Scientists have genetically engineered a fungus to produce toxins usually found in the venom of spiders and scorpions in a bid to fight malaria-carrying mosquitoes.
The work uses a fungus already known to infect and kill mosquitoes that carry malaria in the wild. When the spores of the fungus, called Metarhizium pingshaensei, come into contact with the mosquito, they germinate and penetrate the insects' bodies, eventually killing their hosts. Yet this process takes time to complete and requires many spores to infect each individual mosquito, meaning it is not an effective or rapid process.
The team's aim was to find a way to engineer the fungus to kill the malaria-carrying mosquitoes in a more effective way, while at the same time making sure it's not a threat to humans or beneficial insects that live in the same environment. The results are published in Scientific Reports.
“We report that our most potent fungal strains, engineered to express multiple toxins, are able to kill mosquitoes with a single spore,” explains co-author Brian Lovett in a statement. “We also report that our transgenic fungi stop mosquitoes from blood feeding. Together, this means that our fungal strains are capable of preventing transmission of disease by more than 90 percent of mosquitoes after just five days.”
The potency of the fungus was enhanced by the addition of several genes that usually code for neurotoxins found in the venom of North African desert scorpions and Australian Blue Mountains funnel web spiders. From this, they were able to create multiple strains of the fungus, which produced the toxins either alone or in combination. This allowed the organisms to kill the mosquito through a variety of different pathways, blocking the calcium, potassium, and/or sodium channels.
This in turn prevents the insects’ neurons from firing properly and thus kills them incredibly quickly. In order to prevent the fungus from potentially infecting and harming other organisms, they added a switch to the fungus that is only activated when it comes into contact with insect blood. Yet this still means it could pose a risk to other insects.
The fungal strains were subsequently tested to see if they would have any negative impacts on important pollinator species, such as honey bees, as well as other insects that might be inadvertently infected if the spores were to be sprayed out in the wild, such as midges and gnats. So far, the researchers report, there are no off-target effects.
The team intend to continue testing the strains in controlled conditions with the aim to eventually release the spores into the wild.