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Subscribe to RSSAfter two African villages started using mosquito nets to fight malaria, the local mosquitoes seemed to change their biting habits to avoid the barriers, according to a French study.
Insecticide-treated bed nets are considered a key weapon in the global fight against malaria, which is transmitted by parasite-carrying mosquitoes and kills more than 650,000 people a year, according to the World Health Organization.
In the study, which appeared in the Journal of Infectious Diseases, French researchers examined mosquito behavior before and after all households in two villages in Benin were given insecticide-treated nets.
They found that mosquitoes seemed to change their hours of "peak aggression" from 2 a.m. or 3 a.m. to around 5 a.m. three years after nets were put up. And in one village, the proportion of mosquito bites inflicted outdoors rose.
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Outdoor bites accounted for 45 percent of all bites at the outset but rose to 68 percent one year later and 61 percent after three years.
The finding is "worrying since villagers usually wake up before dawn to work in crops, and as such they are not protected by mosquito nets," senior researcher Vincent Corbel, of the Montpellier, France-based Institute of Research for Development, said in an email.
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Still, the results come from just two villages in one country. "We cannot extrapolate to a wider geographical area and/or a different entomological context," Corbel warned.
Malaria rates climbing again
Mosquito nets have been credited with spurring big drops in malaria deaths, and a report for the Cochrane Collaboration, an international group that publishes rigorous reviews, estimated that for every 1,000 children protected by an insecticide-treated net, five to six lives would be saved every year.
But in recent years, malaria cases have started to climb again in certain African countries, Corbel said. Experts have mainly been concerned about mosquitoes' growing resistance to the insecticides used in bed nets and for indoor spraying.
In Key West, there's talk of releasing genetically modified mosquitoes to fight dengue fever, a mosquito-borne illness. WFLA's Brooks Garner reports.
A malaria researcher not involved in Corbel's study said the results of the study should be interpreted with caution.
One reason is the difficulty in getting reliable measures of mosquito "biting behavior" over time, according to Thomas Eisele, from the Tulane University School of Public Health and Tropical Medicine in New Orleans.
In this study, Corbel's team used the standard way of gauging mosquito activity -- the "human landing catch" -- which, as the name implies, means that a mosquito collector lets the pest land on his skin, then catches it.
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The researchers had mosquito collectors do three different rounds, indoors and outdoors, at each village: Once before the nets were given to all households, then again one year and three years afterwards.
Eisele said measuring biting behavior can be "fraught with error" and added: "This study was conducted over only a couple of years, which would likely be insufficient to detect evolutionary changes in biting behaviors within the same species."
Corbel said the study challenges the "dogma" that malaria-transmitting mosquitoes in Africa bite exclusively at night.
"Long-lasting insecticidal nets were developed to protect people at night when they are sleeping," he said, noting that if mosquitoes shift to early morning and outdoor biting, the nets might not be enough to keep malaria under control.
Copyright 2013 Thomson Reuters. Click for restrictions.
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It would make sense, if the female mosquitoes are hungry and can't get food, to change when they eat. After all, if our stores were to change the hours of operation, wouldn't we adjust and our behaviors accordingly down the road?
Hummmmmmmmmmmm .. It's just to hard to believe that mosquitoes are getting any smarter than they already are! lol
And nobody believed me when I was saying that the skitters are getting organized...
We need to be modifying the parasite, not the behavior of the host.
The host will adjust its eating habits.
But if we make the parasite unable to replicate or move to its next stage then we really have something.
.
That would be a good idea, US, but it's also expensive and research-intensive. Mosquito nets are cheap and available now.
Sf-
But if something doesn't work, is it really cheaper?
We already know that minor variances in mosquito subspecies vary their feeding times and other feeding habits. It could be that the generations of mosquitoes that feed at 3 AM have been mostly killed off so now another subspecies albeit similar strand of mosquitoes are now more prominent as they are more numerous, no change in behavior, just different subspecies behavior .
The problem is that they treated the nets. Had they not treated the nets and used regular ones, this behavior would not have occurred so quickly.
This could also be natural selection in action. Deny the food to the mosquito's that would normally bite in the middle of the night while supplying food to those that bite during the morning and the ones that bite at night die off while the ones that bite in the morning thrive. So in the end you didn't change their behavior as much as you gave an advantage to the morning biters.
Bring back DDT and you don't have to worry about which mosquito is smarter.
Doesn't sound like natural selection, but more survival instinct. The timing of the peak in bites changed, not necessarily the quantity of bites (i.e. fewer or more mosquitos biting).
As someone else mentioned, behavior adapts to the change in food availability. If your store is closed, you go to another store that is open. If all the stores are closed, you eventually adapt to that and adjust the time when you go to the store.
Bill:
The left wingers would NEVER allow that to happen! No matter how many people die!!
Just look at what Bed Bugs are doing in the U.S.A.
of course this is simple natural selection. Most mosquitoes do not live for more than a few weeks or months. so it is highly unlikely to be a learned behavior.
almost certainly, those that already preferred 5:00 AM breakfast buffets, survived when their night owl cousins, starved.
I agree. This appears to be natural selection. If it was simply hungry mosquitoes not getting a meal at their preferred time so eating later in the night the effect would be almost immediate and not change much over the years.
The expert quoted in the article as saying that there was not enough time for selection maybe was not thinking of the controlled experiments in the lab that show you can alter heritable behavior of a population in relatively few generations. I remember a classic study using fruit flies that showed a heritable change of attraction of smell and flight patterns (using tube mazes that allowed flies to have a choice and then allowing the flies choosing particular paths to breed) in I think about ten generations. I forget exactly but since fruit flies have a one month generation the experiment was unlikely to go on much longer than that. Certainly a few years would be enough time for an animal with such a short life cycle if the selective pressure was strong enough.
Ditto.
It wouldn't take that many life cycles for mosquitoes that did their biting early in the morning to reproduce at much higher rates than those during sleeping hours. After not too many generations, the majority of mosquitoes would be morning feeders.
Since their time of female mosquitoes feeding on blood is triggered somehow by the time of day (or more accurately night), it wouldn't need to be much of a mutation to alter that time trigger just a bit.
Wow, a brain the size of a mosquito and they apparently can reason. Two thoughts: How long before they have nuclear weapons? Or, perhaps we can transplant the brains into politicians.
Hey Bob,,,
Good post, thanks. (However, I think we already have blood sucking politicians.)
I am glad however, for any on-going study of mosquitoes. They are quite possibly the most dangerous animal on the planet.
They are second most dangerous behind the politicians.
Mosquitoes have (indirectly, to be fair) killed more people over the course of humanity's lifetime than all the wars and famines put together. They are nature's dirty syringes.
That said, they're also a really important part of the food chain, so we probably can't kill them all without causing severe damage to the ecosystems where they live. Hmmm...
Flies have also killed more people than all the wars combined!!
These mosquitos were breed in Area 51 and have since spread out over the world. They observed the technological science there and have since evolved.
I like your conspiracy theory... it's rather silly.
Interesting finding - Are we witnessing an ability within Nature to adjust?
NO, It's called adaptation.
It's the same thing girls.
It's not technically the same thing (evolution refers to gradual changes to a species' genetic code over time, while adaptation is simply finding a way to better exploit the environment), but close enough.
For those keeping score, this is indeed adaptation.
or it is natural selection. in just 3 years, evolution is not likely.
Those mosquitoes that already evolved to prefer mornings simply kept eating and the night owls starved.
Howy - change due to natural selection is an example of evolution and a few years is enough time for a short lived species like mosquitoes to undergo adaptive evolution. It's not speciation if that's what you mean.
I'm not saying this was conclusively shown in this case yet but the evidence supports adaptive evolution through the process of natural selection. A study showing the heritability of feeding behavior and variation in the population would support the claim.
It's weird how we are all talking about the same thing but using different terms.
This isn't evolution. It is a change in the behavior of the bug's prey. The percentage of outdoor bites increased when it became harder for them to bite indoors. That's pretty freakin obvious. Their preferred time to bite was 2-3am. Since this is when people are asleep under nets, the bugs now bite when people first come outside - 5am!
This is not surprising, amazing, or interesting. It is not a behavior change except to say they bite when food is available.
radagast - it depends - they really ought to have checked behavior right after introduction of the nets to distinguish behavior response of individuals from changes in the populations behavior over time which would indicate evolution.
However, since malaria transmission went down initially and then back up after a while there is some evolutionary change. That doesn't mean that the difference in mosquito behavior is the change increasing malaria spread but it may. Another possibility is an increased resistance to the insecticides on the nets as the article stated.
DDT at 5AM will take care of the problem. But that's not PC is it?
WHO's anti-malaria campaign of the 1950s and 1960s relied heavily on DDT and the results were promising, though temporary.
There were not deaths to malaria “unnecessary” due to a ban on DDT which never occurred in Africa or Asia, while DDT was plentiful and cheap to anyone who wanted to use it (still pretty much the case today). Let’s repeat that: DDT has never been banned in Africa or Asia.
Largely without DDT (though DDT is not banned), malaria infections fell from peak DDT-use years of 1959 and 1960, from 500 million infections per year, to fewer than 250 million infections today — that’s a decrease of 50%. Phenomenal when we consider the population of the world has doubled in the same time. Deaths dropped from 4 million annually in those peak-DDT-use years to fewer than 800,000 per year today — a decrease of more than 75%. Progress continues, with Integrated PestManagement (IPM); bednets now do better, and more cheaply, what DDT used to do but largely cannot anymore — stop the bites.
Maybe the mosquitoes fly around all night and cannot find anything to bite so they keep looking until dawn.
If these mosquitos put in overtime and it's not in the contract you know they are scabs.
You know what the difference between a mosquito and a politician is?
A mosquito just sucks your blood; a politician will suck the marrow out of your bones.
Also, the politicians have smaller brains.
A mosquito and a politician will both suck your blood. The mosquito won't tell you it's for your own (or the common) good.
Another difference: One is a predatory blood-sucker. The other is an insect.
is that the same as a Mama Grizzly with Lipstick?
Yes, yes Howy61, You are so cool, calm and collected. Just French kiss that Mama Grizzly all night long and you won't notice a single Mosquito bite.
Duh. Mosquitoes go where the food is. Who would have thunk it?
Of course there is a higher percentage of bites during the day if the nighttime biting was curtailed. The question is are there a higher number of bites during the day... I would imagine there would be an increase because the hungry ones that did not get fed at night will still be on the prowl later in the night/morning. The real, most important, question is are there fewer bites overall or have we just changed when they happen? I hope we are seeing fewer bites and less disease!
Of course - just as the proportion of outside bites will increase if inside bites decrease. Numbers please?
You aren't, by chance, a government grant writer, are you?
The thing is that mosquitoes can't really hunt during the day without getting eaten by something else. There are a lot more predators out and about, and mosquitoes are a prime food source. So any change in the availability of food would have to be weighed against the chances of BECOMING food.
Either poor experimental design or poor reporting/editing regarding the percentages. I suspect the latter.
I am appalled that no one else caught on to this. I guess that's what happens when you substitute an agenda for critical thinking.
I don't think it's agenda - I think the numbers are there in tables in the scientific paper, but the reporter has to distill the info into a reportable summary, so probably used the info in the abstract or in the conclusion.
No need for conspiracy or agenda, just an attempt to translate scientific language into everyday language in a relatively concise manner.
Why not use sticky strips that they stick to when they land on them. Or baited traps with very small holes so they kill only mosquitoes and not other insects that may be beneficial. (Sticky traps might also work for politicians so they can feel how frustrated we feel sometimes.)
You'd have to place sticky strips all over your body to catch them... also, it's hard to "bait" mosquitoes since they're attracted to the CO2 released from humans. That's why the most effective means of getting rid of them developed so far is to put a poisonous barrier between them and their target; mosquitoes zero in on the human but have a hard time detecting the net.
The mosquitoes magnet is the BEST way to catch them it releases CO2 to attract them.
Don't know if either of you check back but thanks for the information.
You can't fool Mother Nature.
Mosquitoes have no intellect! This is adaptation by Natural Selection. I hope Obama reads this article and stops interfering with the process of human evolution. The beautiful creatures we are today is because of the relentless pressures of evolution and natural selection. If Nature was socialist we would still be amoebas...
What?!?! Evolution? Obama? You must be confused because it's the republicans that don't believe in Evolution. Read the bible. That's where all their answers are.
Or we are the species we are today because of our tendency to work in groups for the common good - 99% of human history was spent very successfully in small egalitarian hunter-gatherer groups.
Bats eat tons of mosquitoes. Plant palm trees. Maybe the nets would work better without the chemicals that drive them away.
Fly paper also works well to catch mosquitoes.
Years ago I read a report that said you could get AIDS or Malaria but not both. If you had either you would not get the other. The report didn't say why. Find a natural enemy of mosquito's and import them. Just don't forget to have a remedy for the prevention.
There's no environment that has mosquitoes that doesn't also have an abundance of mosquito predators. They're a prime food source wherever they live. So I doubt bringing in more predators will really impact the mosquito population more than the other populations (importing foreign species has a mixed record for success).
Wade - that is pretty silly. If you've had malaria you should still wrap it up!
Everyone in Africa has had malaria. Africa has the highest rates of AIDS. Do the math. That nonsense is just some of the retarded crap that came out of South Africa's war against the science of AIDS in the past 25 years. They also said that condoms GIVE you AIDS and that Western medicine makes you gay.
Please do not repeat those ridiculous lies.
Wade may have it confused just a bit. Sickle-cell anemia does inhibit malaria, which is probably why this detrimental genetic disease persists in Africa. Mild cases of the anemia give an immune advantage against malaria, but the severe cases are as bad or worse than the malaria itself.
HIV, on the other hand, mainly infects the white blood cells responsible for immunity. People with HIV/aids would be more susceptible.
So let me see if I got this straight...
The nets seem to be working, so mosquitoes are feeding at other times in the day.
Leave it to the French to come to this fascinating conclusion. No wonder they're broke.
@ Sluggo...I think you missed the obvious; it isn't just France.
France is broke for the same reason everyone else is: overpopulation.
Population density also increases the frequency of exposure, the variety, and the lethality of diseases- and the populations of vectors like mosquitoes.
Regardless...you won't see politicians asking people not to have kids, or censuring people with large families- whether they can feed them without government assistance or not.
Worse, several religions promote breeding as a political tactic (more people means more votes) in an era when the carrying capacity of most global environments has been reached or exceeded.
No one has found an effective long-term way to reduce population growth; most efforts to date have resulted only in the smartest people- who see the danger most clearly- having the fewest kids.
As a consequence, we're selecting for stupid- which is bad.
If that meme prevails, population growth will accelerate- so we'll inevitably break every bank out there, literal and figurative, and then a lot of people will die.
Hey Sluggo
We're broke too.
Mosquitoes carry a variety of diseases- and penetrate the skin to feed, delivering those diseases directly into our bloodstream.
At the bottom, there's a link to a website with broad information on mosquitoes, including what they might be carrying in your area and ways to eliminate or reduce both the local population of mosquitoes and your exposure to them.
Given the uptick in incidents of West Nile and the potential for introduction of Dengue, Yellow Fever and Malaria to the United States- global warming, regardless of what you may think causes it, makes this more likely with every passing year- it's worth a few minutes of your time to read up on them- before they feed up on you.
http://www.mosquito.org
Mosquitoes may just be smarter than we give them credit for.
I am sure PETA will be all over it and demanding protection for them.
DDT. The EPA ignored the evidence and banned it anyway.
http://whatthecrap.wordpress.com/2007/07/03/the-ban-of-ddt-science-that-wasnt/
http://www.foxnews.com/story/0,2933,55843,00.html
http://www.21stcenturysciencetech.com/articles/summ02/DDT.html
Interesting. I had heard about the negative effects of DDT, but I never knew that there was a scientific counter-claim.
SF - those are NOT scientific counter claims. They have become conspiracy bull@!$%# spread by conservatives who hate the EPA. Michael Crichton is well known for his refusal to believe anything scientific that he can't warp into a B-rated book about science gone wrong.
There was a great deal of deliberation and scientific evidence besides the slanted right-wing ideas in the links above. In the end the courts and the scientific world found more than enough evidence to ban DDT. The links above point to a few game birds suggesting that hunting was the primary cause for their disappearance. Yet thousands of species of birds were dwindling - their shells not fully formed, or formed too thinly. DDE levels in the shells were found to coincide directly with the amount of malformation. In the few tests where DDT was fed directly to birds (in one instance pheasants) it was not administered in real world doses nor was it administered long enough to build up in the animals' system. This was discussed in many court cases. The links above are merely a rehash of just one small part of the controversy - without bothering to give the final outcomes or the counter - counter evidence that refutes it. This is a familiar tactic by those who deny facts and history.
DDT is poisonous to birds.
Two million Blacks die each year from malaria while US Liberals ban DDT which was used to wipe malaria out in the US. Genocide by Democrats!
Jamie - WTF?
Malaria has never been a problem in the USA. That is a tropical disease. Also DDT kills birds. I bet you don't remember the book Silent Spring about the disappearance of songbirds? I guess you don't remember that bald eagles were a rare sight until DDT was banned? Spray on some OFF and you'll be fine. Dump out standing water on your property and you won't have mosquitoes.
Good lord.
DDT was banned in 1972. Let's see now, who was president in 1972?
It's elementary my dear Watson. The nobility behind the BIS in Basel consider most Africans as well as 2 Billion others who live on $2 or less a day to be useless eaters who ought to be eliminated for the welfare and sustainability of the Global enviroment. These world-ruling, faux-liberals are irritated by the dogooders trying to save the ones they want eliminated.
Seriously? This study is basing this supposed change in behavior on the percentages of outdoor versus indoor bites? Of course indoor bites will go down with the nets, so the real data isn't in what percentage of the bites were inside or out, but how many bites were inside or out. The number of outdoor bites could be remaining unchanged, yet the percentage would go up if there were less indoors.
And if the hours of biting have changed, well that is because the mosquitoes are still hungry. This isn't exactly a change in behavior of the mosquitoes, but a change in the availability of its prey. I'm sure they would prefer to bite in the earlier hours of 2-3 rather than at 5am. The only way to test if the mosquitoes have truly changed their behaviors is to remove the nets and see if they keep biting at 5am and if the bites continue to be predominantly outside.
Then again, it's Africa. So who really cares?
Daylight savings time is the answer. Cured every problem in the USA.
pos web site
It s obvious the mosquitoes are smarter then the people..
Yes, mosquitos are smarter than some people Al. You may be one of them. Are you smarter than a 5th Grader? Take the test. Try to multiply faster than a mosquito. Then define a bit, a bite and an 8 bit byte before the mosquitos gets 8 bites in.
how adaptive. so are people.
When we have: Africa for Africans, Asia for Asians, White Countries for Everybody, what do we have overtime?
We have solid Black only and Solid Asian only countries, exclusively for Blacks and Asians, based upon exclusive genetics and culture. Culture is respected and so tolerable to these groups. They do not need to tolerate massive inflows of invaders and made to tolerate foreign cultures.
We have more and more non-whites in White countries since the right of Whites to exclusive territory is denied them.
We have fewer and fewer White people.
When we mix more non-whites and fewer Whites in the same living space, what do we get?
In time, White extinction. Its called White genocide because this does not happen by chance. It is being forced upon Whites just like a rapist does not take no for an answer.
How is this not so? How is this not White genocide?
Anti-racist is a codeword for anti-white.