Biting back: mosquito that can't get malaria

A malaria-carrying mosquito. Photo / Supplied.

A novel weapon in the battle against malaria has been developed by scientists: the malaria-proof mosquito.

Researchers at the University of Arizona have created a genetically modified insect that is incapable of transmitting the disease to humans.

The advance could lead to the release of modified mosquitoes into malarial regions of the world to prevent the transmission of one of the world's biggest killers.

Malaria infects an estimated 250 million people a year and causes nearly a million deaths, mostly among the under-5s.

Michael Riehle, an entomologist who led the research, said: "We were surprised how well this works. We were just hoping to see some effect on the mosquitoes' growth rate, lifespan or their susceptibility to the parasite, but it was great to see that our construct blocked the infection process completely."

Most efforts to tackle the disease rely on controlling mosquitoes by spraying insecticide and using bed nets, or on treating victims with anti-malarial drugs.

Not all mosquitoes transmit malaria - only the female anopheles, of which there are about 25 species. They feed on blood and each time they bite an infected human or animal they ingest malaria parasites. These later migrate to the salivary glands and the disease is passed on.

To break this life-cycle, the scientists inserted a gene to enhance the action of the enzyme Akt, which is involved in the mosquito's growth rate and immune function. The aim was to ramp up Akt function to help the insect's immune system fight off the malaria parasite, and to cut its lifespan, because mosquitoes only transmit malaria towards the end of their lives.

Studies showed modified mosquitoes carrying two copies of the altered gene lost their ability to transmit malaria altogether. But to be effective, the modified mosquitoes must be given an advantage over natural populations of the insects so they can compete with and, over time, displace them. At present they exist only in high-security laboratories with no chance of escape. Riehle said this was the hardest task.

- Independent