WHO looks to DDT for malaria control
In an important policy shift, the World Health Organisation (WHO) on Friday announced that it is urging the use of the pesticide DDT to control the spread of malaria, a mosquito-borne disease that kills about one million people a year, most of whom are infants and young children in Africa.
The announcement by the director of the WHO’s global malaria department, Dr Arata Kochi, stressed that the use of the controversial pesticide, which was banned in the United States in 1972 due to concerns about its effect on animal and human health, should be confined to what is called indoor residual spraying (IRS).
“We must take a position based on the science and the data,” Kochi told reporters in Washington, DC.
“One of the best tools we have against malaria is indoor residual house spraying. Of the dozen insecticides WHO has approved as safe for house spraying, the most effective is DDT.”
He added: “Extensive research and testing has ... demonstrated that well-managed indoor residual spraying programmes using DDT pose no harm to wildlife or to humans.”
Some public-interest and health groups, however, immediately challenged that assessment.
“This approach takes us in exactly the wrong direction,” said Dr Paul Saoke, director of Physicians for Social Responsibility in Kenya. “DDT is a short-sighted response with long-term consequences, and WHO should be helping countries fight malaria with safer and more effective alternatives.”
“Reliance on pesticides, especially DDT, as a silver-bullet solution for malaria protection is extremely dangerous,” according to Jay Feldman, executive director of Beyond Pesticides, a Washington-based public interest group.
He noted that government agencies both here and in other countries have classified DDT as an agent that may cause cancer and nerve damage and disrupt the human and animal endocrine systems.
Indeed, DDT is one of 12 chemicals to be phased out globally under the Stockholm Convention on Persistent Organic Pollutants, substances that are both toxic and persist in the environment—in plants, water, and animal tissue—for many years.
In 2001, the same year that the convention was concluded, the WHO itself published a plan of action for reducing reliance on DDT to control malaria in countries where it was used.
Developed during World War II, DDT, the abbreviation for dicholoro-diphenyl-trichloroethane, was hailed as a “miracle” for its effectiveness in combating malaria, typhus and other insect-born diseases. In 1955, the WHO launched a worldwide programme to eradicate the disease, primarily through the use of the pesticide.
While the effort proved spectacularly successful in reducing mortality, particularly in parts of Asia and Latin America, resistance emerged in many mosquito populations over time, reducing its impact.
At the same time, environmentalists—notably Rachel Carson, whose 1962 bestselling book Silent Spring, about DDT’s effects on the health of birds and their offspring, created a national sensation—began documenting how DDT entered and persisted in the food chain, wreaking havoc on animal populations in the wild. Led by Scandinavia, most industrialised countries had banned DDT by the late 1970s.
While DDT was still being used in many developing countries, global agencies, including the WHO, and foreign-aid donors over the next two decades promoted alternatives, including pesticides that were considered safer than DDT, insecticide-treated bed nets, and drugs designed to prevent or treat malaria.
But progress in reducing the spread of the disease, which infects about 500-million people a year, has been limited, particularly in Africa, due to a variety of problems ranging from weakness of the region’s healthcare systems to the costs and maintenance of bed nets and the speed with which the most deadly malaria parasite, particularly Plasmodium falciparum, develops resistance to drugs.
As a result, the pressure to rehabilitate DDT as a major component of the effort to curb the disease has been rising steadily in recent years, particularly given evidence, cited by the WHO on Friday, that DDT is the most effective of the pesticides used in IRS.
Indoor spraying is the application of long-acting insecticides on the walls and roofs of houses and animal shelters in order to kill malaria-carrying mosquitoes that land there. One application may last as a long as a year.
Fourteen sub-Saharan countries are currently using IRS, and 10 of those, including South Africa, are using DDT, according to the WHO. In addition, the Global Fund to Fight Tuberculosis, Aids and Malaria has endorsed the strategy and is currently financing its use in 41 countries.
The US also stands poised to devote increased resources to IRS. Last year, President George Bush announced his President’s Malaria Initiative, a five-year, $1,2-billion plan to reduce malaria-caused mortality by 50% in 14 sub-Saharan African countries. The initiative, which is administered by the US Agency for International Development, has earmarked $20-million for IRS programmes in 2007, up from only $1-million last year.
“Under the leadership of President Bush, the US has begun to support indoor spraying for malaria control in Africa, including programmes using DDT,” said Oklahoma’s Republican Senator Tom Coburn, who hailed the WHO’s decision to endorse the use of DDT as “bold” and “revolutionary”.
“I hope that these strong new policies on spraying and DDT from the WHO will encourage more donors to do the same,” he said.
In endorsing the use of DDT, the WHO’s Kochi stressed that it should be applied only as recommended and, under no circumstances, used outdoors or for agricultural purposes, as was done in the US before the 1972 ban.
“DDT presents no health risk when used properly indoors,” he said, adding in an appeal to the environmental community: “Help save African babies as you are helping to save the environment.”
That argument, however, is not accepted by many activists. “DDT is not a harmless chemical,” said Kristin Schafer, programme coordinator for the North American section of the Pesticide Action Network, “despite the claims of its aggressive promoters” who, she added, receive support from the pesticide industry.
“While we agree that short-term DDT use may be appropriate in limited cases, we are very concerned that WHO appears to be bowing to pressure from these advocates and backtracking from their commitments to help countries fight malaria without DDT,” she said.
She noted that Vietnam reduced malaria deaths by 97% and malaria cases by 59% when it switched in 1991 to a DDT-free malaria-control programme based on drug distribution, bed nets and local health-education projects.—IPS