In 2000 the CSIRO launched the Australian Government–funded Biological Control of Cane Toad Program. The aim of this research initiative was to develop a solution for long-term biological control of cane toads. The program involved engineering a virus which would infect young toads and stop them developing into adults.
The program ended in 2008 when an independent review team found that managing the local impacts of cane toads, rather than attempting to eradicate the species, was a more effective long-term approach. It was also established that the release of the proposed virus may not receive approval due to regulations on the use of genetically modified organisms in the environment.
In 2008 the Australian Government funded the second and final review of this research project, which covers the period February 2003 to April 2008.
About the report
The aim of the second review was to assess:
- the progress of research by the CSIRO on the development of a self-disseminating viral vector that disrupts the development of cane toads
- the technical feasibility of developing this research to the point of offering a new and effective control method for cane toad populations in Australia (including consideration of the political implications of releasing such an organism)
- the opportunities provided by other avenues of research into cane toad control and the relative potential for these to provide broad-scale cane toad control.
What the report found
The research performed by the CSIRO team was of high scientific quality and a number of aspects of the research program were successful and published in peer-reviewed literature. These included the development of a cane toad breeding colony, the identification of genes differentially expressed in tadpoles and toadlets, and the construction of BIV recombinant viruses.
However there are still major technical hurdles to overcome in developing a self-disseminating genetically modified cane toad control agent. The long-term feasibility of the approach is also questionable for several reasons, including the availability of an acceptable viral vector, the difficulty of generating an appropriate immune response from virally expressed proteins, and the difficulty of obtaining approval for release.
The lack of a national and international risk assessment and management plan for the release of a virally-vectored genetically-modified organism, regardless of exact product specification, is also a major deficit challenge and should be an essential part of any further program in this area.
The first review (Hazell et al. 2003) acknowledged that the development of a fully tested and approved biocontrol for cane toads was a long-term solution. As a result, it recommended that the then Environment Australia consider other avenues to address the problem in the short to medium term.
However key constraints in assessing the relative merits of alternative control approaches (including integrated control), and in comparison to the CSIRO biocontrol approach, are:
- incomplete knowledge of ecological impacts
- lack of cost-benefit analyses of each approach
- lack of environmental impact assessments for each approach
- uncertainty associated with regulatory approvals, especially for genetic approaches.
Recommendations for future research
The review team recommended that tight selection and performance criteria be used for future investment decisions in alternative approaches to cane toad control, and that this process include more comprehensive population modelling of their practicality and efficiency.
No practical alternative approach to broad-scale cane toad control has yet been demonstrated, so continued investment in multiple alternative approaches is needed. Of all alternative approaches reviewed, the review team believed four had potential for more effective local and possibly broader scale control, either on their own or in combination:
- the cane toad-specific lungworm parasite and the use of an alarm pheromone
- the bioprospecting approach to search for new pathogens overseas
- development of a cane toad-specific poison
- the ‘daughterless male’ approach for the special condition of a closed population.