* Technology could be used to spread infertility in rodents
* Builds on promising lab experiments with mosquitoes
* Idea controversial given potentially irreversible effects
By Ben Hirschler
LONDON, Dec 5 (Reuters) - Rodents have joined mosquitoes in the cross-hairs of scientists working on a next-generation genetic technology known as "gene drive" to control pests.
Researchers in Scotland said on Tuesday they had developed two different ways to disrupt female fertility in rats and mice, building on a similar approach that has already been tested in the lab to eliminate malaria-carrying mosquitoes.
So-called gene drives push engineered genes through multiple generations by over-riding normal biological processes, so that all offspring carry two copies. Usually, animals would receive one copy of a gene from the mother and one from the father.
The technique is extremely powerful but also controversial, since such genetically engineered organisms could have an irreversible impact on the ecosystem.
Concerns about the proliferation of mutant species have led some to call for a gene drive ban, but Bruce Whitelaw of the University of Edinburgh's Roslin Institute believes that would be short sighted.
"A moratorium would prevent the research which is required for us to understand if and how this can be used in an advantageous way for our society," he told reporters in London.
"We need to have an understanding of what gene drive can do and how it can be controlled so that decisions are based on knowledge rather than fear."
A key appeal of a gene drive is its durable effect on pests, whether they are disease-carrying insects or crop-eating rodents. And since relatively small numbers of animals would need to be released initially, it is likely to be quite cheap.
It also offers a humane way to eliminate unwanted populations of sentient mammals like rats, which are typically killed with poison and traps.
Still, researchers agree more work is needed on the risks and potential unintended consequences of release of such animals.
Whitelaw and his colleagues, who published details of their rodent work in the journal Trends in Biotechnology, hope as a next step to build self-limiting gene drives that would burn out after a certain number of generations.
If their approach is successful, the gene drives could potentially be applied to help control a range of other non-insect pest species, such as rabbits, mink and cane toads.
Currently, an older approach called "sterile insect technology" is being used in some areas to fight mosquitoes. Intrexon's Oxitec unit has already deployed its sterile male mosquitoes, whose offspring die when young, in Brazil.
But because Oxitec's mosquitoes last only one generation, a vast number must be released to swamp their wild counterparts.
Existing approaches to fighting pests, particularly mosquitoes, have so far shown mixed success, with insecticide resistance increasing in many parts of the world and drugmakers struggling to develop good vaccines against complex diseases such as dengue. (Reporting by Ben Hirschler; Editing by Mark Potter)