The team, at the Pest Animal Control Cooperative Research Centre (PAC CRC) in Canberra, has already applied for permission to carry out field trials with a similar virus that makes European mice infertile. Advocates of this form of biological control say it is more humane than existing strategies such as poisoning, shooting or spreading lethal diseases.

From cats to camels, feral mammals cost Australia hundreds of millions of dollars each year in lost agricultural production and environmental damage, and have driven some native mammals and birds to extinction.

"Australia has lost more mammal species than the rest of the world combined in the past 400 years," says project director Tony Peacock. But the prospect of genetically engineered viruses being released into the wild is still likely to spark a fierce debate.

The viruses make females infertile because they have an added gene for a protein from the zona pellucida, the thick layer surrounding the egg. Females infected with one of the transgenic viruses produce antibodies against their own eggs, damaging them and blocking fertilisation- a process called immunocontraception.

For rabbits, geneticists chose to engineer the myxoma virus, which devastated populations when it was released in Australia half century ago. But many rabbits have become resistant, and less lethal strains have edged out the original virus.

Four years ago, researchers selected the rabbit ZPB gene as the most promising of three zona pellucida genes to insert into the myxoma virus. But this sterilised less than 25 per cent of rabbits. Now they have switched to the ZPC gene, with much better results.

In two trials in May, New Scientist has learned, the latest transgenic myxoma virus sterilised 8 out of 11 female domestic r
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Contact: Claire Bowles
claire.bowles@rbi.co.uk
44-207-331-2751
New Scientist
7-Aug-2002