Scientists in Australia are developing a gene drive as a new way to control the country's vast population of invasive rabbits, in what researchers describe as the latest and most promising biological control yet. The work draws on laboratory techniques similar to in vitro fertilisation, with the aim of engineering a genetic tool capable of suppressing rabbit numbers across the landscape.
To carry out the research, teams head into the field, to sites such as Mount Rothwell, in search of well matured and healthy wild rabbits, using highly trained hunting and detection dogs to locate them. It is the reproductive organs of both the male and the female rabbits that the scientists require, and once these are carefully removed they are packed in ice and taken back to the laboratory.
Inside the lab, the material collected is left to mature overnight before researchers attempt to achieve fertilisation, a step they describe as the critical first stage toward generating a genetic biocontrol, or gene drive, for rabbits. The scientists work to obtain usable, live and healthy sperm from the testes, which is then added to eggs that have been matured in vitro.
The push for a gene drive comes because Australia's previous biological weapons against rabbits have repeatedly lost their power. The myxoma virus, introduced in the early 1950s, was extraordinarily successful, and from 1996 a rabbit specific calicivirus spread rapidly and lethally across the country, sharply cutting numbers for a time.
Over the years, however, the rabbits developed immunity and those viruses lost their virulence. In 2017 a new strain, rabbit calicivirus 2, arrived and for a while had the same dramatic effect, but its effectiveness has since waned as well, leaving authorities once again searching for a more durable answer to the problem.
That is why the gene drive is generating excitement among researchers, who suggest it could be the most effective tool they will ever have for getting rid of rabbits. At the same time, they are careful to stress that it is a fairly radical proposal, one that needs a considered approach before any decision is taken on whether to actually use it in the wild.
The stakes behind the research are considerable. Rabbits cost the Australian agricultural industry more than 200 million dollars in lost production every year, with control measures running into tens of millions of dollars and environmental damage that is near impossible to calculate. At Mount Rothwell, where two thirds of the property is now rabbit free and cleared of foxes and cats, native animals not seen on the mainland for a century have returned, offering a glimpse of what removing the pest could achieve.