Gene-editing of mosquitoes could annihilate lethal viruses

Scientists could put disease-spreading mosquitoes in their crosshairs, but would the outcome be positive?
Aedes aegypti

New developments in genetic engineering could help eradicate certain deadly diseases completely. Several scientists and biochemists around the world are considering the Aedes aegypti (more commonly known as the yellow fever mosquito) and how to stop the way that it spreads disease among humans across the globe.

Mosquitoes are statistically the most lethal insect on Earth when it comes to human life. Scientists have identified the chief culprit as the Aedes aegypti, a specimen that is notorious for the proliferation of yellow fever, malaria, dengue fever and the Zika virus.

The number of human lives that mosquitoes claim annually (over 500,000 in 2015 alone) dwarfs that of any other insect and moreover, any other member of the animal kingdom. Over 3 500 species of mosquito have been documented on Earth but only a few dozen of them carry viruses or parasites that are harmful to humans.

Scientists are working on ways to diminish this threat and new gene-editing methods seem to be a powerful solution. Researchers are able to alter the mosquitoes’ DNA, programming them to develop as males only. American entomologist and virologist Zach Adelman and biochemist Zhijian Tu recently co-authored research on changing the sex-assignation of the insect species to halt its reproduction. Their findings, in tandem with a new gene-editing tool known as Crispr/Cas9, would ensure that female yellow fever mosquitoes die out.

Given that only female mosquitoes "bite" humans, wiping them out would cut down the number of disease cases rapidly. Using genetic engineering to ensure only male Aedes aegypti reach adulthood would also mean that finding a mate to reproduce would become difficult or even impossible for them, collapsing the population of the species within a few generations.

“If you’re successful, then you end up with all males and the local population crashes,” Tu told the Wall Street Journal.

Though the benefits to humanity would be clear and fast, the ability to wipe out an entire species could cause an uproar. This gene-editing programme has the ability to drive the yellow fever mosquito to total extinction. Some may view the removal of a fellow species in its entirety from the face of the Earth as too severe of a solution. Nature conservationists around the world devote great resources to the preservation of animals and the conservation of diversity. Should the total elimination of another species be condoned as a humanitarian cause? 

The development of genetic engineering throughout history has been fraught with conscientious obscurity, but this case does not seem to have major pitfalls. The gene drive concerned should provide relief to plagued countries much faster than the development of a vaccine for any of the illnesses above would. The Crispr/Cas9 gene drive is designed to duplicate genes through successive generations quickly.

Some scientists, entomologists included, have voiced their concern regarding the outcomes of weaponised gene drives while many in the public sphere regard the power of genetic engineering as ‘playing God’ and that editing DNA is akin to tampering with laws of nature.

It is certain that the population of the yellow fever mosquito would be devastated by these genetic adjustments and much research on its effects should still be done before it is applied. That even the most dangerous kinds of mosquito also pollinate different plants during their lifetime must be accounted for. Fortunately, some current research shows that even in the niche cases wherein mosquitoes pollinate orchids, their absence would not upset the ecological balance. 

Scientists have cautioned that such an effective gene-editing system would still have to be painstakingly accurate and confined to the yellow fever mosquito. As one of the insect's close relatives, the Aedes aegypti formosus is a mosquito that inhabits forests and poses no threat to humans. It would have to remain unaffected by the marginal chance of cross-breeding with a mosquito that carries the destructive gene.

Even though all insects form part of a larger food chain, cutting the Aedes aegypti out of its hierarchy does not seem to hold major negative effects in store. Entomologists agree that humans are this particular species’ only target, thus the environmental effect would be minimal. According to American entomologist Michael Doyle: “They’re so tiny, a bat would have to eat thousands of them to equal a couple of moths.”

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