The most dangerous animal on Earth isn’t the shark, or the lion, or even the hippopotamus. It’s so small, in fact, it could sit on the tip of this pencil. Biologists estimate that they have killed nearly half of all humans ever born, and today accounts for more than 45 million years of lost human life every year. [SLAP] BLEEP mosquitoes. [MUSIC] A mosquito is any of more than 3,000 species of tiny annoying flies in the family Culicidae. Among those species that feed on blood, the vampire action is carried out solely by the females, who require the proteins and nutrients in animal blood in order to lay their eggs.
Blood-sucking mosquito species have very discerning palates when it comes to which species they feed on. Mosquitoes that prefer birds, for instance, may not suck our blood. Only a few hundred species are actually known to poke tiny holes in humans. Among humans, mosquitoes are known to be more attracted to some of us than others. I recommend making friends with one of these people, and invite them to your next BBQ as a natural bug decoy! And if you already get invited to a lot of BBQs, it’s probably you. Mosquitoes can detect exhaled CO2 from over 100 feet away, so heavy breathers watch out.
They also show preferences for certain blood types, pregnant women, and particular populations of skin bacteria. Body odor chemicals like octenol, lactic acid… and this one, don’t you laugh!… are skeeter magnets, as well as ethanol secreted through the skin after we’ve been drinking. While we used to think insect repellents like DEET worked by blocking a mosquito’s smell receptors, new research suggests that the bugs just really, really hate the smell. Although we call them bites, mosquitoes actually “poke”. Evolution has molded the mouthparts of these “ectoparasites” into highly-specialized face daggers, enclosed within a sheath called the labium. As they enter the skin, they are unsheathed and the flexible mandible seeks out a blood vessel… OH MY GOD what is it doing?! MAKE IT STOP. When the mosquito finally taps into sanguine sustenance it uses its tongue-like labrum to slurp up a belly full of blood. Our immune system reacts to the foreign proteins in their saliva, resulting in red bumps on our skin.
So you really only have yourself to blame for the itching. But mosquitoes didn’t become the largest killer of humans thanks to us scratching ourselves to death. In fact, it’s not really mosquitoes that do all that killing. The actual culprits are even smaller. Meet Plasmodium falciparum, the most common cause of deadly malaria. This microscopic protozoan parasite swims its way into our bloodstream via the mosquito’s salivary glands, where it infects liver and red blood cells, often resulting in a deadly fever. When another mosquito feeds on malaria-infected human blood, the parasite can sexually reproduce, mutate, and spread. Today, malaria kills about a million people per year, and sickens half a billion.
So what can we do about it? We do see signs of an ongoing evolutionary arms race against malaria inside our own genomes. People who carry one copy of the sickle cell gene mutation, a trait common in tropical regions like sub-Saharan Africa, show resistance to the disease, likely by disrupting the parasite’s blood cell life cycle. Yet malaria persists. Insecticides and other chemicals are effective, but often harm the environment or wipe out beneficial insects along with the bad. Anti-malaria drugs like artemisinin, while cheap and effective, carry a risk of resistance, and they’re completely ineffective against viral mosquito-borne illnesses like Dengue fever.
So, why don’t we just get rid of mosquitoes? Is such a thing even possible? Yes it is. Maybe. Oxford University biologists have created genetically engineered male mosquitoes with a mutation that kills 100% of their offspring. When these males are released into the wild, they mate with females, and all the eggs are duds. And in those places, and mind you this has ACTUALLY been done, Dengue-carrying swarms have plummeted. This works. Well, it works for US at least. In some ecosystems, mosquitoes are important pollinators, or food sources for other organisms. Eliminating mosquitoes, even just specific disease-carrying species, MIGHT lead to other negative effects that we can’t predict. But does human health outweigh those environmental concerns?
Is expensive genetic engineering better than, say, a net over a bed? And could it be, like science writer David Quammen says, that mosquitoes are in some ways defending the world’s wilderness from even wider human invasion? With their tiny swords, and their diseases 🙂 Guarding the jungle. These are difficult questions. They force us to put the health of our own species at odds with another’s, and the answers aren’t simple. I wanna know what you think, I put some links in the description to check out, so talk about it in the comments.