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# Posted 5:57 PM by David Adesnik
DDT REDUX: Many thanks to all of you have written in with links and opinions about the relationship between DDT and malaria in the developing world, a subject about which I still have much to learn.
Before getting to the more complex issue of whether DDT can prevent malaria, I'd like to address the straightforward factual question of whether there is currently a ban on the use of DDT. Nick Kristof suggested that such a ban exists. Citing the Malaria Foundation International (MFI), Tim Lambert responded that Kristof was simply wrong. The Belmont Club (Hat tip: TB) responds, however, that MFI wouldn't be celebrating its efforts to prevent a ban unless there had been a very strong push by environmentalists to impose one.
This brings us to the issue of whether there is a sort of implicit or de facto ban on the use of DDT that results from European pressure on the developing world. Blogger CR points to this article as an example of how the EU can impose such a ban by threatening to close its markets to nations such as Uganda that want to use to DDT to stop the spread of malaria. Moreover, according to RF,
While there is no international ban on DDT use, western aid agencies often provide a large percentage of the anti-malaria budgets of many poorer nations. These agencies are opposed to using DDT for malaria prevention, probably due to bans on its use in their own countries. Without this funding to support DDT spraying, these nations can not afford it and are forced to adopt less cost effective measures encouraged by western agencies.
The reluctance of donors to fund DDT spraying is also cited as a major obstacle by Tina Rosenberg, whose NYT Magazine article on malaria and DDT seems to have influenced Nicholas Kristof.
When it comes to the issue of whether spraying is effective, I'd like to thank JZ of Africa Fighting Malaria (AFM) for sending in a long letter on this subject. As JZ points out, AFM is prominent advocate of increasing the use of DDT, so hers should not be considered an impartial opinion. JZ is still confident, however, that there is enough evidence on her side to overcome potential concerns about bias. As she points out,
DDT is a powerful spatial repellent, [and] this characteristic of it keeps mosquitoes from entering the house. Second[,] for the mosquitoes that do enter the house, DDT is a powerful contact irritant.
Anopheles mosquitoes like to hang out on the walls for a bit and groove before biting. When they come into contact with DDT, they [become] tetchy and some are so irritated by it that they will exit the house without biting. Third[,] DDT is toxic to mosquitoes, and will kill some preventing the from spreading malaria further.
JZ acknowledges that mosquitos have often developed resistance to DDT and that this is a serious challenge for disease prevention efforts. Nonetheless, DDT has scored some important victories over malaria even in recent times:
The classic example is [the] experience of South Africa in the late 1990's, where the reintroduction of DDT combined with the introduction of Coartem as a first treatment dropped malaria rates by 80% in one year in KwaZulu Natal province. South Africa's experience has been duplicated in Zambia, where an area using [indoor residual spraying] dropped malaria rates by 50% one year and another 50% the next.
Sounds good to me. But once again, I am only beginning to learn about this issue so my opinions are very much open to new arguments evidence.
For those interested in more information about malaria and DDT, reader CH recommends this article from the Washington Monthly and reader NJ says he attended an informative lecture by Paul Driessen, author of Eco-Imperialism: Green Power, Black Death.
University of Maryland scientists are working on a genetically-engineered fungus that would kill the malaria parasite. The battle against malaria continues to challenge doctors, scientists, and public health officials. Now, a team of British and American scientists have developed a novel and promising approach to malaria control. Malaria kills about a million victims a year, mostly children in Africa, and almost half the world's population is at risk. The malaria parasite is carried from victim to victim by mosquitoes, which are increasingly developing resistance to the insecticides used to kill them.
As an alternative to chemicals, University of Maryland professor Raymond St. Leger and his colleagues have been working on a genetically-engineered fungus to control malaria-carrying mosquitoes. One possibility they considered was using the fungus to kill the mosquito, the way insecticides do. "The problem with that is, if the mosquitoes have evolved resistance against chemical insecticides, they could also evolve resistance against the pathogen," St. Leger explained. "So we did something different. We took genes which encode anti-malarial, anti-parasite proteins - so we put those into the fungus."
The result is a fungus that kills the parasite directly. And, the genetic modification of the fungus could be adjusted to counter resistance in the malaria parasite as it evolves. St. Leger says the anti-malaria fungus could be used just like chemical insecticides. "So you could apply it on cotton sheets hanging inside houses which the mosquitoes would light on - netting, bed netting, on walls, baited traps or as sprays. That's how it could be applied, just [as] you would apply a chemical insecticide," he says. It may be a couple of years before this modified fungus is approved for use. But it wouldn't be the first fungus-based product on the market. A similar modified fungus is already in use against locusts in Africa, Australia and China, and at a cost comparable to chemical insecticides.
And St. Leger says that using genetically-modified fungi to control disease may be a very promising field, for example, in a disease carried by ticks. "We can put a gene for an antibody there which will knock out lyme disease. We're working with another strain which attacks the parasites in tsetse fly. Dengue virus is also susceptible to a particular gene we're working with. So we can actually manipulate and model these pathogens to produce specific pathogens targeted to different insects."
Source
The most effective anti-malaria treatment developed so far is artemisinin, a plant-derived drug that is expensive and often unavailable. Now, after a decade-long research effort, scientists have found a novel way to cheaply mass-produce artemisinin. The new, bio-synthetic version of the drug could be a major advance in the battle against malaria. Whenever he travels to Africa, Jack Newman says he arrives prepared with his own supply of artemisinin. I always keep it in my back pocket in case I get malaria," said Newman. "Again, in three days you are cured. The American researcher hopes others infected with the parasitic illness might soon have easy access to the drug, too. Newman is co-founder of Amyris, a U.S. biotechnology company that, in collaboration with researchers at the University of California Berkeley and the Canadian National Research Council, developed a process for making large quantities of a semi-synthetic version of artemisinin, offering people with uncomplicated malaria a cure in just three days.
A young girl with malaria rests in the inpatient ward of the Malualkon Primary Health Care Center in Malualkon, in the South Sudanese state of Northern Bahr el-Ghazal
Artemisinin is a compound that until now has been derived exclusively from an ancient, bitter herb called wormwood. It is up to 95 percent effective in curing uncomplicated malaria infections but, because it is derived from a plant, artemisinin is frequently in short supply, and expensive. Newman and his colleagues figured out a way to make an unlimited supply of artemisinin using a technique that combines biotechnology and a simple yeast fermentation process. He says they extracted DNA from the wormwood plant and inserted it into yeast cells ..to fire up a big fermentation, like beer fermentation, but instead of making beer, you are actually making [an] anti-malarial drug," he said. "And you can do it in hundreds of thousands of gallons and, of course, make it in an industrial fashion, the same way we make penicillin; very, very inexpensively. The process yields a chemical precursor to artemisinin, which is used in the production of the drug.
The innovation was made possible in large part by grants totaling $53.3 million from the Bill and Melinda Gates Foundation to the drug development arm of PATH, an international non-profit group that has been leading the fight against malaria and other diseases. PATH helped move the artemisinin research out of the UC Berkeley labs to Amyris for scale-up, and then to the pharmaceutical company Sanofi Pasteur, for production of the yeast-based artemisinin. The company says it is distributing the drug free of charge. Sanofi also plans to share the recipe with other drug makers so they, too, can use the technology to manufacture and distribute it on a no profit, no loss basis, according to Amyris's Jack Newman. Basically, by using synthetic biology, weve been able to stabilize the production so theres always material available and make it at a very low cost," he said.
Newman says the yeast-based drug is identical to plant-derived artemisinin in terms of effectiveness. It is being formulated with a second anti-malaria compound to reduce the chances of drug resistance. So far, Newman says, Sanofi plans to make 70 million doses of what he calls malaria cures this year. Using synthetic biology, next year the company will scale up production to 120 million doses, which will be distributed globally pending World Health Organization approval. Jack Newman and his colleagues describe their production of a semi-synthetic version of the anti-malarial drug artemisinin in an article published in the journal Nature.
Source
Researchers found that infected insects were three times more likely to be lured towards a human scent. They believe that the deadly parasites are seizing control of their biting hosts and boosting their sense of smell. The research is published in the journal Plos One. Dr James Logan, from the London School of Hygiene and Tropical Medicine (LSHTM), said: "One thing that always surprises me about parasites is how clever they are. They are these ever-evolving organisms that seem to be one step ahead of us the whole time."
Smelly feet
To carry out the study, the researchers infected malaria mosquitoes (Anopheles gambiae) with the most deadly form of parasite, Plasmodium falciparum. They placed about 100 of the infected insects into a container, along with some nylon stockings that had been previously worn by volunteers for 20 hours. "It is a very effective way of collecting body odour... the odour can remain attractive for months," explained Dr Logan.
The scientists repeated the experiment with uninfected insects. They found that mosquitoes carrying the deadly parasite were three times more likely to be attracted to the smelly stockings. The scientists believe this is because the tiny parasitic organisms are manipulating their hosts' sense of smell. Dr Logan said: "We think it is giving them a heightened sense of smell. We are hypothesising there is an alteration somewhere in their olfactory system that allows them to find us quicker."
Smart tactics
By making humans an easier target, the parasite is more likely to be passed into the blood stream - ensuring its survival and continuing the spread of the deadly disease. The researchers will now begin a three-year project, funded by the Biotechnology and Biological Sciences Research Council (BBSRC), to learn more about how the parasites are doing this. Dr Logan said that understanding how the malaria-infected mosquitoes respond to human odour could help them to fight the disease.
He said: "If we know how the parasite is able to manipulate the olfactory system... perhaps we can identify new attractants for infected mosquitoes and we will be able to increase our efficiency with trapping techniques." According to the latest figures, the World Health Organization said there were about 219 million cases of malaria in 2010 and 660,000 deaths. Africa is the most affected continent: about 90% of all malaria deaths occur there.
BBC News - Malaria parasite lures mosquito to human odour
Scientists say they have been able to demonstrate that the most common cause of the tropical disease elephantiasis can be virtually eradicated - even in lieu of medication - if those at risk sleep under nets treated with chemicals that kill mosquitoes. Lisa Reimer, a lecturer at the Liverpool School of Tropical Medicine, was part of the team in Papua New Guinea studying progress over several years in eliminating the disease, caused by tiny worms most frequently injected into people by mosquitoes.
Reimer tells VOA she was surprised at how effective anti-malaria bed nets laced with insecticide could be at combating lymphatic filariasis - whose most horrifying symptom, elephantiasis, is the massive swelling of skin and tissue. "Filariasis is only picked up by mosquitoes late in the evening, so this is the time when people are more likely to be protected by their bed nets. So we found that bed net use actually is a greater barrier against filariasis transmission whereas malaria transmission may still be occurring outside the times when the user is under the net," said Reimer. Reimer is the lead author on a paper about the findings, being published in the New England Journal of Medicine.
A leg disfigured by elephantiasis
The team involved researchers from institutes in Papua New Guinea, the United States, the United Kingdom and Australia. Reimer says mass annual administration of drugs to residents of five villages in Papua New Guinea nearly eliminated the parasite from humans but did not stop its transmission by mosquitoes. "If we can reduce mosquito-biting rates then we're able to increase the thresholds below which the disease prevalence will move to zero. So by controlling mosquitoes we're making the targets for the mass drug administration more obtainable," she said.
The World Health Organization (WHO) has a goal of eliminating lymphatic filariasis as a public health problem by the year 2020. The treated nets block female mosquitoes from securing blood, which is essential for them to produce offspring. The insecticide also cuts in half the insect's life span, preventing the parasite from being transmitted. The WHO estimates that 120 million people suffer from lymphatic filariasis. About one-third of those have been disfigured or debilitated by the disease. Infection is usually acquired in childhood but the profound visible manifestations become evident later in life.
Treated Bed Nets Critical to Eradicating Debilitating Tropical Disease
I'm still wondering 7 years later, why DDT isn't being used more liberally in areas of high infections.
Annie -
Somehow I think you might feel a little differently if a known carcinogen was being sprayed where you live.
This is a more complex issue than you might imagine...DDT is effective, but not so effective that it removes the problem of malaria entirely. In badly afflicted areas people still need to use mosquito nets, repellant and pale-coloured or pemethrin-infused clothing at sunset.
DDT has only ever been a bandaid solution. What is needed is either an effective vaccine, or a biological solution such as irradiation and/or draining swamps and/or introducing predators like bats and birds - which DDT kills, of course.
Annie -
Actually, I am in countries badly effeted by malaria for around 3 months per year. That is why I am concerned about the issue, and have some knowledge of the situation.
Many people who smoke never get cancer. This does not mean smoking is not dangerous.
Keeping in mind that many birds eat mosquitoes....
Because of its lipophilic properties, DDT has a high potential to bioaccumulate, especially in predatory birds.[41] DDT, DDE, and DDD magnify through the food chain, with apex predators such as raptor birds concentrating more chemicals than other animals in the same environment. They are very lipophilic and are stored mainly in body fat. DDT and DDE are very resistant to metabolism; in humans, their half-lives are 6 and up to 10 years, respectively. In the United States, these chemicals were detected in almost all human blood samples tested by the Centers for Disease Control in 2005, though their levels have sharply declined since most uses were banned in the US.[42] Estimated dietary intake has also declined,[42] although FDA food tests commonly detect it.
DDT - Wikipedia, the free encyclopedia
Annie -
Actually, I am in countries badly effeted by malaria for around 3 months per year. That is why I am concerned about the issue, and have some knowledge of the situation.
Many people who smoke never get cancer. This does not mean smoking is not dangerous.
Keeping in mind that many birds eat mosquitoes....
Because of its lipophilic properties, DDT has a high potential to bioaccumulate, especially in predatory birds.[41] DDT, DDE, and DDD magnify through the food chain, with apex predators such as raptor birds concentrating more chemicals than other animals in the same environment. They are very lipophilic and are stored mainly in body fat. DDT and DDE are very resistant to metabolism; in humans, their half-lives are 6 and up to 10 years, respectively. In the United States, these chemicals were detected in almost all human blood samples tested by the Centers for Disease Control in 2005, though their levels have sharply declined since most uses were banned in the US.[42] Estimated dietary intake has also declined,[42] although FDA food tests commonly detect it.
DDT - Wikipedia, the free encyclopedia
...Debunking False Claims About DDT
While critics of Silent Spring have tended to focus on the one-sidedness of Rachel Carsons case or on those of her claims that have not held up over time, the fraudulence of Silent Spring goes beyond mere cherry-picking or discredited data: Carson abused, twisted, and distorted many of the studies that she cited, in a brazen act of scientific dishonesty.[27]
Charles T. Rubin, The Green Crusade (Lanham, Md.: Rowman & Littlefield, 1994), 3844. Rubin, unlike other critics of Silent Spring, closely compares some of Carsons claims to the original studies she cites as sources for her information. He finds a pattern in which she misrepresents the studies or takes claims out of context so as to make the harm of pesticides seem greater, more certain, or more unprecedented than the original source indicates. Ibid., 3940.
So the real tragic irony of the millions of deaths to malaria in the past several decades is that the three central anti-DDT claims made by Carson and other activists are all false. We shall examine each in turn.
Claim #1: DDT Causes Cancer in Humans. In the late 1960s and early 1970s, the average American could be expected to ingest DDT in food and drink at levels of around 30 micrograms per day.[28]
R. E. Duggan and P. E. Corneliussen, Dietary Intake of Pesticide Chemicals in the United States (III), June 1969-April 1970, Pesticides Monitoring Journal 5, no. 4 (1972): 331341. This comprehensive multi-year study, conducted by scientists working for the Food and Drug Administration, was cited by EPA reports well into the 1970s. My figure of 30 micrograms per day is an extrapolation from their data, assuming an average weight of around 68 kg (150 pounds) and working from the fact that the study assumed a diet almost twice the average intake of the average individual.
(Note: 1 gram = 1,000 milligrams = 1,000,000 micrograms.) Numerous studies of workers with intense exposure to DDT in the workplace, sometimes by factors of thousands more than the average dose either in factories or in the field using DDT to combat malaria have failed to show any convincing evidence of patterns of associations between DDT and cancer incidence or mortality, according to the World Health Organization.[29]
World Health Organization, DDT in Indoor Residual Spraying: Human Health Aspects (Geneva: WHO, 2011), 71.
The thousands of individuals in these studies were regularly exposed to hundreds or perhaps thousands of times the amount of DDT that the average American would have been exposed to, but cancer rates seem not to have been elevated.[30]
D. Ditraglia et al., Mortality Study of Workers Employed at Organochlorine Pesticide Manufacturing Plants, Scandinavian Journal of Work, Environment & Health 7, no. 4 (1981): 140146; Wong et al., Mortality of Workers Potentially Exposed to Organic and Inorganic Brominated Chemicals, DBCP, TRIS, PBB, and DDT, British Journal of Industrial Medicine 41, no. 1 (1984): 1524; H. Austin et al., A Prospective Follow-Up Study of Cancer Mortality in Relation to Serum DDT, American Journal of Public Health 79, no. 1 (1989): 4346; Cocco et al., Proportional Mortality of Dichloro-Diphenyl-Trichloroethane (DDT) Workers: A Preliminary Report, Archives of Environmental Health 52, no. 4 (1997): 299303; P. Cocco et al., Cancer Mortality and Environmental Exposure to DDE in the United States, Environmental Health Perspectives 108, no. 1 (2000): 14; Cocco et al., Cancer Mortality Among Men Occupationally Exposed to Dichlorodiphenyltrichloroethane, Cancer Research 65, no. 20 (2005): 95889594; Purdue et al., Occupational Exposure to Organochlorine Insecticide and Cancer Incidence in the Agricultural Health Study, International Journal of Cancer 120, no. 3 (2007): 642649.
A great many studies of specific cancers breast cancer, lung cancer, testicular cancer, liver cancer, prostate cancer, and more over many decades have failed to show significant evidence of cancer as a result of exposure to DDT.[31]
World Health Organization, DDT in Indoor Residual Spraying, 7183. There is, however, some evidence that exposure to DDT before puberty may be linked to breast cancer later in life; see ibid., 7175.
There is scientific evidence that ingesting DDT or its byproduct DDE can cause mice to develop tumors, but only if they are fed at least ten times the amount per day (by body weight) that a person would normally expect to ingest.[32]
Ibid., 5261.
Cancer studies of other mammals have been less conclusive.[33]
Ibid., 6164.
In other studies of the effects of DDT on mammals, rats fed with large doses of the substance were found to have their reproductive lifespans increased by 65 percent (from 8.91 months to 14.55 months).[34]
Alice Ottoboni, Effect of DDT on the Reproductive Life-Span in the Female Rat, Toxicology and Applied Pharmacology 22, no. 3 (1972): 497502.
Heavily dosed dogs also experienced no ill effects, and in fact were found to be healthier than the control group, as DDT freed them of infestation by roundworms.[35]
Alice Ottoboni, Glenn D. Bissell, and Alfred C. Hexter, Effects of DDT on Reproduction in Multiple Generations of Beagle Dogs, Archives of Environmental Contamination and Toxicology 6, no. 1 (1977): 83101.
Summarizing all of the relevant research, the U.S. government reported in 2002 that there is no clear evidence that exposure to DDT/DDE causes cancer in humans.[36]
ATSDR, Toxicological Profile for DDT, DDE, and DDD, 2002, 25.
That assessment is a vindication of the legal conclusion of Judge Edmund Sweeneys 1972 report on DDT for the EPA: DDT is not a carcinogenic hazard to man.[37]
...
Those with actual scientific backgrounds, have been appalled by what Carson's, "Silent Spring" unleashed. Untold deaths and sufferings by those least able to stand up for themselves and demand reasonable combative measures:
Millions die in Africa from Malaria and it doesn't take much DDT to control the mosquito population.. DDT is safe
Those with actual scientific backgrounds, have been appalled by what Carson's, "Silent Spring" unleashed. Untold deaths and sufferings by those least able to stand up for themselves and demand reasonable combative measures:
Absolutely -it isshocking to think that people should be told that they were being poisoned with known carcinogens. They had no right to know.
They should have been happy to watch their children die for the greater good of mankind.
And birds...who cares about birds?
