Mouse biocontrol on horizon by Julian Lee

Hoping to sterilise around two-thirds of the house mouse population.

Farmers plagued by mice can look forward to throwing away the baits and traps as Australian scientists come close to developing a novel control method.

Grant Singleton of the Pest Animal Control Cooperative Research Centre (PAC CRC) said a bio-control method to dramatically reduce house mouse numbers should be ready for consideration within three years.

"It will complement, or perhaps even replace, traditional poisoning and trapping and significantly reduce the estimated $15 million a year lost due to mouse damage and control actions," he said.

Supported by growers and the Federal Government through the GRDC, the bio-control method prevents mice from breeding by sterilising them with a modified mouse cytomegalovirus (MCMV). MCMV is common among mice in Australia, but has been altered to include a gene that codes for the mouse egg coat protein (ZP3).

When infected by this modified virus, the mouse's immune system reacts to both the virus and the introduced ZP3 egg coat protein. Antibodies are produced that in future matings prevent sperm from attaching to the egg, rendering the mouse sterile.

Dr Singleton said, even if it were feasible, the aim is not to eradicate or totally sterilise all mice, but rather to manage mouse plagues. "We hope to sterilise around two-thirds of the population, which will keep it below the level that really hurts farmers economically," Dr Singleton said.

The technique is working in the laboratory with wild mice. Researchers have also shown that the modified virus will sterilise mice previously infected with the non-modified version of the virus.

With such positive results and field release on the horizon, the researchers are keen to dispel any misconceptions about genetically modified viruses.

Media virus

The recent media storm surrounding the research on genetically modified mouse-pox virus and its potential application to human disease research is unrelated to the house mouse research, according to Lyn Hinds, Research Program Manager at the PAC CRC.

"We are not considering mouse-pox virus as a potential biological control agent. Mouse-pox does not exist naturally in Australia. It occurs in one laboratory and is

used as a model system because its molecular biology is well known. In contrast MCMV our virus of choice, is common in Australian house mice and specific to the house mouse, so we are not introducing a totally new species.

"Even so, we are doing research to ensure that the introduced ZP3 protein is also specific, and that the combined virus/ZP3 organism is still specific," Dr Hinds said.

This double insurance aims to make sure other species, particularly the 65 species of native rodents in Australia, are not affected.

The PAC CRC must also address social and political concerns about the use of genetically modified organisms.

Coming up in June, a four-day consultation period will include a cross-section of the community — farmers, GRDC, the Australian Conservation Foundation, Bureau of Rural Sciences, animal welfare bodies and regulatory bodies.

"It will be a two-way process to help prioritise the research and address all issues of concern," Dr Hinds said.

Furthermore, "we won't be walking away from the virus once released. In fact, it is at that point that we really need to keep on top of the ecology to see if its effectiveness is maintained," Dr Singleton said.

Still to be researched are methods for distributing the virus over large geographic areas and monitoring the spread of the virus within local mouse populations. "These may lead to beneficial spin-offs from the GRDC investment and will be available to farmers in the near future, with the bio-control not too far behind," Dr Singleton said.

Bio-control researchers at the Pest Animal Control Cooperative Research Centre are based at CSIRO Sustainable Ecosystems and the Department of Microbiology, University of Western Australia.

Program 32.1 Contact: Dr Grant Singleton 02 6242 1658 email:

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