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WHO recommends DDT to control malaria

BMJ 2006; 333 doi: https://doi.org/10.1136/bmj.333.7569.622-b (Published 21 September 2006) Cite this as: BMJ 2006;333:622
  1. Christiane Rehwagen
  1. BMJ

    The pesticide dicophane (DDT) should once more play a part in controlling malaria, the World Health Organization has announced. DDT has been banned for agricultural use in many countries since the 1970s because of fears about its harmful effects on the environment and human health.

    Almost 30 years ago, widespread indoor spraying with DDT and other insecticides to control malaria were phased out. But WHO is now recommending the use of indoor residual spraying, not only in epidemic areas, but also in areas with constant and high rates of transmission of malaria, which includes all of Africa.

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

    Inside residual spraying involves applying long acting insecticides to the walls and roofs of houses and shelters of domestic animals to kill the mosquitoes carrying malaria that land on these surfaces.

    DDT was extremely successful in controlling malaria in the middle of the 20th century, and WHO actively promoted its use for this until the early 1980s. But increased health and environmental concerns surrounding DDT caused WHO to stop promoting it and to focus instead on the other two main interventions to fight malaria (drug treatment and insecticide treated bed nets).

    Deaths from malaria have continued to rise since the 1970s, however, and countries affected by the disease and members of the scientific community have demanded that DDT should be used again for inside residual spraying. Additionally, extensive research and testing, published in the latest report of the UN joint meeting on pesticide residue in 2000, have shown that well managed programmes of spraying DDT indoors pose no harm to humans or to wildlife.

    “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.”

    Evidence from countries that continued using DDT showed that correct and timely use of indoor spraying can reduce malaria transmission by up to 90%. In the past, India was able to use DDT effectively to substantially cut the number of malaria cases and deaths. South Africa reintroduced DDT for indoor spraying in 2000 and has kept cases of and deaths from malaria at all time lows since then and is moving towards elimination of malaria. Today, 14 countries in sub-Saharan Africa are using indoor residual spraying, and 10 of those are using DDT, but in other countries it is still banned for public health use.

    Pierre Guillet from WHO's parasitic diseases and vector control unit explains, “We have enough evidence to base our current recommendations on, however we do need more data that show the level of exposure from indoor residual spraying. We also need to establish a system to monitor adverse effects of insecticides, especially DDT under operational conditions.”

    More information on malaria and the environment in countries that continued to use DDT against WHO's recommendation will be published next year, said a spokesperson from WHO.

    WHO also called on all malaria control programmes worldwide 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 support to accelerate and manage this intervention effectively.

    See www.who.int/malaria for more information. The report of the UN joint meeting on pesticide residue is available at www.inchem.org/documents/jmpr/jmpmono/v00pr01.htm.

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