SYDNEY, Australia (UPI) -- Researchers have developed a process to genetically engineer viruses to decimate targeted feral pests, such as mice and rabbits, by making them sterile.

The researchers, from the Pest Animal Control Cooperative Research Center in Canberra, said they have been working on the project for more than 10 years. The process, called immuno-contraception, causes infected females to produce antibodies against their own eggs, damaging them and blocking fertilization.

The immuno-contraception idea has already been tested against a major pest, the European house mouse. An engineered herpes virus, Murine cytomegalovirus, has produced 100 percent sterilization of female mice in laboratory trials.

It is an idea with massive global implications, researchers said.

"In Australia, mouse plagues cost the country $75 million in lost production," the project director, Tony Peacock, told United Press International.

Overseas, the rodent problem is even bigger. "Rice field rats in Asia eat $9 billion worth of rice every year," Peacock said. "That's one-third of the Asian rice crop. If we can successfully develop the virus in mice, as we appear to be able to do, then we believe we can also do it in rats."

The research team also is working on engineering a virus for rabbits -- Australia's number one feral pest, which causes widespread erosion -- by adding a gene to the myxoma virus that devastated rabbit populations when it first appeared in Australia 51 years ago.

In the intervening years, many rabbits have become resistant to myxoma and less lethal strains have surfaced.

This led scientists to release a virus called the rabbit calicivirus disease in the 1990s, which drastically reduced rabbit populations. Today, however, about 300 million rabbits dwell in southern half of the country.

Peacock said he hopes the transgenic myxoma virus will be even more effective than the original strain. In two trials this year, it sterilized eight out of 11 female domestic rabbits -- a success rate of over 70 percent.

"We're not promoting the virus as a magic bullet," Peacock said. "There will always be a residual population. It will need to be used as part of an integrated approach."

Clearly he is hoping the expression, "to breed like rabbits," eventually will become a thing of the past.

Peacock said apart from its effectiveness, the virus is more humane than other lethal methods such as poisoning and shooting, giving most rabbits no more than a fever for a few days. It also is easily transmitted by mosquitoes and fleas, involves no toxic chemicals that could otherwise affect non-target species and is far more cost-effective than traditional methods such as ripping burrows.

Biological controls are not new to Australia. In recent years, bacteria, parasitic wasps, sap-sucking bugs and parasitic worms all have been released into the wild. Although many have been successful, some species themselves have become problems. The cane toad, introduced in Queensland in 1935 to control beetles that were ruining sugarcane crops, is an infamous example of a biological agent that multiplied out of control.

Such experiences have left some scientists, politicians and the public wary of releasing new biological controls.

However, the team has received support from other experts in the field.

"The research has strong support from us and from animal welfare groups," Andrew Leys, Statewide Pest Coordinator for the New South Wales National Parks and Wildlife Service, told UPI. "Even if it reduces rabbit numbers by just 50 percent, it would be wonderful."

Quentin Hart, from the National Feral Animal Control Program, was more circumspect. "Our attitude to fertility control is that it's a good thing if it works and if it is safe," he told UPI. "But there are a lot of political and technical hurdles to overcome when you talk about releasing a modified organism into the environment. And even if you overcome these, you need to sterilize a large proportion of the target population to have an effect."

Peacock estimates the research team is some five years away from the point when it can release the virus into the wild.

The research is reported in the August 10 issue of New Scientist magazine.

Copyright © 2002 United Press International. All rights reserved. http://www.upi.com/view.cfm?StoryID=20020809-084844-5516r

Comment
From Frances
8-10-2

WHY target the female population? You know the implications of this? If they can do this with rodents they'll find a way to do it on othermammals - including humans. Right?

(Probably already done and sitting on a biowar lab shelf -ed)