They are our apex predator, the deadliest hunters of human beings on the planet. - By
July 28, 2019 - It has been one of the most aggravating sounds on earth for more than 100 million years — the humming buzz of a mosquito.
She gently lands on your ankle and inserts two serrated mandible cutting blades and saws into your skin, while two other retractors open a passage for the proboscis. With this straw she sucks your blood, while a sixth needle pumps in saliva that contains an anticoagulant that prevents that blood from clotting. This shortens her feeding time, lessening the likelihood that you splat her across your ankle.
The female mosquito needs your blood to grow her eggs. Please don’t feel singled out. She bites everyone. There is no truth to the myths that mosquitoes prefer women over men or blondes and redheads over those with darker hair. She does, however, play favorites. Type O blood seems to be the vintage of choice. Stinky feet emit a bacterium that woos famished females, as do perfumes. As a parting gift, she leaves behind an itchy bump (an allergic reaction to her saliva) and potentially something far worse: infection with one of several deadly diseases, including malaria, Zika, West Nile, dengue and yellow fever.
Mosquitoes are our apex predator, the deadliest hunter of human beings on the planet. A swarming army of 100 trillion or more mosquitoes patrols nearly every inch of the globe, killing about 700,000 people annually. Researchers suggest that mosquitoes may have killed nearly half of the 108 billion humans who have ever lived across our 200,000-year or more existence.
Flying solo, the mosquito does not directly harm anyone. It is the diseases she transmits that cause an endless barrage of death. Yet without her, these pathogens could not be vectored to humans. Without her, human history would be completely unrecognizable.
The mosquito and her diseases have accompanied traders, travelers, soldiers and settlers (and their captive African slaves) around the world and have been far more lethal than any manufactured weapons or inventions.
Malarious mosquitoes patrolling the Pontine Marshes facilitated both the rise and the fall of the Roman Empire. Initially shielding the Eternal City from the Visigoths, Huns and Vandals, they eventually pointed their proboscises inward on Rome itself. Mosquitoes defended the Holy Land during the Crusades by laying waste to armies of cross-adorned Christian soldiers. By infecting European soldiers with malaria and yellow fever, they reinforced numerous successful rebellions in the Americas during the late 18th and early 19th centuries, including the British surrender at Yorktown during the American Revolution.
Mosquitoes also played a role in steering slave ships from Africa across the Atlantic, because plantation owners in the Americas believed that Africans withstood the onslaught of mosquito-borne disease better than indigenous slaves or European indentured servants. During the American Civil War, Confederate forces suffered from shortages of the antimalarial drug quinine, and the mosquito eventually helped hammer the final nail in the coffin of the institution of slavery. But these examples only scratch the surface of her historical impact.
Malaria, a parasitic disease, is the unsurpassed scourge of humankind. Dr. W. D. Tigertt, an early malariologist at Walter Reed Army Medical Center, said, “Malaria, like the weather, seems to have always been with the human race.” He continued, “And as Mark Twain said about the weather, it seems that very little is done about it.” Even today, more than 200 million unlucky people contract malaria each year.
Malaria often produces a synchronized and cyclical pattern of symptoms: a cold stage of chills and shakes, followed by a hot stage marked by fevers, headaches and vomiting, and finally a sweating stage. After a period of respite, this progression repeats itself. For many, especially children under 5, malaria triggers organ failure, coma and death.
Mosquitoes also transmit a catalog of viruses: dengue, West Nile, Zika and various encephalitides. While debilitating, these diseases are generally not prolific killers. Yellow fever, however, is the viral exception. It can produce fever-induced delirium, liver damage bleeding from the mouth, nose and eyes, and coma. Internal corrosion induces vomit of blood, the color of coffee grounds, giving rise to the Spanish name for yellow fever, vómito negro (black vomit), which is sometimes followed by death.
Today, roughly four billion people are at risk from mosquito-borne diseases. As our ancestors can attest, our battle with the mosquito has always been a matter of life and death, and it’s beginning to look as though this confrontation is coming to a head.
In “Silent Spring,” Rachel Carson wrote that “our attitude toward plants and animals is a singularly narrow one,” that “if for any reason we find its presence undesirable or merely a matter of indifference, we may condemn it to destruction forthwith.” She could not have anticipated the arrival of Crispr — the gene-editing technology that can tremendously speed up the meaning of “forthwith.”
Unveiled in 2012, Crispr snips out a section of DNA sequencing from a gene and replaces it with another one, permanently altering a genome. This innovation has been called the extinction machine because it allows us to intrude on natural selection to wipe out any undesirable species. Crispr has been used to design mosquitoes that produce infertile offspring. If those mosquitoes were released into the wild, the species could become extinct. Humanity would never again have to fear the bite of a mosquito.
And yet, it would also mean that science fiction would become reality. “We can remake the biosphere to be what we want, from woolly mammoths to nonbiting mosquitoes,” Henry Greely, the director of the Center for Law and the Biosciences at Stanford University, told Smithsonian magazine. The question is: “How should we feel about that? Do we want to live in nature, or in Disneyland?”
We also have valid, although yet unknown, reasons to be careful what we wish for. If we eradicate disease-vectoring mosquito species, would other mosquito species or insects simply fill the ecological niche? Would one disease be swapped out for another? What effect would eliminating mosquitoes (or any other animal) have on mother nature’s biological equilibrium?
But perhaps now, as in the past, we are underestimating the mosquito. She evolved to endure global showers of the eradication chemical DDT and may genetically outflank Crispr as well. History has shown the mosquito to be a dogged survivor. She has ruled the earth for millions of years and has killed with unremitting potency throughout her unrivaled reign of terror. She has steered the course of history, scratching her indelible mark on the modern world order.
Dr. Rubert Boyce, the first dean of the Liverpool School of Tropical Medicine, bluntly stated in 1909 that the fate of human civilization would be decided by one simple equation: “Mosquito or Man?” Across the ages, we have been locked in a life-or-death struggle for survival with the not-so-simple mosquito. Historically, we did not stand a chance.