Not long ago the world seemed poised for victory in its struggle against malaria. Armed with new drugs and potent pesticides, the World Health Organization (WHO) declared in 1955 that the disease would soon be eradicated. Obviously, things haven’t gone according to plan. Today the number of cases is rising worldwide. Malarial parasites now infect an estimated 270 million people every year, killing up to 2 million (far more than AIDS) and causing at least 100 million cases of acute illness. And health officials fear the situation could soon take a turn for the worse. People are flooding into malarial areas in unprecedented numbers to claim land, seek riches or escape oppression. At the same time, the disease is growing ever more resistant to once curative drugs. In Southeast Asia, drug resistance is advancing so rapidly that some strains could soon be untreatable. Overall, says Dr. Louis Miller, head of malarial research at the National Institutes of Health in Maryland, “we’re worse off than we were in 1950.”
Malaria is among the original human afflictions; experts speculate that malarial parasites first infected Homo erectus a million years ago, in the forests of Southeast Asia, then spread westward into Africa and Europe, eventually following Columbus to the New World. The illness starts with aches and a fever, often accompanied by vomiting. A child infected with a virulent strain can die within hours of the first symptoms, as ravaged blood cells clog capillaries and deprive the brain of oxygen. Milder cases are marked by drenching sweats and shaking chills, followed by months or even years of anemia and periodic fevers. The effects are particularly dire during pregnancy, for anemia can both slow the growth of a fetus and cause premature delivery. The WHO estimates that in heavily infested areas, up to 80 percent of first-time mothers are anemic and 40 percent of their babies are born dangerously underweight.
Until the late 19th century, the source of this scourge was a mystery. Few scientists even suspected mosquitoes of playing a role. But in 1880, the French physician Charles Laveran spotted a strange microbe in the blood of afflicted patients, and other researchers began to trace the complex web linking the mosquito, the parasite and the illness. The process starts when a feeding mosquito deposits the parasite, in a threadlike form, into a person’s bloodstream. The parasite travels to the liver and re-emerges, in vastly increased numbers, as a ring-shaped particle. In this new guise, it burrows into red blood cells to feed on hemoglobin and continue reproducing. At regular intervals, the infected red cells explode, unleashing a new generation of parasites into the bloodstream. People living in highly malarial areas develop partial immunity by struggling through countless bouts of illness, but travelers and immigrants are always vulnerable. And in regions where malaria strikes only occasionally, everyone is a potential target.
Doctors started treating malaria long before they knew what caused it. The first recorded breakthrough came in the 17th century, when European missionaries learned that the bark of South American cinchona trees contained the potent but toxic remedy now known as quinine. Chloroquine, introduced in 1943 by the U.S. military, was as potent as quinine-yet it was longer-acting, cheaper to produce and so well tolerated that people could take regular doses to prevent the disease. Today’s arsenal includes several related compounds as well. But drug treatment is not the only way to fight the disease. During the early 1900s, many countries mounted engineering projects to deprive mosquitoes of places to breed, and by 1950, pesticides were achieving the same effect. One newly developed agent, DDT, was so potent that any surface coated with it would poison mosquitoes on contact for six mouths.
The WHO’s 1955 eradication program called for five years of intensive spraying, combined with aggressive chloroquine treatment for people who contracted the illness. But the agency inexplicably excluded Africa from the program. And as the tropical-disease expert Robert S. Desowitz recounts in his book “The Malaria Capers,” the effort didn’t always proceed smoothly in other parts of the world. Sometimes DDT would kill off a community’s cats, causing an explosion of rats and a loss of crops. Or it would cause everyone’s roof to collapse, by exterminating the wasps that normally kept palm-eating caterpillars in check. Such misadventures eroded the program’s political support, as did the hostility of Western environmentalists. To make matters worse, some mosquitoes grew resistant to DDT, or simply learned to avoid it.
Treating patients proved just as complicated. Even a successful antimicrobial drug serves ultimately to wipe out only the most susceptible strains of a pathogen. As other, more resistant strains flourish, the drug loses its effect. Doctors can slow the process by prescribing a treatment sparingly and ensuring that every user receives a full course. But chloroquine was so cheap and abundant that people bought it for pennies on street corners and used it sporadically to treat symptoms. By the late 1960s, with DDT falling from favor and chloroquine losing its punch, eradication was out of the question.
Since then, some countries have succeeded spectacularly at managing the scourge, but the global situation has worsened. Throughout much of Africa, Asia and Latin America, more people are getting infected, and the average case is getting harder to treat. The greatest burden falls on Africa, where Plasmodium falciparum, the most dangerous of malaria’s four common strains, strikes nearly 100 million people each year, killing the better part of a million children. Road building and urbanization have helped speed transmission of the illness, by making people more mobile and placing them in closer contact. And the continent’s crushing poverty continues to deprive stricken patients of care that could save them. Kenya now spends only about $10 per capita on health services each year. Local clinics sometimes lack the equipment to do a simple blood smear, and hospitals are growing more crowded even as their funds are cut back.
The scene at Nyanza Provincial Hospital, in the western Kenyan town of Kisumu, is typical. To reach ward 6, you climb a stairwell that reeks of stale urine. The hall echoes with the droning wail of a “hospital child,” a severely retarded boy, probably 6 years old, who was abandoned on a street corner two years ago. Two rooms of the ward are reserved for children with Burkitt’s lymphoma, a deadly yet curable cancer often associated with chronic malaria. The children have puffy tumors protruding from their faces and other parts of their bodies. The treatment they need is available locally for about $400, but most can’t possibly afford it. “There is so much suffering and we know it could be better,” says Dr. Margaret Maloba, a general practitioner in the ward. “When they come in, I’ve already prepared myself psychologically. They can live or die; I’ll just do my best.”
The situation is no less volatile on the other side of the Pacific. In Thailand, where health officials have successfully controlled malaria for several decades, nearly 55 million people are now sitting directly between two teeming reservoirs of the world’s deadliest strains. In the densely forested hills that separate the country from Myanmar (formerly Burma) on one side and Cambodia on the other, the falciparum parasite has become increasingly resistant to all available treatments. And as in Brazil, social changes are forcing people and the parasite into ever closer contact.
Myanmar’s political upheavals have pushed thousands of refugees across the Thai border in recent decades, and their constant movement makes malaria control all but impossible. Some 15,000 new cases, 70 percent involving falciparum, occur annually among the 30,000 Karen tribespeople living along the frontier. In many villages, infant-mortality rates approach 30 percent. Newcomers to the area are at particular risk. “I’ve been sick more than I’ve been well,” says Thu Yein, a 25-year-old student turned guerrilla who is recuperating from what he says is his 20th bout with falciparum in four years.
The epidemic on the border with Myanmar is dwarfed by the one taking shape along the Cambodian frontier. Cambodia’s Pailin region, famed for its rubies and its virulent malaria, has long drawn gem hunters from Thailand and beyond. The ruby rush turned into a stampede in 1988, when the Khmer Rouge gained control of the area and officially opened it to Thai miners. This year alone, more than 250,000 miners have entered Cambodia through Thailand’s Trat province. As the miners return home carrying drug-resistant falciparum, health officials fear they will infect local mosquitoes and seed broader outbreaks.
But that has yet to happen. Despite the borderland epidemics, Thailand’s overall caseload has held steady in recent years, and the death toll has fallen. Much of the credit belongs to clinics like the one at Muangdan, a Thai-Cambodian border village frequented by itinerant miners. The clinic is nothing fancy-just a tin-roofed shed bearing a sign that warns MALARIA KILLS. IF YOU HAVE FEVER, CHILLS, HEADACHE, GET YOUR BLOOD SAMPLED HERE. It does a brisk and vital business. Of the 63 miners who stopped in on a recent day, 10 needed treatment for falciparum.
Unfortunately, success has a dark side. Thailand’s liberal use of medication to treat and prevent malaria has made it a global cradle for drug resistance. Chloroquine and the related drug Fansidar, still marginally effective in most parts of the world, are now useless against the falciparum parasite in Thailand. Backup drugs such as mefloquine and halafantrine are fast losing their effect, and so is the old standby quinine. Experts say that without new therapies, Asia could face wholly untreatable strains of malaria by the end of the decade. Dr. Adrian Hill, a malariologist at Oxford University, has suggested the death toll could reach 10 million a year.
As Thailand’s experience makes clear, malaria is still largely a treatable illness. The vast majority of today’s deaths are needless, resulting not from exotic new strains of the Plasmodium parasite but from a lack of cheap, simple interventions. New remedies will soon be essential, but drug companies have largely given up looking for them. From a commercial perspective, it makes little sense to turn out costly pharmaceuticals for people who can’t afford shoes. The U.S. military, traditionally the world’s leader in malaria research, has drastically cut its commitment as well. Altruism has never played a big role in malaria research. Quinine enabled Europe to colonize the tropics. Chloroquine grew out of efforts to protect U.S. troops abroad. Without an empire or an army on the line, the developed world will need a new rationale for fighting malaria. At the moment, the best one is that 2.1 billion people-about 40 percent of the world’s population-are in danger.
Developed countries are now largely free of malaria, but it remains well entrenched across the tropical world. The greatest burden falls on Africa.
97 million cases a year. The tropical region’s leading killer of children claims 5% under 5.
1 million cases a year. The settlement of mosquito-infested rain forests in Brazil has exposed millions to the disease.
9 million cases a year. New, hard-to-treat strains are rapidly gaining ground.
