Scientists engineer mosquito STD to combat malaria

To combat the deadly diseases spread by mosquitoes, entomologists often turn to the blood-sucking insect’s reproductive life. Deactivating their sperm, using a mosquito kill bucket to take out mosquito larvae, and now researchers are creating something akin to a sexually-transmitted disease just for mosquitoes. In a study published earlier this year in the journal Scientific Reports, a team of scientists from the United States and Burkina Faso in West Africa, detailed how they delivered a deadly fungal infection to female mosquitoes. The females are the ones who bite and spread disease to humans. 

The invention could be the latest tool in the fight against malaria, which killed about 597,000 people in 83 countries in 2024. Children under five in sub-Saharan Africa bear the heaviest burden of this disease, accounting for about 76 percent of all malaria deaths in the region. Fighting malaria has slowed recently, as the insects have developed a resistance to some chemical treatments and mosquito-borne parasites have become more resistant to antimalarial drugs.

“It’s essentially an arms race between the mosquitoes and us,” study co-author and University of Maryland entomologist Raymond St. Leger said in a statement. “Just as they keep adapting to what we create, we have to continuously develop new and creative ways to fight them.”

[ Related: After EEE death in New Hampshire, here’s what to know about the mosquito-borne virus. ]

Part of what makes combatting mosquitoes so difficult is just how quickly they adapt to control methods. As bed nets, spraying, and other traditional indoor control methods lose efficacy over time, mosquitoes have learned to avoid them by flying outside and waiting to feed instead. 

In this new study, the team sought to target these hard-to-reach mosquitoes by engineering a naturally occurring fungus called Metarhizium. This fungus has widely been used for pest control of other insects in agricultural settings. The team altered Metarhizium so that it produced insect-specific neurotoxins that kill when it is injected into a female mosquito’s body. Spraying the male mosquitoes with Metarhizium fungal spores could ensure that the fungus spread to the female mosquitoes that the males mated with. 

In tests conducted in Burkina Faso, nearly 90 percent of the female mosquitoes died within two weeks after mating with the males carrying the modified fungus. Only 4 percent mortality was reported in the control group without the modified fungus. Importantly, the modified Metarhizium fungus is harmless to humans, despite being so deadly to female mosquitoes. 

“What makes this fungus particularly promising is that it works with existing mosquito behavior rather than against their natural habits,” St. Leger said. “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.”

Additionally, the team also observed that the male mosquitoes that were treated with the fungus transferred the deadly fungal spores to female mosquitoes for up to 24 hours after their first exposure. This indicates that the male mosquitoes treated with the fungal strain might be releasing into the environment, continually spreading the fungus during multiple mating encounters.

“Interestingly, we noticed that the presence of the fungus did not deter female mosquitoes from mating with infected males. Mating rates stayed the same, which makes this fungus a very powerful mosquito population control tool,” St Leger said. “And the fungus additionally made infected mosquitoes less able to sense insecticides, and much more susceptible to them, so it’s really a double blow against them.”

When used with more traditional mosquito control methods, using the modified Metarhizium could be a powerful new tool if it can be brought up to scale. When used with more traditional mosquito control methods, using the modified Metarhizium could be a powerful new tool if it can be brought up to scale. According to St. Ledger, the team is working out how best to integrate this new technology with other mosquito control approaches. 

“We are also developing indoor fungus application, hanging black cotton sheets treated with fungal spores on household walls,” St. Ledger tells Popular Science. “When mosquitoes encounter these sheets, they become infected, leading to their eventual fungus-induced death. 

Other application methods including using baited taps that lure mosquitoes to the fungus are being developed. Using several mosquito control techniques will likely achieve better control than any one approach. 

“Mosquitoes are the world’s deadliest animal. It’s believed that they alone, by transmitting disease, have killed half of all human beings who have ever lived,” St. Leger noted. “Being able to eliminate mosquitoes quickly and effectively will save people all over the world.”

To help keep you and your loved ones safe from mosquitoes this summer, the Centers for Disease Control and Prevention (CDC), recommends:

• Removing any standing water that collects in garden tools, toys, bins, etc. from outside your home
• Ensuring your window screens do not have any large holes in them
• Using Environmental Protection Agency (EPA)-registered insect repellents.
• Wearing loose-fitting, long-sleeved shirts and pants.

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