Genetically-modified mosquitoes, resistant to the parasite that causes malaria, have been created by U.S. researchers.

Credit: PNAS

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WASHINGTON: Genetically-modified mosquitoes, resistant to the parasite that causes malaria, have been created by U.S. researchers.

The work raises the possibility of one day stopping the spread of the disease, according to a study published this week in the U.S. journal Proceedings of the National Academy of Sciences.

The research team from Johns Hopkins University in Baltimore, Maryland, combined equal numbers of genetically engineered and natural mosquitoes in the laboratory and let them feed on malaria-infected mice. The genetically-engineered mosquitoes outbred natural mosquitoes, and might be able to replace them if released into the wild.

The genetically-altered insects survived in greater numbers and laid more eggs. After nine generations, 70 per cent of the mosquitoes were genetically-modified compared to 50 per cent at the outset of the experiment, Marcelo Jacobs-Lorena and his colleagues wrote in their paper.

The study suggested that when feeding on malaria-infected blood, "transgenic malaria-resistant mosquitoes have a selective advantage over non-transgenic mosquitoes," the authors wrote.

The lab-altered mosquitoes competed equally well with natural insects when fed non-infected blood but did not outbreed their natural counterparts in that case.

Critically, for the strategy against malaria to be effective, transgenic mosquitoes would have to outbreed the natural insects when feeding off untainted blood.

Additionally, further research is still needed before the altered insects could be released into the wild, as only a small percentage of mosquitoes in nature are exposed to malaria, the authors wrote. Still, the research carried "important implications for implementation of malaria control by means of genetic modification of mosquitoes."

The experiment used the malaria parasite Plasmodium berghei, and not the more dangerous parasite - P. falciparum - the deadliest of the four parasites that cause malaria in humans.

U.S. researchers announced in December 2006 that they had developed an experimental vaccine that would neutralise the malaria parasite inside its mosquito host.

The vaccine targets the Plasmodium falciparum parasite inside the gut of the mosquito, blocking the organism's development and preventing further transmission of the disease.

Each year 350 to 500 million people are infected with malaria and 700,000 to 2.7 million die from the disease, including more than a million children in Africa, according to the World Health Organisation.