Peacock says if the virus could sterilise 70 to 80 per cent of wild females, rabbits would decline to densities similar to those in Europe and become a relatively minor pest. But even if it were only 50 per cent successful, it would still end the episodic plagues that have ravaged the country.
The immunocontraception idea has already been proved in another major pest, the European house mouse (New Scientist, 26 April 1997, p 4). An engineered herpes virus, murine cytomegalovirus, has consistently produced 100 per cent sterilisation of female mice in lab trials. The PAC CRC will apply to the Office of the Gene Technology Regulator later this year for permission to conduct the first contained field trial of the transgenic mouse virus at Walpeup, in north-western Victoria. Peacock says extensive consultation would precede any release.
The virus appears to sterilise female mice for life, but it is too early to know if the same will be true with rabbits, which are longer lived. So the team plans to add other genes to the myxoma virus to try to boost the contraceptive effect.
If the government decides to release such viruses, Peacock thinks populations should decline rapidly as breeding slows and natural mortality and predation take their toll. Other researchers think the effects will only be temporary, as natural selection will favour animals with a mutated zona pellucida protein that evades the immune response.
But Peacock points out that sperm can only fertilise eggs if the proteins on their head bind to the ZP proteins. So for resistance to appear, both egg and sperm proteins would have to mutate simultaneously yet still be able to bind to each other, which is extremely unlikely.
However, the viruses could be accidentally
'"/>
Contact: Claire Bowles
claire.bowles@rbi.co.uk
44-207-331-2751
New Scientist
7-Aug-2002