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Fighting malaria by changing mosquito DNA

In a cramped, humid laboratory in London, mosquitoes swarming in stacked, net-covered cages are being scrutinized for keys to controlling malaria.
A technician uses an electron microscope showing the female mosquito's ovaries and the DNA inside them at malaria expert, Professor Andrea Crisanti's lab, at London's Imperial College, London.Alastair Grant / AP
/ Source: The Associated Press

In a cramped, humid laboratory in London, mosquitoes swarming in stacked, net-covered cages are being scrutinized for keys to controlling malaria.

Scientists have genetically modified hundreds of them, hoping to stop them from spreading the killer disease.

Faced with a losing battle against malaria, scientists are increasingly exploring new avenues that might have seemed far-fetched just a few years ago.

"We don't have things we can rely on," said Andrea Crisanti, the malaria expert in charge of genetically modifying mosquitoes at London's Imperial College. "It's time to try something else."

Malaria kills nearly three million people worldwide every year, mostly in sub-Saharan Africa. Millions of bed nets have been handed out, and villages across the continent have been doused with insecticide. But those measures haven't put a significant dent in malaria cases.

After a string of failed initiatives, the United Nations recently announced a campaign to provide bed nets to anyone who needs them by 2010.

Some scientists think creating mutant mosquitoes resistant to the disease might work better.

"We still have a malaria burden that is increasing," said Yeya Toure, a tropical disease expert at the World Health Organization.

"Under such circumstances, we have to investigate whether genetically modified mosquitoes could make a difference," said Toure, who is not involved in the Imperial College research.

The Bill & Melinda Gates Foundation has found the work so promising it has invested nearly $38 million into genetic strategies to stop mosquitoes from transmitting diseases like malaria and dengue fever.

"This is one of those high-tech, high risk innovations that would fundamentally change the struggle between humans and mosquitoes," said Dr. Regina Rabinovich, director of infectious diseases development at the Gates Foundation.

Mosquitoes bred to be immune to malaria could break the disease's transmission cycle. "That is the nirvana of malaria control," said Rabinovich. "It would potentially transform what the field looks like."

In 2005, Crisanti proved it was possible to create a genetically modified mosquito by inserting a gene that glowed fluorescent green in males.

Among other possibilities, he and his team are now planning to create sterile male mosquitoes to mate with wild female mosquitoes, thus stunting population growth. They are also trying to engineer a malaria-resistant mosquito.

Last year, American researchers created mosquitoes resistant to a type of malaria that infects mice. Others are altering the DNA of the mosquitoes that spread dengue.

But not everyone thinks these super mosquitoes are such a good idea. Some scientists think there are too many genetic puzzles to be solved for modified mosquitoes to work.

The malaria-causing parasite, which mosquitoes then transmit to humans, is simply too good at evading anything scientists might devise to protect the mosquito, argued to Jo Lines, a malaria expert at London's School of Hygiene and Tropical Medicine.

"It's a series of arms races that the parasite has consistently won," Lines said. Whenever mosquitoes have developed genes resistant to the malaria-causing parasite, the parasite has always found a way around it, Lines said.

Quantity might also be a problem. "You are going to need to produce billions of these mosquitoes if this is ever going to work," Lines said.

Some environmentalists worried that genetically modified mosquitoes might wreak havoc in the ecosystem.

"Can't we just give mosquito nets to people instead of looking at these really complex technological fixes that mess with the very delicate balance of nature and evolutionary history?" asked Gillian Madill, a genetic technologies campaigner at Friends of the Earth in Washington.

Rabinovich said rigorous testing would be done before releasing any genetically modified mosquitoes into the wild.

"It's not nice to fool with Mother Nature," she said. "But if you can come up with another way of tackling (malaria), this is not something that one walks away from without fully evaluating it."

Over the next year, Crisanti hopes to finalize plans for a test release of genetically modified mosquitoes in southern Italy. There, millions of the insects will be set loose in large cages to determine things like how they might interact with wild mosquitoes and how many would be needed to knock out malaria.

Crisanti acknowledged there might be unintended consequences of releasing genetically modified mosquitoes into the wild, although he could not predict what they might be.

The scientist said it was a risk worth taking.

"I think there is a moral good to doing it," he said. "If we do this right, the mosquitoes will get rid of malaria for us."