Researchers Create Mosquito STD to Combat Malaria, Effective Against Insecticide-Resistant Bugs

Researchers Create Mosquito STD to Combat Malaria, Effective Against Insecticide-Resistant Bugs

A team of researchers, including a University of Maryland entomologist, has developed a novel method to combat malaria by exploiting a mosquito’s mating behavior as a fatal vulnerability.

They engineered a naturally occurring fungus, Metarhizium, to act as a sexually transmitted disease (STD) for mosquitoes. This fungus is designed to deliver insect-specific neurotoxins that kill female mosquitoes (the ones responsible for biting humans and spreading malaria) when they mate with infected males

Male mosquitoes are sprayed with spores of the modified Metarhizium fungus. When these males mate, they transfer the deadly fungus to female mosquitoes. This method exploits the mosquitoes’ natural mating behaviors rather than trying to alter or avoid them.

Published in the journal Scientific Reports earlier this year, the team’s study reveals how this innovative approach exploits mosquito mating behavior to deliver a deadly fungal infection to female mosquitoes—the ones responsible for biting and spreading disease to humans.

The researchers’ invention could have wide-ranging implications for controlling malaria, which kills over 600,000 people annually, with children under five in sub-Saharan Africa bearing the heaviest burden. In recent years, progress in fighting malaria has slowed as mosquitoes developed resistance to chemical treatments and mosquito-borne parasites became more resistant to antimalarial drugs.

“It’s essentially an arms race between the mosquitoes and us,” explained study co-author Raymond St. Leger, a Distinguished University Professor of Entomology at UMD. “Just as they keep adapting to what we create, we have to continuously develop new and creative ways to fight them.”

The researchers supercharged fungi, engineering them to express toxins based on those found in venomous creatures, such as spiders and scorpions.

Entomologists at the University of Maryland traveled to West Africa to test their theory out. They took venom from spiders and scorpions and mixed it with fungus native to that region. Each spore of that supercharged fungus, which is microscopic in size, meant death to mosquitoes. And even better, “Doesn’t hurt people,” said Raymond St. Leger, a professor at the University of Maryland who led the study.

#UMD entomologists mixed spider and scorpion venom with native fungus to develop a "Mosquito STD" to combat malaria.@UMDEntomology's Raymond St. Leger spoke with @WTOP's @JDDsays about the potential of this new weapon in the fight to #EndMalaria. https://t.co/mjqVhP3cMX

— UMD Science (@UMDscience) June 6, 2025

The researchers studied this Metarhizium-based insecticide in a malaria-endemic region of Burkina Faso, a landlocked country in West Africa, bordered by a number of Mali, Niger, Benin, and Ghana. The results were astonishing, as indicated in the team’s published study in Science, especially as they were focused on killing insects known to be resistant to current pesticides.

The effectiveness of this fungus for controlling mosquitoes was trialed in near-field conditions in Burkina Faso in a setup called MosquitoSphere. Approximately 75% of wild insecticide-resistant mosquitoes released into the environment became infected with the transgenic fungus, causing population collapse within 45 days.

It must be noted that though the modified Metarhizium fungus is deadly to female mosquitoes, it is harmless to humans.

These are outstanding developments, especially given the surge in mosquito-borne diseases in our country. In fact, it is being reported that there is an unprecedented surge in mosquito activity and West Nile virus (WNV) cases across the Las Vegas Valley, marking one of the most active mosquito seasons in recent history.

As of early June 2024, SNHD [Southern Nevada Health District] has identified 91 mosquito pools, comprising 3,081 mosquitoes from 16 ZIP codes, testing positive for WNV. Additionally, two mosquito pools, comprising 46 mosquitoes from two ZIP codes, have tested positive for the virus that causes St. Louis encephalitis.

The Health District’s Mosquito Surveillance Program has also received an increased number of complaints from the public about mosquito activity. Increased awareness and reporting of mosquito activity are attributed to the expansion of Aedes aegypti mosquitoes throughout the region. In 2025 so far, SNHD has set 1,048 traps in Clark County in a total of 61 zip codes and collected a total of 12,641 mosquitos. These are sent to the Southern Nevada Public Health Lab to be identified and analyzed for potential viruses.

“We have seen a very active mosquito disease surveillance season,” said Vivek Raman, Environmental Health Supervisor at SNHD. Human cases of West Nile virus have spiked dramatically, with 20 people testing positive in 2024—a stark increase compared to just two cases in 2022 and none in the previous two years.

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