Oxitec, based at Abingdon near Oxford, have been pioneering a new approach to tackling dengue fever, a mosquito-borne disease that infects between 50 and 100 million people, and is estimated to kill perhaps 25,000 deaths. It is less lethal than malaria which affects 350m – 500m people each year and kills about 1m people a year, including very many children. The new approach pioneered by Oxitec is a modern variant of the old ‘sterile male’ technique which released sterile male mosquitoes into the wild so that no offspring would be produced by their mating. In the new version the mosquitoes which carry dengue fever are genetically modified so that their offspring will die before maturity. Released in large numbers into the wild each year, they steadily reduce the number of mosquitoes that survive to breed and infect people with dengue fever.
Promising research has been ongoing for a while by other companies to develop variants of the anopheles mosquito which will not act as host to the plasmodium that causes malaria. Part 1 is not difficult; scientists turn on a gene in the insect’s gut that controls SM1 peptide, for example, stopping development of the plasmodium inside the mosquito, and rendering its bite free of malaria. Unfortunately Part 2 has proved more difficult. The modified mosquito also has to be ‘fitter’ than its unmodified rivals, and more likely to survive and breed. The snag is that genetic modification usually makes the mosquito ‘weaker’ than its cousins in the wild. The hope is that now the genome of both the anopheles mosquitoes and the malarial parasites have been sequenced, they will lead researchers to new modifications that produce non-malarial mosquitoes ‘fitter’ than their wild counterparts. It’s a very exciting field that could see the conquest of a scourge that has killed more people than all the wars of human history.
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