mosquitoes

Weekend Diversion: If you hate mosquitoes...

esiegel — Sun, 28 Jul 2013 09:10:25 +0000

Weekend Diversion: If you hate mosquitoes...

"If you think you're too small to have an impact, try going to bed with a mosquito." -Anita Roddick

There's a lot to enjoy when it's warm and tropical, which it is many places this time of year. The flowers are out, the Sun often shines, and there's no shortage of spectacular music. Have a listen to to West Virginia-based band The Recipe, as they rock out (and give a shout-out to Neil Armstrong's moonwalk) in their great song,

Whiskey Pickle.

But there's an unwelcome visitor that comes along with this kind of weather: the mosquito.

Image credit: public domain image; source unknown.

Some people seem to be particularly attractive to mosquitoes, and I happen to be one of them. While the itchy, red bumps that ensue from the bites are annoying enough, the also carry infectious (and sometimes deadly) diseases, including malaria, west nile virus, dengue fever and chikungunya, among others.

Image credit: Africa Science Technology and Innovation, via http://www.africasti.com/.

Until recently, the only way to prevent infection was through mosquito netting, which can be expensive, are often difficult to use, and don't really allow you to go outside and live the life you normally would. They're great for keeping mosquitoes out while you're trying to sleep, but that's fairly limited protection.

Image credit: Derric Nimmo / Oxitec, via the New York Times.

More recently, they've managed to genetically engineer mosquitoes that neither carry nor infect humans with some of these viruses. This is great, but it's a herculean task to replace all the normal mosquitoes that serve as disease vectors with this benign version.

Instead, there may be a simple, inexpensive and incredibly effective way to simply keep mosquitoes away from humans in the first place, and I'm so excited for it I simply had to introduce it you you.

Image credit: Kite Patch project on Indiegogo.

Meet the Kite Patch! A small, square patch that you affix to your clothing, the Kite Patch renders any humans in a large area around it completely invisible to mosquitoes! They're working on a large field test now, and this could be the biggest breakthrough ever in the fight against mosquito-borne diseases.

Image credit: Kite Patch on Indiegogo, via http://www.indiegogo.com/projects/kite-patch.

Best of all, you can kick in a relatively small amount of money toward this project and receive a set of patches for yourself, each one which will effectively render you and your entire family immune to mosquitoes for 48 hours! For someone who's basically mosquito-bait like me, this is a summer evening's dream-come-true!

Image credit: Kite Patch on Indiegogo, via http://www.indiegogo.com/projects/kite-patch.

I'm so happy to bring you something remarkable that's also doing such good in the world, and if you've got a few minutes, you might enjoy watching this short video about the Kite Patch.

So whatever you're doing, I hope you liked hearing about this wonderful project, and I hope you're having a fantastic weekend!

esiegel Sun, 07/28/2013 - 05:10

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And yes that kite is very nice

But just the other day, I read a New York Times article on a low tech mosquito repellent for out on the patio on a summer evening with friends. The rotating fan. http://www.nytimes.com/2010/07/13/health/13real.html?_r=0

If it's that simple why have I never read about this before.

Well this weekend my wife and friends were sitting eating by the pool. They were bait; I was swimming and OK. My wife said, "we're being eating alive. get the fan."

I had told her about the fan idea and had already gone out and bought a pedestal rotating fan $39.99.

A couple minutes later, no more mosquito bites. Yes, it works great.

But of course I don't have a long enough extension cord to bring my rotating fan everywhere. So kite. Very nice.

A couple of footnotes about kite patches.

"Our U.S. backers will be the first to receive Kite Patches after we gain U.S. EPA approval. " So if you donate money don't expect any patches soon. because...

"If that works, they expect — with EPA approval — to market the three-square-inch patch in the United States in about a year." So another year before EPA approval. "

"The Kite Patch developer, Olfactor Laboratories, says that their product works in much the same way as DEET — blocking mosquitoes’ carbon dioxide receptors. But, the Kite Patch uses chemicals that are so safe they are considered “food grade flavours” by the Food and Drug Administration.
Presumably the patch would be safer than repellents made from chemicals like DEET, PMD, and Picaridin."

OK so a nice test is coming up. We get to see if "food grade flavours" are really safe or just have been assumed safe. I hope they are safe.

I know, I know safe for humans and the rest of nature but not safe for mosquitos.

How exactly does that work?
Tradeoffs, tradeoffs; well I'm hoping for kite approval. I mean there is a war on mosquitos going on out there.

Mosquito borne diseases
http://www.cdc.gov/ncidod/diseases/list_mosquitoborne.htm

will believe it when I see it :) until then, good old Autan :D

I contributed last week, Gamechanger? I don't know, improve quality of life...I hope so. Perhaps we will simply present the biological imperative for mosquitos to evolve within the next couple mosquito generations...inadvertently providing more proof of the evolutionary process.

This is great, but I don't see how it can work. The difficulty with these things isn't really the chemical choice, its making sure the chemical is present in the right concentration where it needs to be - and I don't see how a simple patch can do that. This one is affixed to clothing, so it can't be a drug that alters your sweat.

So...how well does a patch on your arm ensure that there is an appropriate concentration around, say, the backs of your knees? My initial thought is: worse than a spray-on, maybe better than a tabletop candle.

It is not possible for the patch to remove all the CO2 around a person since CO2 will diffuse very quickly

my bet is that the chemicals released by the patch somehow kills the ability of the mosquito to detect CO2 and for that to be effective mosquito will need to come very close to the patch

it will not be a perfect solution but definately very good.

"the team identified several compounds that block mosquitoes from sensing CO2, including 2,3-butanedione, 1-hexanol, 1-butanal, and 1-pentanal. These could very well be the secret ingredients in the Kite Patch... Olfactor Laboratories has been raising money to test the patch in Uganda, which Kite co-founder calls "one of the toughest proving grounds there is" because of its huge mosquito population and high rates of malaria infection. If that works, they expect — with EPA approval — to market the three-square-inch patch in the United States in about a year... The group has already raised money from the Gates Foundation and the National Institute of Health, and they've started an indiegogo campaign to pay for the manufacture. You have until August to invest, and for $10 you can fund 5 patches used in their field testing in Uganda. For $35 you can give 10, and get 10 if they are approved by the EPA."

So they are very serious. Best of luck; marlaria is well terrible.

http://www.sciencedaily.com/releases/2001/08/010828075659.htm

better donate 35$ for irrigation in Uganda so they can plant catnip. repels mosquitos and is also great food rich in vitamins and minerals. :)

is a bit cynical to use Africa as a marketing ploy. Mosquito patch doesn't do anything for Uganda or anything humanitarian.... it's not like it cures aids or cancer... just another commercial product. To say "other products don't work or are toxic" is just the same BS as rest. Would like to see them eat their patches as a proof of concept that their product isn't toxic to a degree. Anyways.. Want to help africa and south asia. Help them to create proper irigation, drain dead canals, properly fight disease carrying insects etc..
Selling them patches is pure capitalism at it's worst. Doesn't do anything about the cause and thus makes it even worse in the long run.

Sinisa Lazarek
Your points are well taken.

Here is a nice summary of the malaria problem and approaches. http://www.gatesfoundation.org/What-We-Do/Global-Health/Malaria Note: though the Gates foundation has given some money to Kite; Kite is not mentioned on the Gates Foundation web site.

As well current price of $3 per Kite patch good for 48hrs seems too expensive for developing countries even if it gets down to $ .03 per patch.

"Eating your Kite patch for malaria" sounds like a good name for their marketing campaign.

There Ethan Siegel stands in some mosquito infested jungle (in his Mr. T outfit of course). Daring mosquitos to bite, none do. Then suddenly, Ethan rips off his Kite patch and eats it. Suddenly, 1000 mosquitos descend upon the unconquerable Ethan; he endures the assault until he reaches in his pocket and opens a package and puts another Kite patch on. Within seconds, the mosquitos disappear. Ethan smiles, "I'm eating only one Kite patch for malaria; this one's stays on."

hahahah.. good one for the commercial :D

bottom line is that if the patch indeed works great for 48h, they really have something, that's almost 6x of what sprays or oils do. And that's cool. Even for 3$. But that's all. And they should raise funds on kickstarter... just leave africa and all that out of it, cause it's bs.

Can send any other mosquito repelant ... will works just as well if that's the point. But from a marketing perspective it's effective. Just don't like it cause it's dirty. Plays on human emotion under false pretense.

Sinisa

The bigger picture health issues around mosquitoes - not just malaria, but West Nile and Dengue Fever - are huge problems that require many things to happen to fully address them. Yes, irrigation, drainage, clean water supplies and so on are vital.

The Kite patch is designed to help people who have to live daily with the threat of contracting mosquito-borne diseases and helping them to combat that threat. It would be used in conjunction with nets at night.

No-one is claiming it's a cure for cancer. However, it's been four years in development and it works. Now it needs to be field tested in real life situations, and Uganda is the choice because it has a serious problem and because some of the team developing Kite have lived and worked there, know the issue and in fact, have had malaria themselves.

DEET is toxic. Fact.

I donated myself last week and I hope this product realizes its potential. According to the science team, behind Kite, it's effective over an area of about a football field around an individual (so 100 yards). That's pretty impressive.

@ MB

"The Kite patch is designed to help people who have to live daily with the threat of contracting mosquito-borne diseases and helping them to combat that threat."

- just like any other commercial mosquito repelent. Hundreds of different brands allready out there.

"However, it’s been four years in development and it works."
- so do other brands.

"DEET is toxic. Fact."
-true.. but DEET is not the only compound used. Icaridin i.e. works just as well and according to EPA and WHO is harmless if used accordingly... And still have no evidence other than KITE's word that their "brew" is not toxic. IMO the reason it's a patch is because it's not that harmless if exposed directly to skin.

"According to the science team, behind Kite, it’s effective over an area of about a football field around an individual (so 100 yards)."
- like I said... when i see it i'll believe it.

Friends -

Grey Fandsen here. Team Lead for Kite Patch. Thought I'd jump in.

I just reviewed so many of your comments. Unfortunately, a few of you have taken liberty as it relates to our technology, our process, and our market strategy. Thanks to you who stuck up for us - particularly because we're working hard on distributing a new technology to market in an open, transparent way. we're also building a product in a new way - from the bottom up.

1. We've worked for over four years in the lab and around the world with the biggest names in vector and mosquito control. Our lab work shows efficacy - as does our field world. This is the first time we're bringing one of the products to market. Of coures the buzz is that it won't work, it won't do this or that, and/or is not approved by XYSKJFSDL commission for red tape.

2. We're building a consumer product from the ground-up, focused exclusively on the needs of individuals who need it (and cannot afford it). We're going straight to where it matters the most - bypassing large bureaucracies, multi-year processes, etc. We're entrepreneurs and scientists. We're working with Uganda, NGOs, non-profits, foundations, governments, etc.k to get this prodocut working for the least amount of cost.

2. Shinisa Lazerek - tough and off-base comments. Really off. Not sure what you do for a living, but telling readers here NOT to support our project is like tell people to not support a new technology that can very well save lives, but the negativity suggests that you' just don't adopt or ant to see new ways of building solutions.

Is our kite Patch 100% perfect? NO WAY! Do we claim this? NO WAY. Do we want people to drop everything and only use Kite? Not yet :)

What we DO need is people to begin changing their view on how innovation gets to real productfs and markets. At this rate, the communities like this have been particularly hard on our process...and particularly blind to what it takes to turn a research paper .

Finally - our work is i100% transparent (except the propriety blends, for now). Our partners range from USDA to U.S. Army, Biogense Europe, etc.

We're crowdfunding our campaign because we believe the most number of people involved in this otherwise-closwed innovation platform is better. We also believe that no one person or commnity hasa monompoly on good ideas.

I hope evryone here knows that data is coming, but only AFTER we develop an amazing prorduct that people in Uganda, Tanzania, Chad, Malia, Angola, and other ountries can afford and use to defend themselves against mosquitoes.

Hang with us. Help us. And know that we're working for the same goals you are. Meanwhile, if we work together, we'll be capable of changing the world.

THANK YOU.

Grey

Mosquito nets work well and are much cheaper per "dose".

Clearing watercourses is cheaper (more cost up front) but bigger and harder to know you're doing enough.

@ Grey Frandsen
"2. Shinisa Lazerek – tough and off-base comments. Really off. Not sure what you do for a living, but telling readers here NOT to support our project is like tell people to not support a new technology that can very well save lives, but the negativity suggests that you’ just don’t adopt or ant to see new ways of building solutions. "

Dear Mr Frandsen,

as to what I do, I'm a graphic designer with over a decade in advertising industry.

As to " telling readers here NOT to support our project..."
I did no such thing. In fact please be so kind and read again post #10 ...
"bottom line is that if the patch indeed works great for 48h, they really have something, that’s almost 6x of what sprays or oils do. And that’s cool. Even for 3$. But that’s all. And they should raise funds on kickstarter… just leave africa and all that out of it, cause it’s bs. "

In fact, this sounds to me like an endorsment and not the opposite. What I did say is that using Africa and undeveloped countries in marketing scheme is dirty and I do stand by that.

The rest what you write is more or less standard PR...

Bottom line.. I have nothing whatsoever against your product. Period. Your marketing strategy is what leaves a sour taste in my mouth.

I'm with Grey on this one.

There are three ways to get new public health measures into circulation: government, private business, and charity notably churches. University science is clearly critical to all three, but in and of itself is concerned primarily with discovery rather than with deployment.

How many of the adverse commenters here would prefer that extreme right-wing fundamentalist churches go over to Africa bearing mosquito nets (and proposals for kill-the-gays laws that come along with, speaking of Uganda!)....?

How many here are willing to work for the tax increases needed to support increased government spending on public health?

To get government to move, you need majorities of voters and majorities of Representatives, and supermajorities of Senators.

To get comparable results in private business all you have to do is earn enough of a profit to keep your investors happy. That task is far more readily accomplished than getting the concern trolls in the Senate to stop bickering and blocking long enough to do anything useful.

There are tasks that can only be done by government, such as providing clean water and sanitation: major engineering projects, things that depend on networked infrastructure that can't readily break even in the short term. But there is a large range of tasks that can be done equally well by government and private business, most notably tasks that involve personal measures that can be scaled to become affordable. That's where Grey and his folks come in (and I don't even know them, much less work for them, I'm a telecoms engineer).

Mosquitos and the diseases they carry are evil. Anything that helps win the war against mosquitos without causing significant ecological damage is good. QED.

"How many of the adverse commenters here would prefer that extreme right-wing fundamentalist churches go over to Africa bearing mosquito nets (and proposals for kill-the-gays laws"

False dichotomy.

Dr. Prof. Siegel, t
Thank you for this.
I'm a sufferer, in a big way. As a musician/adventurer, I've traveled a deal and have been the only one, in company, bitten, in tons of countries/jungles -- and I'm terribly allergic.

I'm convinced my reckless blood thwacks out mosquito brains then the tiny jerks get addicted (my blood type's more like a proof) and I become the shmorgishborg.

Thus, my support "kite" has.
Thanks again.

Ps. Your sciency stuff's the best. I read the hell out this blog. Cheers!

As a former researcher in the field of pheromones, I find myself really rather skeptical of this company and their products. The usual way to determine what a compound is doing to insect senses is by crude bio-assay, or by electrophysiology (such as that pioneered by Prof John Pickett of Rothamsted Research), and the lack of mention of this sort of research methodology, and the seeming lack of such expertise in the research team is rather worrying.

Then there is the Kite product its self. It appears to be a plastic compound, which even if it has a hidden reservoir of solvents cannot be emitting all that much vapour; this vapour is then supposed to disrupt CO2 sensing by mosquitos and to do so efficiently and via a non-toxic route? Sorry, but I simply do not think that one's a likely story at all and the "secret ingredients of which we do not speak" are going to remain secret for about as long as it takes someone to stick some into a gas chromatograph!

Finally, with mosquitos the homing system is not purely CO2 but other chemical cues as well, and visual/heat cues at shorter ranges. Disrupting all of this is difficult, hence the reasons for using DEET, Icaridin and pyrethrins in anti-insect formulations.

I'll believe this one when I see it, and I'll not be holding my breath.

How exactly does the kite patch keep the mosquitos away?
15320074

@ Comment number 2: Your site about mosquito-borne diseases doesn't seem to work anymore. Here is an updated version: http://www.mosquitofixes.com/mosquito-borne-diseases-usa/

Worth Reading: Alcohol in homeless shelters, fossil-fuel subsidies, and "suicide mosquitoes"

lborkowski — Fri, 03 Feb 2012 10:55:07 +0000

Worth Reading: Alcohol in homeless shelters, fossil-fuel subsidies, and "suicide mosquitoes"

A few of the recent pieces I've liked:

Ruth Marcus in the Washington Post: Why the poor should concern Romney

Scott Carlson in The Chronicle of Higher Education: America's Health Threat: Poor Urban Design

Maia Szalavitz at Healthland: The Wet House: Homeless People with Alcoholism Drink Less When Booze Is Allowed (Also see Matt Stroud at The Atlantic Cities: Why More Homeless Shelters Should Allow Alcohol)

Matthew Yglesias at Slate: Dirty Money: The astonishing new data showing that simply eliminating inefficient fossil fuel subsidies could achieve half the world's carbon reduction goals

Rafaela von Bredow in Der Spiegel: The Controversial Release of Suicide Mosquitoes

lborkowski Fri, 02/03/2012 - 05:55

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homeless shelters

mosquitoes

Thanks for the link love.

Beer makes humans more attractive to malarial mosquitoes

edyong — Thu, 04 Mar 2010 07:00:18 +0000

Beer makes humans more attractive to malarial mosquitoes

We've all heard about "beer goggles", the mythical, invisible eyewear that makes everyone else seem incredibly attractive after a few pints too many. If only beer had the reverse effect, making the drinker seem irresistibly attractive. Well, the good news is that beer does actually do this. The bad news is that the ones who are attracted are malarial mosquitoes.

Anopheles gambiae (the mosquito that transmits malaria) tracks its victims by their smells. By wafting the aromas of humans over thousands of mosquitoes, Thierry Lefevre found that they find the body odour of beer drinkers to be quite tantalising. The smell of tee-total water drinkers just can't compare. The somewhat quirky conclusion from the study, albeit one with public health implications, is that drinking beer could increase the risk of contracting malaria.

Lefevre recruited 43 men from Burkina Faso and sent them individually into one of two sealed, outdoors tents. One tent was kept unoccupied. In the second, the volunteer had to drink either a litre of water (just shy of two pints) or a litre of dolo (a local 3% beer and the country's most popular alcoholic drink). A fan pumped air from the tents, body odour and all, into the two forks of a Y-shaped apparatus. Both branches met in a third arm, which ended in a cup full of mosquitoes. The insects had to decide which branch of the Y to fly down and two pieces of gauze trapped them in their chosen path (and saved the volunteers from an infectious bite).

Lefevre showed that the smell of a beer drinker, 15 minutes after chugging his litre, increased the proportion of mosquitoes inclined to fly into the tubes, and the proportion (65%) who headed down the beer-scented fork. The smell of water-drinkers had no effect, nor did the smell of the occupied tent before its inhabitant started drinking.

What is it about a beer drinker that is so appealing? No one knows. Mosquitoes are drawn to the smell of carbon dioxide, but the beer drinkers weren't exhaling any more of this gas after their drink. Something about the smell of beery body odours attracts mosquitoes. Mosquitoes also fancy body heat, but beer actually lowered the volunteers' temperature by a fraction of a degree. Metabolising beer probably releases a slew of chemicals that mosquitoes are drawn to but the identity of these airborne attractants is a mystery. Nor do we know if the chemicals in question are specific to beer, or common to all alcoholic drinks.

This study is perfect tabloid fodder, but it has a very serious side. To mosquitoes, not all humans are equal. The bloodsuckers are quite picky about whom they suck from, and an important global study revealed that in problem areas, 20% of people receive 80% of all malaria infections. As such, it's quite important to work out what makes one person a delectable feast and another person a bloody turn-off.

Beer can't explain all of this variation by any means. After all, Lefevre found that some people were naturally attractive to mosquitoes without drinking anything; beer merely boosted these natural charms. So a pint of lager in the African sunset isn't going to guarantee a raging malarial fever, but it might increase the risk of one.

There are other reasons to think that the beer effect may be more serious than shown in this study. For a start, A.gambiae is a night biter. It's most active after sunset, which probably coincides with the time its prey is most likely to smell of beer. Drinking moderate to heavy amounts of alcohol can also suppress the immune system so regular beer drinkers are not only more likely to encounter malarial mosquitoes but they could be more vulnerable to the parasites they carry. And finally, at least one previous study showed that Aedes mosquitoes, carriers of dengue fever, are drawn to the aroma of beer drinkers, so the public health implications may go beyond just malaria.

Finally, Lefevre even puts forward a completely speculative, but cool, idea - perhaps the fact that mosquitoes wear beer goggles isn't just a coincidence. It's possible that they might have evolved a slight preference for the smell of beer-drinkers, either because their blood is full of nutrients or as he dryly notes, "possibly due to reduced host defensive behaviours"! As Lefevre says, "This hypothesis is appealing but requires further investigations."

Reference: LefÃ¨vre, T., Gouagna, L., DabirÃ©, K., Elguero, E., Fontenille, D., Renaud, F., Costantini, C., & Thomas, F. (2010). Beer Consumption Increases Human Attractiveness to Malaria Mosquitoes PLoS ONE, 5 (3) DOI: 10.1371/journal.pone.0009546

More on mosquitoes:

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edyong Thu, 03/04/2010 - 02:00

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Tabloid headline- "to avoid malaria, you should drink beer for breakfast, not dinner".
Or, "Gin and tonic, not beer: a drinkers guide to avoiding malaria"
How do we know the mozzies don't feel the alcohol?
I wish they'd done it with plasmodium carrying mozzies and with plasmodium free mozzies.

I think the reason why they didn't separate out Plasmodium carriers vs. non-carriers is that they wanted to do the study with mosquitoes from populations that hadn't been bred in the lab. So the mozzies in the study were hatched in a lab, but the eggs were laid by pregnant females caught in the wild. Why this is important isn't clear to me, but they make a thing of it in the paper. Anyway, more work to do. It would also be interesting to test other alcoholic beverages

Interesting article. We have terrible mosquito problems around here (Virginia) but I don't know that the beer drinker in the house suffers worse. On the other hand, he smokes so maybe that is a deterrent.

Oh Ed, there's a typo in the first para...The bad news is that the ones who are attracted [at] malarial mosquitoes.

Since you mention that mosquitos are attracted to carbon dioxide, was the beer in question carbonated? Have other carbonated beverages been tested?

Typo fixed - thanks.

@4 - doesn't really matter because the beer didn't increase the concentration of CO2 in the tent air.

I was immediately left wondering why the decision was made to test beer vs water in the first place. Did the authors already suspect a link between beer consumption and 'attractiveness of odour'...? A quick read of the paper answered the question, it seems that a previous study had already made the link between beer consumption and 'odour attractiveness' to laboratory bred Aedes mosquitoes and the authors wished to test the link in malaria mosquitoes from natural populations. I can't find a full copy of the previous study online though (its past my bedtime so I've only looked for a few minutes) so I'm still wondering why that particular link was suspected in the first case. I wonder if it was already part of some common folklore that drunk people are more prone to bites.

In any case, I'm not usually prone to being bitten. I think I might get a case of beer on the weekend and conduct some experiments of my own on my local population of mosquitoes.

This is incredibly interesting. I'm always attacked relentlessly by the mosquitoes here in North Carolina, especially compared to some of my friends.

But this study has some important implications for tailgating during football season!

Shouldn't they have had them drink the beer outside of the tent first, and then enter the tent for the test? How do we know that the odor of the beer itself wasn't still in those tents, mixed in with the odor of the beer drinkers? Does it explain this in the paper?

@Ed: Couldn't belching from the beer tent (esp. if chugged) produce a slight bump in CO2 emissions which the mosquitoes could pick up on?

The title should have been Beer makes humans more attractive. The rest is a detail.

One of my children is a mosquito magnet. It will be interesting to find out more about mosquito preferences. (I will advise her that when she is of age to avoid beer while camping!)

Nathan, did you see the title for Figure 2? ;-)

Jason and Eve - sorry, no time tonight, but the paper's open access and not too difficult a read.

So we have carbon dioxide, nonanal, and now beer that makes us delicious.

Did I read the nonanal findings from Not Exactly Rocket Science? I don't see it in the "more on mosquitoes", but I don't remember where I heard that one...

@Ed: One problem with lab mosquito populations is that they quickly become slow. If you've ever been in a lab that raises houseflies, it's fun swatting the ones that escape, because their reaction time is absolutely terrible. Probably some strong behavioral changes as well, such as rapid selection for willingness to feed on the blood bag membrane.

Anyway, a bunch of things you'd rather not have to account for in your experimental design! So they kept it as close to wild behavior as reasonably possible.

I seem to recall something about the smell of feet being attractive to mosquitoes; if any sort of yeast is involved in that effect, it could follow that beer would cause greater attractiveness. Unfortunately, in that study they were culturing bacteria, although if generalized it could imply that mosquitoes are attracted to feet in other ways also. If so, there might be a whole host of chemical attractants active, and yeast or other fungus could be among of them.

A little contrived, but testable!

I assume the local beer used in the experiment is a live-yeast home-brew, not factory-bottled?
Folklore in Australia claims that drinking home-brewed beer (non-pasteurized live yeast beer) acts as a mosquito repellent, providing you've been consuming the stuff for 6 weeks or so.
But in southern Australia there are no malaria- carrying mosquitoes - yet. Perhaps this needs testing.

Did I read the nonanal findings from Not Exactly Rocket Science?

Probably not - I try to feature only the most anal of discoveries.

ChrisM - Thanks for that.

A.Fleming - The idea that Aussies might drink home-brewed beer for 6 weeks straight does not surprise me in the slightest ;-)

Maybe that explains why mosquitos tend to ignore me, being Australian and a homebrewer... but now I'm confused. Mosquitos are attracted to beer drinkers, or at least Burkinabe males aged between 23 and 40 who drink dolo prepared from the fermented dough of sorghum. But mosquitos are repelled by beer drinkers, or at least according to folklore, Australians who drink homebrew. To be safe, I'll continue to avoid drinking dolo and being Burkinise and stick with homebrew...

@Ed Yes, I've learned to appreciate the wonders of my colon and all it contains thanks to your features.

NSF is where I read that article, in case anyone else is interested: http://www.nsf.gov/discoveries/disc_summ.jsp?cntn_id=116286&org=NSF

Apparently nonanal gives off a fruity odor, as opposed to nutty.

[blockquote]
But in southern Australia there are no malaria- carrying mosquitoes - yet.
[/blockquote]

between Dengue Fever, Ross River Virus, and the tradition of going "fishing" with half a litre of bait and four hundred litres of beer, a local follow up on this is probably going happen any second now...

But in southern Australia there are no malaria- carrying mosquitoes - yet.

Vitamin B1 (Thiamin) deters mesquitoes as most backpackers know. Beer depletes this vitamin in the system. Mystery solved.

The only control is water, rendering the study silly. To say that beer has a specific effect, you need to test it against other foods, taken in similar caloric amounts, at a minimum.

Perhaps a non-specific increase in blood sugar is responsible, for example. It's highly plausible that mosquitoes would be attracted to blood with a higher glucose content. But then almost any snack or meal would have the same effect.

John -

Hard liquor depletes vitamin B1 (except in Australia, where they fortify to prevent Wernicke-Korsikoff syndrome).

Beer, at least high quality all-malt beer, is loaded with thiamine.

One parasite to rule them all - Wolbachia protects against mosquito-borne diseases

edyong — Thu, 24 Dec 2009 12:32:45 +0000

One parasite to rule them all - Wolbachia protects against mosquito-borne diseases

This is an updated version of the first post I wrote this year. The scientists in question were looking at ways of recruiting bacteria in the fight against mosquito-borne diseases, such as dengue fever. They've just published new results that expand on their earlier experiments.

Mosquitoes are incredibly successful parasites and cause millions of human deaths every year through the infections they spread. But they are no match for the most successful parasite of all - a bacterium called Wolbachia. It infects around 60% of the world's insect species and it could be our newest recruit in the fight against malaria, dengue fever and other mosquito-borne infections.

Wolbachia doesn't usually infect mosquitoes but Scott O'Neill from the University of Queensland is leading a team of researchers who are trying to enlist it. Earlier this year, they published the story of their first success. They had developed a strain that not only infects mozzies, but halves the lifespans of infected females. Now, as the year comes to an end, they're back with another piece of good news - their life-shortening bacteria also guard the mosquitoes from other infections.

It protects them against a species of Plasmodium, related to the parasite that causes malaria in humans, as well as the viruses responsible for dengue fever and Chikungunya. Infected insects are less likely to carry parasites that cause human disease, and those that do won't live long enough to spread them. It's a significant double-whammy that could have a lot of potential in controlling mosquito-borne diseases.

Using Wolbachia for biological control makes sense because the bacterium uses many self-serving strategies that allow it to spread like wildfire. And because it's transmitted in the eggs of infected females, all of its strategies involve screwing over male insects, whose sperm are useless to it. Sometimes it kills males outright before they're even born. Sometimes, it turns them into females.

In other subtler cases, it ensures that infected males can only mate successfully with infected females. If they try to breed with uninfected ones, the embryos die at an early stage of development. This strategy is known as "cytoplasmic incompatibility". It gives infected females (who can produce living young with any male they like) a competitive advantage over uninfected females, who can only start the next generation with uninfected males. Once Wolbachia gets a foothold in a population, massive swathes of it eventually become carriers. This is exactly what O'Neill's strain does - it induces complete cytoplasmic incompatibility. Once introduced into a natural population, it should invade with tremendous zest.

The strain also halves the lifespan of the Aedes aegypti mosquito. This might seem like a flimsy victory, but it's an important one. Once an individual sucks up a mouthful of infected blood, it takes two weeks for any parasites or viruses they've drink to reproduce in their gut and travel back to their salivary glands. Only then do they become infectious. This means that mosquitoes only really pose a threat to human health once they're old and they are fairly short-lived insects anyway. Any technique that slashes their already limited lifespan will have a huge impact on controlling the diseases they carry.

Even though Wolbachia lowers a female's lifespan, they don't hurt her egg-laying ability, or kill her off before she gets a chance to breed. So a Wolbachia-based approach would never drive a mosquito to extinction - it would just kill older individuals before they become capable of spreading disease.

Now, O'Neill's team, led by Luciano Moreira, have found that their Wolbachia recruits have a second advantage - they stop mosquitoes from becoming vectors for the viruses and parasites that cause human disease. The bacterium almost entirely prevented infections by dengue virus, even if it was injected directly into their bodies. Even after five generations of breeding with wild mosquitoes, the offspring of the Wolbachia carriers still resisted dengue virus. Moreira found similar results for the Chikunguya virus.

He also pitted his WolbachiaÂ-carrying mozzies against Plasmodium gallinaceum, a parasite that infects birds, but is closely related to P.falciparum that causes human malaria. A week after the mosquitoes had fed on contaminated blood, Moreira found 26 times less Plasmodium DNA in insects defended by Wolbachia, and the number of individuals that could potential transmit the parasite had halved.

Wolbachia sets the mosquito's immune system on high-alert, switching on a few important immune system genes. Even if any viruses or parasites slip through, it's possible the bacterium outcompetes them for important nutrients like fatty acids and cholesterol. The viruses responsible for dengue and Chikunguya need cholesterol from their host to replicate themselves and Plasmodium needs a loan of fatty acids. But Wolbachia demands these molecules too and Moreira thinks it may simply be better at fighting for them.

So far, so promising, but O'Neill acknowledges that there's a lot of work to be done before his strain of Wolbachia can prove its worth for human health. So far, he has only shown that it interferes with infection by P.gallinaceum and not the Plasmodium species that causes human malaria. Likewise, he has only shown that Wolbachia does the job in the A.aegypti mosquito, rather than Anopheles gambiae, the main vector for human malaria.

Then there are the practical aspects. It's likely that Wolbachia's anti-male strategies will allow lab-infected mosquitoes to rapidly spread the bacterium. Certainly, earlier studies have found that Wolbachia can infect an entire laboratory population of mosquitoes within just a few generations. But that still needs to be tested, first in contained greenhouse settings and then later in field experiments. Computer models will also help to understand whether releasing infected mosquitoes will make a sizeable dent in the wild population, how long that would take, and whether resistant strains would eventually evolve.

Reference: Moreira et al. 2009. A Wolbachia Symbiont in Aedes aegypti Limits Infection with Dengue, Chikungunya, and Plasmodiu. Cell DOI: 10.1016/j.cell.2009.11.042

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edyong Thu, 12/24/2009 - 07:32

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If Wolbachia is successfully introduced into wild mosquitoes, and becomes widespread, malaria will first drop, but in time selective forces will favor "resistant" forms of Plasmodium (and the other pathogens).

The advantage of using a biological control agent in this manner is that selective pressure works both ways. As much as mosquitos with resistance to wolbachia may be selected, those wolbachia that can evade the mosquito's resistance will also be selected.

Wolbachia IS cool! They do some crazy things in their female-boosting game. In some insects they even cause the males to turn into females, or encourage the females to reproduce by parthenogenesis (virgin birth). Amazing little microbes.

This certainly sounds promising, but I'm reminded of the myxomatosis used to kill off feral rabbits in Australia- they eventually developed a resistant rabbit population. Then they brought in another virus- I think it was a parvovirus (?)- and now, not many years later, the rabbits are appearing again. What makes the rabbits so adapted to our "foreign" environment, that they can survive in sufficiently resistant numbers to save their species from two fullblown biological attacks? Mosquitoes are rather ubiquitous and so I thought they might become resistant to Wolbachia fairly swiftly as well... Hmm...thoughts?

The other concern with biological control is what the control agent will do to *other* species.

I'm not an arthropod, so I guess I don't have to worry about it getting into *my* gametes - at least, not unless it makes quite a few evolutionary leaps - but what about every other prey animal, insectivore, or blood-drinking insect (e.g. horseflies?)

Flies!

awild — Tue, 12 May 2009 09:50:56 +0000

Flies!

Eastern Treehole Mosquito

My commercial gallery now has flies!

Diptera photographs at alexanderwild.com

I feel sort of embarassed at how few fly images I have, considering the importance of the group. That's something I'll try to remedy as we get into this summer's photography season.

awild Tue, 05/12/2009 - 05:50

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Åwietny blog i super fotki , dodajÄ do ulubionych , pozdrawiam, Andrzej :)

Good work. I especially like the cecidomyiid.

The cecidomyiid and others are cool, but I am completely taken by the horsefly with racing striped eyes! http://www.alexanderwild.com/gallery/8164894_6FhJk#533007107_wPbuN

The Burrard-Lucas brothers on shooting mosquito emergence

sb admin — Thu, 23 Apr 2009 15:17:59 +0000

The Burrard-Lucas brothers on shooting mosquito emergence

Nature photographers William & Matthew Burrard-Lucas explain the magic behind some recent images of mosquitoes emerging from their pupae.

While they list the equipment and lighting they used for the session, the key factor seems to have been the determined patience with which they watched pupae develop over two weeks so that they'd be able to catch the event in the scant 5 minutes it took to complete. Although the gadget industry does its best to convince us that photography is all about owning the latest and best gear, it remains true that the best images come from the most skilled and most patient photographers.

Also, if you have time, check out the brothers' spectacular night shot of a Brazilian caiman. Wow.

sb admin Thu, 04/23/2009 - 11:17

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On Assignment: Mosquito Larvae

sb admin — Tue, 14 Apr 2009 21:50:33 +0000

On Assignment: Mosquito Larvae

Aedes triseriatus, Eastern Treehole Mosquito (Larva)

I have a symbiotic relationship with other scientists. They let me in on their cutting-edge studies, giving me and my camera unfettered access to their charismatic little subjects. When the research is published and the science press picks up the breaking story my photos go along for the ride, sometimes garnering license fees. If the story is big enough, the photos are also positioned for the textbook market. In return, the researchers get photos that help them promote their work in talks and on laboratory web pages.

On Monday I stopped by the Illinois Natural History Survey to shoot Barry Alto's mosquitoes. Barry has some work coming out soon about the ecological interactions between a native species (Aedes triseriatus) and an introduced species (Aedes albopictus) and needed photos of mosquito larvae. That's a new subject for me, so I was happy to take them on.

How to get a natural-looking shot out of a lab colony? Here's the set:

With a flash head positioned behind the beaker, the backlit leaf glows. A second flash from the front provides a bit of fill at low power. The lighting arrangement proved effective:

I used a different strategy for the introduced species, Aedes albopictus. They were thick in their rearing containers, so I just backlit the mass of pupae and larvae and took a few shots until I had one that worked.

The full session took about 500 exposures to get about 10 good images for Aedes triseriatus and about 200 more for Aedes albopictus. Digital photography has its advantages. Here is a screen capture from my RAW conversion program showing a small part of the workflow:

Technical details (close-up shots):

Lens: Canon MP-E 1-5x macro lens
Body: Canon EOS 20D
Flash: Canon MT-24EX twin flash
Settings: variable

sb admin Tue, 04/14/2009 - 17:50

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insects

mosquitoes

Photography

Fantastic work, Alex! Just stumbled on this blog via a link at the NY Times. Glad I did. Absolutely fascinating, and I learned a lot, too. I'll be back. Thanks for sharing.
Keith

Digital photography has definitely been a life-saver for nature photographers (and I guess other photographers too).

Being free from worry about wasting valuable film allows you to get a much better selection of shots to pick the best of the best from.

I have a question:
When taking photos of with flash - do you worry that the flash can damage, harm or distress insects or other light sensitive organisms (I'm thinking mostly small invertebrates)?
Is this something that you (or others) have looked into, or has it not really been something you have thought of?

Great images Alex. Love those wriggling larvae.

Thanks guys.

Z- I know that some vertebrates are sensitive to flash, but I've never seen evidence that insects have problems with it. Flies will often jump when the flash goes, smaller-eyed insects don't seem to even notice. And insects I've photographed repeatedly don't seem to show any signs of vision degradation. This may be because insect eyes are robust across a wider range of light intensity, as they lack the delicate aperture of the vertebrate iris & ultra-sensitive retina.

In any case, the flash can't be as damaging as the ethanol I use to pickle those insects that are destined for museum collections after I'm done with them.

Excellent photos! Looking forward to seeing many more - you are a great addition to SB!

In any case, the flash can't be as damaging as the ethanol I use to pickle those insects that are destined for museum collections after I'm done with them.

thanks..

Mosquitoes harmonise their buzzing in love duets

edyong — Fri, 09 Jan 2009 08:45:00 +0000

Mosquitoes harmonise their buzzing in love duets

To our ears, the buzz of a mosquito is intensely irritating and a sign of itchiness to come, but to theirs, it's a lover's serenade. The high-pitched drone of a female is a siren's song that attracts male mosquitoes. And a new study shows that when the two love-bugs meet, they perform a duet, matching each other's buzzing frequency with careful precision.

The female Aedes aegypti mosquito (the carrier of both dengue and yellow fever) beats her wings with a fundamental frequency of about 400Hz, producing a pitch just slightly lower than concert A. Males on the other hand, have a fundamental frequency of around 600Hz, about one D above middle C.

Lauren Cator and colleagues from Cornell University discovered the sonic secrets of courting mosquitoes by tethering individuals to pins and moving the females past the males. On two-thirds of these fly-bys, the amorous mosquitoes harmonised. Neither took the lead - instead, both buzzers shifted their flight tones so that the male's second harmonic (the second multiple of his fundamental frequency) and the female's third had a mutual frequency of about 1,200 Hz. They synchronised in this way for about 10 seconds.

Lacking ears like ours, mosquitoes hear with their antennae and structures called Johnston's organs. But for decades, the wisdom of textbooks has said that males are deaf to any frequency over 800Hz and females are completely deaf. Cator disproved that by using miniature electrodes to show that the Johnston's organs of both sexes produced electrical signals in response to frequencies as high as 2000 Hz.

The duets depended on one partner hearing the other. If they were deafened by removing their antennae, or by gluing the antennae to the Johnston's organs, nothing happened. But seeing another mosquito wasn't necessary - individuals were all too happy to match the frequency of an electronically produced tone, even one that is set below or above the insect's natural flight tone.

Cator suggests that a male mosquito's ability to match the tone of his partner is the result of sexual selection. Perhaps females can judge the best mates by selecting those who can match their frequencies with the greatest skill. That will need to be tested in future studies but for now, one thing is clear - falling for one song makes the female less likely to fall for another.

Cator found virgin females were about three times more likely to match an electronic tone than those who had already mated. That backs up other research which suggests that Aedes aegypti females aren't keen to mate again for a fair while after they've done it once. Cator even suggests that releasing sterile males could be a way of controlling mosquito populations in the wild - it would lead to fruitless matings that would prevent females from engaging in productive ones later.

Reference: L. J. Cator, B. J. Arthur, L. C. Harrington, R. R. Hoy (2009). Harmonic Convergence in the Love Songs of the Dengue Vector Mosquito Science DOI: 10.1126/science.1166541

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edyong Fri, 01/09/2009 - 03:45

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fundamental frequency

I'll try to remember this the next time I'm in mosquito country and swatting.

I heard on NPR (and I'm not saying they're an authority) that actually the 1200Hz note was an overtone. That is to say that the insects don't double (the male) or triple (the female) their wing buzzing frequency, to match each other at 1200 Hz they just subtly alter their tones around the 400 and 600 Hz ranges such that the overtone is manifested.

You know, when I read that, I thought, "Yes. That's right. That's what I said, isn't it?". Now, reading back, that's absolutely not what I said - what I wrote implied that they shift their fundamental frequency didn't it? Nuts.

Also managed to get the lead researcher's name wrong - Cator not Calor.

All round accuracy FAIL, methinks. /slaps self on hand - must do better.

Note that the text has now changed to correct my cock-ups.

"(...) releasing sterile males could be a way of controlling mosquito populations in the wild - it would lead to fruitless matings that would prevent females from engaging in productive ones later."

Unless the sterile males are less skillful in getting their frequencies right. In fact, it seems that any release of males into a wild population for mosquito control (e.g. genetically modified ones) needs to take this into account.

Yeah absolutely. It's clear that there's a lot of work to do before any approach that involves releasing genetically-engineered males can be done successfully. For example, a study last year showed that we're not even entirely clear about what criteria mosquitoes use to select mates - surely a fundamental consideration for these sorts of strategies?

Protecting health by genetically engineering mosquitoes

sporte — Fri, 02 Jan 2009 14:51:38 +0000

Protecting health by genetically engineering mosquitoes

Mosquito-borne diseases, like Dengue and Malaria, are serious problems in many parts of the world. While some people are working on treatments for mosquito-carried disease, others are looking at ways to treat the mosquitoes.

Figure 1. Image of Aedes aegypti from the Public Health Library

tags: tropical disease, yellow fever, dengue, insect control,
malaria

Controlling insect activities by messing with their genomes isn't a new idea. In many parts of the world, screwworms are controlled by damaging their genomes on a large scale by treating the flies with X-rays and releasing the sterile males out into the environment. The sterile males aren't as healthy or as successful at mating, but they are sent out in such large numbers that they outnumber their fertile counterparts, making this program a success. Unfortunately, for a number of reasons, this approach isn't a good method for controlling mosquitoes.

Now, a group from Australia has found another way to modify mosquitoes.

They injected Wolbachia into mosquito eggs and created new strains of mosquitoes with half the lifespan of a normal mosquito (1, 2). This is important because many disease-causing organisms need to go through a developmental stage in the mosquito. Parasites, like those that cause malaria, and viruses, like Dengue, are picked up when a mosquito bites someone. They must reproduce in the gut and move into the salivary glands before they can be injected during a mosquito bite. Since this process takes about two weeks, a mosquito with a shorter life span will have less time to spread infections.

Figure 2. An insect embryo containing Wolbachia (green) (3).

Wolbachia are bacteria that normally live as symbionts in many species of mosquitoes, as well as fruit flies, and nematodes. They just haven't been found in Aedes aegypti. Wolbachia pipientis wMelPop, also shortens the life time of infected fruit flies and it modifies the ability of its host to reproduce. If a fly or mosquito is female, the Wolbachia are inherited by the fly's offspring. If an infected fly is male, and the female is uninfected, the embryos usually die, through a phenomenon known as cytoplasmic incompatibility (CI) (3).

Cytoplasmic incompatibility is also useful because it makes it less likely that Aedes aegypti mosquites will become resistant to Wolbachia infection. According to the Science paper, evolution of resistance is also less likely because the mosquitos will experience less selection pressure. And no signs of resistance have appeared in the ten years that people have been working with infected laboratory strains of D. melanogaster.

Jeremy Yoder and the Seattle Times have articles about this topic as well.

References

C. J. McMeniman, R. V. Lane, B. N. Cass, A. W.C. Fong, M. Sidhu, Y.-F. Wang, S. L. O'Neill (2009). Stable Introduction of a Life-Shortening Wolbachia Infection into the Mosquito Aedes aegypti Science, 323 (5910), 141-144 DOI: 10.1126/science.1165326
A. F. Read, M. B. Thomas (2009). MICROBIOLOGY: Mosquitoes Cut Short Science, 323 (5910), 51-52 DOI: 10.1126/science.1168659
S. Zabalou (2004). Wolbachia-induced cytoplasmic incompatibility as a means for insect pest population control Proceedings of the National Academy of Sciences, 101 (42), 15042-15045 DOI: 10.1073/pnas.0403853101

sporte Fri, 01/02/2009 - 09:51

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biotechnology

Genetics & Molecular Biology

peer-reviewed research

mosquitoes

public health

Why can't they modify the mosquitoes so that they won't bite humans anymore...

Thanks for the nod! The result is pretty awesome - although it seems to be an open question where the equilibrium will be between the cytoplasmic incompatibility and the life-shortening effects of Wolbachia.

No problem Yoder. I found your post when I was ready to put this up and liked it.

I got what you intend,saved to my bookmarks, very decent website .

Life-shortening bacteria vs. dengue mosquitoes

edyong — Thu, 01 Jan 2009 16:12:43 +0000

Life-shortening bacteria vs. dengue mosquitoes

The mosquito Aedes aegypti sucks the blood of people from all over the tropics, and exchanges it for the virus that causes dengue fever - a disease that afflicts 40 million people every year. The mosquito has proven to be a tough adversary and efforts to drive it from urban settings have generally failed in the long-term. So how do you fight such an accomplished parasite? Simple - use a better parasite. In fact, try the most successful one in the world, a bacterium called Wolbachia.

Wolbachia's success rests on two traits. First, it targets the most diverse group of animals on the planet, the insects, infecting the majority of species and about one in eight individuals. Second, it spreads like wildfire by using several extremely self-serving strategies, all of which screw over male insects in some way or other. Wolbachia passes from one generation to the next in the eggs of infected females. But without similar access to sperm, males are useless to it and has evolved a number of ways of dealing with that. Sometimes it kills males outright before they're even born; sometimes it turns them into females.

In other subtler cases, it ensures that infected males can only mate successfully with infected females. If they try to breed with uninfected ones, the embryos die at an early stage of development. This strategy is known as "cytoplasmic incompatibility" and while it's still unclear how it works, there's no doubt that it does. It gives infected females (who can mates with any male they like) a competitive advantage over uninfected females, who are restricted to uninfected males. With this upper hand, massive swathes of a given population eventually become Wolbachia-carriers.

Conor McMeniman and colleagues from the University of Queensland have found a way to use that to their advantage. They have found a strain of Wolbachia that can halve the lifespan of the Aedes mosquito and that induces complete cytoplasmic incompatibility. If introduced into a natural population, it should invade with tremendous zest.

Shortening a mosquito's lifespan may seem like a flimsy victory, but McMeniman recognises it as an important one. Only old mosquitoes really pose a threat to human health because it takes about two weeks for an individual to become infectious after it first sucks up a mouthful of infected blood. The virus first need to reproduce in its gut before travelling back to its salivary glands, where it can spread further. Because mozzies are short-lived anyway, most die before they reach that point, which means that any technique that slashes their already limited lifespan will have a huge impact on controlling the diseases they carry.

Finding a strain of Wolbachia that infects the Aedes mosquito wasn't easy. In a cruel twist of fate, the uber-bacterium doesn't naturally infect either of the mosquito groups that carry dengue or malaria, despite being relatively unfussy about its choice of hosts. But that doesn't mean it can't - a study four years ago proved that Wolbachia can infect Aedes aegypti and can spread to an entire laboratory population within a few generations. The race was on to find the right strain.

McMeniman's group found one called wMelPop, which naturally infects the fly Drosophila melanogaster and halves its lifespan. To acclimatise the strain to a new host, the team cultured it in mosquito cells for three years, producing a version with a preference for mosquitoes instead of Drosophila.

Their new wMelPop strain had all the right traits. It successfully infected mosquitoes and was passed down through over 30 generations. Virtually all of the larvae born to infected females carry Wolbachia themselves. And once infected, a female's days are numbered; under realistic conditions (including tropical temperature and humidity, and daily blood meals) Wolbachia halved the normal mosquito lifespan, just as it does in Drosophila. McMeniman even proved that these shortened lives were solely due to the bacteria by showing that the mosquitoes lived to their usual age if they were cured with a dose of antibiotics.

The Wolbachia strain was also clearly causing cytoplasmic incompatibility. When uninfected or cured individuals breed, over 80% of eggs eventually hatch. But when infected males mated with uninfected females, not a single one of 2,500 eggs produced a living larva.

This trinity of nigh-total inheritance, strong cytoplasmic incompatibility and life-shortening power is exactly the combination of traits needed if Wolbachia can be used as a weapon to control wild populations of mosquitoes. Certainly, strains with similar properties spread well enough in other insect species. Even though Wolbachia lowers a female's lifespan, they don't hurt her egg-laying ability, or kill her off before she gets a chance to breed. So a Wolbachia-based approach would never drive a mosquito to extinction - it would just kill older individuals before they become capable of spreading dengue fever.

It also means that the mosquito is under very little pressure to evolve resistance to the bacterium, because it's quite capable to raising hundreds of offspring before its life is cut short. Indeed, there's no evidence that Drosophila (the natural host of wMelPop) has evolved any resistance to it in over a decade.

You could, however, imagine that the loss of older mosquitoes would simply trigger the evolution of dengue viruses that develop more rapidly. It's certainly a potential downer, but the viruses are already under such pressures because mosquito lives are so naturally short. The fact that they don't already develop quickly suggests that there's some cost in doing so even if quick-off-the-mark viruses do evolve, it's likely that they'll be weaker versions of existing ones.

McMeniman's study is a promising start, but his enthusiasm is quite rightly tempered by a call for more research. His study hasn't shown that the approach would work, just that it can (and has a good chance of doing so). The next step is to do field-cage trials, where contained populations of infected mosquitoes are monitored under (mostly) natural conditions. And we'll need better models that simulate the spread of the bacterium and assess the potential for evolving resistance, no matter how small.

As a side note, this amusingly captioned image was released along with the paper. The caption reads: "Success of the experiments was dependent on human bloodfeeding of mosquitoes. That's McMeniman in the photo - he's a PhD student (read: the most junior person in the lab and, thus, lunch).

Reference: C. J. McMeniman, R. V. Lane, B. N. Cass, A. W.C. Fong, M. Sidhu, Y.-F. Wang, S. L. O'Neill (2009). Stable Introduction of a Life-Shortening Wolbachia Infection into the Mosquito Aedes aegypti Science, 323 (5910), 141-144 DOI: 10.1126/science.1165326

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edyong Thu, 01/01/2009 - 11:12

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