Biological control of rabbits in australia – an ongoing co-evolutionary arms race
CSIRO Health & Biosecurity, GPO Box 1700, Canberra, Australian Capital Territory 2601, Australia.
Wild European rabbits have enormous impacts on Australia’s agricultural industries and environment, currently costing over $200 million in production losses annually, and threatening 304 native plants and animals. To manage the damaging rabbit plagues of the last century, Australia introduced two biological control agents, a poxvirus, Myxoma virus, in the 1950s and a calicivirus, rabbit haemorrhagic disease virus, in the 1990s. This has been tremendously successful, with the cumulative benefits of biocontrol agents to Australia’s agricultural industries estimated at $70 billion over the last 60 years. However, due to inevitable host-pathogen co-evolution, biocontrol agents must be used strategically to maximise and prolong their effectiveness. Australia has adopted a pipeline approach to rabbit biocontrol, which aims to successively introduce new viruses to boost control efforts, as part of a broader integrated rabbit management program. The introduction of biological control agents into naive populations from a single point source provides a unique opportunity to study the spread, establishment, and evolution of emerging pathogens. Of particular interest is how closely related viruses interact with each other - a viral competition experiment on a continental scale. For caliciviruses in particular, our data show that recombination appears to be an important mechanism for generating genetic diversity, with multiple recombinant viruses emerging in the last three years. Understanding the mechanisms behind the epidemiological fitness, or lack thereof, of different virus strains enables strategic, targeted use of biocontrol agents to maximise the impacts of control programs. This has the potential to prolong the effectiveness of existing virus strains in a manner analogous to strategic use of antibiotics to delay the development of antimicrobial resistance.