A scientist holds a tube containing mosquito larvae to be tested for malaria in Karatina, Kenya.

Washington -- Despite the toll in human lives taken daily by an ancient parasite on the world's poorest and most vulnerable, there are effective ways to fight deadly malaria and a range of international efforts to understand and control the disease.

Malaria infects more than 500 million people a year and kills more than 1 million -- mostly infants, young children and pregnant women, and most of them in Africa. Fighting the disease takes the determined work of many around the world, all of whom are recognized on April 25, World Malaria Day.

The commemoration -- instituted by the World Health Organization’s (WHO) World Health Assembly in 2007 -- is an opportunity for countries in affected regions to learn from each other's experiences, for new donors to join a global partnership against malaria, for research and academic institutions to explain their scientific advances to experts and the public, and for partners, companies and foundations to showcase their successes.

“Malaria is a horrible, perennial, ancient disease that goes back millennia,” Dr. James Herrington, director of the Division of International Relations at the National Institutes of Health’s Fogarty International Center, told America.gov. “Because of that, the mosquito has become very adapted and persistent in its ability to transmit the parasite that causes the disease. But that’s not to say [malaria] can’t be eliminated.”

SEPARATING MOSQUITOES AND PEOPLE

Malaria is a mosquito-borne disease caused by the one-celled Plasmodium falciparum parasite and three closely related species. Each parasite lives part of its life in people and part in mosquitoes. The parasites are transmitted to people in the bites of infected female Anopheles mosquitoes.

In the United States, malaria was a long-term problem in the steamy southeast. In 1947, the Public Health Service’s Communicable Disease Center -- now the Centers for Disease Control and Prevention -- and the health agencies of 13 Southeastern states launched the National Malaria Eradication Program. It consisted mainly of applying the chemical dichlorodiphenyltrichloroethane (DDT) to inside surfaces of rural homes and buildings in counties where malaria was prevalent.

At the same time, the Tennessee Valley Authority was modifying waterways in that region to generate hydroelectricity and eliminate swamps where mosquitoes could lay eggs. Also at the same time, growing U.S. prosperity was drawing millions of Americans away from the mosquito-infested countryside and into cities. By the end of 1949, malaria no longer was a significant public health problem.

Most DDT uses were banned in the United States in 1972 after the chemical was linked to environmental and public health damage. In 2006, despite an ongoing debate about the chemical’s safety, WHO issued a statement promoting the use of indoor spraying -- but not agricultural use -- of DDT for malaria control in areas where the disease is endemic (prevalent).

“One of the successes we can point to,” Herrington said, ‘is that the use of DDT or DDT-like compounds have demonstrated the ability to be an insecticide as well as a repellant. It keeps mosquitoes that are infected with the parasite away from people.”

The public health community, Herrington added, supports WHO’s restrictions on the outdoor uses of DDT.

KEY INTERVENTIONS

According to WHO, key interventions for controlling malaria include indoor spraying; prompt treatment with artemisinin, a medicine derived from the sweet wormwood plant, combined with a second or third anti-malarial drug; and use of insecticide-treated bed nets.

Combining artemisinin -- which interrupts the human half of the parasite’s life cycle -- with drugs like sulfadoxine-pyrimethamine and amodiquine keeps the parasites from becoming resistant to any one of the drugs.

“When used correctly in combination with other anti-malarial drugs in artemisinin combination therapies,” a WHO announcement read, “artemisinin is nearly 95 percent effective in curing malaria and the parasite is highly unlikely to become drug resistant.”

A problem is that it takes 18 months to grow the natural artemisinin product and no one yet has been able to synthesize the compound in the laboratory.

But, according to Joel Breman, Martin Alilio and Nicholas White in a summary to “Defining and Defeating the Intolerable Burden of Malaria III: Progress and Perspectives,” a 42-paper supplement published in December 2007 in the American Journal of Tropical Medicine and Hygiene, a coalition of public and private partners supported by the Bill and Melinda Gates Foundation is using synthetic biology to manufacture a low-cost artemisinin derived from microbes.

The third intervention, insecticide-treated bed nets, separates people and mosquitoes. The parasite-transmitting Anopheles mosquito feeds at night, Herrington said, so the nets have been very effective.

“They’ve been shown through studies,” he added, “to reduce malaria mortality by almost a third in children in malarious areas in Africa.”

In addition to these tools, and over the long term, Herrington said, malaria education programs, research and economic development will be the best ways to fight the disease.

“Malaria is both a result and a cause of poverty,” he said. “Economic development is really key as a long-term tool for fighting this terrible disease.”

More information about malaria is available on the WHO Web site and in the malaria supplement posted on the Fogarty International Center website.

A transcript of remarks by first lady Laura Bush on World Malaria Day is available on the White House website.