Mosquito-killing fungi engineered with spider, scorpion toxins to fight malaria

*Exposure to just ten minutes of light at night suppresses biting, manipulates flight behaviour in Anopheles gambiae
A mosquito-killing fungus genetically engineered to produce spider and scorpion toxins could serve as a highly effective biological control mechanism to fight malaria-carrying mosquitoes, scientists report. The fungus is specific to mosquitoes and does not pose a risk to humans. Further, the study results suggest that the fungus is also safe for honey bees and other insects.

Malaria kills nearly half a million people every year, according to the World Health Organization (WHO). In some of the hardest-hit areas in sub-Saharan Africa, the mosquitoes that carry the malaria parasite have become resistant to traditional chemical insecticides, complicating efforts to fight the disease.

A new study from the University of Maryland and colleagues from Burkina Faso, China and Australia suggests that a mosquito-killing fungus genetically engineered to produce spider and scorpion toxins could serve as a highly effective biological control mechanism to fight malaria-carrying mosquitoes. The fungus is specific to mosquitoes and does not pose a risk to humans. Further, the study results suggest that the fungus is also safe for honey bees and other insects. The study was published online in the journal Scientific Reports on June 13, 2017.

The researchers used the fungus Metarhizium pinshaensei, which is a natural killer of mosquitoes. The fungus was originally isolated from a mosquito and previous evidence suggests that the fungus is specific to disease-carrying mosquito species, including Anopheles gambiae and Aedes aegypti. When spores of the fungus come into contact with a mosquito’s body, the spores germinate and penetrate the insect’s exoskeleton, eventually killing the insect host from the inside out.

Also, scientists at the University of Notre Dame have found that exposure to just 10 minutes of light at night suppresses biting and manipulates flight behaviour in the Anopheles gambiae mosquito, the major vector for transmission of malaria in Africa, according to new research published in the journal Parasites and Vectors. Critical behaviours exhibited by the species, such as feeding, egg laying and flying, are time-of-day specific, including a greater propensity for nighttime biting.

Insecticide-treated bed nets and walls have helped prevent bites and reduce malaria, but researchers say mosquitoes are adapting to preventive conditions, leaving adults and children vulnerable in the early evening and early morning hours — when they are not under the nets or in the house.

For the study, Duffield and his team tested the mosquitoes’ preference to bite during their active host-seeking period by separating them into multiple control and test batches. Control mosquitoes were kept in the dark, while test batches were exposed to a pulse of white light for 10 minutes. Researchers then tested the propensity of the mosquitoes to bite immediately after the pulse and every two hours throughout the night, holding their arms to a mesh lining that allowed uninfected mosquitoes to feed while remaining contained. Results indicated a significant suppression. In another experiment, mosquitoes were pulsed with light every two hours, and using this multiple pulse approach the team found that biting could be suppressed during a large portion of the 12-hour night.