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For the first time, malarial mosquitoes have been modified to be infertile and pass on the trait rapidly – raising the possibility of reducing the spread of disease. The mosquito species Anopheles gambiae is a major carrier of dangerous malaria parasites in sub-Saharan Africa, where 90 per cent of annual malaria deaths occur. Malaria infects more than 200 million people each year and causes more than 430,000 deaths.

Researchers at Imperial College London have genetically modified Anopheles gambiae so that they carry a modified gene disrupting egg production in female mosquitoes. They used a technology called ‘gene drive’ to ensure the gene is passed down at an accelerated rate to offspring, spreading the gene through a population over time.

Within a few years, the spread could drastically reduce or eliminate local populations of the malaria-carrying mosquito species. Their findings represent an important step forward in the ability to develop novel methods of vector control.

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Normally, each gene variant has a 50 per cent chance of being passed down from parents to their offspring. In the Imperial team’s experiments with Anopheles gambiae, the gene for infertility was transmitted to more than 90 per cent of both male and female mosquitoes’ offspring.

The technique uses recessive genes, so that many mosquitoes will inherit only one copy of the gene. Two copies are needed to cause infertility, meaning that mosquitoes with only one copy are carriers, and can spread the gene through a population.

The results are published today in the journal Nature Biotechnology.

“The field has been trying to tackle malaria for more than 100 years. If successful, this technology has the potential to substantially reduce the transmission of malaria,” Professor Andrea Crisanti

“As with any new technology, there are many more steps we will go through to test and ensure the safety of the approach we are pursuing. It will be at least 10 more years before gene drive malaria mosquitos could be a working intervention,” added Professor Austin Burt

Many current measures to control malaria rely on reducing populations of malarial mosquitoes, such as insecticides and bed nets. These have proven very successful in reducing the spread of malaria, however these approaches face important costs and distribution challenges, as well as growing issues of resistance.

A control measure relying on genetic spread through a targeted population of malaria mosquitoes could complement these interventions without adding dramatically to the health budget of resource-constrained countries.

“There are roughly 3,400 different species of mosquitoes worldwide, and while Anopheles gambiae is an important carrier of malaria, it is only one of around 800 species of mosquito in Africa, so suppressing it in certain areas should not significantly impact the local ecosystem,” said lead author Dr Tony Nolan from the Department of Life Sciences at Imperial.

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