Nearly thirty years after phasing out the widespread use of indoor spraying with DDT and other insecticides to control malaria, the World Health Organization (WHO) today announced that this intervention will once again play a major role in its efforts to fight the disease. WHO is now recommending the use of indoor residual spraying (IRS) not only in epidemic areas but also in areas with constant and high malaria transmission, including throughout Africa.

“The scientific and programmatic evidence clearly supports this reassessment,” said Dr Anarfi Asamoa-Baah, WHO Assistant Director-General for HIV/AIDS, TB and Malaria. "Indoor residual spraying is useful to quickly reduce the number of infections caused by malaria-carrying mosquitoes. IRS has proven to be just as cost effective as other malaria prevention measures, and DDT presents no health risk when used properly.”

WHO actively promoted indoor residual spraying for malaria control until the early 1980s when increased health and environmental concerns surrounding DDT caused the organization to stop promoting its use and to focus instead on other means of prevention. Extensive research and testing has since demonstrated that well-managed indoor residual spraying programmes using DDT pose no harm to wildlife or to humans.

"We must take a position based on the science and the data," said Dr Arata Kochi, Director of WHO’s Global Malaria Programme. “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.”

Indoor residual spraying is the application of long-acting insecticides on the walls and roofs of houses and domestic animal shelters in order to kill malaria-carrying mosquitoes that land on these surfaces.

“Indoor spraying is like providing a huge mosquito net over an entire household for around-the-clock protection,” said U.S. Senator Tom Coburn, a leading advocate for global malaria control efforts. “Finally, with WHO’s unambiguous leadership on the issue, we can put to rest the junk science and myths that have provided aid and comfort to the real enemy – mosquitoes – which threaten the lives of more than 300 million children each year.”

Views about the use of insecticides for indoor protection from malaria have been changing in recent years. Environmental Defense, which launched the anti-DDT campaign in the 1960s, now endorses the indoor use of DDT for malaria control, as does the Sierra Club and the Endangered Wildlife Trust. The recently-launched President’s Malaria Initiative (PMI) announced last year that it would also fund DDT spraying on the inside walls of households to prevent the disease.

“I anticipate that all 15 of the country programs of President Bush’s $1.2 billion commitment to cut malaria deaths in half will include substantial indoor residual spraying activities, including many that will use DDT,” said Admiral R. Timothy Ziemer, Coordinator of the President’s Malaria Initiative. “Because it is relatively inexpensive and very effective, USAID supports the spraying of homes with insecticides as a part of a balanced, comprehensive malaria prevention and treatment program. “

Programmatic evidence shows that correct and timely use of indoor residual spraying can reduce malaria transmission by up to 90 percent. In the past, India was able to use DDT effectively in indoor residual spraying to cut dramatically the number of malaria cases and fatalities. South Africa has again re-introduced DDT for indoor residual spraying to keep malaria case and fatality numbers at all-time low levels and move towards malaria elimination. Today, 14 countries in Sub-Saharan Africa are using IRS and 10 of those are using DDT.

At today’s news conference, the World Health Organization also called on all malaria control programmes around the world to develop and issue a clear statement outlining their position on indoor spraying with long-lasting insecticides such as DDT, specifying where and how spraying will be implemented in accordance with WHO guidelines, and how they will provide all possible support to accelerate and manage this intervention effectively.

“All development agencies and endemic countries need to act in accordance with WHO’s position on the use of DDT for indoor residual spraying,” said Richard Tren, Director of Africa Fighting Malaria. “Donors in particular need to help WHO provide technical and programmatic support to ensure these interventions are used properly.”

Indoor residual spraying is one of the main interventions WHO is now promoting to control and eliminate malaria globally. A second is the widespread use of insecticide-treated mosquito nets. While the use of bed nets has long been encouraged by WHO, the recent development of “long-lasting insecticidal nets” (LLINs) has dramatically improved their usefulness. Unlike their predecessors, the long-lasting nets need not be re-dipped in buckets of insecticide every six months as they remain effective for up to five years without retreatment.

Finally, for those who do ultimately become sick with malaria, more effective medicines are increasingly becoming available. Unlike previous antimalarials that have been rendered useless in many regions due to drug resistance, Artemisinin Combination Therapies (ACTs) are now recommended. These lifesaving medications are becoming more widely available throughout the world. In January of this year, WHO took stringent measures to help prevent future resistance to antimalarial medicines by banning the use of malaria monotherapy. An example of the negative consequences of drug resistance is apparent in the threat it poses to intermittent preventive treatment in pregnancy (IPTp), a crucial strategic intervention to protect pregnant women from the consequences of malaria.

Potential funding to scale up the availability of all three of these strategic interventions has dramatically increased over the past few years through the inception of the Global Fund to Fight AIDS, TB and Malaria, World Bank plans to significantly increase its funding for malaria, and the launch of the President’s Malaria Initiative.

“With serious money finally becoming available to fight malaria, it is more imperative than ever that WHO provides sound technical guidance and programme assistance to ensure timely and effective use of these resources,” said Dr Kochi.

Each year, more than 500 million people suffer from acute malaria, resulting in more than 1 million deaths. At least 86 percent of these deaths are in sub-Saharan Africa. Globally an estimated 3,000 children and infants die from malaria every day and 10,000 pregnant women die from malaria in Africa every year. Malaria disproportionately affects poor people, with almost 60 percent of malaria cases occurring among the poorest 20 percent of the world’s population.