A New Way of Thinking About Malaria Prevention

Since I'm here in Orlando in the middle of summer, I am reminded of mosquitos. Indeed, although Orlando is now in Orange County, Florida, the original name of the county in the 19th century was Mosquito County. We know a lot more about malaria (such as its connection to mosquitos) than people did then, but efforts to control deaths from malaria have still focused mainly on prevention and treatment. Insecticides designed to kill mosquitos and drugs designed to treat malaria in an infected person run the risk of actually creating stronger mosquitos and parasites that are then ever harder to deal with. But, what about trying to change the parasite itself? Researchers at The Johns Hopkins University have just published a paper in the Proceedings of the National Academy of Sciences about their search for a way to genetically alter the malaria parasite. The paper is not yet available free to the public, but the LA Times has summarized it in a story today.

Insecticides have a major flaw, said Marcelo Jacobs-Lorena, a malaria expert at Johns Hopkins University and an author of the new study. "When insecticides are used — say, inside of houses — many of the mosquitoes in the area get killed but some will always survive. It's a perfect way to select for resistance," he said. That's because the mosquitoes most resistant to insecticides will survive and have insecticide-resistant offspring. The same problem exists for anti-malaria drugs.

As a result, Jacobs-Lorena said, mosquito populations have continued to thrive, becoming more immune every day to the poisons we expose them to.
Ten years ago, his group was the first to show that mosquitoes could be genetically engineered to produce anti-malarial proteins in their guts, rendering them incapable of harboring the parasite. The idea was that the insects would be released into the wild and spread their new genes around.

For a variety of reasons, that approach turned out not to work so well, so the team has embarked on a new strategy.

Instead of modifying mosquitoes, they are genetically engineering bacteria that naturally live in the mosquito gut. The altered bacteria produce several parasite-killing proteins, including one that inserts itself into the outer membrane of the parasite, causing it to leak its contents and die.

The devil is obviously in the details, but this is the kind of creative thinking that is necessary with such a complex and deadly disease.