Save the whales. Save the red-eyed tree frog. Save the condor. Save the spotted owl. Part of our make-up as modern humans includes concern about the creatures with whom we share the planet. We’re not like early men, who hunted mammoths and mastodons to extinction. Nor are we like the fashionable of the nineteenth century, who saw several birds with attractive tails dwindle into oblivion because well-dressed ladies wanted those feathers in their hats. Nor are we like those who hunted the passenger pigeon to extinction, because it was a cheap and easy way to feed slaves.
But right now, a researcher from the University of California Irvine, working together with a British research company, has proposed a way to annihilate a species of creature from the face of the earth. Who is the target? None other than the noble beast Aedes aegypti. Quick! Print out the “Save the Aedes aegypti” bumper stickers! Take up a collection! Stoke the public outrage!
As it turns out, there isn’t much outrage to stoke. Why? Aedes aegypti is a mosquito, and not too many animal lovers are going to rush to pin a “Save the Mosquitoes” bumper sticker on the back of their Toyota Prius.
Aedes aegyptiis not just any mosquito. This bug is a small creator of large problems. For starters, it bites only humans – not
animals – and is responsible for spreading dengue fever, yellow fever and Chikungunya, another insect-borne fever disease that is common in both Africa and Asia, and endemic in Thailand. The critter thrives in the tropical regions of the world, wreaking havoc and spreading disease, killing the very young, the elderly and the immunocompromised. (And in the case of yellow fever, sometimes even the strong and healthy.) Dengue fever affects between 50 and 100 million people living in tropical regions all over the world each year, and there is no cure or vaccine for it. There are more than a few people who think the world would be a better place without our friend A. aegypti.
But how do you go about eradicating an entire species of mosquito? The little buggers are rather numerous, and make rabbits seem like slow breeders. If you’re Dr. Anthony James of the Department of Microbiology and Molecular Genetics and Department of Molecular Biology and Biochemistry at the University of California, Irvine, you get them to eliminate themselves. It’s called “autocide,” and it involves a spot of genetic engineering.
Let’s review what we know about mosquito biology. As in most of nature, the males fertilize the females. Males don’t bite people or animals, they feed on nectar and other plant sugars. It’s the female who bites, looking for a “blood meal” to help her lay her eggs. Eggs take only two or three days to develop, so once the female has deposited her eggs, she returns for another cycle of mating, blood-sucking and egg-laying. Meanwhile, her eggs hatch on stagnant water (as little as one teaspoon is required) and turn into larvae, then pupae, then eventually become adult mosquitoes. Female mosquitoes can live as long as a month, so in her short lifespan she can mother a whole lot of little blood-suckers. If she’s the type to bite humans and carry diseases, this makes her very dangerous.
What Dr. James and his research partners have done is make an alteration to the genes of Aedes aegypti, essentially creating a new mosquito. The male of this new and improved mosquito looks and acts a lot like the standard variety, except for one key difference: the females he fathers cannot fly. If a male carrying the modified genes mates with a wild female, causing her to lay eggs, her male offspring will be normal, but her female offspring will be flightless, leaving them “stuck” where they were laid, unable to fly, mate and lay eggs of their own. In the meantime, the still-winged males, carrying the genetic mutation, fly on and find more wild females to mate with, producing even more flightless females, carrying on the cycle until the goal is achieved: no more Aedes aegypti mosquitoes. The effects on the female mosquito and not the male were made possible by the discovery that female mosquitoes possess a kind of muscle protein that the boys just don’t have, possibly since females need to be able to fly engorged with blood, making them heavier than the males during reproduction. The gene was designed to target this protein.
In their research (published here in the proceedings of the National Academy of Sciences of the United States of America), James and his colleagues found that by introducing male mosquitoes carrying the modified gene, called OX3604C, to cages full of wild mosquitoes, they were able to achieve a significant reduction in the number of eggs laid and the overall number of adult mosquitoes by weeks five to eight. By the eighth week, a majority of the larvae in the cages carried the modified gene. The populations of mosquitoes in the test cages reached extinction within 10 to 20 weeks of the initial release of the genetically modified males.
Dead. Extinct. Gone to join the choir invisible, as Monty Python would have it.
While the researchers initially wondered whether the modified males would be able to compete successfully with wild males for the favors of the lady mosquitoes, their experiment proved that the males carrying OX3604C had just as much macho sex appeal as the males who were made entirely by nature. (This was not the case in previous experiments in which male mosquitoes were rendered sterile by radiation: the modified males were weakened by the radiation and therefore passed over by females looking for a big strong mosquito to settle down and raise a family with.)
The genetic modification solution, should it ever get a green light for widespread use (more on this later) would be easy to deploy. Mosquito eggs have a little quirk that helps boost the survival of the species: after being laid in a dry environment (as opposed to the wet environment they need to hatch), the eggs can remain viable for years, waiting for the right patch of stagnant water to fall into. What this means is that eggs laid by a female who has mated with an OX3604C male can be easily stored and then “deployed” into a tropical or subtropical environment. As a matter of fact, the “cure” for some mosquito-borne hemorrhagic fevers could be mailed in an envelope.
Perfect solution, right? Nobody in his or her right mind would speak up on behalf of the mosquitoes of the world. Nobody gives his kids adorable stuffed mosquito toys to play with, and few people smile indulgently and exclaim “How adorable!” when they see a raft of mosquito eggs or larvae on the surface of a stagnant puddle.
It’s not that easy. While few people may carry deep, abiding love for mosquitoes in their souls, the wider ramifications of wiping a species of mosquito from the face of the earth need to be considered. But for a moment, let’s return to that “green light” on field trials.
Among Dr. James’ co-authors on the research paper are employees of Oxitec Ltd., a bio-research company headquartered in Oxfordshire, England. Oxitec, which “built” the A. aegypti males carrying the OX3604C gene, is so confident that the modified mosquitoes will cause no wider environmental harm that it has begun field testing in the Cayman Islands and in Malaysia, New Scientist has reported. The company found during its field trials on Grand Cayman that release of its genetically modified mosquitoes ultimately killed about 80 percent of the population of A. aegypti on the island.
Amazing, huh? Beyond yellow fever and dengue fever, there is malaria, which is generally considered to be the number one killer of humanity throughout the history of mankind. Nearly a quarter of a billion people are infected with malaria each year, and as many as one million of those infected die. Next to the devastation caused by malaria, there is Japanese encephalitis and West Nile virus, the latter a serious health threat that has managed to find its way into some non-tropical parts of the world (the U.S. state you may live in, probably.) Considering the widespread prevalence of all this mosquito-borne disease, a world without these little buggers would be a great place, right?
Think of the positive effects on the environment. To combat mosquito-borne illness, untold amounts of nasty chemicals like DDT are released into the environment every year, covering the planet with a toxic fog of insecticide designed to kill mosquitoes, but ultimately finding its way into the bodies of people, pets and wildlife. Think of all the insecticide the world wouldn’t have to use if mosquitoes didn’t exist.
Still, not everybody is happy with the idea. Despite the broad upside, critics wonder about the unintended consequences of wiping out one or more species of mosquito, and Oxitec has been the target of critics who believe it’s too soon to take the experiment out of the lab.
For starters, what sort of creatures eat these mosquitoes? Birds and bats? Anything else? Do fish that locals rely on for food consume the mosquitoes? Are any of the creatures that eat mosquitoes pollen carriers? Will a dearth of mosquitoes cause these creatures to suffer and die, leaving food crops unpollenated? Will an even nastier predator take advantage of the mosquitoes’ absence to move in? And then there’s a smaller voice among the critics: people who believe that humans do not have the right to wipe a species of animal off the face of the planet, even an animal as odious as the mosquito.
For the sake of argument, let’s leave the latter group out and focus only on the “wider environment effects” consequences. In 2010, the journal Nature queried a group of scientists who specialize in insect ecology and mosquito biology to try and find a consensus about whether the world would suffer without mosquitoes. They considered not only the disease-carrying variety, but all mosquitoes. There are 3,500 named species of mosquito on planet Earth (though only a few hundred bite humans and animals) and they can be found on most continents and in a variety of different habitats, from tropical to sub-tropical and even sub-arctic. (There are times in Alaska and Northern Canada when anyone who wishes to remain healthy cannot enter the woods without protective gear.) While many of the scientists’ views differed wildly – some estimated that a dearth of mosquitoes could decimate the populations of migratory birds – there were a surprising number of experts who believe that the disappearance of mosquitoes wouldn’t make that great an ecological hole in the world, and the hole it did make could be quickly filled by nature. Mosquito-eating birds, for example, could probably switch to munching other bugs that, in a world without mosquitoes, would emerge in large numbers to take the place of the little bloodsuckers.
Not everyone agrees with this consensus, however. An article that appeared in October 2011 in Scientific American raised a host of issues, including wondering whether the genetically modified mosquitoes might not modify themselves into something very different that does a lot more than render females unable to fly. Some experts wonder whether the eradication of one species of mosquito might not make room for another specifies, unaffected by the genetic modifications, to move in, carrying even worse diseases that the location human population has no means or immunities to fight. The authors of the paper even wonder if changing the vector of an insect-borne viral disease – eradicating its primary carrier – won’t cause the virus itself to evolve into something even more virulent than before. The paper also wonders if the scientific world can entirely trust research and conclusions developed, in part, by a private company that will ultimately benefit financially from the implementation of the solution it helped create. Other critics of this kind of research – not the philanthropists, obviously – wonder what will happen to world population if tropical diseases are eradicated and one of nature’s most voracious culling mechanisms is taken out of action.
While most of these are good questions, they do need to be weighed alongside the devastation – both historical and existing – mosquito-borne diseases inflict on the world. Most deaths from malaria occur in sub-Sahara Africa, and most of the dead are children. While the developed world despairs, decade after decade, of the inability of most of Africa to pull itself even into developing world status, it’s not hard to wonder what the Dark Continent could do if the number one killer of its children were eradicated.
So what do you think: would you want to live in a world without mosquitoes?