Suchergebnisse

Context
Pindone is used to control rabbits in Australia and New Zealand, but the secondary non-target risks presented by pindone-poisoned rabbits are poorly known.

Aims
We aimed to generate new data on residual concentrations of pindone in poisoned rabbits for use in a review of the secondary poisoning risks posed to non-target animals in New Zealand.

Methods
Laboratory rabbits were offered pellet bait containing 0.25 g kg–1 pindone in three trials to simulate a range of bait uptake scenarios: single exposure and low or high chronic exposure. Residual pindone concentrations measured in body tissues of laboratory rabbits that had ingested known exposures of pindone were compared with those in wild rabbit carcasses collected after three pindone-baiting operations. Residues in the faeces of some laboratory rabbits were also measured.

Key results
Highest concentrations of pindone residues were in the liver and fat tissue of poisoned rabbits, with consistently lower concentrations in muscle tissue. A dose–response relationship between pindone exposure and liver residue concentrations was found only at the highest chronic exposures. Rabbit carcasses collected after field-baiting operations had generally higher pindone residue concentrations than did laboratory rabbits that had ingested known lethal amounts of bait. Unmetabolised pindone was excreted in rabbit faeces.

Conclusions
The occurrence of the highest residual pindone concentrations in rabbit liver was consistent with the known tissue distribution of anticoagulants in mammals; however, the co-occurrence of similar-range pindone concentrations in rabbit fat has not been previously described. Re-ingestion of soft faecal pellets (caecotrophy) in rabbits that have eaten pindone bait may function as a secondary exposure to increase or prolong their oral exposure to pindone. Some rabbits poisoned following field pindone-baiting operations are likely to have consumed well in excess of a lethal amount of bait.

Implications
Concentrations of residual pindone in fat and liver of poisoned rabbits suggest that secondary poisoning hazard to some non-target predators and scavengers is high. The lack of field-based assessments of the non-target impacts of pindone is a marked information gap that needs to be addressed.

Zona pellucida fertility-control vaccines are being developed in New Zealand to control an introduced marsupial pest, the brushtail possum (Trichosurus vulpecula). In this study recombinant possum ZP3 protein (rZP3) and a possum ZP3 peptide (amino acids 334–361) (both known to block fertility in possums) were examined for their potential to induce species-specific, or at least marsupial-specific, infertility. Laboratory mice (a 'model' eutherian mammal species) and domestic chickens (a 'model' bird species) immunised with possum rZP3 or possum-infertility ZP3 peptide in Freund's adjuvants showed no reduction in a range of parameters indicative of reproductive performance. The lack of contraceptive effects on mouse and chicken fertility is an encouraging result in terms of rZP3 and ZP3 peptide specificity, and these promising antigens are to be expressed in a bacterial ghost vaccine system for mucosal delivery to possums and the effects on possum fertility evaluated. Ultimately, a much wider range of non-target species will need to be screened and tested once the antigens have been successfully formulated in their final delivery vehicle.