London: In a pioneering work towards eradicating malaria, scientists have modified mosquitoes to produce sperm that will only create males.
The new genetic method 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.
"Malaria is debilitating and often fatal, and we need to find new ways of tackling it. For the very first time, we have been able to inhibit the production of female offspring and this provides a new means to eliminate the disease," said lead researcher Andrea Crisanti, professor from department of life sciences at Imperial College, London.
In the first lab tests, the method created a fully fertile mosquito strain that produced 95 percent 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.
"The hope is that if this could be replicated in the wild, this would ultimately cause the malaria-carrying mosquito population to crash," Crisanti noted.
In this new 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.
It took researchers six years to produce an effective variant of the enzyme.
"Our goal is to enable people to live freely without the threat of this deadly disease," concluded Roberto Galizi from Imperial College London.
According to latest estimates by the World Health Organisation (WHO), over 3.4 billion people are at risk of contracting malaria and an estimated 627,000 people die each year from the disease.