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MALARIA: THE STING OF DEATH

The Killer Bug

There are solutions, but most come down to one thing: commitment.

June 5, 2005

When the sun goes down in Africa, death stalks the children. It seldom comes from jungle cats or venomous snakes, but often from bugs smaller than a toddler’s thumbnail. Every year, their deadly sting kills more people than at Hiroshima and Nagasaki, more than December’s tsunami in Asia, more than the combined Union and Confederate casualties in the Civil War. If a biblical plague slaughtered every man, woman and child in Philadelphia, it would not equal some estimates of the death toll from malaria in the last 12 months.

Well, some might say, the world is full of tragedy. We can’t cure all disease or save all lost children. But these acres of graves are the needless legacy of a disease that we have known how to cure for a century. And each life might have been saved for about $2 � less than the price of a latte.

Public health authorities can only guess how many people die of malaria because most of the victims never make it to a clinic; the estimates range from 1 million to 3 million a year. Most of the dead are children under age 5, and 90% had the misfortune to be born in sub-Saharan Africa, a land trapped somewhere between the modern world and the Stone Age.

A Timeless Disease

Malaria’s origins can’t be traced to a specific time period; the disease may be as old as civilized man (some speculate that it arose around the time humans started clustering in agricultural communities). A Chinese medical text from 2700 BC describes its symptoms. It is a bug carried by a bug � a parasite carried in the salivary glands of the anopheles mosquito. Humans and mosquitoes live in a vicious circle of infection. The mosquito gets the parasite by stinging a human who is already infected with it, then stings an uninfected human and passes it on.

The word malaria means “bad air” in Italian, because for centuries people thought that fetid vapors, particularly from swamps, were responsible for its spread. Then, in 1897, a Nobel Prize-winning British physician named Ronald Ross discovered that the mosquito was responsible.

The response around the world was to attack the bloodsuckers where they lived. One of the most successful programs started in 1904, when the U.S. military began draining swamps in the Panama Canal Zone � malaria and yellow fever were killing or disabling so many workers that the completion of the canal was in jeopardy.

In the 1930s, a similar approach was taken in the American South, where the parasite was thriving. During World War II, DDT was developed and sprayed in millions of U.S. homes. The drugs primaquine and chloroquine were added to the older quinine as effective treatments, and, by 1953, malaria was all but eradicated in the United States.

It was a heady time. The world had seemingly conquered a disease that had shadowed man’s footsteps for millenniums; anything seemed possible. In the late 1950s, the World Health Organization led a campaign to eliminate malaria from the rest of the world, pumping the equivalent of billions of today’s dollars into the quest � an amount that, given today’s politics, seems almost incomprehensible. Workers armed with DDT sprayers descended like Blackhawks over Baghdad on the huts and houses of the Third World.

But the malaria parasite is one of nature’s more perfect killers, and this eradication effort was largely a failure. Malaria rates were reduced in some parts of the world, but in places with a more severe problem than this country had ever faced, the mosquitoes simply started developing resistance to the insecticide. And the DDT armies didn’t even try to fight the bugs in sub-Saharan Africa, where the problem was deemed so severe that such efforts would be pointless. Today, malaria kills more people than ever.

A Very Modest Goal

The WHO failure discouraged ambitious anti-malaria programs for decades. Then, in 1998, the WHO and the World Bank established the Roll Back Malaria partnership. In 2000, the G-8 club of industrialized nations identified three pandemics that it would work to cure, and in 2002 established the Global Fund to Fight AIDS, Tuberculosis and Malaria.

A very modest anti-malaria goal was set in 2000 by the United Nations as part of its Millennium Development Goals: to halt and begin to reverse the rise in the incidence of malaria by 2015. The Bill and Melinda Gates Foundation (whose president is married to the editor who supervises this page) also focuses on malaria eradication, further attracting attention to the disease.

Yet the U.S. government spends about half as much on malaria per year as it spends in one day in Iraq. It also places a lower priority on malaria than other diseases, spending 30 to 40 times more in the fight against AIDS than on malaria, maybe because Americans get AIDS but not malaria.

It is absurd, of course, to argue that one global epidemic is more deserving of attention than others. But fighting one disease need not divert resources from the battle against another. And, in the case of malaria, negligence is especially immoral given the cost and effectiveness of available treatment. Anti-malaria combination therapies cost about $2 a treatment in Africa (though that is still far too expensive for large numbers of Africans to afford).

The Sick Continent

Sub-Saharan Africa is an economic sinkhole, stuck in what Columbia University economist Jeffrey Sachs calls a “poverty trap.” Other poor corners of the globe, such as India and East Asia, are making progress, showing marked improvement in per capita income over the last decade and a half. Sub-Saharan Africa is standing still, if not getting poorer. Is it that its governments are too corrupt, or its farming methods too ancient, or its ethnic tensions too corrosive?

These are all factors. But none is unique to sub-Saharan Africa, and other places with these problems still have managed to reduce poverty. What is unusual about this region is the burden of disease, more intense than anywhere else on Earth. And one of the most insidious is malaria. The WHO estimates that the disease costs the African economy about $12 billion a year. Just about everyone living in sub-Saharan Africa gets malaria at least once a year. Most survive but suffer from anemia, recurring fevers and physical weakness. Many children also survive an infection, but with impaired physical and cognitive development.

Among the more cruel paradoxes of malaria is that this disease that kills millions of children also fuels overpopulation. In countries with high infant mortality, parents have a grim way of playing the odds, knowing they have to have a lot of children to make up for the ones who won’t make it past the age of 5.

Looking Ahead

The malaria parasite is remarkably complex and adaptable. As soon as scientists discover a new drug to fight it, the parasite starts developing resistance. Ditto for the mosquitoes that carry it, which eventually build resistance to poison sprays.

As a result, many health experts, particularly those who remember the WHO failure of the 1950s and ’60s, are skeptical that malaria can ever be eradicated. But no one doubts that its toll on humankind can be substantially reduced. And even achieving only the U.N.’s millennium goal of reversing the rise of the disease would save thousands, if not millions, of lives.

There won’t be a magic bullet � the solution will involve a combination of drugs, better availability of treatment, bed nets, insecticide spraying and, ideally, a vaccine. The Gates Foundation is in the process of selecting one country in which it will provide all the available resources, and measure the results. That kind of measurement is critical. Deadly as it is, malaria is rightly considered among the more soluble diseases plaguing Africa, one that can be fought effectively at comparatively low cost, which is why this killer bug is once again drawing so much attention. But unless data are presented showing that anti-malaria programs work, that money will quickly dry up.

In the coming months, The Times will examine some of the key challenges in the battle against malaria. There are solutions, but most come down to one thing: commitment. Most of the world’s richest countries made lofty promises to fight malaria at the turn of the millennium. In the years since, these pledges have not been met.

The result of this failure is a sting of death afflicting millions. The United States and other rich nations have it in their power to easily prevent this sting, and we will have it on our conscience if we fail to do so.

Copyright 2005 Los Angeles Times

washingtonpost.com

If Malaria’s the Problem, DDT’s Not the Only Answer

By May Berenbaum

Post

Sunday, June 5, 2005; B03

In the pantheon of poisons, DDT occupies a special place. It’s the only pesticide celebrated with a Nobel Prize: Swiss chemist Paul Mueller won in 1948 for having discovered its insecticidal properties. But it’s also the only pesticide condemned in pop song lyrics — Joni Mitchell’s famous “Hey, farmer, farmer put away your DDT now” — for damaging the environment. Banned in the United States more than 30 years ago, it remains America’s best known toxic substance. Like some sort of rap star, it’s known just by its initials; it’s the Notorious B.I.G. of pesticides.

Now DDT is making headlines again. Many African governments are calling for access to the pesticide, believing that it’s their best hope against malaria, a disease that infects more than 300 million people worldwide a year and kills at least 3 million, a large proportion of them children. And this has raised a controversy of Solomonic dimensions, pitting environmentalists against advocates of DDT use.

The dispute between them centers on whether the potential benefits of reducing malaria transmission outweigh the potential risks to the environment. But the problem isn’t that simple. This is a dispute in which science should play a significant role, but what science tells us is that DDT is neither the ultimate pesticide nor the ultimate poison, and that the lessons of the past are being ignored in today’s discussion.

The United Nations Environment Program has identified DDT as a persistent organic pollutant that can cause environmental harm and lists it as one of a “dirty dozen” whose use is scheduled for worldwide reduction or elimination. But some DDT advocates have resorted to anti-environmentalist drama to make their case for its use in Africa.

They have accused environmental activists of having “blood on their hands” and causing more than 50 million “needless deaths” by enforcing DDT bans in developing nations. In his best-selling anti-environmentalist novel “State of Fear,” Michael Crichton writes that a ban on using DDT to control malaria “has killed more people than Hitler.”

Such statements make good copy, but in reality, chemicals do not wear white hats or black hats, and scientists know that there really are no miracles.

Malaria is caused by a protozoan parasite that is transmitted by mosquitoes. For decades, there have been two major strategies for curbing the disease: killing the infectious agent or killing the carrier. Reliably killing the protozoan has proved difficult; many older drugs are no longer effective, new ones are prohibitively expensive, and delivering and administering drugs to the susceptible populace presents daunting challenges. Killing the carrier has long been an attractive alternative.

And DDT has been an astonishingly effective killer of mosquitoes. DDT (which stands for the far less catchy dichloro-diphenyl-trichloroethane) is a synthetic chemical that didn’t exist anywhere on the planet until it was cooked up for no particular purpose in a German laboratory in 1874. Decades later, in 1939, Mueller pulled it off a shelf and tested it, along with many other synthetic substances, for its ability to kill insects. DDT distinguished itself both by its amazing efficacy and its breadth of action — by interfering with nervous system function, it proved deadly to almost anything with six, or even eight, legs. And it was dirt-cheap compared to other chemicals in use — it could be quickly and easily synthesized in chemical laboratories from inexpensive ingredients.

Soon after its insecticidal properties were discovered, DDT was put to use combating wartime insect-borne diseases that have bedeviled troops mobilized around the world for centuries. It stemmed a louse-borne typhus outbreak in Italy and prevented mosquito-borne diseases in the Pacific theater, including malaria and yellow fever, to almost miraculous effect. This military success emboldened governments around the world to use DDT after World War II to try to eradicate the longtime scourge of malaria. And in many parts of the world, malaria deaths dropped precipitously. This spectacular success is why many people are calling for the use of DDT specifically for malaria control.

At the same time that malaria deaths were dropping in some places, however, the environmental persistence of DDT was creating major problems for wildlife, as famously documented in Rachel Carson’s classic 1962 book, “Silent Spring.” By 1972, the pesticide had become the “poster poison” for fat-soluble chemicals that accumulate in food chains and cause extensive collateral damage to wildlife (including charismatic predators such as songbirds and raptors), and a total ban on the use of DDT went into effect in the United States.

What people aren’t remembering about the history of DDT is that, in many places, it failed to eradicate malaria not because of environmentalist restrictions on its use but because it simply stopped working. Insects have a phenomenal capacity to adapt to new poisons; anything that kills a large proportion of a population ends up changing the insects’ genetic composition so as to favor those few individuals that manage to survive due to random mutation. In the continued presence of the insecticide, susceptible populations can be rapidly replaced by resistant ones. Though widespread use of DDT didn’t begin until WWII, there were resistant houseflies in Europe by 1947, and by 1949, DDT-resistant mosquitoes were documented on two continents.

By 1972, when the U.S. DDT ban went into effect, 19 species of mosquitoes capable of transmitting malaria, including some in Africa, were resistant to DDT. Genes for DDT resistance can persist in populations for decades. Spraying DDT on the interior walls of houses — the form of chemical use advocated as the solution to Africa’s malaria problem — led to the evolution of resistance 40 years ago and will almost certainly lead to it again in many places unless resistance monitoring and management strategies are put into place.

In fact, pockets of resistance to DDT in some mosquito species in Africa are already well documented. There are strains of mosquitoes that can metabolize DDT into harmless byproducts and mosquitoes whose nervous systems are immune to DDT. There are even mosquitoes who avoid the toxic effects of DDT by resting between meals not on the interior walls of houses, where chemicals are sprayed, but on the exterior walls, where they don’t encounter the chemical at all.

The truth is that DDT is neither superhero nor supervillain — it’s just a tool. And if entomologists have learned anything in the last half-century of dealing with the million-plus species of insects in the world, it’s that there is no such thing as an all-purpose weapon when it comes to pest management. DDT may be useful in controlling malaria in some places in Africa, but it’s essential to determine whether target populations are resistant; if they are, then no amount of DDT will be effective.

We have new means of determining whether populations are genetically prone to developing resistance. DDT advocates are right to suggest that DDT may be useful as a precision instrument under some circumstances, particularly considering that environmental contamination in Africa may be less of a problem than it has been in temperate ecosystems because the chemical can degrade faster due to higher temperatures, moisture levels and microbial activity. Moreover, resistance evolves due to random mutation, so there are, by chance, malaria-carrying mosquito species in Africa that remain susceptible to DDT despite more than two decades of exposure to the chemical.

But environmentalists are right to worry that the unwise use of DDT, particularly where it is likely to be ineffective, may cause environmental harm without any benefit. In 2000, I chaired a National Research Council committee that published a study titled “The Future Role of Pesticides in U.S. Agriculture.” Our principal recommendation is germane to discussions of malaria management: “There is no justification for completely abandoning chemicals per se as components in the defensive toolbox used for managing pests. The committee recommends maintaining a diversity of tools for maximizing flexibility, precision, and stability of pest management.”

Overselling a chemical’s capacity to solve a problem can do irretrievable harm not only by raising false hopes but by delaying the use of more effective long-term methods. So let’s drop the hyperbole and overblown rhetoric — it’s not what Africa needs. What’s needed is a recognition of the problem’s complexity and a willingness to use every available weapon to fight disease in an informed and rational way.

Author’s e-mail: maybe@uiuc.edu

May Berenbaum is head of the department of entomology at the University of Illinois, Urbana-Champaign.

� 2005 The Washington Post Company