DDT: Malaria's answer in Africa?
June 16, 2002
By Tom Carter
THE WASHINGTON TIMES
Imagine seven jumbo jets, each packed with women and children, crashing into the ground every day — day after day, year after year — adding up to more than 2 million deaths a year. Now imagine that many, if not most, of those deaths could have been prevented with limited use of DDT, the chemical insecticide that brings a grimace of revulsion, fear and horror at its mention.
"What you need is a whole set of arrows in the quiver. Along with mosquito nets, other insecticides and drugs, DDT needs to be one of them," said Mr. Attaran, an immunologist and lecturer at Harvard University's Center for International Development.
Mr. Attaran, also a lawyer who once worked for Canada's Sierra Club, is leading a worldwide crusade to bring back DDT. He says people who oppose DDT are simply ignorant of the science. It is safe when used properly, cheap and effective.
A global plague
Although malaria is found on every continent, in more than 90 countries of the world, 90 percent of those affected live in sub-Saharan Africa.
It is as deadly, if not more so, than HIV/AIDS or tuberculosis. Every day, more than 3,000 African children under the age of 5 succumb to the violent shaking chills, the raging fevers, the drenching sweats and excruciating head and body aches that accompany the parasitic infection.
In its later stages, children with malaria go into uncontrollable seizures. A virulent case can kill a child in 24 hours. Despite billions of dollars and decades of research, there is still no vaccine that is good for more than a few weeks.
According to the U.N. World Health Organization (WHO), malaria kills one child under the age of 5 every 30 seconds.
"It is a death toll that far exceeds the mortality rate from
AIDS," according to the WHO fact sheet on malaria.
It is cheap, three to five times cheaper than the pyrethroid insecticides prescribed by the WHO and the U.S. Agency for International Development (USAID).
It is more effective than the alternatives — a few ounces sprayed on the inner walls of a dwelling once a year confers protection. And despite its pariah status, numerous scientific studies indicate that for humans, it is less poisonous than aspirin.
A bad reputation
DDT's status as the ultimate icon of environmental evil began with the 1962 publication of "Silent Spring" by Rachel Carson.
At the time, U.S. farmers were dumping an estimated 80,000 tons of DDT on fields each year. As a result, the bald eagle, the majestic symbol of the United States dating back to its early days as an independent nation, was in danger of becoming extinct in the lower 48 states.
DDT from agricultural use had washed into the rivers and streams, where it had entered the food chain. It had gotten into the fish that the eagles and other birds of prey ate. It had caused their eggs to become too fragile to hold tiny embryos. The eggs cracked under their own weight.
The chemical settled in the fat deposits of everything from the smallest critters in the animal kingdom up to human beings.
One study in 1966 found that the average American teen-ager consumed 12.4 milligrams (0.0004 ounces) of DDT year. Because it was so deadly to many birds, people assumed it had to be bad for humans as well, even if scientific evidence of human toxicity never entered the equation.
So pervasive was the anti-DDT hysteria, that the public outcry is often cited as the beginning of modern environmental activism in the United States.
In 1972, a decade after the publication of "Silent Spring," DDT was banned in the United States.
Keep it indoors
Today, advocates of limited DDT use in the battle against malaria warn that it should never again be used in farming.
But yearly spraying of houses in malaria-prone areas in Asia, Latin America and Africa, they say, would dramatically cut the toll.
Today, the experience of South Africa and neighboring Mozambique in dealing with malaria vividly illustrates the battle lines in efforts to bring back DDT.
For 50 years, South Africa used DDT to control its malaria, but in 1996 its new democratic government, concerned about research finding DDT in mothers' breast milk, succumbed to international pressure and stopped using the chemical.
Almost overnight, South Africa's malaria rate jumped from just a few thousand cases a year to more than 50,000 a year, overtaking the number of new cases of HIV/AIDS infection.
Last year, to howls of protest from environmentalists, the WHO and other international agencies, South Africa began "IRS," — indoor residual spraying of house walls with DDT — at two grams (0.07 ounces) per square meter (1.2 square yards) on internal walls — and saw a raging malaria epidemic end in eastern South Africa, along the boarder with Mozambique. Thanks to DDT, the epidemic has been stopped cold, and South Africa is pressing Mozambique to follow suit.
But Mozambique wants nothing to do with a chemical that is banned in most of the world. It argues that an insecticide too dangerous for American houses is too dangerous for African use.
"How do you think we eradicated malaria in the United States? DDT," said Mr. Attaran when asked about Mozambique's concerns.
Interest in Uganda
In Uganda, government scientists and doctors who work to control the nation's No. 1 killer are quietly discussing reintroducing of DDT.
"There is nothing that says DDT is a problem when used explicitly as an indoor spray," said Michael Okia, senior entomologist for Uganda Malaria Control, in an interview in Kampala, Uganda.
"We've been discussing it. South Africa has shown there are no problems with DDT, as long as it is used only as an indoor spray for malaria and not for agriculture or to control other insects like cockroaches."
He said he would like to be able to target DDT use for areas where malaria epidemics break out like clockwork — during the two rainy seasons each year.
The high cost of alternative insecticides makes inexpensive DDT especially attractive.
"It is fine for rich countries to dictate to us what we can and cannot use, but where do we get the money? We are already a poor country," Mr. Okia said. "I do not know of any developing country that has the money" to use only Western approved chemicals.
The fear is that the international aid agencies, which keep Uganda afloat, will withdraw their financial support if Uganda reintroduces DDT to save its children.
World Bank says no
The World Bank recently gave Eritrea $5 million to deal with its rampant malaria but only on condition that it cease using the DDT within two years. And the British Medical Journal has reported that international aid to Mozambique, which funds 80 percent of the nation's health budget, continues to flow but that the "donors refused to allow the use of DDT." That alone would explain Mozambique's stand on DDT despite the fact that malaria is the nation's second-highest killer.
Ugandan officials understand that the threat to cut aid over DDT is real.
"We will have to talk with our stakeholders, but we think there is a way that we can use DDT," Mr. Okia said.
Scientists and researchers say that the people who oppose DDT are environmentalists and policy-makers with little or no scientific training.
"There is no big controversy in the scientific community over DDT. The controversy is between scientists vs. the politicians and environmental activists," said Donald Roberts, professor of tropical public health at the Uniformed Services University of the Health Sciences in Bethesda.
Mr. Roberts was one of more than 400 scientists, Nobel Prize winners and medical doctors from 57 countries who signed an "open letter" last year demanding that DDT be allowed for malaria control.
"At worst there are small heath risks, and very large benefits to DDT house spraying," the letter said. "It would be a terrible error to eliminate DDT, which probably saves hundreds of thousands of lives a year from malaria."
Harvard's Mr. Attaran, who organized the petition, said environmentalists are correct when they say DDT may be a cancer-causing carcinogen, even if there is not a single scientific study that confirms the possibility.
Costs vs. benefits
But doctors, he said, use "known carcinogens" every day to treat various diseases because the "reward" — the disease is treated — is greater than the "possible risk" of developing cancer.
"Children are dying. It is worth the possible risk," Mr. Attaran said.
Mr. Roberts accused Western environmentalists of caring more
about birds than about African children.
Mr. Roberts, who has focused on malaria and its prevention for 35 years, said there are four types of malaria transmitted to humans by at least 35 species of Anopheles mosquito.
All four types can kill, but plasmodium falciparum is the most deadly. For a mosquito bite to become a lethal injection, a mosquito must first bite and drink the blood of someone who carries the malaria protozoa. It then must live inside the mosquito for 10 to 14 days while the parasite incubates and matures.
When mature, the parasite migrates to the mosquito's salivary glands. When the mosquito bites again, it leaves behind some of its saliva, which carries the parasite. In humans, it goes straight to the liver. Seven to 14 days later, malaria symptoms appear.
Most malaria victims contract the disease after being bitten indoors, while sleeping. To stop malaria, it is only necessary to break the cycle. That is where DDT comes in.
Protect the house
mosquitoes from coming inside for the nighttime feast. Mosquitoes are
astonishingly sensitive to the chemical. Most will not even fly into
a room that has been sprayed. Those that do usually do not stay long
enough to feed. If they light on a sprayed wall, the minute amount of
DDT absorbed through their feet will kill them before they can bite
DDT was discovered by a Swiss chemist, Paul Herman Muller, just before the start of World War II. It was used throughout the war for lice prevention. Entire cities in Italy were dusted to control the typhus carried by the lice. DDT was effective against insects and it seemed to work forever. In addition, it was virtually harmless to humans. In 1948, Mr. Muller won a Nobel Prize for his discovery.
In the first two decades after the war, it was used to target the mosquitoes that carry malaria, and the results were staggering. Malaria rates in Sri Lanka dropped from 2.8 million cases and 7,300 deaths in 1946, to 17 cases and no deaths a few years later.
In 1963, DDT funding in Sri lanka ended, and just six years later, Sri Lanka recorded 520,000 cases of malaria. India's annual death rate from malaria plummeted from 800,000 to virtually zero in the early 1960s.
In 1935 the United States had approximately 130,000 cases of malaria annually, resulting in about 4,000 deaths. In the 20 years after the war, DDT eradicated malaria in southern Europe and the United States. There was also a drop in other insect-borne diseases including kala azar, dengue fever, sleeping sickness, typhus, yellow fever and West Nile virus, all of which are making dramatic comebacks today.
In 1970, the National Academy of Sciences said that DDT had saved untold millions of lives that would have otherwise been lost, concluding: "To few chemicals does man owe as great a debt as to DDT."
Advocates of its reintroduction today say that statement remains true 30 years later.
"When used correctly and with restraint, DDT appears to be irreplaceable in antimalaria programs," wrote Andrew Spielman and Michael D'Antonio in last year's best seller "Mosquito: A Natural History of Our Most Persistent and Deadly Foe."
Opposition still strong
But the forces against DDT remain formidable.
Environmental interests — led by the World Wildlife Fund and Greenpeace — point to a single study in Mexico that indicates that DDT shows up in mothers' breast milk and shortens lactation.
There is also limited research that suggests DDT may disrupt hormones in humans. However, those findings have not been duplicated by independent researchers, despite several tries.
According to DDT advocates, while the chemical is deadly for mosquitoes, other insects and some birds, there are no independently verified studies that show that DDT is harmful to humans.
"You could eat a spoonful of it and it wouldn't hurt you," Mr. Roberts said.
In fact, in 1957 a research team actually fed a man 35 milligrams (0.001 ounces) of DDT a day for two years, with no ill effects.
"DDT is less toxic than aspirin," said Ronald Rosenberg, who spent the past 25 years running tropical disease laboratories for the U.S. Army in Asia and Africa. Now at the U.S. Department of Agriculture in Beltsville, Mr. Rosenberg, a retired colonel, said the army was interested in malaria because it was a "war stopper," making soldiers so sick they could not pull a trigger.
After years in Bangladesh, Kenya and Indonesia, Mr. Rosenberg advocates using DDT as "part of the arsenal in health control." He said the biggest problem with using DDT is that without proper controls — and there are few if any controls in the places where malaria is rampant — the chemical could be diverted to agriculture.
"Whoever is in charge of malaria control should have the option of using DDT, and if it is used properly, not much will get into the environment," he said. "The problem is there will be a black market for it for rice, or tomatoes or whatever. I saw this happen in Bangladesh."
More importantly for malaria control, mosquitoes began to develop a resistance to DDT when it was widely used on farms.
"No one is arguing that DDT should be used in agriculture again," said Mr. Roberts. "It is true, DDT kills birds, but the primary source of DDT is dietary. People don't eat house walls. Birds don't eat house walls. We have a globally binding treaty that DDT cannot be used for agriculture, but if we can use it for mosquito control, we can save some lives."
While there are no studies proving DDT harms people, most are still scared of the chemical. And there is a cosmetic downside to using it. It leaves an unsightly residue on the walls of houses and huts where it is used. Also, there is evidence that it makes bedbugs more active.
USAID spent about $50 million last year on malaria programs, compared with about $300 million for AIDS. The figure was increased to about $65 million for 2002.None of the money spent by USAID at this time buys DDT, although a recent treaty permits a "narrow window for procurement of DDT," said Dennis Carroll, who heads USAID's malaria program. Mr. Carroll said, "DDT procurement by USAID is not likely to happen soon."
Mr. Carroll said his agency is betting on prevention, medical intervention and mosquito nets dipped in pyrethriods — a synthetic insecticide originally found in chrysanthemums — to lower malaria's death rate by 50 percent by 2010.
"The question of IRS, indoor residual spraying, from a health perspective in Africa is a nonissue, a sideshow," he said. "In tropical Africa, it has not been shown to be effective. The housing construction does not allow for the kind of coverage that gives protection. It is very safe to say that for the vast majority of Africa, DDT is not a good match."
He said studies in Nigeria in the 1970s and 1980s showed that house spraying had no demonstrable impact on public health because the average person received 50 to 1,000 bites a year. As it only takes one bite to transmit malaria, with that much transmission, indoor spraying was highly ineffective, he said.
He said it does work in parts of Asia and Latin America, but in Africa, where 90 percent of all malaria occurs "it is not a practical option."
Mr. Roberts said the WHO's "Garki Project" in Nigeria from 1969 through 1970 is often cited by DDT opponents as evidence that DDT and indoor spraying is ineffective.
"In reality, DDT was not even used in the project," he said. "Where DDT was used in Nigeria it was, to varying degrees, successful."
Harvard's Mr. Attaran said there are plenty of places in Africa where DDT would "work spectacularly." He put Malawi and Mozambique at the top of the list.
The use of DDT to control malaria in Uganda was studied by the WHO in 1959-1960. Called the Uganda Malaria Eradication Pilot Project, researchers did house spraying in the north of the Kigezi, in Western Uganda and in part of the Masaka district, in central Uganda. They called their results "remarkable." The WHO study concluded that using DDT for malaria eradication in large areas of Uganda was "feasible."
"A reduction of this magnitude in such a short space of time has seldom, if ever, been seen in tropical countires," wrote J. de Zulueta, a WHO malaria specialist in the January 1961 edititon of the East African Medical Journal.
"Nobody ever said that DDT will work in all places. For a strategy to be valid it has to work in some places. You need walls. South Africa is in Africa and it works spectacularly there," Mr. Attaran said.He said those in Congress who care about Africa and African children should stipulate that USAID spend some of its malaria funding on DDT for Africa.
Nets not enough
Mr. Rosenberg said that bed nets work if they are used but that the $5 needed to buy them put bed nets way down the list of what most families want. According to surveys in rural Africa, most want a bicycle first, a radio second and a plastic bucket third. The bed net comes in at No. 6, he said.
"Indeed they work very well. A [Centers for Disease Control] study just in and one from Oxford three years ago show that bed nets can reduce the disease by 30 to 50 percent," he said. "We did a survey, and they'd say, 'Sure, we know bed nets work, and they prevent malaria, but what I really need is a bicycle.'"
Doctors and malaria specialists in Uganda said that the international net campaign — called Roll Back Malaria — is designed to cut malaria in half by the year 2010. It is funded by the WHO, the World Bank, USAID and other international agencies, but critics say the the campaign is limping along.
"It is not working as well as we had hoped," said Dr. Peter Langi, head of Uganda's malaria-control program. "We have to convince the people of their benefits."
Two years ago at Abuja, Nigeria, African heads of state met with international aid agencies and promised to put malaria eradication at the top of the agenda. But according to Mr. Attaran, it was mostly rhetoric. At that meeting, the World Bank pledged an additional $300 million to $500 million to help fight malaria, but so far little has been spent.
"There is only one thing cheaper than DDT when dealing with malaria, and that is doing nothing. And that is exactly what they are doing nothing," he said. "It all very well to say we like bed nets, but what is the goal, to be politically correct or to save lives? If you want to save lives, it makes sense to use DDT."