Oral toxicity of p-aminopropiophenone to brushtail possums (Trichosurus vulpecula), dama wallabies (Macropus eugenii), and mallards (Anas platyrhynchos).

Development of p-aminopropiophenone (PAPP) as a toxicant for pest predator management in New Zealand and Australia prompted investigation of its toxicity to potential nontarget species. Acute oral toxicity of PAPP in brushtail possums (Trichosurus vulpecula), dama wallabies (Macropus eugenii), and Mallards (Anas platyrhynchos) was estimated in pen trials, carried out between February 2000 and September 2001. The susceptibility of possums (LD50>or=500 mg kg(-1)) and wallabies (LD50 89 mg kg(-1)) to PAPP was low in comparison to noncarnivorous placental mammal species, but ducks (LD50 38 mg kg(-1)) were more susceptible than other bird species. These results suggest that the nontarget hazard to possums and wallabies from PAPP bait applied for pest predator control would be low. However, future development of PAPP as a vertebrate pest control agent should include rigorous assessments of the hazard posed by bait formulations to bird species and provision for delivery techniques that could mitigate exposure of nontarget birds.

Behavioural, biochemical, and pathological responses of possums (Trichosurus vulpecula) poisoned with phosphorus paste.

AIM: To investigate the behavioural, biochemical and pathological responses of possums following poisoning with phosphorus paste, in order to assess the implications for the welfare of possums. METHODS: After ingestion of phosphorus paste by wild-caught possums (18 high dose, nine low dose, and 12 non-poisoned controls), behavioural observations were made at 15-min intervals for 24 h or until death. Serum biochemistry, and gross and microscopic pathology were assessed at 3-hourly intervals in a further 21 possums. RESULTS: Possums that ingested phosphorus paste developed an abnormal posture (high incidence of crouching after 4-8 h), mild congestion of the gastric mucosa, and elevated levels of creatine kinase (CK) in serum after 3-6 h. Retching was observed in 67% possums, and 44% vomited at least once. Possums were prostrate from about 18 h after eating the poison, and the response to handling, an indicator of consciousness, was lost at about 24 h, followed by death at 25 h. CONCLUSION: The main welfare concern was the possibility of discomfort or pain caused by the congestion of the gastric mucosa, as indicated by the crouched posture adopted by poisoned possums. Retching and vomiting may also have caused pain and distress. The degree of pain or discomfort would depend on the degree of congestion of the gastric mucosa, which was typically mild, and on the duration and severity of retching and vomiting, which were typically short and mild. Possums remained conscious until 1 h before death, implying that they were able to experience pain and distress from the effects of ingestion of phosphorus for almost the entire period of illness, which lasted for approximately one day.

Transmission of Leptospira interrogans serovar Balcanica infection among socially housed brushtail possums in New Zealand.

Leptospira interrogans serovar balcanica is a potential vector being investigated for spreading a biological control agent among introduced brushtail possums (Trichosurus vulpecula) in New Zealand. As previous studies have shown that possums are unlikely to contract leptospirosis through a contaminated environment alone, the objective was to determine whether L. interrogans serovar balcanica could be transmitted between sexually mature, socially housed possums. Possums were infected experimentally with L. interrogans serovar balcanica and housed in pairs or groups with uninfected possums for either 70 or 140 days, during the breeding or non-breeding seasons. No transmission occurred between any infected and uninfected possums during the non-breeding season. However, transmission occurred between females that had been socially housed in pairs or groups in the breeding season. Mixed sex transmission also occurred in pairs and groups, both from males to females and from females to males. Mixed sex transmission usually occurred rapidly (< 44 days) and was not associated with the production of offspring. No transmission occurred between males during the breeding or the non-breeding seasons. Transmission probably occurs as a result of affiliative or sexual behaviour, but is unlikely to occur through fighting. The social transmission pathways determined in this study suggest that L. interrogans serovar balcanica may have the transmission attributes desired in a vector for biological control.

Metastatic mineralisation in brushtail possums (Trichosurus vulpecula) from Kawau Island.

AIMS: To describe the nature and incidence of metastatic mineralisation in brushtail possums (Trichosurus vulpecula) caught on Kawau Island. METHODS: Wild-caught possums were individually housed in captivity over a 24-month period and fed a cereal-based mash diet. Possums that became debilitated were examined post mortem for evidence of metastatic mineralisation of the heart, major blood vessels and kidneys. Serum and aortic segments were collected from affected animals and were analysed for mineral composition. Non-debilitated animals and possums that were experimentally poisoned with cholecalciferol were examined as a comparison. RESULTS: Fifteen of 42 possums (36%) captured on Kawau Island and housed in captivity were debilitated as a result of metastatic mineralisation of the walls of the aorta and/or of the kidney tubules, with four further possums having evidence of mineralisation when humanely killed. Phosphate and ammonium deposits were found in the aorta, and calcium deposits in the kidney tubules. Serum phosphorus and calcium levels were elevated in the debilitated animals. Similar lesions were found in only one of 288 possums captured from other North Island areas and housed in captivity over the same time period. CONCLUSION: Possums from Kawau Island appear to be more predisposed to metastatic mineralisation than possums from other areas of the North Island. The lesions observed in these possums were similar to those caused by cholecalciferol poisoning.

Duration of cyanide-induced conditioned food aversions in possums.

Learned aversions developed following sublethal ingestion of poisons are reported to be long-lived in many pest species. This study aimed to identify the duration of bait aversions following poisoning with a common poison (cyanide) used for possum control in New Zealand. Groups of possums with bait aversions (following cyanide poisoning) were reexposed to the bait (flavoured food) in a 2-choice test, at intervals of 1, 3, 6, 12, or 24 months. The relative intakes of the bait (used as the measure of bait aversion) did not differ between treatments (0.21, 0.21, 0.27, 0.32, and 0.20) for the 5 groups, respectively. The effect of repeated reexposures to the bait was also tested. The proportion of flavoured food eaten was 0.11, 0.19, 0.23, 0.33, and 0.36 for 1 to 5 reexposures, respectively. There was a significant increase in intake with repeated exposure. Thus, cyanide-induced aversions were strong and lasted for at least 24 months. The aversions weakened over several reexposures to the bait, but only for those individuals that had weaker initial aversions.

Leptospirosis in brushtail possums: is Leptospira interrogans serovar balcanica environmentally transmitted?

In New Zealand, the biological control of introduced brushtail possums (Trichosurus vulpecula) may be the only affordable option for achieving a significant long term reduction in pest numbers on a national scale. Leptospira interrogans serovar balcanica is among the potential biocontrol agents and vectors currently being investigated for this purpose. As the transmission pathways of L. interrogans serovar balcanica between possums are poorly understood, the objective of the study was to determine whether infection could result from exposure to contaminated environments. Sixteen individually housed, uninfected possums, in three groups, were regularly exposed over a period of 32 days to contaminated cages or grass enclosures of 16 other experimentally infected possums all shedding leptospires in their urine. None of the 16 challenged possums developed serological evidence of L. interrogans serovar balcancia infection. These results suggest that this organism is unlikely to be transmitted environmentally, supporting previous circumstantial evidence that social contact may be required for transmission of L. interrogans serovar balcanica between possums.

Effects of experimental infection with Leptospira interrogans serovar balcanica on the health of brushtail possums (Trichosurus vulpecula).

Data on changes in the condition and feeding behaviour of captive brushtail possums (Trichosurus vulpecula) following an experimental infection with Leptospira interrogans serovar balcanica are presented. The daily food intake of nine experimentally infected possums was recorded for 47 days before and 24 days after balcanica inoculation (0.5 ml intraperitoneally containing about 10(8) organisms). Body weight was recorded seven times between 42 days before and 96 days after inoculation. The mean daily food intake of infected possums decreased significantly throughout the 24-day recording period after infection with balcanica. The mean body weight of infected possums had decreased significantly by day 26 after inoculation but had fully recovered by day 96 after inoculation. Uninfected and control possums showed no significant changes in mean daily food intake or mean body weight over the experimental period. These data suggest that the health of possums is temporarily affected by infection with balcanica, but that overt disease caused by balcanica is unlikely. These findings support previous research suggesting that balcanica has only subclinical effects on possums.

The influence of local tumor ulceration on the effectiveness of endocavitary radiation for patients with early rectal carcinoma.

BACKGROUND: Endocavitary radiation therapy is an alternative to surgical therapy for some early rectal carcinomas. Careful patient selection is necessary to ensure good results. The purpose of this study was to examine the authors' experience with endocavitary radiation at their institution from 1984 to 1991 to determine which factors were associated with treatment failure to provide for better future patient selection. METHODS: Thirty-two patients with carcinoma of the rectum, not apparently involving the muscle wall, underwent 75-120 Gy of endocavitary radiation as potentially curative therapy. Treatment was given as a series of 2-4 doses of 30 Gy at three weekly intervals. Twenty-two patients had polypoid tumors, 5 sessile, and 5 ulcerated. RESULTS: After a mean follow-up of 43 months (range, 6-103 months), 4 of 5 patients (80%) with ulcerated tumors developed local recurrences, compared with only 4 of 27 (15%) with sessile or polypoid lesions. Not only was the incidence of local recurrence greater for patients with ulcerated tumors (P = 0.009), but the time to recurrence was shorter also (P = 0.0001). Tumor size, anterior or posterior location, and dose of radiation received did not affect the rate of recurrence. CONCLUSIONS: These results indicate that superficial polypoid and sessile rectal tumors can be managed successfully with endocavitary radiation. Ulcerating tumors are likely to recur locally within a short time and therefore should be considered for surgical treatment initially.

Cyanide induced aversions in the possum (Trichosurus vulpecula): effect of route of administration, dose, and formulation.

Possums (Trichosurus vulpecula) are New Zealand's main vertebrate pest. Control practices using poisons are likely to remain the most cost effective methods for the immediate future but poisons may be avoided in the field. A series of experiments were conducted to determine whether cyanide bait avoidance involved conditioned food aversions (CFA) induced by sublethal cyanide ingestion. Food aversions were conditioned in three experiments using intraperitoneal or oral routes of administration with three different cyanide formulations over a range of doses. Across all experiments there was a direct relationship between dose and the proportion of animals developing CFAs. When administered orally, doses greater than 5 mg/kg resulted in more than 50% of surviving animals developing aversions. Route of administration or formulation appeared to have no differential effect on development of CFA. Although there was considerable variation between individuals in the degree of aversion shown this may be one mechanism that could account for poor possum kill rates in some poisoning operations.