DEADLY CARGO: The Anopheles mosquito carries the malaria parasite responsible for disease and death in much of the tropics.
Image: EVA-MARIA PASIEKA Corbis
In Brief
- Vaccines against malaria have encountered repeated failures. New technological approaches have revived the push for an agent that would provide lifelong immunity.
- Late-stage clinical trials will finish this winter on a vaccine that has been under development since the 1980s. It could reduce cases of the most lethal form of malaria by half.
- Even as this work moves forward, researchers are proceeding with other strategies for new vaccines, such as a weakened form of the parasite that is cultured in mosquitoes.
- Because malaria has been so hard to fight in the past, researchers must moderate outsize expectations to keep hopes from being dashed yet another time if new vaccine candidates fail.
More In This Article
Right now, somewhere in the world—in a petri dish in Baltimore, maybe, or in the salivary glands of a laboratory-bred mosquito in Seattle, or in the bloodstream of a villager in Ghana—resides a chemical compound that could help eradicate human history’s biggest killer. Scientists have many promising malaria vaccine candidates in the works, and for the first time one has reached advanced human trials. If it or another candidate is even partly effective in people, it could save the lives of millions of children and pregnant women. It would be the only vaccine yet developed against a human parasite, an achievement of Nobel caliber. And it could, in its first-generation form, be distributed in Africa as soon as 2015.
“If all goes well, five years from today, a vaccine could start being implemented in a wide way in six- to 12-week-old children,” says Joe Cohen, a scientist who is leading some of the most promising research. “It is a fantastic achievement. We are all very proud of that.” This is an extraordinary moment for malaria vaccine research. So why isn’t Regina Rabinovich singing from the rooftops?
This article was originally published with the title Halting the World's Most Lethal Parasite.
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23 Comments
Add Comment"History's biggest killer" can be controlled with DDT.
Reply | Report Abuse | Link to thisIt is safe, cheap, effective and we have it now.
While we watch malaria rates increase in the third world and the risk of its reintroduction to developed nations,(it happened with bed bugs),we have a weapon of mass survival sitting on the shelf because of unfounded fears.
I have to agree. But, this is what happens when human life is either not valued, or given the same value as a bird whose egg shells may become thinner as a result of it indirectly consuming DDT. Who was it that say "Look at the birds of the air ... are you not of more value than they?" I guess we have our answer!
Reply | Report Abuse | Link to thisWow. I agree that human life is more important then animals, but if there it
Reply | Report Abuse | Link to thisis an option for both why not explore it?
Most of the places where malaria kills people DDT is still used. They quit using DDT in US because it decimated the bird populations and it was becoming useless. Roaches could actually eat the stuff
Reply | Report Abuse | Link to thisI have extensive experience with vector control efforts in western N. America, particularly with mosquito abatement.
Reply | Report Abuse | Link to thisThe effectiveness of DDT is limited by the development of resistance in the target species. Applications of a spectrum of products, each used in turn then retired for a time, is much more effective in mosquito control efforts.
Even more effective is the application of Bti to larval habitats prior to emergence of adults. Integrated pest management, striking at every stage of development in the life cycle of the target species is even more effective.
Once you have infected adults in the air, the genie is out of the bottle.
Oddly, the introduction of the three spine stickleback, a small but voracious and hardy fish, into larval habitats, is a fairly effective control measure due to it's edge water feeding habits.
Like so many other compounds, DDT is persistent and accumulative in the environment, and it's long term application is ultimately counter productive. I invite you to investigate the history of DDT and review the actual results and compare it to the collateral damage it inevitably provokes, only to loose its efficacy after several years of use. Clearly, DDT is not the answer to the problem of malaria.
The relief this substance provides is temporary, but the adverse consequences of it's prolonged use endure much longer. You may find it useful to spend a decade or two in the field, engaged in actual vector control efforts before you jump to unfounded and confounded conclusions.
l
Quote: Oddly, the introduction of the three spine stickleback, a small but voracious and hardy fish, into larval habitats, is a fairly effective control measure due to it's edge water feeding habits.
Reply | Report Abuse | Link to thisAnswer: Why would you find that odd ? I was thinking what IF people disposed of their waste cooking oil into water containing larval habitats. WOULD that disallow the mosquitos from acquiring the air they need in the larval stage ?
llwellyn, I too have had "extensive experience with vector control",(30 years), but in the Southern U.S. and 2 years in Afghanistan.DDT works as a powerful, non-contact repellent and contact irritant, this was proven in the 1940's before the first instance of DDT resistance in mosquitos was found.Using IVC, (integrated vector control), that you described is not cost effective, applicable and unproven for malaria control.DDT for malaria control, especially in rural areas is cheap, has long residual, repellency, irritant actions and is safe.Records from North, Central and South America show as numbers of DDT-sprayed houses declined, malaria incidence increased.A spot treatment the size of a dime sprayed on an inside wall of a house can protect a whole family from malaria and death for one year at a cost of less than a dollar.DDT saves lives and money.
Reply | Report Abuse | Link to thisIn response to ironjustice:
Reply | Report Abuse | Link to thisSurface treatments such as oils are not as effective against larva as they are for pupa, since some larva have some ability to clean their siphon tubes. The oil must spread aggressively and be applied in a timely fashion at rates sufficient to cover all the surface. Left over cooking oils are generally poor at this. (I've tried a lot of products) When the water contains heavy vegetation such as algae mats or duck weed, surface treatments fail, regardless of the quality of the product. A successful application unfortunately also reduces populations of many non target species just as effectively as it limits the mosquito population.
The success of the three spine stickle back fish was a surprise to me when you consider that an almost completely successful predator that succeeds in the near elimination of a prey species suffers it's own subsequent crash.
As it turns out, this fish is a non discriminating predator, chomping on just about anything it can fit it's mouth around. This can also result in population reductions of non target species. There are limits though. Regular floods must endure long enough to distribute the fish throughout the watershed, and species that prey on this fish can exercise a degree of control on its spread and effectiveness. And of course, there is the ever present limiting factor of available food.
Look at the problem this way:
Reply | Report Abuse | Link to thisIf you have fire burning somewhere, and the smoke is a problem, is it more effective to try to deal with the smoke, or to go put out the fire? In areas where mosquito populations breed year around, and therefore serve as a vector for the parasite year around, the treatment of homes with DDT is helpful, but only until the mosquitoes acquire resistance. Next, people do not live their entire lives in their homes. They go to work. They socialize and conduct a great deal of business outdoors.
As far as home treatments go, there are other products that work fairly well and do not share the resistance problem exhibited by DDT. They do cost more though.
I will grant you that money for mosquito abatement in third world countries is woefully inadequate, and in my opinion, if those folks were white Christians, the problem would have been more promptly addressed with outside aid. That leaves folks like you with very meager resources to to conduct successful integrated pest management programs, which are comparatively expensive. On the other hand, IPM programs conducted correctly are VERY effective. I've done that. It works.
Source reduction, while labor intensive, can be effective in some instances. In efforts such as these, you're actually reducing fuel for the fire rather than dealing with the smoke. I'd also like to mention that window and door screens are almost as effective as DDT, but they again require money, maintenance, and community education. I do understand that money is in very short supply in your area of the world. None the less, an aggressive campaign using DDT,( or any organo-phosphate), will eventually backfire when the target species acquire resistance, and by the very nature of the compounds you apparently advocate, they will. Then what? Then, you're stuck back where you were to began with, without a anything to use, and the kids get sick and die again. Where's the profit for the community? A program such as you propose has a life span of about 6 years. So do that if it works for now, but plan to change gears, because you will eventually have to. Attack the critters where they breed. Drain what water you can. Put fish in the rice fields. Float oil on breeding water when and where it will work but use care. Screen windows and doors and make sure people use them. Use bedding nets when possible. Attack every part of the life cycle of mosquitoes you can.
Relying on a single element of control will fail, no matter how much you spend.
Respectfully submitted,l.
Anopheles mosquitoes enter houses between 5 p.m.to 9:30 p.m. and during early hours of morning. The mosquitos start biting late in the evening, the peak of biting activity is midnight and early hours of morning.Most women & children are in bed in Third world countries at this time.The residual, repellency and irritant actions of DDT keeps out even resistance mosquitoes.DDT has not failed yet, it either kills or repels anopheles mosquitoes.IVM works in the westerm North American middle class suburbs but not in tropical, monsoon affected Third World nations.
Reply | Report Abuse | Link to thisBottom line DDT saves lives and is cost effective.
If it works use it. It's still manufactured and distributed where laws do not prohibit it.
Reply | Report Abuse | Link to thisMirco-encapsulated pyrethrins accomplish the same thing, and do not exhibit the same mammalian toxicity as organophosphates. Nor are resistance problems as severe. Have you considered using it once every seven years to address the resistance problem?
As I mentioned before, window and door screens accomplish the same thing. A wet rag tossed at resting adults gets them too.
It sounds to me as though the adults must wait until a flight envelope opens in the wee morning hours when interior temperatures drop. Mosquito nets here would serve you very well. DDT and mosquito nets. Two elements. That is the beginning of IPM.
Here, anopheles species are dealt with mostly in the larval stage with IPM techniques. (Putting out the fire rather than dealing with the smoke) If you have the resources and labor, it works very well indeed, though I do understand that tropical locations in third world countries can ill afford that protection due to poverty, and a lot of water almost year around. It's not that it doesn't work there though, it's because no one there can afford the necessary measures. It's a lot of dog gone work, and as you know, the products aren't cheap. If you had the money, it sounds to me like your understanding is up to the task to beat the problem.
There, I imagine a lot of households keep free ranging chickens and other fowl, which as you know, serve as viral reservoirs. Here, in many locations, domestic fowl are not legal to keep close at hand for that very reason.
Still, I stand by my first inclination, that a mosquito control problem based on a single element of control will eventually fail.
By all means, if DDT works for a while, and lives are saved, do that. Just don't be too surprised that the effectiveness of your efforts gradually diminishes over time. Because it will. Not because I say it will, but because mosquitoes adapt and respond to environmental changes very rapidly. Here, we worry about mosquito born viral diseases when drought conditions compress the water fowl and mosquito breeding seasons together in both time and space. Of course, you already know to watch your bird migrations, and particularly when newly hatched birds are confined to nests with no feathers. Birds are a big part of the life cycle of the pathogen. Two elements of amplification, and the weather that drives the water that drives them. Attack on every front you can. One life lost to this is one to many.
l
Quote: attractants of plant origin (fruit or flowers) with a toxic sugar bait can reduce the populations of the malaria-transmitting mosquitoes
Reply | Report Abuse | Link to thisAnswer: I had wondered the above about malaria when I had read killer bees were / are attracted to citrus. I wondered whether the northward bound bees could be halted if the US were to establish a 'line' of greenhouses which would 'catch' the influx of bees at the narrowest point between Mexico and the US. The influx of bees has become established in the US so I think the 'window' was missed. But it seems it may have worked ?
Anyone know how they would use citrus fruits as BAIT and STILL use it as a repellant ?
Reply | Report Abuse | Link to this"How to Make a Natural Mosquito Repellant"
Soak the rinds of your citrus fruits in water for several days to infuse the scent in the water.
Bottle your homemade infusion in the spray bottle"
"Attractants of plant origin (fruit or flowers) with a toxic sugar bait can reduce the populations of the malaria-transmitting mosquitoes"
DDT is not an OP, it is a Chlorinated Hydrocarbon, big difference.You are wrong about resistance,pyrethroid resistance is widespread in western and southern Africa and was first reported in the late 1990's. Studies show that mosquitoes resistance to both DDT and pyrethroids are also repelled by DDT but not pyrethroids.The repellant action of DDT also reduces bites and malaria transmission;I quote a WHO researcher that explained,"...it will not kill them but their DNA is frightened of it."
Reply | Report Abuse | Link to thisCorrect me if I am wrong but birds are not a reservoir for the human malaria parasite although there was reports of human deaths in Asia of monkey malaria last year.
The USDA and state agencies set up AHB traps everywhere along that line.Some got through.AHBs can take over EHB hives, both managed and feral colonies.We are just going to have to learn to live with them.
Reply | Report Abuse | Link to thisThe fruit is the bait , the peel and oils in it might be the repellent. A bait cannot be repellent.
Reply | Report Abuse | Link to thisJust use Deet, it is EPA and CDC recommended.
You are correct that I mistakenly identified DDT as an OP. It is not. You are also correct that birds have not yet been demonstrated to be a reservoir of human malaria. I did however state correctly that DDT is persistent and accumulative. It's use in agriculture earned it a world wide reputation as a bane to wildlife. In this regard it is at least as bad as, (perhaps worse?), than the OP's which are bad enough. So while it's very limited household application as a repellent may be immediately effective, you will likely see less mosquitoes in homes, (a very good thing), but more resting behavior outside, beneath the overhangs of a roof for instance. (perhaps not such a good thing) DDT saved many hundreds of thousands of lives, perhaps millions of lives. So have antibiotics.
Reply | Report Abuse | Link to thisYou correctly state that pyrethroid resistance has been demonstrated. In fact though, almost any substance continuously used non stop invokes resistance, including antibiotics. That is why IPM recommends a resting period for applications of almost any product. I once again without reservation state that a correctly administered IPM program will work anywhere, though with year around mosquito production in the tropics, the expense often exceeds what local, regional, or national governments feel they can allocate. Sadly, they often show no such reservations regarding weapons procurement.
Market driven, market driven, market driven.
Your best choice now, under the circumstances I imagine you must operate in, is DDT. I believe though, that in the long run, given the character of mosquitoes, and of this substance, it's selection is much less attractive. But that topic is not strictly a vector control one. Because vector control involves the manipulation of biological systems though, it is a topic that ought not to be ignored in vector control decisions. Even the prolonged use of Bti as a larvacide can lead to resistance. Switching products from time to time can help greatly reduce the problem. In my opinion, as far as home protection goes, sturdy screens are by far and away the very best bet. They are effective against much more than mosquitoes, and if care is taken in the installation and maintenance, They can last more than long enough to pay for themselves....and they eliminate the use of any compounds.
Well, shifting gears to dengue fever,an outbreak,local according to the CDC, in the Florida Keys seems to have spread to Miami.The Florida Mosquito Control Association founded in 1922, following an epidemic of dengue fever in Miami, has come full circle.
Reply | Report Abuse | Link to thisI'm sorry to hear that.
Reply | Report Abuse | Link to thisBefore I stepped away from the trade, my concerns were almost exclusively focused on mosquitoes that pack one sort of arbovirus or another. Anopheles are present here, but fortunately the parasite is not. Yet. Aedes are present here, but fortunately not aegypti. Yet. We were constantly worried over a host of Aedes species, with a scattering of critical Culex and Culiseta, and a few much less dominant species of several other genera. Beneath one of the worlds great migratory routes, we have many birds that winter over in the tropics, sometimes very significant snowfalls, flood irrigation, and feisty rivers hosting difficult marsh lands full of a host of birds.
Fortunately we have hard winters in the inland mountains, so year around mosquito production is not the problem it is to the south in California or in the coastal ranges and valleys where the temperate rain forests and agriculture dominates. Our snow pool hatches are something to see, and our local rivers are in flood for the entire summer due to irrigation reservoirs in the highlands. And we have Aedes vexans as well.
Fortunately we have sticklebacks and water bugs, and compared to a region like Afghanistan, money to devote to mosquito abatement.
Dengue sucks, and I'm really surprised you have not mentioned it, since some parts to the country there ought to provide good habitat for aegypti. I'm relieved, (and puzzled), to see that Afghanistan was not trashed like Pakistan. The coming of winter should put some of the mosquito borne disease concerns to bed for a while, but it may very well bring it's own brand of further misery to the folks already rendered homeless, with poor prospects for next year's crops. And then, you have social discord and war to deal with as well. One of the last things on the minds of authorities in such troubled times are mosquitoes. And perhaps worst yet, the Afghanistan has attracted the attention of the industrialized world due to the remarkable mineral deposits dicsovered in years most recent. I come from mining country, and although it does generate revenue, if it is not conducted correctly, it leaves a mess behind that rivals the ravages of war, expressed for generations to come.
As if that region of the planet didn't already have enough trouble.
l
Afghanistan is a mostly DRY place,the Northwest and Northeast get most of the rain. I guess the floods in Pakistan increased the mosquito population.Dengue wasn't a problem when I was there '06 to'09.Malaria and leishmaniasis and the Taliban were the main concern. I was a DOD contractor. I worked with the Army's Preventive Med, USAID,ISAF and NATO forces.Did you know that a rodent glue board can stop bleeding almost as fast as a hemcon bandage?
Reply | Report Abuse | Link to thisMost water bugs in Asia and Africa carry the bacteria that causes Buruli ulcer disease so they are not used very much there.
Regarding DDT: The worst aspect of its use was that it was widespread, used on fields and sprayed from planes. If sprayed on walls where people live, it will be used where the most dangerous mosquitoes are, will cost very little, will have little environmental impact, mosquitoes won't have a chance to gain immunity as quickly since only those threatening humans will be affected.
Reply | Report Abuse | Link to thisAnother thought altogether regarding the concept of immunizing mosquitoes from malaria using humans as vectors: It should be possible to immunize mosquitoes earlier in their life cycle than just when they bite humans. Place in whatever they normally feed upon or in other animals if they take the blood meal from others.
Remember me when you get your Nobel Prize.
Doctor Tom Kollars with MEVLABS has developed a new mosquito bait that is very sucessful and safe. Check out the provector flower or mevlabs online.
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