Malaria: prevention and treatment

(it holds back human and economic development)

Malaria is a Global Problem

After centuries of fighting malaria—and conquering it in much of the world—it is amazing what we still do not know about the ancient scourge, including what determines life and death in severely ill children in its clutches.

  • Investigators are studying malaria survivors and tracking many other leads in efforts to develop vaccines.
  • Most important, proven weapons—principally, insecticide-treated bed nets, other antimosquito strategies, and new combination drugs featuring an ancient Chinese herb—are moving to the front lines.
  • Malaria not only kills, it holds back human and economic development. Tackling it is now an international imperative.
  • A Villain in Africa

  • Four principal species of the genus Plasmodium, the parasite that causes malaria, can infect humans, and at least one of them still plagues every continent except Antarctica to a lesser or greater degree.
  • Today, sub-Saharan Africa is not only the largest remaining sanctuary of Plasmodium falciparum—the most lethal species infecting humans—but the home of Anopheles gambiae, the most aggressive of the more than 60 mosquito species that transmit malaria to people.
  • Every year 500 million falciparum infections kill Africans, leaving one million to two million dead—mainly children.
  • In addition, within heavily hit areas, malaria and its complications may account for 30 to 50 percent of inpatient admissions and up to 50 percent of outpatient visits.
  • The clinical picture of falciparum malaria, whether in children or adults, is not pretty.
  • In the worst-case scenario, the disease’s trademark fever and chills are followed by dizzying anemia, seizures and coma, heart and lung failure—and death.
  • Those who survive can suffer mental or physical handicaps or chronic debilitation.
  • Lessons of History

  • Malaria was not always confined to the tropics—until the 20th century, it also plagued such unlikely locales as Scandinavia and the American Midwest.
  • The events surrounding malaria’s exit from temperate zones and, more recently, from large areas of Asia and South America reveal as much about its perennial ties to poverty as about its biology.
  • Take, for example, malaria’s flight from its last U.S. stronghold—the poor, rural South.
  • The showdown began in the wake of the Great Depression when the U.S. Army, the Rockefeller Foundation, and the Tennessee Valley Authority (TVA) started draining and oiling thousands of mosquito breeding sites and distributing quinine (a plant-based antimalarial first discovered in South America) to purge humans of parasites that might otherwise sustain transmission.
  • The TVA engineers who brought hydroelectric power to the South also regulated dam flow to maroon mosquito larvae and installed acres of screen in windows and doors.
  • As malaria receded, the local economies grew.

  • Then came the golden days of DDT (dichlorodiphenyltrichloroethane).
  • After military forces used DDT powder to aerially bomb mosquitoes in the malaria-ridden Pacific theater during World War II, public health authorities took the lead.
  • Five years later selective spraying within houses became the centerpiece of global malaria eradication.
  • The resistance to malaria requires constant upgrading!

  • By 1970, DDT spraying, elimination of mosquito breeding sites, and the expanded use of antimalarial drugs freed more than 500 million people, or roughly one third of those previously living under malaria’s cloud.
  • Sub-Saharan Africa, however, was always a special case: with the exception of a handful of pilot programs, no sustained eradication efforts were ever mounted there.
  • Instead the availability of chloroquine—a cheap, man-made relative of quinine introduced after World War II—enabled countries with scant resources to replace large, technical spraying operations with solitary health workers.
  • Dispensing tablets to almost anyone with a fever, the village foot soldiers saved millions of lives in the 1960s and 1970s.
  • Then chloroquine slowly began to fail against falciparum malaria.
  • With little remaining infrastructure and expertise to counter Africa’s daunting mosquito vectors, a rebound in deaths was virtually ordained.
  • Along the way, economists learned their lesson once again.
  • Today in many African households, malaria not only limits income and robs funds for basic necessities; such as, food and youngsters’ school fees, it fuels fertility because victims’ families assume they will always lose children to the disease.
  • On the regional level, it bleeds countries of foreign investment, tourism, and trade.
  • Continent wide, it costs up to $12 billion a year, or four percent of Africa’s gross domestic product.
  • In short, in many places malaria remains entrenched because of poverty and, at the same time, creates and perpetuates poverty.
  • Battling the Mosquito

    Some highly intelligent residents of malaria-plagued communities still believe that an evil spirit or certain foods cause the illness, a fact that underscores yet another pressing need: better malaria education.

  • Nevertheless, long before Ronald Ross and Giovanni Batista Grassi learned in the late 19th century that mosquitoes transmit malaria, savvy humans were devising ways to elude mosquito bites.
  • Writing almost five centuries before the common era, Herodotus described in The Histories how Egyptians living in marshy lowlands protected themselves with fishing nets: “Every man has a net which he uses in the daytime for fishing, but at night he finds another use for it: he drapes it over the bed. . . . Mosquitoes can bite through any cover or linen blanket . . . but they do not even try to bite through the net at all.”
  • Based on this passage, some bed-net advocates view nets steeped in fish oil as the world’s earliest repellent-impregnated cloth.
  • It was not until World War II, however, when American forces in the South Pacific dipped nets and hammocks in five percent DDT, that insecticides and textiles were formally partnered.
  • After public opinion turned against DDT, treating bed nets with a biodegradable class of insecticides—the pyrethroids—was the logical next step.
  • It resulted in a breakthrough.
  • The first major use of pyrethroid-treated nets paired with antimalarial drugs, reported in 1991, halved mortality in children younger than five in the Gambia, and later trials, without the drugs, in Ghana, Kenya.
  • With wide enough use, whole families and communities benefited from the nets— even people who did not sleep under them.
  • Insecticide-treated bed nets also have drawbacks.
  • They work only if malaria mosquitoes bite indoors during sleeping hours—a behavior that is not universal.
  • Nets make some sleepers hot, discouraging use.
  • Until recently, when PermaNet and Olyset—two long-lasting pyrethroid-impregnated nets—became available, nets had to be redipped every six to 12 months to remain effective.
  • In addition, at $2 to $6 each, nets with or without insecticide are simply unaffordable for many people.
  • Insecticide resistance could also undermine nets as a long-term solution: mosquitoes genetically capable of inactivating pyrethroids have now surfaced in several locales, including Kenya and southern Africa, and some anophelines are taking longer to succumb to pyrethroids, a worrisome adaptive behavior known as "knockdown resistance".
  • Because precious few new insecticides intended for public health use are in sight (largely because of paltry economic incentives to develop them), one solution is rotating other agricultural insecticides on nets.
  • Some malarial specialists advocate use of DDT for home spraying to fight mosquitoes.

  • Decoding the olfactory clues that attract mosquitoes to humans in the first place is another avenue of research that could yield dividends in new repellents.
  • For the time being, old fashioned, indoor residual spraying with DDT remains a valuable public health tool in many settings in Africa and elsewhere.
  • Applied to surfaces, DDT is retained for six months or more.
  • It reduces human-mosquito contact by two key mechanisms—repelling some mosquitoes before they ever enter a dwelling and killing others that perch on treated walls after feeding.
  • Treating the Sick

  • Anti-mosquito measures alone cannot win the war against malaria— better drugs and health services are also needed for the millions of youngsters and adults who, every year, still walk the malaria tightrope far from medical care.
  • Some are entrusted to village herbalists and itinerant quacks.
  • Others take pills of unknown manufacture, quality, or efficacy (including counterfeits) bought by family members or neighbors from unregulated sources.
  • In Africa, 70 percent of antimalarials come from the informal private sector—in other words, small, roadside vendors as opposed to licensed clinics or pharmacies.
  • Despite plummeting efficacy, chloroquine, at pennies per course, remains the top-selling antimalarial pharmaceutical that is drunk by Africans.
  • The next most affordable drug in Africa is sulfadoxine-pyrimethamine, an antibiotic that interferes with folic acid synthesis by the parasite.
  • Unfortunately, P. falciparum strains in Africa and elsewhere are also sidestepping this compound as they acquire sequential mutations that will ultimately render the drug useless.
  • Preventing, as opposed to treating, malaria in highly vulnerable hosts—primarily African children and pregnant women—is also gaining adherents.
  • More investments in the fight against malaria are needed

  • Once again the world is coming to terms with the truth about malaria: the ancient enemy still claims at least one million lives every year while, at the same time, imposing tremendous physical, mental and economic hardships.
  • Given our current tools and even more promising weapons on the horizon, the time has come to fight back.
  • This is an ancient disease that is both preventable and curable, but it still claims at least one million lives every year.
—Compiled from information located in
"Tackling Malaria" by Claire Panosian Dunavan
Scientific American; December, 2005; pages 57-63.

Pointing to a page about mosquitoes Extensive information about mosquitoes and their behaviors is available here with special illustrations for greater understanding.