ACCORDING to the World Health Organisation, malaria affects hundreds of millions of people around the world, killing more than 400,000 annually. Decades of insecticide use has failed to control mosquitoes that carry the malaria parasite and has led to insecticide-resistance among many mosquito strains. In response, scientists began genetically modifying mosquitoes and other organisms that can help eradicate mosquitoes. Until now, none of these transgenic approaches made it beyond laboratory testing.
In a research paper published in the May 31, 2019, issue of the journal Science, a team of scientists from the University of Maryland and Burkina Faso described the first trial outside the laboratory of a transgenic approach to combating malaria.
The study showed that a naturally occurring fungus engineered to deliver a toxin to mosquitoes safely reduced mosquito populations by more than 99% in a screen-enclosed, simulated village setting in Burkina Faso, West Africa.
“No transgenic malaria control has come this far down the road toward actual field testing,” said Brian Lovett, a graduate student in UMD’s Department of Entomology and the lead author of the paper. “This paper marks a big step and sets a precedent for this and other transgenic methods to move forward.”
“We demonstrated that the efficacy of the transgenic fungi is so much better than the wild type that it justifies continued development,” said Raymond St. Leger, a Distinguished University Professor of Entomology at UMD and co-author of the study.
The fungus is a naturally occur- ring pathogen that infects insects in the wild and kills them slowly. It has been used to control various pests for centuries. The scientists used a strain of the fungus that is specific to mosquitoes and engineered it to produce a toxin that kills mosquitoes more rapidly than they can breed. This transgenic fungus caused mosquito populations in their test site to collapse to unsustainable levels within two generations.
“You can think of the fungus as a hypodermic needle we use to deliver a potent insect-specific toxin into the mosquito,” said St. Leger.
The toxin is an insecticide called Hybrid. It is derived from the venom of the Australian Blue Mountains funnel-web spider and has been approved by the Environmental Protection Agency (EPA) for application directly on crops to control agricultural insect pests. “Simply applying the transgenic fungus to a sheet that we hung on a wall in our study area caused the mosquito populations to crash within 45 days,” Lovett said.
“And it is as effective at killing insecticide-resistant mosquitoes as non-resistant ones.”
Lovett said laboratory tests suggest that the fungus will infect the gamut of malaria-carrying mosquitoes. The abundance of species that transmit malaria has hindered efforts to control the disease, because not all species respond to the same treatment methods. –University of Maryland