How Venom from Spiders Kills Malaria Mosquitoes

In the 1980s, the village of Soumousso in Burkina Faso helped launch one of the most powerful weapons against malaria: insecticide-treated bed nets, which had early field trials there and went on to save millions of lives. But as mosquitoes developed resistance to widely used insecticides, the nets lost some of their power. Now, researchers are hoping the village can help make history again by testing a new countermeasure: a genetically modified (GM) fungus that kills malaria-carrying mosquitoes. In tests in a 600-square-meter structure in Soumousso called the MosquitoSphere—built like greenhouse but with mosquito netting instead of glass—the fungus eliminated 99% of the mosquitoes within a month, scientists report in the  magazine Science.

MosquitoSphere, Burkina Faso

The fungus also has clear advantages, however: It spares insects other than mosquitoes, and because it doesn’t survive long in sunlight, it’s unlikely to spread outside the building interiors where it would be applied.  Fungi naturally infect a variety of insects, consuming the host’s tissues in order to reproduce, and they have been used for decades to control a wide variety of crop pests….Researchers have tested dozens of different fungal strains against disease-carrying mosquitoes, but none was effective enough to pass muster. So researchers from the University of Maryland (UMD) in College Park and the Research Institute of Health Sciences & Centre Muraz in Bobo-Dioulasso, Burkina Faso, endowed a strain called M. pingshaense with a gene for a toxin isolated from spider venom that turns on when it contacts hemolymph, the insect version of blood. In the lab, the team showed its creation could kill mosquitoes faster and that just one or two spores could cause a lethal infection. 

Burkina Faso was a promising place for a field test: Unlike many countries in Africa, it has an established system to evaluate and approve the use of GM organisms. It also has one of the highest rates of malaria in the world, and insecticide-resistant mosquitoes are widespread. For those and other reasons, the U.S. National Institutes of Health funded the MosquitoSphere, which is specifically designed to test GM organisms.

Excerpts fromGretchen Vogel  Fungus with a venom gene could be new mosquito killer, Science, May 31, 2019

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