GM mosquitoes open up new front in war on malaria

Biologists today said they had devised a new weapon against malaria by genetically engineering mosquitoes which produce mostly male offspring, eventually leading to a population wipe-out.
The sex selection technique produces a generation of mosquitoes which is 95-per cent male, as opposed to 50 per cent in normal populations, they reported in the journal Nature Communications.
So few females are left that the mosquito population eventually collapses, curbing the risk to humans from the malaria parasite that the blood-feeding females transmit.
"Malaria is debilitating and often fatal and we need to find new ways of tackling it," said study leader Andrea Crisanti, a professor at Imperial College London.

"We think our innovative approach is a huge step forward. 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."
Malaria kills more than 600,000 people each year, with young children in sub-Saharan Africa on the frontline, according to the UN's World Health Organisation (WHO).

The result of six years' work, the method focuses on Anopheles gambiae mosquitoes, the most dangerous transmitters of the malaria parasite.
The scientists injected a stretch of enzyme DNA into the genetic code of male mosquito embryos. The modification essentially shreds the X chromosome during sperm production in adulthood.

As a result, almost no functioning sperm carried the X chromosome, which determines female offspring. Instead, most sperm carried the Y chromosome, which produces males.
The modified mosquitoes were put to the test in five cages, each containing 50 genetically modified males and 50 normal, wild females.
In four of the five cages, the entire population was wiped out within six generations because of the progressively greater shortage of females.
Modified male mosquitoes produced only modified male heirs, which did the same until there were no females left.