.048 0.04 Example 4: Appetite Suppression Toxic doses of cholecalciferol induce appetite suppression. Therefore, to optimise the amount of cholecalciferol used as a synergist, different concentrations of cholecalciferol were included in anticoagulant baits and the time to appetite suppression measured (Figure 1). Low concentrations of cholecalciferol so.0075% wt/wt did not suppress appetite and resulted in low mortality, whereas concentrations 0.025% wt/wt caused an immediate loss of appetite and this resulted in possums not ingesting sufficient toxicant for it to be lethal. Cholecalciferol at concentrations of 0.01% wt/wt and 0.015% wt/wt suppressed the 12 Intellectual Property Office of N.Z. 0 9 SEP 2005 RECEIVED appetite of possums after they had feed on bait for 7 days and optimised mortality of possums.

Example 5: Humaneness The humaneness of a poison is a function of the duration of sickness behaviour, clinical signs during sickness behaviour, and time to death. The new bait reduced the time to death from 21.5 days with baits containing an anticoagulant only (i.e., that contained only brodifacoum or coumatetralyl) to 13.5 days (for baits containing cholecalciferol and an anticoagulant) (Table 4).

Possums showed few overt signs of distress after ingesting lethal amounts of the new anticoagulant bait. The clinical signs of poisoning were suppression of appetite 2-5 days before death, possums remaining in nest boxes, lethargy, and finally death. The symptoms of poisoning were calcinosis of the lung, haemorrhage in the lung, and haemorrhage of blood vessels in the heart. This contrasted with existing anticoagulant baits, where massive haemorrhage was noted in the peritoneum, vital organs, sub-cutaneous tissue and muscle; with external haemorrhage also apparent in many possums.

Table 4. The effect of different concentrations of cholecalciferol in bait (containing 0.03% coumatetralyl) on times to death, and the observed haemorrhage during a post-mortem necropsy of poisoned possums.

Concentration of cholecalciferol in bait Time to death (±SE) Percentage with haemorrhage in lung Percentage with blood in or around the pericardium Percentage with free blood in abdomen Percentage with haemorrhage in muscle 0 21.5±1.0 60 N/A 75 90 0.0075 16.6±1.4 71 50 8 0.01 14.5±0.6 63 51 0 0 0.015 13.5±0.6 92 0 0 0.025 8.2±1.0 100 0 0 N/A = not assessed 13 Intellectual Property Office of N.Z. 0 9 SEP 2005 RECEIVED Example 5: Field efficacy of bait Cereal baits containing 0.03% encapsulated coumatetralyl, 0.013% cholecalciferol and 5% lucerne were presented in bait stations spaced at 100 m intervals in discrete plantations of forest containing moderate densities of possums. The 5 consumption of bait was monitored at weekly intervals and percentage kills measured from the proportion of 100 leg-hold traps catching possums before and after the application of toxic baits. The percentage of possums killed in replicated field trials with the new bait was higher than the percentage killed with the existing brodifacoum baits (Table 5). Although the new poison did not kill all possums in a 10 period of 2 months, this is most likely a result of some possums not being exposed to bait for long enough and immigration of some new possums into control areas.

Table 5. The percentage of possums killed in field trials with 5 types of anticoagulant bait during a period of 2 months.

Bait Toxicants (nominal concentration) Pre-poison trap catch (%) Post-poison trap catch (%) Percentage kill ±95% CI Mean kill per bait Existing anticoagulant bait 0.002% brodifacoum .4 2.0 87.0 ±4.5 76.0 8.7 3.0 65.0 ±17.2 New anticoagulant bait 0.013% cholecalciferol + 0.03% coumatetralyl 18.3 1.0 94.5 ±6.0 93.2 12.4 1.0 91.8 ±4.8 The percentage of possums killed during a period of 2 months was compared with 15 the percentage kills with existing brodifacoum baits at similar sites during previous research (Figure 2). The new baits killed at a much faster rate than existing brodifacoum baits. For all possums to find bait stations and then feed on bait, the field trials indicate that bait should be presented to possums for slightly longer than the 8-week period used during field evaluations of the product. Brodifacoum baits in 20 comparison may take up to 6 months of continuous baiting to kill all possums.

Example 6: Residues in Carcasses During field trials a search of each field site was undertaken and a sample of 14 Intellectual Property Office of N.Z. 0 9 SEP 2005 ni=ni=i\/[=n possum carcasses collected. The livers were removed from possum carcasses during necropsy and forwarded to a toxicology laboratory for residue analysis. The level of residue in the livers of possums poisoned with baits containing 0.03% coumatetralyl and 0.13% cholecalciferol was only a quarter of that in possums poisoned with baits containing 0.002% brodifacoum (Table 6).

Table 6. The concentration of residual brodifacoum and coumatetralyl in the livers of possums that died during field trials of bait.

Bait type used to poison possums Mean anticoagulant residue (± S.E.) ug/g Brodifacoum baits 1.22 ±0.17 Coumatetralyl + cholecalciferol 0.30 ± 0.14 Not only did the new bait outlined in this patent contain % of the anticoagulant residues that brodifacoum baits contained, the residues are significantly less toxic than brodifacoum residues (Table 7). Cholecalciferol residues have been demonstrated to present a very low risk of secondary poisoning. The likelihood of secondary and tertiary poisoning of non-target species with the anticoagulant in the new bait is extremely low. For example, if the amount of liver required to kill scavenging rats is modelled, then approximately 150-250 times as much liver is required to kill rats with residues of coumatetralyl (a 1st generation anticoagulant) as the livers of possums that contain brodifacoum residues (a 2nd generation anticoagulant).

Table 7. The risks of secondary poisoning from the livers of possum carcasses poisoned with the baits outlined in this patent and with possums livers containing brodifacoum.

Toxicant Liver conc. (pg/g) LD50 of liver to rats (grams) Risks of secondary poisoning Brodifacoum 1.2 6 (multiple feeds) 43 (single feed) High: Kills predatory birds and scavengers Coumatetralyl 0.3 1000 (multiple) 11000 (single) Low: Predatory birds and scavengers survive poisoned rats Intellectual Property Office ef N.Z. 09 SEP 2005 RECEIVED Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims.

REFERENCES Bai, M. K., Krishnakumari, M. K., Majumder, S.K. 1978. Toxicity of calciferol, warfarin, and their combinations to Rattus norvegicus (albino) and R. rattus. Pesticide Science 9: 44—50.

Eason, C.T., Spurr, E.B. 1995. Review of the toxicity and impacts of brodifacoum 10 on non-target wildlife in New Zealand. New Zealand Journal of Zoology 22: 371— 379.

Eason, CT., Wickstrom, M., Henderson, R., Milne, L., Arthur, D. 2000. Non-target and secondary poisoning risks associated with cholecalciferol. New Zealand Plant Protection 53:299—304.

Eason, CT., Wright, G.R., Mime, L.M., Morris, G.P. 2002. Laboratory and field studies of brodifacoum residues in relation to the risk of exposure to wildlife and people. Science for Conservation. 23 p.

Henderson, R.J., Frampton, C.M., Thomas, M.D., Eason, C.T. 1994. Field evaluations of cholecalciferol, gliftor, and brodifacoum for the control of brushtail 20 possums (Trichosurus vulpecula). Proceedings 47th N. Z. Plant Protection Conference: 112 —116.

Jolly, S.E., Henderson, R.J., Frampton, C., Eason, C.T. 1995. Cholecalciferol toxicity and its enhancement by calcium carbonate in the common brushtail possum. Wildlife Research 22: 579—583.

Sridhara, S., Krisnamurthy, T.R. 1992. Potentiation of anticoagulant toxicity to Rattus rattus by two non-steroid anti-inflammatory drugs. Pp 2 12—217 in: J.E. 16 Intellectual Property Office of N.Z. 0 9 SEP 2005 RECEIVED Borrecco & R.E. Marsh Eds.) Proceedings of 15th Vertebrate Pest Conference, University of California, Davis.

Tanikawa, T., Kusano, T. 1993. Acute toxicity of a mixture of warfarin and vitamin D3 to laboratory rats. Japanese Journal of Sanitary Zoology 44: 197—201. 17 Intellectual Property Office of N.Z. 0 9 SEP 2005 RECEIVED

Claims (19)

WHAT I CLAIM IS:

1. A synergistic bait composition to kill possums containing cholecalciferol and at least one first generation anticoagulant.

2. The composition of claim 1 wherein the quantity of cholecalciferol in the bait is from 0.005 to 0.8 % wt/wt.

3. A synergistic bait composition to kill possums containing calciferol and at least one first generation anticoagulant.

4. The composition as claimed in claim 3 wherein the quantity of calciferol in the bait is from 0.005 to 0.8 % wt/wt.

5. The composition as claimed in any one of the above claims wherein the composition also includes a calcium source.

6. The composition of claim 5 wherein the calcium source is lucerne or calcium carbonate.

7. The composition as claimed in any one of the above claims wherein the first generation anticoagulant or anticoagulants are selected from one or more of: coumatetralyl, diphacinone, pindone, warfarin and chlorophacinone.

8. The composition as claimed in any one of the above claims wherein the first generation anticoagulant or anticoagulants are included at a rate of 0.005 to 0.1% wt/wt.

9. A method of poisoning a possum by administration of a bait composition wherein the composition includes cholecalciferol and at least one first generation anticoagulant.

10. A method of poisoning a possum by administration of a bait composition wherein the composition includes calciferol and at least one first generation anticoagulant. 18 Intellectual Property Office of N.Z. 0 9 SEP 2005 RECEIVED

11. The method as claimed in either claim 9 or claim 10 wherein the bait composition is administered to a possum on a daily basis.

12. The method as claimed in any one of claims 9 to 11 wherein the bait composition is administered in chronic doses for a time period of 5 or more days.

13. The use of cholecalciferol and at least one first generation anticoagulant in the manufacture of a bait to poison a possum.

14. The use of calciferol and at least one first generation anticoagulant in the manufacture of a bait to poison a possum.

15. A composition including cholecalciferol and at least one first generation anticoagulant substantially as hereinbefore described with reference to the examples and Figures.

16. A composition including calciferol and at least one first generation anticoagulant substantially as hereinbefore described and with reference to the examples and Figures.

17. A method of poisoning a possum using a bait including cholecalciferol or calciferol in combination with at least one first generation anticoagualent substantially as hereinbefore described and with reference to the examples and Figures.

18. The use of cholecalciferol and at least one first generation anticoagulant substantially as hereinbefore described and with reference to the examples and Figures.

19. The use of calciferol and at least one first generation anticoagulant substantially as hereinbefore described and with reference to the examples and Figures. Rav Henderson by his authorised agents JAMES & WELLS