WHO calls for more DDT use vs. malaria

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By LAURAN NEERGAARD, AP Medical Writer Fri Sep 15, 11:18 AM ET

WASHINGTON - The World Health Organization on Friday called on more developing countries, particularly in Africa, to begin spraying the controversial pesticide DDT to fight malaria.


The difference: DDT, longed banned in the United States because of environmental damage, is no longer sprayed outdoors. Instead it's used to coat the inside walls of mud huts or other dwellings and kill mosquitoes waiting to bite families as they sleep.

A small number of malaria-plagued countries already use DDT, backed by a 2001 United Nations treaty that set out strict rules to prevent environmental contamination. But the influential WHO's long-awaited announcement makes clear that it will push indoor spraying with a number of insecticides - and that DDT will be a top choice because when used properly it's safe, effective and cheap.

"We must take a position based on the science and the data," said Dr. Arata Kochi, the WHO's malaria chief. "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."

"It's a big change," said biologist Amir Attaran of Canada's University of Ottawa, who has long pushed for the guidelines and described a recent draft. "There has been a lot of resistance to using insecticides to control malaria, and one insecticide especially. ... That will have to be re-evaluated by a lot of people."

The U.S. government already has decided to pay for DDT and other indoor insecticide use as part of
President Bush's $1.2 billion, five-year initiative to control malaria in Africa.

Kochi has positioned indoor spraying as an important but neglected third weapon �- along with insecticide-treated bed nets and new medications �- in the war on malaria, which infects half a billion people each year and kills more than 1 million, most of them children.

While some well-known environmental groups have signed on to WHO's decision, it has generated some concern from groups like the Pesticide Action Network, which says there are questions about its effects on developing children.

But proponents argue that until better strategies are developed, carefully controlled DDT use is warranted because in recent years, nothing else has succeeded in lowering deaths from malaria.

"Indoor spraying is like providing a huge mosquito net over an entire household for around-the-clock protection," said Sen. Tom Coburn, R-Okla., a physician who has urged stronger international anti-malaria programs.

DDT is easily history's most notorious insecticide. While it isn't classified a human health hazard, it was banned in the U.S. in 1972 after decades of widespread agricultural spraying led to environmental damage around the globe.

DDT never disappeared in developing countries, although political pressure and lack of funding meant few continued to use it. Then a 2001 United Nations treaty that aims to wipe out a dozen of the world's most dangerous chemicals carved out one exception for DDT: indoor anti-malaria spraying, under strict conditions to prevent environmental contamination.

Why? When small amounts are sprayed on interior walls, DDT forms a residue that both repels mosquitoes �- discouraging them from flying into the house �- and kills those that rest on the walls, explained Clive Shiff, a professor at Johns Hopkins University's Malaria Research Institute. It has to be applied only about once a year.

Bednets soaked in different insecticides already are used to protect sleeping families. But if the nets are torn or aren't used every night, a mosquito can infect someone. Plus, mosquitoes can develop resistance to those nets' chemicals, Shiff added, pointing to a 2002 malaria outbreak in part of South Africa using bednets. DDT in those houses quelled the outbreak.

"It would be naive to say DDT is a magic bullet for malaria. It isn't," stressed Attaran. It won't work in some places where mosquitoes already are resistant to a range of insecticides, he noted. He suspects DDT will be of most use in eastern Africa, where that problem hasn't yet emerged.

Attaran called for research "to make sure we're using insecticides and DDT not in a willy-nilly way but in an optimal way in the right places."

Nor, scientists cautioned, is indoor spraying alone a solution, as mosquitoes bite everywhere. Countries are being encouraged to adopt comprehensive malaria programs that also include newer, more effective medications, as Bush's malaria chief, Adm. R. Timothy Ziemer, was to outline Friday.

"President Bush has directed Admiral Ziemer to use the most safe and effective tools available to control and combat malaria in Africa," said White House spokeswoman Emily Lawrimore. Indoor spraying "programs are an important part of his Presidential Malaria Initiative to save thousands of people from a highly treatable and preventable disease."

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AP White House Correspondent Terence Hunt contributed to this report.