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How this works. What is malaria? What causes malaria? What are the symptoms of malaria? How is malaria diagnosed? Life-threatening complications of malaria. How is malaria treated? Tips to prevent malaria. More than twenty times that many Africans die every day of malaria. Malaria parasites have spent centuries adapting to life in the human body, and as a result have grown cagey. The parasites are transmitted to human beings through the saliva of the female mosquito, which is so efficient at this task that it is sometimes described as a flying syringe.
Once injected, the parasites quickly retreat to the liver, where they mature and multiply.
It is not until they re-emerge in the bloodstream and invade the blood cells that symptoms appear. By this time the parasites have reproduced thousands of times. They thrash about, popping blood cells, clogging blood vessels, debilitating their host, and in some cases killing within hours. Like HIV and tuberculosis, malaria does not elicit what is called a complete immune response in human beings: we can be infected with these microbes repeatedly, or carry them for any amount of time, without developing a full resistance to them.go
The Aroma of Malaria Infection
Nor do we develop a protective immune response to these diseases, as we do for such infections as polio, measles, and smallpox. Whatever immune reaction we develop appears to occur deep in the cell, and is devilishly difficult to elicit.
Never yet has a vaccine been proved successful against a parasite, and malaria is a particularly difficult target for a vaccine, because in each of the several stages it goes through, it has the opportunity to take hold in the host. Because it is so deadly, the malaria parasite has wielded surprising influence over the way human beings have evolved. Sickle-cell anemia, an excruciating and usually fatal genetically transmitted blood disorder, offers the most dramatic example. Historically, victims of sickle-cell disease, who have inherited the sickle-cell gene from both parents, were generally sick much of their lives and tended to die young, often before they had the opportunity to bear children.
This should doom sickle-cell in terms of natural selection, which by definition selects for characteristics that ensure that an organism will live long enough to reproduce itself. But the sickle-cell trait, which occurs in people who get the gene from just one parent, is not lethal, and in fact confers partial protection against malaria. People who have the sickle-cell trait may get sick with malaria, but they are unlikely to die of it. The evolutionary fact that human beings have taken on a lethal blood disorder in exchange for partial protection against malaria shows the unprecedented power of the disease.
Malaria inspires such fear that forty years ago the World Health Organization targeted it for global eradication. Worldwide investment in the project ran into the hundreds of millions of dollars, with some Third World countries kicking in 30 to 50 percent of their health-care budgets. The main thrust of the effort was the spraying of powerful, long-lived insecticides into the interior walls of homes. The target was the Anopheles gambiae mosquito, which carried P.
Hut after hut was sprayed, and untold legions of A. Malaria rates went down, and hopes for public health soared.
Malaria | Nature Reviews Disease Primers
But the optimism was short-lived. Meanwhile, for complex reasons, mosquitoes where malaria was solidly endemic started showing resistance to the insecticides. In the Global Eradication of Malaria Program was replaced with a global malaria- control strategy. But in reported malaria incidence was far higher than what it had been fifteen years earlier. This made a real impression on me. We thought we'd licked malaria in India, but of course we were terribly wrong. The WHO now estimates that malaria kills as many as 2.
Children infected repeatedly with malaria over a period of about five years generally develop a partial resistance that allows them to carry the parasite in their blood without getting deathly or even overtly ill.
History of malaria
Adults develop this partial immunity too, in somewhat less time. But this does not mean that they can no longer be infected; it means only that their bodies have learned to keep the symptoms in check. Malaria parasites have a voracious appetite and in just a few hours can suck as much as a quarter pound of hemoglobin out of the red blood cells of an infected human being. Hundreds of millions of African children and adults are chronically infected with malaria, and are anemic much of the time. Bernard Nahlen, a physician who is studying malaria in Kenya, told me that one in twenty children in the villages surrounding his clinic are so anemic that were their blood tested in the United States, they would be rushed to a hospital for emergency transfusions.
ON the main road leaving Dakar through the savanna of western Senegal traffic thins and the landscape thickens with sorghum, melon, and peanut farms. Manioc sprouts in bushy clumps, and nomadic herders thread flocks of bony goats and long-horned cattle through clumps of mango and baobab trees. Lamine Diawara, a physician, an entomologist, and a commander in the Senegalese army, pulls our pickup truck over to ask directions from a group of people selling oranges by the side of the road. One of them, a man of about twenty in a tattered knee-length tunic and a headdress, swings first a canvas sack of peanuts and then himself into the bed of the pickup.
Diawara shrugs and drives on. The truck he has borrowed to make the journey is finicky and slow; we pass horse-drawn carts but no cars.
Dignified in his sharply pressed military uniform, Diawara is uncomfortable with silence, and his voice is soft but urgent. Since morning he has spoken of almost nothing but malaria. But it is malaria that keeps Africa down. Diawara is taking me to a village where he often comes to observe and treat patients. The village is a cluster of thatched huts some distance off the main road, on a dirt track that dissolves into a grassy path. Here most of the women have infants slung on their backs, as do some girls who appear to be as young as five.
Young men relax in the shade while their wives pound sorghum and sort seeds. The children crowd Diawara, who strides off to seek the elders, five of whom emerge beaming from one of the huts, hands outstretched in greeting. Speaking in Woloff, Diawara asks permission to show me around, and they volunteer to serve as guides.
I ask if they have been ill lately. The head elder nods, and says he has suffered from malaria four times this season.
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The others indicate that they, too, have been afflicted. We visit the village clinic, a cement-block hut hung with posters promoting "safe love" in English and Arabic. Inside there are no medical supplies, no equipment, and no lights. There are no medical personnel; a teenager trained in recognizing malaria symptoms comes in from time to time to hand out anti-malaria medications. This is the best that can be hoped for in rural areas, because anti-malaria drugs are costly; often there is no money for them.
Related Malaria (Perspectives on Diseases and Disorders)
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