Pondering mosquito-cide

2010-08-13

in Politics, Science, The environment

Generally speaking, it seems like a bad thing when human beings eliminate an entire species. That said, it is usually done by accident, as a consequence of habitat destruction and pollution. To a considerable extent, we should probably scale back those harmful activities, and think about backing up some DNA in the meantime.

In at least one case – the eradication of smallpox – the destruction of a species seems unambiguously excellent. Indeed, it is a shame we didn’t manage to finish the job, and that Russia made such huge quantities of smallpox as a weapon. Mosquitoes are another candidate for a species we could wipe out without guilt, especially since ecologists are arguing that they don’t serve a major ecological role.

The ethical question is: if it were practical to do so, should humanity exterminate all mosquitoes?

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{ 19 comments… read them below or add one }

Matt August 13, 2010 at 7:03 pm

I’m doing my part with my handy mosquito zapper wand. The pop a mosquito emits when thousands of volts surge through it is a satisfying noise: it means the risk of you getting bitten has just decreased.

I wonder, though, when we spend money to eliminate diseases and in this hypothetical case, disease carrying insects, we should also have someway to spend money to promote birth control: The quality of life for those already living should go up, but lack of disease should not also lead to more (unneeded) population.

R.K. August 13, 2010 at 8:55 pm

How often has humanity been ignorant of the consequences of its actions? Especially when ecology is involved.

Who’s to say that wiping out mosquitoes isn’t something we would come to regret?

BuddyRich August 14, 2010 at 8:26 am

I hate mosquitoes as much as the next person but they are close to the bottom level of many food chains. Eliminating them could have a ripple effect throughout many ecological systems with disastrous consequences… or higher order predators could adapt and find new food sources, though either way there would be short term consequences.

I’d even argue that eliminating smallpox (and other diseases) as much as we have has altered established food chains, as mankind’s numbers have multiplied and look what we’ve gone on to do to the rest of the natural environment.

Will mother nature eventually balance our numbers back down and is there even an equilibrium? Perhaps global warming is one such way, the evolution of “super bugs” is another…

http://www.cbc.ca/health/story/2010/08/11/uk-lancet-new-superbug.html

In the short term, it looks like we’ve got the upper hand, or at least it looks as if there is no harm done but in the long run of the evolutionary ladder who is to say, as we are relatively young as a species?

Not that it is unethical to adapt and survive as we do, it is also part of our makeup. Saving lives by the elimination of fatal disease is a good thing, in my opinion, but how we eliminate those diseases and the consequences of unchecked population growth are both issues that have yet to confront us.

Pearl August 14, 2010 at 10:19 am

Aren’t bats and songbirds struggling enough without taking away another food source? We have no idea how species intricately interrelate. Nature is sturdy and rebounds past all expectations but still, the gesture of eradication is more than one needs to do.

Gail August 14, 2010 at 1:46 pm

“…usually done by accident, as a consequence of habitat destruction and pollution”

not to minimize those mechanisms of species extinctions, but I think mostly, we eat them…

Byron Smith August 14, 2010 at 3:08 pm

Perhaps the mosquitoes could be preserved in a controlled environment in case we regret their removal.

Gail August 14, 2010 at 3:39 pm

Afraid we will have many more mosquitos, with the bats dying off:
http://www.recordonline.com/apps/pbcs.dll/article?AID=/20080320/NEWS/803200313/-1/NEWS

alena August 15, 2010 at 2:03 pm

I once visited a project in Sudan where researchers were trying to render female mosquitoes sterile in order to reduce and eventually eliminate them. According to their study, the mosquitoes that were not altered simply produced more eggs to replenish the mosquito population. It seems to me that human intervention has not improved the balance of nature.

Milan August 16, 2010 at 12:23 pm

not to minimize those mechanisms of species extinctions, but I think mostly, we eat them…

I think habitat destruction is a far more serious cause of extinction than direct human consumption (or indirect consumption, like the fish we catch use as food in fish farms).

The primary importance of habitat destruction is supported by some academic research, such as Barbault, R. and S. D. Sastrapradja. 1995. Generation, maintenance and loss of biodiversity. Global Biodiversity Assessment, Cambridge Univ. Press, Cambridge pp. 193–274. They found it to be “the greatest threat to organisms and biodiversity.” Also, there is Temple, S. A. 1986. The problem of avian extinctions. Ornithology 3: 453-485 which concludes that “82% of endangered bird species [are] significantly threatened by habitat loss.”

R.K. August 16, 2010 at 2:25 pm

The issue here isn’t really whether we should wipe out all mosquitoes or not, but rather those types that spread human disease: the genus Anopheles in the case of malaria, and the species Aedes aegypti in the case of yellow fever, dengue fever and Chikungunya.

Given that there are about 3,500 species of mosquitoes found throughout the world, eliminating one problematic genus and one problematic species seems likely to have a limited ecological effect.

That said, there is still some reason to worry that the unanticipated consequences of such a program could be worse than the current burden from these diseases.

. August 26, 2010 at 3:57 pm

“Biology professors like to ask what animal kills the most people. Their poor students humiliate themselves by calling out grizzly bear, tiger, cobra, even hippo. The right answer, of course, is the female mosquito—no fur, no fangs, just a hypodermic needle on the wing. She’s less than a quarter-inch long, has six legs, and is the most efficient transmitter of disease in the animal kingdom. She uses scent to find us, attracted by the lactic acid and other ingredients in perspiration. She also senses the carbon dioxide in our exhalations and follows the slipstream back to our faces. The more you sweat and pant as you shoo her away, the more attractive you become.

She’s not revolting to look at, but elegant, small, sleek, long-legged, and fragile. We might be willing to give her a milliliter of blood, even with the itchy welt, if we didn’t worry about what she might give back. The worst of the many pathogens a mosquito may carry is malaria, which kills more than 1 million people a year, two-thirds of those in sub-Saharan Africa and most being children under 5.

There’s no sense trying to rehabilitate the reputation of such a creature; nobody loves a mosquito, and nobody loves a mosquito hugger. However it’s unfair to malign all 2,600 described species of mosquito when it’s just 80 or so—3 percent—that drink human blood. Among those 2,520 relatively blameless kinds of mosquitoes, there’s even one we’d like to see in greater numbers: Toxorhynchites, the mosquito that eats other mosquitoes. As larvae, the Toxorhynchites wrigglers eat their cousins, then turn on their siblings, and often keep attacking until only one is left. This drama takes place in small amounts of water in hollows in trees or similar small puddles. The tree-hole mosquitoes, including the disease-bearing Aedes, have adapted to using discarded tires as breeding grounds. As anyone who has tried knows, it’s very hard to drain water out of a tire.”

Byron Smith August 27, 2010 at 7:57 am

Since I’ve weighed on other scientific trivia about which I really know very little, I thought I’d do so again.

what animal kills the most people
Surely if we consider all human history then there would be more deaths from Yersinia pestis (bubonic plague) or if we’re allowed to include viruses, then Variola major (smallpox)?

I guess that since the question is phrased in the present tense, malaria kills an estimated 1-1.5 million people each year, while TB kills something like 1.8 million and if we include viruses there an estimated 2.5-2.8 million AIDS deaths. (These numbers vary quite a bit, but all sources I found generally put them in this order.)

Byron Smith August 27, 2010 at 7:59 am

Oops – novice error. Bacteria are not animals. I should have paid closer attention to the question.

Byron Smith August 27, 2010 at 8:13 am

But let’s go for the other obvious candidate and put together a few rough estimates.

Manslaughter = 55,000 p.a.
Murders = 100,000 p.a.
Suicides = 1,000,000 p.a.
Executions = officially about 2,000 p.a., but might be as high as 10,000 p.a. due to mistrusted figures from China
Other homicides (e.g. war) = varies considerably but perhaps average of 1.8 million p.a. during 20thC.

Putting those all together (and noting that it is the malaria parasite, not the mosquito, that kills), there is a good case for saying that Homo sapiens is the animal that kills the most people.

(Abortion = 42,000,000 p.a.)*
*If abortion is included as the killing of a person, then the answer is clear.

Tristan August 27, 2010 at 1:25 pm

“I think habitat destruction is a far more serious cause of extinction than direct human consumption (or indirect consumption, like the fish we catch use as food in fish farms).”

Aren’t fish farms potentially a form of habitat destruction?

. October 22, 2010 at 11:04 am

Here at Casa Superbug, we’re in the midst of moving 1,200 miles, so I’m a little slower reading email than I really ought to be. That’s scant excuse, unfortunately, for not noticing one of the biggest global-health stories in years. Mitigating circumstance: Almost everyone else missed it too.

The news is the effective eradication of rinderpest, a viral disease of cattle. Rinderpest does not infect humans, and even in animals it barely occurs in the Americas (or Australia or New Zealand), though until recently it was common and devastating in Africa, South Asia and the Middle East. So unless you are a large-animal veterinarian or a cattle farmer, the disease might never have been on your radar.

So why care that it is on the verge of being removed from the world? Because this marks the first time that a disease of animals has ever been eradicated — and only the second time that any disease has been eradicated at all. The first was smallpox. That was 30 years ago.

Milan October 22, 2010 at 11:19 am

Rinderpest eradication looks like a promising example of a long-term global collaboration achieving an important result.

. October 13, 2016 at 12:56 am

The trouble with such ideas is that they give evolution a powerful incentive to select its way around the problem. Over time, that could make them less effective. One option that might avoid that problem is a “gene drive”, a new technique that tweaks genomes in a way that ensures that the modified, damaging traits are inherited by all of a mosquito’s offspring. Gene drives are highly controversial: if they work, they could give humans the power to wipe out—with minimal effort—any species that engages in sexual reproduction. They are also experimental and confined to labs; no one knows how effective they would be in the wild. Last week the Bill and Melinda Gates Foundation, a charity, announced it would boost its funding of gene-drive research to $75m. That will speed up the work—and the debate about deliberately wiping out a species.

. August 7, 2017 at 7:45 pm

Engineering gene drives to do humanity’s bidding in this way proved, however, devilishly difficult. The idea therefore languished until 2015, when Valentino Gantz and Ethan Bier of the University of California, San Diego, used CRISPR-Cas9, a recently discovered gene-editing tool, to make a gene drive that could be inserted anywhere in a target genome that they chose.

Those findings sparked concerns about the effects gene-drive-carrying organisms could have if they were ever to be released into the world. For example, a gene drive that somehow hopped from a target species into the genomes of other animals might wipe them out before anything could be done about it. A study published in PLOS Genetics, by Philipp Messer of Cornell University and his colleagues suggests, however, that those who would deploy gene drives against scourges such as malaria face a more immediate hurdle: such drives simply may not work. Just as insects and pathogens evolve resistance to new pesticides and antibiotics, so gene drives, too, may provoke resistance—and may do so far faster than many suspected.

CRISPR-Cas9 gene drives have, though, a significant drawback. When the drive cuts the genome but fails, for some reason, to insert itself into the incision, the cell instead inserts new genetic letters to replace those cut away by the enzyme before it rejoins the severed DNA strands. This process often changes the letter sequence at the site. That means the guide RNA can no longer recognise it. And that, in turn, means the organism (and its progeny) are now resistant to the drive.

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