Genetically-modified mosquitoes could help wipe out malaria

Scientists have successfully modified mosquitoes to produce sperm that will only create male offspring, pioneering a fresh approach to eradicating malaria.
Researchers from Imperial College London have tested a new genetic method that distorts the sex ratio of Anopheles gambiae mosquitoes, the main transmitters of the malaria parasite, so that the female mosquitoes that bite and pass the disease to humans are no longer produced.
In the first laboratory tests, the method created a fully fertile mosquito strain that produced 95 per cent male offspring.
The scientists introduced the genetically modified mosquitoes to five caged wild-type mosquito populations. In four of the five cages, this eliminated the entire population within six generations, because of the lack of females.

Researchers believe that if this could be replicated in the wild, it would ultimately cause the malaria-carrying mosquito population to crash.
This is the first time that scientists have been able to manipulate the sex ratios of mosquito populations.

"Malaria is debilitating and often fatal and we need to find new ways of tackling it. We think our innovative approach is a huge step forward," said lead researcher Professor Andrea Crisanti from the Department of Life Sciences at Imperial College London.
"For the very first time, we have been able to inhibit the production of female offspring in the laboratory and this provides a new means to eliminate the disease," Crisanti said.

According to latest estimates by the World Health Organisation, over 3.4 billion people are at risk from contracting malaria and an estimated 627,000 people die each year from the disease.
"What is most promising about our results is that they are self-sustaining. Once modified mosquitoes are introduced, males will start to produce mainly sons, and their sons will do the same, so essentially the mosquitoes carry out the work for us," added Dr Nikolai Windbichler, also a lead researcher from the Department of Life Sciences at Imperial College London.
In the experiment the scientists inserted a DNA cutting enzyme called I-PpoI into Anopheles gambiae mosquitoes. In normal reproduction, half of the sperm bear the X chromosome and will produce female offspring, and the other half bear the Y chromosome and produce male offspring.

The enzyme that the researchers used works by cutting the DNA of the X chromosome during production of sperm, so that almost no functioning sperm carry the female X chromosome.
As a result the offspring of the genetically modified mosquitoes was almost exclusively male.
The study was published in the journal Nature Communications.