By James Gallagher for BBC News
31 May 2019
A fungus - genetically enhanced to produce spider toxin - can rapidly kill huge numbers of the mosquitoes that spread malaria, a study suggests. Trials, which took place in Burkina Faso, showed mosquito populations collapsed by 99% within 45 days. The researchers say their aim is not to make the insects extinct but to help stop the spread of malaria. The disease, which is spread when female mosquitoes drink blood, kills more than 400,000 people per year. Worldwide, there are about 219 million cases of malaria each year.
Conducting the study, researchers at the University of Maryland in the US - and the IRSS research institute in Burkina Faso - first identified a fungus called Metarhizium pingshaense, which naturally infects the Anopheles mosquitoes that spread malaria. The next stage was to enhance the fungus. "They're very malleable, you can genetically engineer them very easily," Prof Raymond St Leger, from the University of Maryland, told BBC News. They turned to a toxin found in the venom of a species of funnel-web spider in Australia. The genetic instructions for making the toxin were added to the fungus's own genetic code so it would start making the toxin once it was inside a mosquito. "A spider uses its fangs to pierce the skin of insects and inject toxins, we replaced the fangs of spider with Metarhizium," Prof St Leger explained. Laboratory tests showed the genetically modified fungus could kill quicker, and that it took fewer fungal spores to do the job. The next step was to test the fungus in as close to real-world conditions as possible. A 6,500-sq-ft fake village - complete with plants, huts, water sources and food for the mosquitoes - was set up in Burkina Faso. It was surrounded by a double layer of mosquito netting to prevent anything escaping.
The fungal spores were mixed with sesame oil and wiped on to black cotton sheets. The mosquitoes had to land on the sheets to be exposed to the deadly fungus. The researchers started the experiments with 1,500 mosquitoes. The results, published in the journal Science, showed numbers soared when the insects were left alone. But when the spider-toxin fungus was used, there were just 13 mosquitoes left after 45 days. "The transgenic fungus quickly collapsed the mosquito population in just two generations," said Dr Brian Lovett, from the University of Maryland. Tests also showed the fungus was specific to these mosquitoes and did not affect other insects such as bees. He added: "Our technology is not aiming to drive the extinction of mosquitoes, what we're aiming to do is break malaria transmission in an area."
New tools are needed to tackle malaria as mosquitoes are becoming resistant to insecticides. The World Health Organization has warned that cases are now increasing in the 10 worst affected countries in Africa. Commenting on the findings, Prof Michael Bonsall, from the University of Oxford, said: "Neat - this is a super-exciting study. The prospects for controlling mosquitoes using this modified fungus are high. Proportionate bio-safety regulations are needed to ensure that the viability of this and other approaches for vector [mosquito] control using genetic methods are not lost through overly zealous restrictions." Dr Tony Nolan, from the Liverpool School of Tropical Medicine, added: "These results are encouraging. We need new and complementary tools to augment existing control methods, which are being affected by the development of insecticide-resistance."
[WOW! If this is as targetable as it seems and effective as it appears it will be incredibly effective against malaria carrying mosquitoes. I do worry some that the fungus could end up killing other insects once it’s released into the wild (once approved for use) but that *might* be a risk worth taking with so much at stake. I wonder if they could GM the fungus to make the mosquitoes sterile. Maybe that might be a better idea than having a fungus out there producing spider venom? Plus it does kind of worry me that it’s so easy to weaponise fungus….. Where could THAT lead…..?]
5 comments:
Interesting stuff. I am cautious of the results of any one study but this could be important. I think that the entire genetic modification thing will bring about a lot of good. But there will inevitably be problems.
@ Brian: Like most technology I think it has great potential for good and evil - it all depends on intention, how its used and who uses it. It's easy to see how the technology can be weaponised but it can also rid the world of malaria.....
so what happens when mosquitos become immune to the fungi? or start communicating it to humans? my bad: i shouldn't think about things that way, i know...
Genetic modification does make me wary but at least we are thinking about and testing for long range effects. We didn't do that for DDT and look what happened. I do wonder if we will even hear about the end of the story.
@ Mudpuddle: I don't think that the mossies can become immune to the fungi - they just co-habit their bodies. Also I don't think you can gain immunity to spider venom quickly enough to survive very long. Although I'm certainly not a biologist or geneticist so.... All such things do carry risks though!
@ Judy: GMing anything is risky. I still don't think we know enough about a creatures genome to mess with it with 100% certainty. Add to that our less than perfect understanding of ecosystems and you have potential for something going very wrong. Here's hoping they've thought of everything!
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