WAGENINGEN, THE NETHERLANDS--If a small band of molecular biologists has its way, the next few years may bring field tests of "designer mosquitoes," genetically modified so they can't transmit diseases such as malaria. But at a workshop here from 26 to 29 June, 20 of the world's leading mosquito ecologists said: Not so fast. Although lab science may be thriving, they said, huge ecological questions remain.
The molecular biologists' ultimate target is Anopheles gambiae, the main vector of the deadliest malaria parasite, Plasmodium falciparum, in Africa. After identifying genes that stop Plasmodium in its tracks, researchers hope to spread the genes through natural mosquito populations by releasing genetically modified mosquitoes. Such golden bugs could save millions of lives, biologists say.
At least in theory. At the meeting, ecologists came up with a discouraging list of questions. For example, would the new mosquitoes be able to find partners? (Past studies showed that lab mosquitoes are less attractive to their natural counterparts.) Would resistance genes be 100% effective in mosquitoes? (If not, the transgenic bugs would barely make a dent in the incidence of malaria, a model suggests.) And would P. falciparum develop resistance to the new genes, as it has to many drugs? (If that happened after an initial success, it could be a disaster, because many people would have lost their immunity.)
Studying many of these issues is a problem in itself. A pilot trial would have to be someplace from which mosquitoes can't escape--Saõ Tomé, one of a handful of islands that form a republic off the west coast of Africa, for example, or perhaps artificial "oases" in the Sahara desert. No matter where, an experimental release raises a host of thorny ethical and regulatory issues.
Feeling "a bit like a ham sandwich on Passover," the only molecular biologist at the workshop, David O'Brochta of the University of Maryland, College Park, admits that he and his colleagues have given little thought to many of these ecological issues. Kate Aultman, program manager for vector biology at the National Institute of Allergy and Infectious Diseases (NIAID), which funds the work on genetically modified mosquitoes, agrees that the ecologists' input is urgently needed. She says NIAID may create a special fund that they can tap.