Dengue Control

August 25, 2011 4:15 AM

Australian scientists have successfully trialled a method for controlling Dengue fever that involves infecting populations of mosquitoes with an endosymbiotic bacteria. The bacteria kills non-infected mosquitoes that mate with an infected individual, is passed to offspring of an infected individual, and confers resistance to Dengue upon infected individuals.

Dengue infects 50-100 million people each year, leading to half a million hospitalisations, and as many as 25000 deaths. WHO info page, WHO factsheet. CDC info page.

Dengue in Texas, previously.

posted by Ahab (56 comments total)

I had Dengue fever, it's pretty rubbish. Dad, who was already quite aged, got knocked around by it very badly. The trucks used to drive up and down the laneway at the back of our house, pumping out the fog. Bloody Townsville, what a shithole.
posted by tumid dahlia at 4:24 AM on August 25, 2011

Hopefully this will work better than those horrible sprays they used to come around with.
posted by infini at 4:26 AM on August 25, 2011

can we just kill all mosquitoes? Like, mosquito genocide?
posted by ReWayne at 4:27 AM on August 25, 2011 [4 favorites]

Dengu: You're Welcome
posted by ShutterBun at 4:32 AM on August 25, 2011

The bacteria kills non-infected mosquitoes that mate with an infected individual

Is that right? the 'gonad-chomping' link seems to say it's just the offspring of the mating that die, unless I'm misreading it.

Great stuff, in any case.
posted by Segundus at 4:36 AM on August 25, 2011 [1 favorite]

can we just kill all mosquitoes? Like, mosquito genocide?

That'll kill off everything that lives off mosquitos, though. Bats are awesome.
posted by longdaysjourney at 4:45 AM on August 25, 2011 [4 favorites]

But think of the mosquito children!
posted by jet_manifesto at 4:51 AM on August 25, 2011

Is that right? the 'gonad-chomping' link seems to say it's just the offspring of the mating that die, unless I'm misreading it.

Aye, that it does - apologies for my misreading - I think I got mixed up in the truly crazy range of ways it messes with them. More eg.s "causing infected males to develop as females, and allowing females to produce fertile offspring without ever mating."
posted by Ahab at 4:55 AM on August 25, 2011

Yeah I don't get why they try to be so selective in what they kill. Why not eradicate mosquitoes entirely?

One interesting thing is that in order to be spread by mosquitoes, diseases have to evolve specifically to survive in both mosquitoes and humans. That's why bed bugs don't carry disease, since there are no diseases that can survive in bedbugs and humans both.


That'll kill off everything that lives off mosquitos, though. Bats are awesome.

Are there any bats that live exclusively on mosquitos?
posted by delmoi at 4:58 AM on August 25, 2011 [1 favorite]

... involves infecting populations of mosquitoes with an endosymbiotic bacteria. The bacteria kills non-infected mosquitoes that mate with an infected individual [and] is passed to offspring of an infected individual ...

I've seen this movie and it does not end well.
posted by alby at 5:02 AM on August 25, 2011 [5 favorites]

Are there any bats that live exclusively on mosquitos?

No, but mosquitoes get eaten by a lot of things, and killing off all mosquitoes would affect all those populations. Other bugs are not necessarily going to breed up to fill the space left by the vacant population within historical time frames, so we could get reductions of other species. Also, the population of humans picnicking outdoors would skyrocket, and who wants that?
posted by GenjiandProust at 5:07 AM on August 25, 2011 [1 favorite]

I hope some thought has been given to possible unintended consequences of the approach. From my extensive research on Wikipedia it appears that this approach is largely benign, although some parasitic diseases are tied to the presence of the bacteria used. Australia has some experience with unintended consequences of releasing non-native species into the wild.

It seems correct to fight dengue with what appears like a fairly gentle manipulation of the existing environment. Does anyone know how possible future harm is weighed by people conducting these experiments? Does anyone keep track of human manipulations of the environment that caused harm to search for lessons to guide our future actions?
posted by TheProudAardvark at 5:10 AM on August 25, 2011

unintended consequences ... some parasitic diseases ... fairly gentle manipulation

What could possibly go wrong.
posted by sammyo at 5:17 AM on August 25, 2011 [1 favorite]

Trying to destroy all mosquitos is foolish and wrongheaded. Inevitably you will fail to kill EVERY mosquito and those that remain will breed resistant to your method of mortality. Uncongratulations, you've made resistant mosquitos because you were fighting evolution.

Instead, alter mosquitos so they are less harmful and simultaneously more successful than non-altered mosquitos and the new mosquitos will dominate and supplant the old ones. Congratulations: you made safer mosquitos because you were working with evolution.
posted by seanmpuckett at 5:19 AM on August 25, 2011 [7 favorites]

I was a little worried by:

The bacteria can infect a wide range of hosts, including insects, where it will live inside the cells of various organs.

which suggests that Wolbachia could be spread to other, unintended, animals. I have no idea how dangerous that might be, but still.

Among its targets, however, is almost always the gonads, where it helps promote its spread by manipulating its hosts to ensure that infected females produce more infected eggs.

And since the females drink blood (as I recall) to get the protein necessary to lay eggs, won't this create more ravenous mosquitoes? Sure, they won't give you Dengue Fever; they will just drain you of all blood....
posted by GenjiandProust at 5:22 AM on August 25, 2011

Why not eradicate mosquitoes entirely?

Is not our eco-system a delicate balance? I'm pretty sure to remove one organism means that some other organism is directly effected as well. I have no love for mosquitoes but that doesn't mean I do not recognize their importance in the great mystery that is life.
posted by Fizz at 5:35 AM on August 25, 2011 [1 favorite]

There are something like 3,000 species of mosquito, and only a couple hundred species that attack humans. We do have some good ways to reduce their population at the larval stage, but you can't just eliminate all the mosquitoes at every stage without seriously messing with the environment.
posted by zennie at 5:41 AM on August 25, 2011

Why not eradicate mosquitoes entirely?

A recent feature in Nature suggests we could.

Yet in many cases, scientists acknowledge that the ecological scar left by a missing mosquito would heal quickly as the niche was filled by other organisms. Life would continue as before — or even better. When it comes to the major disease vectors, "it's difficult to see what the downside would be to removal, except for collateral damage", says insect ecologist Steven Juliano, of Illinois State University in Normal. A world without mosquitoes would be "more secure for us", says medical entomologist Carlos Brisola Marcondes from the Federal University of Santa Catarina in Brazil. "The elimination of Anopheles would be very significant for mankind."

Interesting also to note that "Elimination of mosquitoes might make the biggest ecological difference in the Arctic tundra, home to mosquito species including Aedes impiger and Aedes nigripes".

Ultimately, there seem to be few things that mosquitoes do that other organisms can't do just as well — except perhaps for one. They are lethally efficient at sucking blood from one individual and mainlining it into another, providing an ideal route for the spread of pathogenic microbes.

"The ecological effect of eliminating harmful mosquitoes is that you have more people. That's the consequence," says Strickman. Many lives would be saved; many more would no longer be sapped by disease. Countries freed of their high malaria burden, for example in sub-Saharan Africa, might recover the 1.3% of growth in gross domestic product that the World Health Organization estimates they are cost by the disease each year, potentially accelerating their development. There would be "less burden on the health system and hospitals, redirection of public-health expenditure for vector-borne diseases control to other priority health issues, less absenteeism from schools", says Jeffrey Hii, malaria scientist for the World Health Organization in Manila.

posted by alby at 5:45 AM on August 25, 2011 [4 favorites]

Is not our eco-system a delicate balance?

Our ecosystem is a delicate chaos. Besides, we eliminate species every day (unintentionally and otherwise). Why not do it intentionally and honestly for once? Even if it is for selfish reasons?
posted by ReWayne at 6:12 AM on August 25, 2011 [3 favorites]

I just always feel like this is Homer going back in time, killing a bug, and then coming back eons later and the world is totally different.

We can't predict what effect killing mosquitos would have on the ecosystem. There just simply isn't a method available to understand all of the implications of such an event.

With that said, while Dengue is horrible, perhaps human populations should be kept in balance. I'm not advocating murder or the intentional spread of disease, but we're already consuming far too many resources as a species. If more people survive but the earth is a hot, stormy and increasingly fragile place to live, what have we really given our descendents?

I know that this disease is a terrible third world disease, and my point is a very First World point, but messing with nature makes me really uncomfortable.

There are a million other examples that I'm sure I'm complicit with in my day to day existence, but this just sounds like a bad road to start heading down.
posted by glaucon at 6:26 AM on August 25, 2011

can we just kill all mosquitoes?

Big citronella has deep pockets.
posted by condour75 at 6:35 AM on August 25, 2011 [7 favorites]

Why not eradicate mosquitoes entirely?

What happens if, in the future, an alien probe tries to contact the then-extinct mosquitoes?
posted by Memo at 6:40 AM on August 25, 2011 [1 favorite]

Call Sam Worthington?
posted by clavdivs at 6:47 AM on August 25, 2011

Ecologically sound or not - I'm still gonna swat as many of the buggers as I can.
posted by gomichild at 7:02 AM on August 25, 2011

Mordin Solus nods approvingly.
posted by Pseudonumb at 7:13 AM on August 25, 2011 [2 favorites]

Also, the population of humans picnicking outdoors would skyrocket, and who wants that?

Smarter than average bears.
posted by Knappster at 7:18 AM on August 25, 2011

One interesting thing is that in order to be spread by mosquitoes, diseases have to evolve specifically to survive in both mosquitoes and humans. That's why bed bugs don't carry disease, since there are no diseases that can survive in bedbugs and humans both.

For now.
posted by emjaybee at 7:19 AM on August 25, 2011

Having had dengue in New Delhi in 1984, I know why they call it break bone fever. The pain was so over the top I went unconscious, oddly in my knees, delirium for hours, lost 15 pounds in a couple of days. So, when I read the post I thought, way to go, whoo hoo, AWESOME! Then I read the comments and now have doubts about messing around with skeeter balls.
posted by nickyskye at 7:29 AM on August 25, 2011

Instead, alter mosquitos so they are less harmful and simultaneously more successful than non-altered mosquitos and the new mosquitos will dominate and supplant the old ones. Congratulations: you made safer mosquitos because you were working with evolution.

Indeed, there are a lot more dogs (700,000,000) than wolves (200,000) and more chickens, cattle, and ferrets than jungle fowl, aurochs, and european polecats.

Success: the domesticated species are both more numerous and less dangerous.

Clearly what's needed is an accellerated breeding program to make mosquitoes either delicious or adorable. Or both.
 
posted by Herodios at 7:44 AM on August 25, 2011 [8 favorites]

With that said, while Dengue is horrible, perhaps human populations should be kept in balance. I'm not advocating murder or the intentional spread of disease, but we're already consuming far too many resources as a species. If more people survive but the earth is a hot, stormy and increasingly fragile place to live, what have we really given our descendents?

I know that this disease is a terrible third world disease, and my point is a very First World point, but messing with nature makes me really uncomfortable.

Messing with nature makes you squirm, but you're OK with not using our considerable scientific resources to try to mitigate a disease because there are an awful lot of people and this disease disproportionately affects the poor ones? Let's deal with our warming, crowded planet by holding our governments and ourselves responsible for global climate change and investing in education and family planning for women in developing countries and not rely on a debilitating, painful and expensive disease to keep human populations in check. This might not be the silver bullet, it might actually have serious unintended consequences. But to shrug our shoulders because it's an effective method for keeping populations down in the developing world (when clearly it's not, since dengue persists and populations increase) is really pretty disgusting.
posted by ChuraChura at 7:52 AM on August 25, 2011 [6 favorites]

Kill mosquitos, we lose dragonflies. Kill dragonflies, we lose a lot of bird. Kill the birds and shortly we die.
posted by blue_beetle at 7:53 AM on August 25, 2011 [1 favorite]

birds
posted by blue_beetle at 7:53 AM on August 25, 2011

What happens if, in the future, an alien probe tries to contact the then-extinct mosquitoes?

They'd go home, instead of spawning the mosquito overlords. I'd call that a win.

The mosquitoes wouldn't, but being dead, they couldn't register their whiny little opinions.
posted by Malor at 8:11 AM on August 25, 2011

What eats mosquitoes.

http://www.mosquito-netting.com/predators.html

If you don't like bats or birds, think of the poor little guppies.
posted by longdaysjourney at 8:18 AM on August 25, 2011 [1 favorite]

I Google Imaged "cute mosquito" and this is what I got. This is a winning ecological strategy, except if the dragonflies also think they are cute and decide not to eat them.
posted by melissam at 8:19 AM on August 25, 2011 [1 favorite]

If you don't like bats or birds, think of the poor little guppies.

They don't *only* eat mosquitos though. Can anyone find a species that eats mosquitos and mosquitos only?
posted by melissam at 8:20 AM on August 25, 2011

Kill the birds and shortly we die.

I don't follow how this step is supposed to work?
posted by Meatbomb at 8:43 AM on August 25, 2011 [1 favorite]

Kill the birds and shortly we die.

I don't follow how this step is supposed to work?

It's Captain Planet!Science.
posted by melissam at 8:53 AM on August 25, 2011

can we just kill all mosquitoes?

I think we would have if it were easily achievable. For one thing, mosquitoes comprise an entire family of insects, over 3,000 species, and it's not easy to find one thing to kill them all (at least, not without killing lots of other stuff in the process). Most mosquito eradication has focused on the species that are known transmitters of disease, and even that has been an uphill battle.

Mosquito eradication was the cornerstone of a lot of early efforts at malaria control. Malaria is spread by mosquitoes in the Anopheles genus, and because the mosquito stage is a necessary part of the Plasmodium parasites' life cycles, eradication of Anopheles mosquitoes would theoretically mean eradication of malaria. But even within that genus, there are 30-40 species that transmit malaria, with ranges all over the world. Of those, the most important as human disease vectors are the Anopheles gambiae, which was once thought to be a single species but is now recognized as a complex of at least seven species, none of which are anywhere close to extinction.

For a good chunk of time in the 1940s and 50s, public health officials thought the wonder-insecticide DDT would save us from malaria. In fact, Paul Muller, the scientist who discovered DDT's insecticidal uses, was awarded the Nobel Prize for medicine. DDT, even in small amounts, is extremely effective at killing mosquitoes. There were large-scale campaigns of indoor residual spraying (IRS), which involves the periodic spraying of pesticides of on walls of houses, to kill mosquitoes as they rest after a blood meal. This was a big part of the successful eradication of malaria in the US South, a project (the National Malaria Eradication Program) which pretty much launched the CDC. Global efforts with DDT spraying helped eradicate malaria in the Balkans, Taiwan, and parts of North Africa, the Caribbean, and the South Pacific. It was a hopeful time. Check out this amazing Walt Disney cartoon from 1943, The Winged Scourge, which features the seven dwarves spraying houses with pesticides and removing standing water.

Things changed pretty dramatically when DDT was discovered to be an environmental hazard, and became the catchword of a nascent environmental movement. There's still a lot of bad blood between public health folks and environmentalists over the DDT issue, and it's not hard to find heated arguments and accusations that DDT opposition is causing millions of deaths or that public health wants to play Frankenstein with nature and kill the bald eagle. I'll just note here that the levels of DDT used in malaria campaigns have never been shown to cause environmental harm- only the much heavier agricultural use of DDT has. But there have also been decent arguments made that DDT was not the main driving factor in successful eradication campaigns and its usefulness has been exaggerated.

Today, IRL is still widely used as a mosquito control method. DDT is, in fact, still used for malaria control in some countries, and there are a dozen other insecticides employed as well. But pesticide resistance is a major problem- mosquitoes are increasingly evolving to be hardier and less susceptible to the pesticides in our arsenal. Spraying is usually used in concert with other vector control methods (nets, screens, removal of standing water). Mosquitoes are unfortunately very strong little fuckers. They breed quickly and have short generations, enabling fast adaptation; larvae can grow even in small puddles and reach maturity in a few days; adults can hide in tiny crevices, safe from sprayed pesticides. The eggs of the mosquito which transmits dengue, Aedes aegypti, can survive in a dessicated state, in a dried out container or pool, for several months.

If you can't find an easy way to kill off one of the 3,000+ species of mosquito, after years of concentrated effort, it's unlikely that you'll find a way to kill all the mosquitoes. Bats and guppies can breathe easy, knowing that if the best minds find a way to kill off the malaria and dengue mosquitoes, there will be plenty others left to eat. Also consider that both Ae. aegypti and the Anopheles mosquitoes were probably originally much more restricted in range, having been spread to new areas by humans, and are thus invasives in much of their current habitats. What with all that, these biological control methods have a lot of promise and may be an effective new tool to reduce suffering and death.
posted by bookish at 8:54 AM on August 25, 2011 [12 favorites]

Herodios: Clearly what's needed is an accellerated breeding program to make mosquitoes either delicious or adorable. Or both.

Mosquito bacon?

MMmmmmh, bacon!
posted by Hairy Lobster at 9:18 AM on August 25, 2011

and the inevitable:

Metafilter: an accelerated breeding program
posted by Hairy Lobster at 9:21 AM on August 25, 2011

Cane toads were my first thought as well, TheProudAdvark.
posted by that's candlepin at 10:18 AM on August 25, 2011

How about instead of wiping out all mosquitoes, we only eliminate the 10-20% of species that bite humans? Every species that needs mosquitoes to eat can still find plenty of food, and we get all the benefits of not having biting mosquitoes around.

Alternately, if genocide of a small fraction of the existent mosquito species is too distasteful or radical, how about a retroviral program that over the course of a decade or so alters the diet of the harmful species? Some of those species find the diet works for them and are no longer part of the problem, others simply can't make a workable energy ROI proposition out of their new diet and die off, but at least we made a halfway decent effort for one of the worst natural enemies we've had since we came down from the trees...
posted by Ryvar at 10:32 AM on August 25, 2011

I also target the gonads, both in love and war.
posted by Bunny Ultramod at 10:48 AM on August 25, 2011

Kill the birds and shortly we die.

I don't follow how this step is supposed to work?

It's Captain Planet!Science.

To be fair, this is pretty much exactly how the Great Sparrow Campaign went. Sparrows ate seeds, so the idea was that killing them would increase crop yield... but the sparrows were also eating insects. Once the birds were gone, the locust population exploded and devastated the rice crop, exacerbating the Great Chinese Famine in which 20+ million died.
posted by vorfeed at 11:06 AM on August 25, 2011 [1 favorite]

This kind of mass use of pathogens to alter an ecosystem has been done before.

In 1911 Felix D'Herelle traveled to Argentina as a microbiologist hired to address the locust problems there. The problem was massive, every other year locusts would create the modern equivalent of billions of dollars worth of damage to cash crops and generate famine on the extraordinarily fertile pampas. It was so bad, and Argentina was rich enough then, that plans were being drawn up to import most of the worlds silver to build massively long 4 meter high walls across the pampas to stop the plagues. Apparently they'd have done it if they thought they could stop theft, but the Ministry of Agricultural Defense had grown to a 3,000 member strong bureaucracy dedicated to extraordinary campaigns to defeat them.

D'Herelle's idea was to spread diseases of the locust itself ahead of the swarms to take advantage of the very terrifying sale that made farmers so helpless, against the plague. He ended up getting funding to find sick locusts, cultivate the disease though serial transfer between 100 locust cages, and thus isolate 100% virulent and contagious strains of a cocobacillus. When thousands of these carcasses were spread out ahead of a swarm they were brought to a epic halt within a few days. After two years of D'herelle's efforts the plagues ceased to be the issue that they once were in Argentina and the Pasteur Institute sent out his cultures to Columbia (where several successful trials were conducted), Cyprus and Algeria where they had significant effect.

What Felix D'Herelle did next is what he is famous for, he found pathogens against bacterial diseases like cholera, dysentery, and staph. Bacteriophages
posted by Blasdelb at 11:56 AM on August 25, 2011 [11 favorites]

How about instead, we dedicate more research money towards coming up with medicine to cure diseases which are mosquito borne - the ones like dengue and malaria that disproportionately affect the global south and kill hundreds of millions a year, but receive far fewer research dollars than things like heart disease and cancer?
posted by ChuraChura at 11:59 AM on August 25, 2011

@ChuraChura The gist of my point is that we can't say with certainty wiping out mosquitos won't have serious effects on the planet's ecosystem. I did not effectively stress that i know my perspective is from the comforts of a first world nation, and that I don't know firsthand how terrible this disease is.

TL;DR Dengue is terrible. Nobody should suffer it. This solution keeps mosquito populations intact but eliminates the disease - brilliant. However, the idea of eliminating all mosquitos will carry no consequences is foolish.

ChuraChura is right - I didn't explain well enough up there that I'm all for this treatment of Dengue, but I do not think it's wise to eliminate all mosquitos.
posted by glaucon at 12:48 PM on August 25, 2011

How about instead, we dedicate more research money towards coming up with medicine to cure diseases which are mosquito borne - the ones like dengue and malaria that disproportionately affect the global south and kill hundreds of millions a year, but receive far fewer research dollars than things like heart disease and cancer?

ChuraChura, that's what the FPP is about. Dengue and malaria are caused and spread by an interconnected web of organisms. You have to go after the organisms that cause them. As 'diseases', they are as different from heart disease and cancer as chalk and cheese.
 
posted by Herodios at 1:31 PM on August 25, 2011

Thanks, Herodios, I do understand zoonotic diseases. My point, inarticulately stated, was that the amount of research dollars going into any disease that disproportionately affects the world's poor is much less than those which disproportionately affect the world's rich. I didn't mean to disregard the (Really Cool) research being reported on in the OP - instead, I was pointing out that most of the comments here are about how it'd be easiest to just get rid of the vector rather than do something to treat the actual disease, and that's a really bizarre way to look at something like dengue fever or malaria - ESPECIALLY when we can't predict how an ecosystem devoid of mosquitoes (or 10% of its mosquitoes or whatever) would function.
posted by ChuraChura at 1:56 PM on August 25, 2011

Sorry, "most of" is uncharitable. "Many" is more like it.
posted by ChuraChura at 1:59 PM on August 25, 2011

There is a moral imperative to minimize human suffering. We must also consider our solution's ramifications to ensure they aren't causing more damage. First, do no harm is another moral imperative. The use of natural pathogens may be the most justifiable approach to combating dengue fever, but none of the material I have seen indicates the degree to which unintended consequences were considered.

I am wary of any proposal involving a significant and irrevocable change to the environment. I suspect we have no idea of the degree of specialization of the predators of mosquitoes and in turn the dependence of other species upon them.
posted by TheProudAardvark at 2:23 PM on August 25, 2011

I've read your detailed environental impact assessment and after some thought I've come to the conclusion that we should kill all the Mosquitos anyway. Those bloodsucking bastards gotta die die die. Gather forth our scientists and bring forth some new chemicals. There is no can't in science.
posted by humanfont at 4:29 PM on August 25, 2011

Our ecosystem is a delicate chaos. Besides, we eliminate species every day (unintentionally and otherwise). Why not do it intentionally and honestly for once? Even if it is for selfish reasons?

Agreed. We should pretty much eliminate all harmful animals, but mosquitoes are a good first step.

There is a moral imperative to minimize human suffering. We must also consider our solution's ramifications to ensure they aren't causing more damage. First, do no harm is another moral imperative. The use of natural pathogens may be the most justifiable approach to combating dengue fever, but none of the material I have seen indicates the degree to which unintended consequences were considered.

Do no harm to people. Animals don't count.
posted by Lovecraft In Brooklyn at 4:52 PM on August 25, 2011

Blasdelb -- thank you. That was excellent.
posted by ltracey at 7:16 PM on August 25, 2011

The pain was so over the top I went unconscious, oddly in my knees, delirium for hours, lost 15 pounds in a couple of days

ODDLY IN YOUR KNEES

I will shout this at the next driver who cuts me off in traffic.
posted by flabdablet at 3:18 AM on August 26, 2011