Transgenic Mosquitoes Cannot Spread Malaria

A transgenic mosquito carrying a gene that confers resistance to the malaria parasite. These mosquitoes had another gene inserted into them to make their eyes fluoresce, to distinguish them from unmodified insects. (Image: PNAS)

A genetically modified (GM) strain of malaria-resistant mosquito has been created that is better able to survive than disease-carrying insects.

The transgenic insect strain carries a gene that prevents infection by the malaria parasite. This provides new hope for one malaria control strategy where the transgenic insects are released into the wild and they then take over because of they out-compete their wild-type relatives whose health is compromised by the malarial parasite. However, it will be at least a decade before the mosquitoes can be released.

"What we did was a laboratory, proof-of-principle experiment; we're not anywhere close to releasing them into the wild right now," said co-author Jason Rasgon from Johns Hopkins University in Baltimore, Maryland.

In the team's laboratory experiments, equal numbers of genetically modified and ordinary "wild-type" mosquitoes were allowed to feed on malaria-infected mice. As they reproduced, more of the GM, or transgenic, mosquitoes survived and they laid more eggs. After nine generations, 70% of the insects belonged to the malaria-resistant strain.

The scientists inserted the gene for green fluorescent protein (GFP) into the transgenic mosquitoes that made their eyes glow green so it was easier to distinguish the two strains.

"To our knowledge, no-one has previously reported a demonstration that transgenic mosquitoes can exhibit a fitness advantage over non-transgenics," wrote Lead author Mauro Marrelli and his colleagues wrote in their PNAS paper.

However, both insect strains did equally well when fed non-infected blood. Unfortunately, for malaria-resistant mosquitoes to be useful, they must survive better than non-resistant mosquitoes even when not exposed to malaria.

"There is quite a lot of research that needs to be done, both in terms of genetics and the ecology of the mosquitoes; and also research to address all the social, ethical and legal issues associated with releasing transgenic organisms into the environment," said Rasgon.

Cited story.

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By David Harmon (not verified) on 20 Mar 2007 #permalink