By Dr Steve Henry- CSIRO
Two introduced rat species (brown rats, Rattus norvegicus; black rats, Rattus rattus) cause major impacts in intensive livestock production industries (e.g. pork and poultry) in rural areas of Australia. The key economic impacts include direct contamination of feed, infrastructure damage and transmission of rodent-borne diseases. Current management of rats relies largely on anticoagulant rodenticide use but this has become problematic due to potential non-target residue issues.
Our project, mainly funded by Department of Agriculture, Fisheries and Forestry with contributions from New Zealand Landcare Research, Orillion, The Poultry Hub and Australian Pork Limited, is assessing the efficacy and delivery of a newly designed analogue of the rat-specific chemical toxin, Norbormide, in Australian intensive livestock production systems. Unlike anticoagulant rodent toxins that are currently used the mechanism of action of this toxin is to induce major peripheral vasoconstriction. The toxin induces death in less than 24h and is rapidly metabolised with no evidence of residues that would lead to non-target or secondary poisoning issues.
In laboratory trials for each species, we have assessed their preferences for different bait substrates. We have also directly determined the amount of toxin required to kill each species. Those results have recently been used to assess known doses of the toxin when presented in preferred food baits. These trials have demonstrated that R. norvegicus and R. rattus are willing to consume the toxic baits in the presence of other food and that they will do so on consecutive nights if their previous consumption did not constitute a lethal dose. There was no apparent development of taste aversion prior to consumption of a lethal dose. The results of the lab trials mean that we can proceed to testing the toxic blocks under the very different conditions of intensive livestock production facilities to determine their feasibility as an alternative to existing control measures. These trials are scheduled for late 2024 and early 2025 and while we have sites with populations of black rats, R. rattus we are particularly looking for sites that have populations of brown rats, R. norvegicus.
In parallel with the laboratory studies, we have been assessing rat population dynamics and behaviour in field sites. These studies have allowed us to refine our rodent sampling and monitoring methods which will be essential when we commence assessment of the efficacy of the toxic bait when delivered in the real world of an intensive livestock system.
This 3-year project is being supported by DAFF funding to CSIRO Health and Biosecurity and contributions with our collaborators in New Zealand Landcare Research, Orillion, Australian Pork Limited and Poultry Hub. Producer involvement in regional Australia has also been key to current progress in the project.
To register your interest in participating in the trial, follow the link below.
https://app.smartsheet.com/b/form/418787f2f773437fb8d103c83347376f
