15 September 2006
Today the World Health Organization (WHO) announced (http://www.who.int/mediacentre/news/releases/2006/pr50/en/index.html) they are giving “indoor use of DDT a clean bill of health for controlling malaria”. Unlike widespread policy of the past quarter century, the WHO will now promote “indoor residual spraying (IRS)” with insecticides, including DDT, as one of three main interventions against malaria, joining insecticide-treated bed nets and artmesinin combination therapies (ACTs) in what could be termed the new “triad against malaria (TAM)”.
Indoor residual spraying (IRS) is defined by WHO as “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”.
In terms of safety, focusing on indoor (not outdoor) use of DDT, the WHO states that “DDT presents no health risk when used properly.” Since WHO stopped advocating use of DDT in the early 1980’s due to health and environmental concerns, “extensive research and testing has since demonstrated that well-managed indoor residual spraying programmes using DDT pose no harm to wildlife or to humans”.
In terms of efficacy, WHO states that of the 12 insecticides they have approved as safe for house spraying, “the most effective is DDT”, according to Dr. Arata Kochi, Director of WHO’s Global Malaria Programme.
More than 500 million persons become ill with acute malaria every year. Over 1 million people die, with more than 860,000 deaths in Sub-Saharan Africa, each year. These deaths are primarily in children and infants, with WHO estimating that 3,000 deaths occur each day. A second high-risk group for death due to malaria is pregnant women, of whom 10,000 die in Africa alone each year, according to the WHO. Understandingly therefore, WHO is now recommending use of IRS “throughout Africa”, including areas with not only epidemic, but also high and constant malaria transmission.
WHO cites supports for indoor spraying with DDT from organizations such as the Sierra Club, the Endangered Wildlife Trust, Environmental Defense, and the President’s Malaria Initiative (PMI). The PMI includes 15 country programs in President Bush’s $1.2 billion commitment to decrease malaria deaths by 50%. WHO also cites dramatic success by India and South Africa in use of IRS, including DDT, to cut malaria transmission and deaths. In fact, WHO notes that already today “14 countries n Sub-Saharan Africa are using IRS and 10 of those are using DDT”.
This new policy by WHO is admirable in that it is based on data supporting the safety record for both humans and wildlife of indoor use of DDT. With sufficient funding to provide safe application of IRS, combined with prevention of malaria by insecticide-treated bed nets, and artemisinin-combination therapy for patients with malaria infection, the number of infections and deaths could dramatically drop over the coming years.
In addition, killing of mosquitoes by IRS, including use of DDT might result in a significant drop in other mosquito-borne diseases that co-exist in malarious parts of the world.
Daniel R. Lucey, MD, MPH
Director, Center for Biologic Counterterrorism & Emerging Diseases
EROne Institutes, Department of Emergency Medicine
Washington Hospital Center
Co-Director, Master of Science (M.S.) Program in Biohazardous Threat Agents and Emerging Infectious Diseases
Georgetown University Medical Center, Washington, DC