Malaria is a global health problem that is caused by a parasite, which is spread by infected mosquitoes. According to the World Health Organization, there were about 263 million malaria cases and 597,000 deaths caused by the disease in 83 countries in 2023. Most deaths happened in children under the age of five.
Since mosquitoes carry malaria, prevention has long focused on preventing mosquito bites, such as with nets, and controlling mosquito populations with insecticides and other measures. Researchers are always looking for new ways to prevent the disease, however. Two new studies have described novel prevention approaches.
Research published in Scientific Reports has shown that male mosquitoes can be exposed to a fungal infection that is then transmitted to many female mosquitoes as they mate, which kills the females.
In this work, the investigators altered the Metarhizium fungi so it would generate neurotoxins that only work on insects, and can kill female mosquitoes when injected into their bodies. When male mosquitoes were sprayed with fungal spores, they spread the fungi to the females as they mated, killing them and clearly reducing offspring.
When this method was tested in the field in Burkina Faso, almost 90% of female mosquitoes were dead within two weeks of mating with males that carried the fungus. This only happened to 4% of females in a control group. The fungus also did not stop the females from mating with the males.
"What makes this fungus particularly promising is that it works with existing mosquito behavior rather than against their natural habits," said Raymond St. Leger, a Distinguished University Professor of Entomology at the University of Maryland. "Unlike pesticides or other chemical control methods that mosquitoes can develop resistance to, this method uses the mosquitoes' own biology to deliver the control agent."
In an unrelated study reported in Applied and Environmental Microbiology, researchers have also isolated compounds from bacteria that were collected from Crete, in the Mediterranean Sea. Some of the compounds were found to be insecticides that can effectively kill Culex pipiens molestus mosquitoes. These mosquitoes are able to transmit pathogens like West Nile Virus and Rift Valley Fever Virus.
Several of the metabolites killed 100% of mosquito larvae within a day of their exposure to the chemicals. They could help scientists develop effective insecticides that have minimal effects on animals and the environment.
Sources: University of Maryland, Scientific Reports, Applied and Environmental Microbiology