Population protecting implants: Targeted control of problem individuals to mitigate cat-astrophic predation

Link To Share This Poster: https://cdmcd.co/WkzLg9
Live Discussion Link: https://cdmcd.co/w3Qnm6

Anton Blencowe and Kyle Brewer, Clinical and Health Sciences Unit, University of South Australia, Adelaide, Australia, Todd McWhorter and David Peacock, School of Animal and Veterinary Sciences, The University of Adelaide, Adelaide, Australia, Katherine Moseby, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, Australia, Katherine Moseby and John Read, Ecological Horizons, Kimba, Australia, John Read, Department of Earth and Environmental Sciences, The University of Adelaide, Adelaide, Australia, Ned Ryan-Schofield, School of Biological Sciences, The University of Adelaide, Adelaide, Australia

Background/Question/Methods
Feral cats present the single greatest predatory threat to endemic terrestrial mammal species in Australia and are considered responsible for the extinction of 11% of the 273 endemic species, with 36% of the remaining species listed as threatened or near threatened. Reintroduction programs aimed at re-establishing threatened populations in predator-free landscapes are often marred by the inability to completely remove feral cats or prevent their incursion. This invariably leads to the unabated predation of reintroduced populations — often by a single ‘problem individual’ — and abject failure of the program. We have developed a toxic implant technology that is designed to mitigate this predation by removing problem individuals following a single predation event. Our ‘Population Protecting Implants (PPIs)’ contain a lethal dose of toxin and are designed to be injected under the skin of a native animal. The implant remains inert until the animal is preyed upon by a feral cat, where it rapidly breaks down in the low pH gastric environment and releases the contained toxin, thereby killing the feral cat. We have developed a propriety implant design and scalable manufacturing process, employing batch-type sequential spray-coating. We assessed the stability of manufactured implants in vitro and in vivo, using hydrogel and murine models, respectively. Implant dissolution and poison release was profiled at low pH in vitro and investigated during preliminary pen trials in vivo.
Results/Conclusions
Manufactured implants exhibited excellent intra-batch variability, with dimensions of 8.34 ± 0.11 mm × 1.63 ± 0.04 mm (length × diameter) (n=50, of 430). This enabled the use of commercially available identification microchip implanters for PPI storage and application. Ongoing experiments have demonstrated implant stability at physiological pH (7.4) for >6 months in vitro (n=5), and at least 3 months in vivo (n=3). At low pH (1.5), implants were found to release 80% of their contents within 2.02 ± 0.04 h (n=3) in vitro. These results were supported in vivo, whereby penned feral cats were fed a rabbit (n=2) or mouse (n=1) carcass containing a single PPI and died 5 h following the onset of symptoms. These preliminary data successfully demonstrate the PPI proof-of-concept, with PPIs exhibiting favourable stability and release profiles. The long-term stability of the PPIs (e.g., >12 months) in vivo is an important future consideration and requires further investigation.