Spores squash malaria mosquitos with spider venom
Billions of people live among widespread mosquito-borne diseases. Worryingly, decades of insecticide usage bred resistant mosquito strains that are affecting hundreds of millions of people and killing hundreds of thousands.
To fight this, researchers have taken a fungus from the wild that naturally infects mosquitos and genetically engineered it to make a spider venom that kills the mosquitos quickly and effectively. For the first time outside of a lab, researchers showed that their spider venom producing spores squashed nearly all mosquito populations in a controlled environment simulating nature in a rural, malaria-endemic area in Africa.
One-quarter of the world’s population — about 2 billion people — lives in areas with rampant mosquito-borne diseases.
Nowhere on earth is more impacted than sub-Saharan Africa where there are more than 200 million reported cases of malaria per year including many children who die at the hands of the disease.
Over the decades, several methods have been developed to control malaria by stopping the mosquitos carrying the virus. Deterrent methods include bed nets or walls and ceilings sprayed with chemical insecticides.
However, there are mosquitos carrying malaria that have gained resistance to these chemical insecticides making them ineffective in neutralizing mosquitos. For these reasons, there is a dire need for practical solutions to fight off these insecticide-resistant mosquitos to prevent rampant spreading of malaria.
Harnessing the Fungus Among’us
Interestingly, there are strains of fungus that can infect adult mosquitos considered not harmful to the environment.
For instance, when a fungus strain called Metarhizium was applied inside homes in Tanzania, the number of times inhabitants were infectiously bitten by mosquitos decreased. However, the inhabitants were not completely protected because this fungus type is a slow and not particularly strong killer of mosquitos.
To overcome this limitation, researchers engineered a Metarhizium strain that produces a potent toxin found in the venom of Australian funnel-web spider H. verusta. This self-synergizing peptide toxin is a nearly perfect clone of the spider’s potent death juice. In the lab, this genetically modified fungus was shown to kill mosquitos faster and at lower amounts than those found in the wild.
However, this research was done in a lab with an enclosed, controlled environment — nature is complex and unpredictable. So, these studies may not mirror what will happen outdoors in real-world rural towns that are plagued with malaria, such as those in sub-Saharan Africa.
Enter the MosquitoSphere
Recently, a team of researchers headed to a rural village in Burkina Faso — a landlocked country in West Africa. Burkina Faso had nearly 8 million cases of malaria in 2017 and is one of the 10 highest malaria burdened countries in the world.
Here, they created a contained facility called the MosquitoSphere. The facility was enclosed in mesh mosquito nets to serve as a barrier and to allow exposure to ambient climate conditions.
Inside, the MosquitoSphere contained several rooms. Some rooms were used for raising and feeding mosquito larvae. Other rooms were used for the actual experiments.
These testing rooms had West African huts with calves that provided meals of blood to the mosquitos. The huts also had breeding sites that simulated a natural mosquito habitat.
In the huts, the researchers hung cotton sheets that provide a resting area for mosquitoes that have taken blood meals from calves in the huts. These sheets were covered in locally-made sesame oil that contained either the genetically engineered Metarhizium or the fungus found in the wild.
Malaria is in’truffle
What they found were that mosquitos including, insecticide-resistant ones, thrived in the MosquitoSphere rooms mimicking the outdoors without fungus. In rooms with fungus found in the wild, the mosquitos didn’t flourish but they survived just fine.
On the other hand, in rooms with the genetically engineered fungus, in just 45 days, they saw huge reductions in each generation of mosquitos and dwindling mosquito populations.
They repeated these experiments with a few different strains of mosquitos, and the researchers saw the same results — the mosquitos floundered against the genetically modified fungus. This means, importantly, that the genetically modified fungus is not limited to targeting one type of mosquito population.
Pesticides with Metarhizium are already registered for agricultural use in several African countries. This means that this sesame-oil spore-spread can be used as a product to control malaria essentially as soon as it can be produced.
Looming GMO shroom questions
There are major questions and concerns for using this type of prevention method — what are the consequences of releasing a genetically modified organism, such as this fungus, into the wild?
For instance, will the genetically modified fungus unintentionally infect other insects, which could cause ecosystems to collapse?
Luckily, the fungus has previously been tested on beneficial and pest insects found in the native environment and were shown to not influence these insects. So, it seems unlikely that insects other than mosquitos potentially carrying malaria will be affected by the introduction of this genetically modified fungus into the wild.
What if the fungus spreads?
Off-site dispersal of the fungus is unlikely, as the spores are large, sticky, and UV-sensitive — they do not naturally become airborne. Applying the spores to sheets in residential sites can help reduce opportunities for spreading the fungus.
On top of this, spores can be made that are contained to areas protected from sunlight — the fungus can be genetically engineered to be sensitive to light. This, in theory, would prevent the spread of the genetically modified fungus from mosquito traps or houses to the wild.