India, world’s top DDT user, socked with malaria increase

July 22, 2015

Were it true that DDT is a magic solution to malaria, by all measures India should be malaria free.

Not only is India not malaria-free, but the disease increases in infections, deaths, and perhaps, in virulence.

Map showing location of Odisha, or Orissa, state, in India. Wikipedia image

Map showing location of Odisha, or Orissa, state, in India. Wikipedia image

Since the late 1990s a small, well-funded band of chemical and tobacco industry propagandists conducted a campaign of calumny against Rachel Carson, environmentalists in general, scientists and health care workers, claiming that an unholy and wrongly-informed conspiracy took DDT off the market just as great strides were beginning to be made against malaria.

As a consequence, this group argues, malaria infections and deaths exploded, and tens of millions of people died unnecessarily.

That’s a crock, to be sure. Rachel Carson’s 1962 book, Silent Spring, inspired an already-established campaign against DDT. But the malaria eradication program begun with high hopes by the World Health Organization in 1955, foundered in 1963 when the campaign turned to central, tropical Africa. Overuse of DDT in agriculture and minor pest control had bred DDT-resistant and immune mosquitoes.  Malaria fighters could not knock down local populations of mosquitoes well enough to let medical care cure infected humans.  (The campaign was not helped by political instability in some of the African nations; 80% of houses in an affected area need to be sprayed inside to stop malaria, and that requires government organizational skills, manpower and money that those nations could not muster.)

Detail map of Odisha state, India; map by Jayanta Nath, Wikipedia image

Detail map of Odisha state, India; map by Jayanta Nath, Wikipedia image

That was just a year after Carson’s book hit the shelves. DDT had been banned nowhere. WHO’s workers tried to get a campaign going, but complete failures stopped the program in 1965; in 1969 WHO’s board met and officially killed the malaria eradication program, in favor of control.

Malaria infections and deaths did not expand with the end of WHO’s campaign.  At peak DDT use, roughly 1958 to 1963, malaria deaths are estimated by WHO to have been as high as 5 million per year, 4 million by 1963. Total malaria infections, worldwide, were 500 million.

The first bans on DDT use came in Europe. When the U.S. banned DDT use on crops in 1972, okaying use to fight malaria, malaria deaths had fallen to more than 2 million annually by optimistic estimates.  Death rates and infection rates continued to fall without a formal eradication campaign. By the late 1980s, malaria killed about 1.5 million each year, a great improvement over the DDT go-go days, but still troubling.

Beating malaria is a multi-step program.  Malaria parasites must complete a life cycle in a human host, and then when jumping to a mosquito, another cycle of about two weeks in the mosquito’s gut, before being transmissible back to humans. Knocking down mosquito populations helps prevent transmission temporarily, but that is only useful if in that period the human hosts can be cured of the parasites.

In the late 1980s, malaria parasites developed strong resistance and immunity to pharmaceuticals given to humans to cure them.  Regardless mosquito populations, human hosts were always infected, ready to transmit the parasite to any mosquito and send drug-resistant malaria on to dozens more.

From about 1990 to about 2002, malaria deaths rose modestly to more than 1.5 million annually.

New pharmaceuticals, and new regimens of administration of pharmaceuticals, increased the effectiveness of human treatments; coupled with much better understanding of malaria vectors, the insects that transmit the disease, and geographical data and other technological advances to speed diagnosis and treatment of humans, and increase prevention measures, WHO and private foundations started a series of programs in malaria-endemic nations to reduce infections and deaths. Insecticide-impregnated bednets proved to be less-expensive and more effective than Indoor Residual Spraying (IRS) featuring DDT or any of the other 11 pesticides WHO authorizes for home spraying.  (Home spraying targets mosquitoes that carry malaria, and limits expensive overuse of pesticides, plus limits and prevents environmental damage.)

Health care workers and most nations made dramatic progress in controlling and eliminating malaria, between 2000 and 2015, mostly without using DDT which proved increasingly ineffective at controlling mosquitoes, and which also proved unpopular among malaria-affected peoples whose cooperation is necessary to fight the disease.

By 2014, fewer than 220 million people got malaria infections, worldwide, a reduction of about 55% over DDT’s peak-use years. This is remarkable considering the population of the planet more than doubled in that time, and population in malaria-endemic areas rose even more. Malaria deaths were reduced to fewer than 600,000 annually, a reduction of more than 80% over peak DDT years. By 2015, malaria-fighters once again spoke of eradicating malaria from the planet.

In contrast, India assumed the position of top producer of DDT in the world, still making it even after China and North Korea stopped making it. But malaria control in India weakened, despite greater application of DDT.  The world watches as DDT, once the miracle pesticide used in anti-malaria campaigns, became instead a depleted tool, unable to stop malaria’s spread despite increasing application.

Were DDT the magic powder, or even “excellent powder” its advocates claim, India should be free of malaria, totally. Instead, Indians debate how best to get control of the disease again, and start reducing infections and deaths, again. Below is one story, rather typical of many that crop up from time to time in India news; this is from the Odisha Sun Times. (Note: Lakh is a unit in the Indian number system equal to 100,000; crore is a unit equal to 10,000,000.)

Odisha has 36% of malaria cases in India; ranks third in deaths

Odisha Sun Times Bureau
Bhubaneswar, Mar 15:

Odisha has earned the dubious distinction of having a hopping 36% share of all malaria cases in India and ranking third in the list of states with the most number of deaths leaving most of its neighbours way behind.

Malaria Mosquito

These startling revelations have been made in a report tabled by the Union Health and Family Welfare department in the Parliament.

What is more disturbing is that the number of persons getting afflicted with the disease in the state is rising every year despite the state government spending crores of rupees to arrest the spread of the disease.

The state government has been spending crores of rupees on a scheme christened ‘Mo Masari’ (“My Mosquito Net’) and has been claiming that the number of afflicted has been falling in the state. But the Central government report has exposed the hollowness of the claim.

According to the report, out of the 10.70 lakh people who were afflicted with malaria in India in the year 2014, about 3.88 lakh (36.26%) were from Odisha. In 2010, around 3.95 lakh were afflicted with the disease. The number had come down to 3.08 lakh in 2011 and had further scaled down to around 2.62 lakh in 2012, the report says.

But the number of malaria patients in Odisha is again rising at a faster pace since then, according to the Health Ministry report.

Even though the neighbouring states of Jharkhand and Chhattisgarh are identified as malaria prone states, much less people are afflicted with malaria in these states as compared to Odisha. In 2014, only 1.22lakh people were affected with the disease in Chhattisgarh while only 96,140 persons were affected by malaria in Jharkhand in the same year.

Statistics cited in the report also reveal that Odisha has left many states behind and has marched ahead of others in the matter of number of deaths due to malaria. It ranks third on this count in the country.

In the year 2014, a total of 535 persons had died of malaria across the country. Out of them 73 (13.64%) were from Odish while Tripura had the maximum number of deaths in terms of percentage at 96 (17.94%) followed by Meghalaya, another hilly state, with a toll count of 78 (14.58%).

Another disturbing fact that has emerged from the report is that out of those who have died of malaria in Odisha, 80 percent are from tribal dominated areas.

The districts of Gajapati , Kalahandi , Kandhamal, Keonjhar, Koraput, Malkangiri, Mayurbhanj, Nabarangpur, Nuapada, Rayagada and Sundargarh account for both the maximum number of deaths due to malaria and maximum number of persons afflicted with the disease.


Hoax victims afraid to discuss their misplaced DDT & malaria anger . . .

July 20, 2015

We see it almost daily — probably because we’ve got searches set to find comments on malaria and DDT.

British robin, or robin redbreast. Image found on Pinterest, and also ironically used to illustrate Pointman's screed for DDT.

British robin, or robin redbreast. Image found on Pinterest, and also ironically used to illustrate Pointman’s screed for DDT. Ironic, because Britain didn’t use as much DDT, and European robins were not so badly affected as U.S. robins. Not sure if Pointman knew that and used the photo to intentionally mislead, or if he’s just really bad at identifying species.

Some well-meaning guy (or woman) writes a long piece about conscience, and then claims to have lost respect for science, or medicine professionals, or the World Health Organization (WHO), or Rachel Carson or environmentalists, or all of them at once, because Rachel Carson’s ban on DDT meant malaria infections and deaths exploded, and libruls just won’t allow anyone to fix it.

If you’re a regular reader, you know that story is impossible, because:

The standard rant against Rachel Carson in favor of DDT is impossible in three ways:

  1. EPA’s regulation cannot travel back in time to cause an end to WHO’s malaria eradication campaign (1963) nine years before the rule was made (1972); nor can history and international law be changed to make EPA’s campaign stop the use of DDT outside the U.S.
  2. Mosquitoes do not migrate thousands of miles, across oceans. EPA’s ban on spraying U.S. crops with DDT, chiefly cotton, did not cause mosquitoes to migrate from Arkansas to Africa to spread malaria.  Had they done so, DDT in Africa had a pretty good chance to getting them, anyway.
  3. A reduction of malaria deaths from 4 million to 584,000, is not an increase in deaths.

These impossibilities do not even act as speed bumps to people in a hurry to condemn science, Rachel Carson, malaria fighters and environmentalists, in a mad rush to praise DDT, a deadly poison that doesn’t do what we hoped it would, any more.

Those undeterred from slandering Rachel Carson and environmentalists often don’t want to be informed of any errors in their rant. And so, Pointman, with a nasty false indictment of science, law and environmentalists, refuses to allow my posts to correct his errors.

His screed here.  It contains at least 6 gross errors, repeating all the impossibilities listed above, and slandering both Rachel Carson and William Ruckelshaus as “mass murderers,” with the false claim that EPA stopped DDT use against malaria.

My response, dealing with a small part of the errors, below (and here at Pointman’s blog; but in moderation, so you can’t see it, at the time of this posting).

EPA’s order banning DDT use in the U.S., on crops, specifically lifted the court-imposed ban on DDT manufacture, and specifically allowed use of DDT in the U.S. or anywhere else on Earth to fight vector-borne diseases — that is, malaria.

DDT manufacture continued in the U.S. until late 1984, when a new law made DDT manufacturers responsible for not poisoning their neighbors and neighborhoods. Most DDT manufacturing arms of larger chemical companies were spun off as separate enterprises, and they declared bankruptcy rather than assume any liability for the poisons they made for huge profits.

See description of EPA order and links to the original documents here: https://timpanogos.wordpress.com/2014/10/29/oh-look-epa-ordered-ddt-to-be-used-to-fight-malaria-in-1972/

I waited several days, and send two notices asking to spring the comment from moderation. I don’t think “Pointman” is interested in discussion.

[Update]
Further reflection, a further thought — “Pointman” probably is not interested in discussion, not because he fears it — he’s probably armed, what does he have to fear? — but because he no longer caresHe’s seen the effects of good intentions gone wrong, and if it ever occurs to him it’s not his intentions, nor his going, that might be wrong, he’ll never let on.

More:


Spreading the news: Environmental Health News says we can learn from saving eagles, to save honeybees now

July 5, 2015

Environmental Health News invites repostings of this story, with attribution and links back to EHN’s original story.

It’s a good article. Can’t improve on it much, so let’s save time and pass it directly.

Can we learn from the success in saving the bald eagle from extinction, to save our domestic bee industry and native American pollinators?

Unintended consequences

How a law that failed to protect eagles could offer a lesson to save honeybees

June 6, 2015

By Peter Dykstra
Environmental Health News

Spraying DDT on a beach

Historic photo from EPA

The Bald Eagle Protection Act, signed into law 75 years ago on June 8, 1940, was well-intended. A multi-pronged assault on the raptors was taking its toll — habitat loss, lead-shot poisoning, and bounty-hunting by ranchers and fishermen all contributed to a growing threat. (Click here to see how this played out in Alaska.)

Congress passed, and President Franklin D. Roosevelt signed, the act to outlaw the “taking” of eagles and their eggs, disruption of their nests, or sale or possession of eagle feathers or parts.

It didn’t work. Bald eagle populations accelerated their decline, for reasons that Congress, wildlife officials, and FDR couldn’t possibly anticipate.

Throughout the late 1930’s Swiss chemist Paul Müller labored to find the right mix of synthetic chemicals to control moths. Not only did dichlorodiphenyltrichloroethane do the trick, but Müller’s lab work found it was effective against lice, houseflies, beetles, and the dreaded mosquito. Müller’s employers, J.R. Geigy AG, applied for the first DDT permit about two months before the Eagle Act passed.

Pest Management Professional Hall of Fame

Swiss chemist Paul Muller, of A. G. Geigy corporation; the man who discovered DDT kills.  Pest Management Professional Hall of Fame

The rest is natural and human history. Cheap to produce and an effective defense against lice-borne typhus and mosquito-borne malaria, DDT quickly became a fixture in farm fields, living rooms, and World War II battle theaters. Müller became a science rock star, garnering a Nobel in 1948 and — wait for it — membership in the Pest Management Professional Hall of Fame in 2004.

But bald eagles continued to decline. So did hummingbirds, robins, ospreys, pelicans and peregrine falcons. Years of science, met with serious blowback from the chemical industry, eventually proved that DDT was thinning birds’ eggshells, not to mention causing impacts in fish, humans, and other mammals. Rachel Carson’s Silent Spring drew international attention to the threat, and in the U.S., DDT was outlawed on the last day of 1972. Bald eagles, ospreys, brown pelicans and peregrine falcons have all since staged remarkable comebacks from the Endangered Species list.

Which brings us to today’s threat to other ecologically priceless wildlife — pollinators. Honeybee populations have been in freefall for more than a decade. Like the threats to eagles, the potential causes are multiple: loss of habitat and native plants, parasites, and a mix of insecticides and fungicides. Newest, and most notable among the suspects, are neonicotinoid pesticides. Like DDT, neonics were developed in the 1980’s and 1990’s and welcomed as a step forward, since they were thought to be effective on insect pests but relatively benign on non-target wildlife and ecosystems. Today they are a billion-dollar agricultural product, ubiquitous on common crops like corn and soybeans.

But mounting evidence shows that neonicotinoids may be part of the frontal assault on bees and other pollinators. In 2013, the European Union banned the use of three of the most contentious types of neonicotinoids, citing a clear and immediate risk.

In 2014, President Obama ordered the creation of a federal pollinator strategy. Its first draft came out last month, calling for everything from creating bee-friendly habitat to further study on neonics and other agricultural chemicals. The first edition of the strategy, issued in May, outlines a multi-year process for re-examining use of neonics.

If the EPA and other federal agencies concur with other studies on the potential harm of neonicotinoids, the U.S. will issue assessments for neonics in 2016 and 2017, and may or may not take action until 2018 to 2020. All of this will take place under a new president who may or may not take interest in protecting bees.

That timetable may work. Or not. Or, with a president with little more than a year left in office and a hostile Congress, it may be a moot point.

But perhaps a more important point is that in 1940, the President and Congress took action on the known threats to eagles. They didn’t know about the chemical risk from DDT. If neonics are as big a threat as the science suggests, the current president and Congress won’t have ignorance as an excuse for waiting.


EHN welcomes republication of our stories, but we require that publications include the author’s name and Environmental Health News at the top of the piece, along with a link back to EHN’s version.

For questions or feedback about this piece, contact Brian Bienkowski at bbienkowski@ehn.org.

Prior to the 20th century, all eagles, including bald eagles were regarded as pest predators and pest carrion eaters.  Populations of the birds plunged between 1492 and 1900.  The first eagle protection law in 1918 did little to stop the decline in eagle populations.  A harder-toothed anti-hunting law in 1941 helped, as discussed above. Anti-environmentalists often seize on these historic facts to claim that DDT was not to blame for the failure of the eagles to recover after 1941.  But recovery of the birds started as soon as DDT was banned.  Fecundity of bald eagle populations rose in direct proportion to the drop in residual DDT and DDT breakdown products in the flesh and fat of eagles.

In Silent Spring Rachel Carson provided 53 pages of notes and citations to science journals, documenting the dangers and the unknowns of DDT and a variety of other chemicals. The book was published in 1962.  It is a tribute to Carson’s meticulous research that every study she pulled from is still accurate today. Later research only supported her conclusions, or in the case of bird damage and eggshell thinning, provided documentation of even more and greater harms.

Do we learn from history?


Early history of EPA: Pesticides regulation and DDT

June 24, 2015

This is an excerpt from EPA’s official shorthand history, online since the 1990s.  I include this part here, dealing with the EPA’s famous regulation of the pesticide DDT, because I refer to it and link to it in several posts — and because over three different administrations, the URL has changed several times.  I fear it will one day go dark.  Here it is for history’s sake, found on June 24, 2015 at http://www2.epa.gov/aboutepa/guardian-epas-formative-years-1970-1973#pest.

Opening to the entire piece; links to subsections go to EPA’s site:

The Guardian: EPA’s Formative Years, 1970-1973

EPA 202-K-93-002
September 1993
by Dennis C. Williams

Table of Contents

The section on DDT hearings and regulation:

Pesticides and Public Health

Unlike the air controversy, which erupted after the agency’s establishment, EPA’s creation coincided with the culmination of the public debate over DDT (dichloro-diphenyl-trichloro-ethane). A chlorinated hydrocarbon, DDT proved to be a highly effective, but extremely persistent organic pesticide. Since the 1940s, farmers, foresters, and public health officials sprayed it across the country to control pests such as Mexican boll weevils, gypsy moths, and pesky suburban mosquitoes. Widespread public opposition to DDT began with the publication of Rachel Carson’s influential Silent Spring. Reporting the effects of DDT on wildlife, Carson demonstrated that DDT not only infiltrated all areas of the ecological system, but was exponentially concentrated as it moved to higher levels in the food web. Through Carson, many citizens learned that humans faced DDT-induced risks. By 1968 several states had banned DDT use. The Environmental Defense Fund, which began as a group of concerned scientists, spearheaded a campaign to force federal suspension of DDT registration–banning its use in the United States. Inheriting Department of Agriculture (USDA) pesticide registration functions, under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) of 1964, EPA was born in the midst of the DDT storm.

In January 1971, a tribunal of the U.S. Court of Appeals in the District of Columbia ordered Ruckelshaus to begin the process of suspending DDT’s registration, and to consider suspending its registration immediately. At the end of a sixty-day review process, the administrator reported that he had found no good reason to suspend DDT registration immediateIy. It and several other pesticides–including 2, 4, 5-T (Agent Orange), Dieldrin, Aldrin, and Mirex–did not appear to constitute imminent health threats. This action infuriated many environmentalists.

By 1971, the Environmental Defense Fund had mobilized effective public opposition to DDT. The furor created by Ruckelshaus’s refusal to stop DDT use prompted many to look for sinister political motivations. Some suggested that Mississippi Congressman Jamie Whitten had used his position as chairman of the agricultural appropriations subcommittee of the House Appropriations Committee to make Ruckelshaus conform to the interests of the agrichemical lobby. While actually, Ruckelshaus took his cautious stance for less menacing reasons.

At its creation, EPA not only inherited the function of pesticide registration from USDA, but also the staff that served that function. The USDA economic entomologists who designed the pesticide registration process in the first place preached the advantages of effective pesticides and minimized discussion of debatable health risks. The same staff that had backed USDA Secretary Clifford Hardin’s earlier claim that DDT was not “an imminent hazard to human health or to fish and wildlife” 8 provided Ruckelshaus with the same counsel.

Rachel Carson's Silent Spring led to banning DDT and other pesticides.

Rachel Carson’s Silent Spring led to banning DDT and other pesticides.

Between March 1971 and June 1972, American newspapers reported both sides of the pesticide debate. Some articles recalled the glory days when pesticides saved thousands of lives in World War II; how they had increased agricultural productivity and allowed relatively few farmers to feed the world’s growing population; and how the most besieged insecticides, such as DDT and Mirex, had little human toxicity. Other journalists praised alternative approaches to pest management such as biological controls (predator introduction, sterile males, and pheromone traps), integrated controls (crop rotation and carefully delimited pesticide use), and refinement of other, less persistent chemicals. Some reported the near panic of Northwestern fruit growers facing beeless, and therefore fruitless, seasons. They attributed the lack of pollinating insects to pesticide use.

Throughout the spring of 1972, Ruckelshaus reviewed the evidence EPA had collected during the agency’s hearings on DDT cancellation and the reports prepared by two DDT study groups, the Hilton and Mrak Commissions. Both studies suggested that DDT be phased out due to the chemical’s persistent presence in ecosystems and noted studies suggesting that DDT posed a carcinogenic risk to humans. In June, he followed the route already taken by several states he banned DDT application in the United States. Though unpopular among certain segments of EPA’s constituency, his decision did serve to enhance the activist image he sought to create for the agency, and without prohibitive political cost.

The DDT decision was important to EPA for several reasons. While it did not stop the debate over what constituted appropriate pesticide use, DDT demonstrated the effect public pressure could have on EPA policy decisions. It also made very visible the tightrope act a regulatory agency performs when it attempts to balance the demands for protection of human and environmental health against legitimate economic demands. Furthermore, EPA’s decision set a precedent for regulatory decision-making. As an advocate of the environment, Ruckelshaus and the agency chose to risk erring on the side of protecting human health at the expense of economic considerations–a course that would bring the agency under heavy criticism before the end of its first decade.


Rachel Carson’s 108th birth anniversary

May 27, 2015

Rachel Carson, the great biologist and author, was born on May 27, 1907.

Last year, Google’s Doodle featured Ms. Carson, and the crazy, ill-informed, hoaxing and hoaxed right wing, came unglued.

Less flap this year, but I suspect it’s only because there’s been no great public recognition of the date.  Hoaxsters who insist DDT was always safe, or that banning DDT on cotton crops in Arkansas and Texas somehow caused malaria in Africa, or that Idi Amin became a great fan of Rachel Carson and stopped spraying DDT in Uganda to save American eagles, or other similarly silly-but-vicious things, or who just hate anything to do with protecting the environment, usually erupt on Earth Day, World Malaria Day, and Rachel Carson’s birthday.

Not much on her birthday this year (but stay tuned).

Meanwhile, our country’s sober liberal conscience, The Nation, looks back at their review of Silent Spring, and does a little cringing. Probably not necessary:

Rachel Carson, date unknown. (US Department of Agriculture) - via The Nation

Rachel Carson, date unknown. (US Department of Agriculture) – via The Nation

It is difficult not to cringe at the sight of the headline to the following review of Rachel Carson’s groundbreaking book, Silent Spring—“Man and Other Pests”—given that it was a review of what was then probably the most influential intellectual contribution by an American woman to date.

Miss Carson is indignant about the unexpected effects of our thoughtless broadcasting of pesticides. She writes persuasively, for she has taken great pains to gather and check her facts. Parts of the book were published in The New Yorker magazine last summer, and immediately provoked wide interest, discussion and controversy. This reaction will undoubtedly intensify with the publication of the book. No one is in a better position than Miss Carson to arouse the indignation of the public and the conscience of the chemical industry, and it may well be that she has made a real contribution to our salvation.

[At The Nation, you can read the entire review quoted from above.]

Happy birthday, Ms. Carson.  You have become a hero to thinking people, conservationists, scientists and women everywhere.

You’ll be pleased to know the American symbol, the bald eagle, is back from extinction’s verge, along with the brown pelican, peregrine falcons and osprey.  You’d be surprised to know that, despite gross abuse of DDT in the 1950s and 1960s that caused mosquitoes all over the world to carry alleles resistance and immunity, DDT was saved from complete worthlessness by a reduction in use, and is still used in a few places today, indoors to protect wildlife, to fight malaria.  You were right about DDT.

You were right about fighting malaria, too.  You said in Silent Spring we should use integrated pest management to battle the mosquitoes that provide a site for part of the life cycle of the malaria parasites, and who then spread the disease.  When DDT failed the malaria eradication campaign in the 1960s, malaria fighters were left with little else. Malaria deaths have plunged, from the 4 million to 5 million per year you knew, to fewer than 500,000 per year now.  Worldwide, we’ve cut malaria deaths 45% just since 1999, when a group of non-governmental organizations and the World Health Organization formally adopted integrated pest management as the best way to fight the disease, and began distributing mosquito nets in a big way.

You were right, Rachel Carson. Humanity is a part of nature, and if we fight nature we end up fighting and killing ourselves.

More:

One of my favorites from Gus Arriola (also appearing at the DDT Chronicles):


Rachel Carson sketch

March 4, 2015

A Canadian artist posted a nice sketch of Rachel Carson on Twitter:

Rachel Carson sketch, by artist @moietymouse

Rachel Carson sketch, by artist @moietymouse

I’m often frustrated at how few good images of Ms. Carson exist on the internet, probably because I see them over and over again in working to stamp out the hoax claims about Carson, DDT and malaria, and environmental protection.

Maybe we can get @moietymouse to make some more? Check out her Twitter feed; maybe she’s got images for sale, and you can encourage her while improving the look of your walls.

Read the rest of this entry »


How is DDT used to fight malaria?

February 20, 2015

Can we dispel common misapprehensions about fighting malaria?

In fighting malaria, DDT is not used outdoors.  Spraying swamps with insecticide does little to combat malaria because malaria-carrying mosquitoes don’t usually breed or rest there, and collateral damage from DDT reduces mosquito predators.

USAID-paid workers conducting Indoor Residual Spraying (IRS) campaign. (Where? When?) USAID photo, via Stanford University, Human Biology 153

USAID-paid workers conducting Indoor Residual Spraying (IRS) campaign. (Where? When?) USAID photo, via Stanford University, Human Biology 153

DDT’s utility in fighting malaria comes from its persistence when used close by humans bitten by those species of mosquito that carry malaria. Malaria is a parasitic disease.  Malaria parasites complete their life cycle in a human host (victim), and any insect taking blood from an infected human gets some of those parasites.  The parasite completes another phase of its life cycle in certain species of mosquito — not flies nor other biting insects — and after about two weeks, mosquitoes can infect humans with newly-ready parasites.

Those species that carry malaria are usually active from about dusk until after midnight.  Consequently, they bite people usually as they sleep.  Because the “blood meal” is heavy, newly-fed mosquitoes usually fly to a nearby wall of the home to excrete water from the meal, so they fly with a lighter load.  If DDT, or some other pesticide, coats that wall, the mosquito will die before being able to pass new parasites on to new victims.

DDT is NOT used to spray outdoors, to fight malaria.  Among other things, outdoor spraying threatens domestic animals and any creature that preys on the malaria-carrying mosquito; as a pragmatic matter, outdoor use affects only a tiny percentage of malaria-carrying mosquitoes. Malaria-carriers tend to breed in small, temporary pools of water from rain; this transience makes outdoor fighting difficult.  Many people fail to understand this crucial point: DDT outdoors doesn’t help in the fight against malaria.  (Other outdoor campaigns can provide relief, such as elimination of old tires, filling potholes in roads, draining raingutters, and generally eliminating the mosquito breeding areas close to human homes, since mosquitoes rarely move more than about 50 yards in their lifetime.)

It’s important to realize that DDT in IRS allows a mosquito a free first bite.  The hope is that bite is from an uninfected mosquito, who will then land on the treated wall of the home and get a fatal dose of pesticide, so that spreading malaria it may have picked up from its victim, is stopped.  Bednets, which form a physical barrier, prevent even the first bite.  Bednets gain effectiveness from treatment with impregnated insecticides.

The U.S. Centers for Disease Control, the lead agency in the campaign to eradicate malaria from the U.S. after World War II, explains this use of DDT in Indoor Residual Spraying, or IRS:

Indoor Residual Spraying

Many malaria vectors are considered “endophilic”; that is, the mosquito vectors rest inside houses after taking a blood meal. These mosquitoes are particularly susceptible to control through indoor residual spraying (IRS).

What Is Indoor Residual Spraying?

As its name implies, IRS involves coating the walls and other surfaces of a house with a residual insecticide. For several months, the insecticide will kill mosquitoes and other insects that come in contact with these surfaces. IRS does not directly prevent people from being bitten by mosquitoes. Rather, it usually kills mosquitoes after they have fed if they come to rest on the sprayed surface. IRS thus prevents transmission of infection to other persons. To be effective, IRS must be applied to a very high proportion of households in an area (usually >80%).

Health workers sparying insecticide on the walls of a wood and adobe dwelling.

Health worker spraying insecticide on the walls of a wood and adobe dwelling, in Indoor Residual Spraying (IRS). CDC image

History of IRS

IRS with DDT was the primary malaria control method used during the Global Malaria Eradication Campaign (1955-1969). The campaign did not achieve its stated objective but it did eliminate malaria from several areas and sharply reduced the burden of malaria disease in others.

Concern over the environmental impact of DDT led to the introduction of other, more expensive insecticides. As the eradication campaign wore on, the responsibility for maintaining it was shifted to endemic countries that were not able to shoulder the financial burden. The campaign collapsed and in many areas, malaria soon returned to pre-campaign levels.

As a result of the cost of IRS, the negative publicity due to the failure of the Malaria Eradication Campaign, and environmental concerns about residual insecticides, IRS programs were largely disbanded other than in a few countries with resources to continue them. However, the recent success of IRS in reducing malaria cases in South Africa by more than 80% has revived interest in this malaria prevention tool.

Rachel Carson understood this use of DDT, and she understood that outdoor use of DDT, such as crop spraying, or fighting insects affecting trees, could induce insects to evolve resistance and immunity to DDT.  In Silent Spring Carson warned that unless outdoor uses were greatly curtailed, DDT would be rendered ineffective to fight diseases.  Fred Soper, the super-mosquito killer from the Rockefeller Foundation who organized and led the UN’s malaria eradication effort, also understood the race against evolution of DDT resistance.  He had hoped resistance would not show up in tropical areas until the 1970s — malaria campaigns around the Mediterranean produced DDT resistance as early as 1948.  Sadly, resistance to DDT was already established in many mosquito populations in tropical Africa before Soper could take the UN’s program to them.  The UN had to abandon the campaign, as CDC’s explanation indicates.

Today, every mosquito on Earth carries some of the alleles of resistance to DDT, and many are immune to it.


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