June 09, 2019
2 min read

Genetically modified fungus provides new option for malaria vector control

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Through genetic modification, researchers have weaponized the fungus Metarhizium pingshaense, which is a natural pathogen to mosquitos that carry malaria. Trials performed in a contained, near-natural environment demonstrated that the fungus successfully suppressed a malaria-carrying anopheline mosquito population.

Writing in Science, Brian Lovett, a doctoral student in the department of entomology at the University of Maryland, and colleagues explained that M. pingshaense effectively delivers mosquito-eliminating toxins to Anopheles species mosquito populations that have developed resistance to insecticide.

“The application of Metarhizium spores inside traditional houses in Tanzania reduced the number of infectious bites, but complete protection was prevented by the pathogen’s low virulence (slow killing and high inoculum loads) and low persistence,” Lovett and colleagues wrote. “To remedy these deficiencies, we engineered a strain of Metarhizium pingshaense (Mp-Hybrid).”

In the laboratory, mosquitos were killed faster using lower spore doses with the Mp-Hybrid, as opposed to the wild-type M. pingshaense fungus. Following these experiments, the researchers conducted a trial in near-field conditions in Burkina Faso, a malaria-endemic country that reported more than 7.9 million cases of malaria in 2017. This was accomplished using what they called the “MosquitoSphere” — near-natural environment complete with animals, huts, plants, and breeding sites made of plastic sheets buried in soil — all enclosed in a greenhouse frame with walls of mosquito netting.

“On the basis of previous studies, we found that suspending Metarhizium in locally produced sesame oil and spreading the suspension on black cotton sheets achieves

a long-term effect in the sphere, and these sheets provide a resting area for mosquitoes that have taken blood meals from calves in the huts,” Lovett and colleagues wrote.

Lovett and colleagues said the engineered fungus infected nearly 75% of the wild insecticide-resistant mosquitos, resulting in a population “collapse” within 45 days.

“Our results show that Mp-Hybrid’s increased virulence and lower inoculum load have produced a product that is more robust and easier to use than the [wild-type] fungus in a setting where malaria is endemic,” Lovett and colleagues wrote. “This finding, together with the greatly reduced blood-feeding propensity of Mp-Hybrid-infected mosquitoes, means that Mp-Hybrid could affect malaria transmission over a broader range of lethal, prelethal, and generational conditions than unmodified Metarhizium.” – by Marley Ghizzone

Disclosures: The authors report no relevant financial disclosures.