Transgenic mosquitoes are bred to fight malaria

Scientists produce altered insects to produce mainly males - the idea being that this leads to the disappearance of the species.

Biologists announced on Tuesday, June 11, 2014, that they have developed a new weapon against malaria. They created genetically engineered mosquitoes to produce mainly male offspring - eventually leading to the disappearance of the entire insect population.

The technique produces a generation of transgenic mosquitoes in which 95% are male, while in normal populations the percentage is 50%. The results were described in an article in the journal Nature Communications. So few females are left that the mosquito population collapses, reducing the risk that humans will come into contact with the malaria parasite (transmitted by females).

"Malaria is a debilitating disease, often fatal, and we need to find new ways to fight it," says study leader Andrea Crisanti, a professor at Imperial College London. "We think our innovative approach represents a breakthrough. For the first time, we were able to inhibit the production of female offspring in the laboratory and this gives us new ways to eliminate the disease."

According to the World Health Organization (WHO), malaria kills more than 600,000 people a year, with sub-Saharan Africa being the primary victims. Result of six years of work, the method focuses on mosquitoes "Anopheles gambiae", the most dangerous transmitters of the malaria parasite.

Scientists injected a piece of DNA enzyme into the genetic code of male mosquito embryos. Basically, the modification breaks up the X chromosome during sperm production in adulthood.

As a result, almost no functional sperm contain the X chromosome, which determines female offspring. In contrast, most sperm carry the Y chromosome, which produces males. Modified mosquitoes were tested in five cages, each containing 50 genetically modified males and 50 normal wild females.

"I am very hopeful that this new approach can ultimately lead to a cheap and effective way to eliminate malaria," says researcher Roberto Galizi.

In four of the five cages, the entire population disappeared in six generations due to the growing lack of females. Modified male mosquitoes produced only modified male heirs, who had the same type of descendants until no more females remained.

"The research is still in its infancy, but I am very hopeful that this new approach may ultimately lead to a cheap and effective way to eliminate malaria from entire regions," said Crisanti's colleague Roberto Galizi. In an independent comment, Oxford University expert Michael Bonsall referred to the research as "very cool work."

"This has important implications for limiting the spread of malaria," he told the British Science Media Center. "It will be very exciting to see the advance of this technology." Scientists are already experimenting with mosquitoes in the wild "Aedes aegypti", which transmit dengue, and have been modified to produce offspring that do not reach adulthood.

They survive for only a week while normal mosquitoes live a month. Brazil and Malaysia have already released clouds of these insects, and in January Panama announced that it will do the same.

However, these programs raise concerns among environmentalists, who draw attention to the unknown impact of genetically modified animals on the balance of biodiversity. They argue that if a mosquito species were eliminated from a region, it would open the opportunity for a competing - and potentially dangerous - species to surface.