The Zika virus, which is spreading like wildfire throughout the Americas and is linked to a head-shrinking birth defect called microcephaly, is just the latest in a long list of mosquito-transmitted diseases that make the insects the world's deadliest animal. It is time to launch a global initiative to eradicate them.
In advanced countries with moderate climates, mosquitoes are more of a nuisance than a threat to public health. But in warmer climates — including places like Florida, where Gov. Rick Scott just declared a health emergency in four counties — mosquitoes are nothing short of a plague.
Malaria, West Nile, dengue, chikungunya, yellow fever and various types of encephalitis are all transmitted by these tiny bloodsuckers. Overall, the World Health Organization estimates that mosquito-borne diseases kill several million people every single year and infect hundreds of millions of others.
Bill Gates, perhaps history’s greatest philanthropist, is using his vast fortune to target diseases like malaria in poor, developing countries. According to his analysis, mosquitoes are by far the deadliest animal on the planet.
It should be noted, however, that not all mosquitoes are bad (to humans, anyway). Some play an important ecological role through pollinating plants, for instance. Others are a major food source for birds and frogs. Only a small fraction of the roughly 3,500 species of mosquito transmit diseases to humans.
Even so, that means at least several dozen species act as human disease vectors. The worst species are Anopheles gambiae, the primary vector of malaria, and Aedes aegypti, which transmits Zika and many other viral infections.
Eradication will not be a trivial undertaking. The most successful public health campaign in world history, the eradication of smallpox, was possible only because the virus was a relatively easy target: It mutated slowly, only infected humans and had no insect vector. It still took nearly 200 years after the invention of the smallpox vaccine to wipe it off the planet.
In contrast, both malaria and the mosquitoes that carry it are known to mutate. Adding yet more complexity to a global mosquito-borne disease eradication effort is the fact that 40 species of the insects are thought to transmit malaria. Toss in all the other aforementioned diseases transmitted by yet more species of mosquito, and the idea of eradicating mosquito-borne disease appears nearly hopeless.
Yet, that doesn’t mean we shouldn’t try. In fact, efforts are already underway to eliminate the most noxious mosquito offenders.
In some parts of the world, insecticides such as DDT are being used. The chemical is certainly effective, but it is hardly an ideal solution. Mosquitoes can become resistant. In addition to being toxic to humans, it also acts indiscriminately, killing beneficial insects and harming other wildlife.
A different approach involves giving mosquitoes a taste of their own medicine: infecting them with their own disease-causing microbe, a bacterium called Wolbachia. This bacterium can shorten mosquitoes’ lifespans and interfere with their reproductive abilities.
Yet another solution involves biotechnology. A genetically modified version of a bacterium called Pantoea agglomerans, normally found in mosquito guts, can interfere with the development of the malarial parasite.
Furthermore, a powerful technique known as “gene drive” uses genetically modified mosquitoes to spread genes throughout wild mosquito populations that cause them to resist being infected by the parasite. And the British company Oxitec has shown great success in reducing mosquito populations by releasing male mosquitoes into the wild that were genetically modified to be sterile.
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Of course, any techniques that rely on biotechnology are prone to controversy because of a large cohort of scientific illiterates, many of whom are influential members of the environmentalist movement. Anti-GMO organizations such as Greenpeace will continue to exploit public ignorance of biotechnology to portray such efforts as unnatural and dangerous. Sadly, anti-GMO propaganda often works.
Society might have to rely upon less sophisticated, but perhaps more amusing, ways to combat mosquitoes and their diseases. One group of researchers has discovered that Viagra can prevent transmission of the malaria parasite by stiffening malaria-infected cells, reducing their ability to infect mosquitoes. Limburger cheese traps can lure the insects to their deaths. There is also a poetic justice pill being developed that humans can take to turn our own blood into a deadly insecticide.
Even if the primary mosquito mischief-makers Aedes aegypti and Anopheles gambiae are wiped out, the diseases they transmit likely will be around for decades. That’s because other mosquito species may fill the ecological niche their dead cousins will have left behind.
Nonetheless, any reduction in the number of mosquito-borne infections is a gigantic win for humanity. We should use every tool we have to wipe them out.
Alex Berezow, founding editor of RealClearScience, holds a Ph.D. in microbiology and is a member of USA TODAY's Board of Contributors.
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