GM mosquito could target malaria

A GENETICALLY engineered strain of malaria-resistant mosquito has been created that is able to survive better than the disease-carrying insects.

If such a mosquito can dominate in the wild, it could prevent humans being infected with malaria.

The insect, produced by United States scientists at Johns Hopkins University, in Baltimore, Maryland, carries a gene that prevents infection by the malaria parasite.

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In cage experiments, equal numbers of GM and ordinary "wild-type" mosquitoes were allowed to feed on malaria-infected mice. As they reproduced, more of the transgenic mosquitoes survived.

After nine generations, 70 per cent of the insects belonged to the malaria-resistant strain.

The scientists, led by Dr Mauro Marrelli, wrote in the journal Proceedings of the National Academy of Sciences: "To our knowledge, no-one has previously reported a demonstration that transgenic mosquitoes can exhibit a fitness advantage over non-transgenics."

The modified mosquitoes had a higher survival rate and laid more eggs.

However, when both sets of insects were fed non- infected blood they competed equally well.

For resistant mosquitoes to be useful in the wild, they must survive better than non-resistant mosquitoes even when not exposed to malaria.

Even so, the researchers concluded: "The results have important implications for implementation of malaria control by means of gen- etic modification of mosquitoes."

GM mosquitoes that interfered with development of the malaria parasite would make it more difficult for the organism to become re-established after it had been eradicated from a target area, they said. Malaria, spread by the single-celled parasite Plasmodium, is endemic in parts of Asia, Africa, and central and South America.

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The organism is passed to humans through the bite of the Anopheles mosquito.

Each year it makes 300 million people ill and causes a million deaths around the world.

Some 90 per cent of cases are in sub-Saharan Africa, where a child dies of malaria every 30 seconds.

But cases arriving in the UK are still rare, and mainly found in holidaymakers and airport workers.

Altogether around 2,000 cases of malaria are brought into the UK each year.

Symptoms of the disease include fever, sweats and chills, tiredness, muscle pain, headache and diarrhoea.

Travellers to countries where malaria is common are advised to take a course of medication to reduce their risk as no vaccine has been available.

But trials of a malaria vaccine are now being carried out in Africa in the hope that one day millions of cases of the disease will be prevented through immunisation.