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HEALTH: WHO Shifts Away from DDT for Malaria Control

Matthew Berger

UNITED NATIONS, May 11 2009 (IPS) - While much of the public health community’s attention is consumed by the H1N1 human swine flu outbreak, efforts are quietly being made to plug away at the continued threat of malaria.

Malaria still kills nearly a million people each year, according to the World Health Organisation (WHO), and approximately half the world’s population remains at risk.

The United Nations Environment Programme, Global Environment Facility and the WHO last week announced 10 projects that would fight malaria while gradually eliminating reliance on the controversial pesticide DDT to kill the mosquitoes that carry the malaria parasite.

In 2006, the WHO raised some alarm in the environmental community by coming out in active support of indoor spraying of DDT, perceived as a slight break from their previous, more passive approval of the chemical’s use.

Last week’s announcement represents “the hope that there will be reduced dependency on DDT in the future,” according to Dr. Keith Carter, regional advisor on malaria for the Pan American Health Organisation, which serves as the WHO’s Americas regional office.

“WHO faces a double challenge – a commitment to the goal of drastically and sustainably reducing the burden of vector-borne diseases, in particular malaria, and at the same time a commitment to the goal of reducing reliance on DDT in disease vector control,” said Dr. Margaret Chan, WHO’s director-general.

The announcement came at the fourth meeting of the parties of the Stockholm Convention on Persistent Organic Pollutants in Geneva. Under the Stockholm Convention, adopted in 2001, DDT and 11 other persistent organic pollutants were banned, though an exemption was made for using DDT to combat malaria.

“WHO policy remains consistent with the Stockholm Conventions,” Dr. Jo Lines, coordinator for vector control and prevention at the WHO’s Global Malaria Programme, told IPS. “It has been and remains the case that WHO recommends DDT in some anti-malaria cases where alternatives are not available.”

The projects, part of the programme “Demonstrating and Scaling-up of Sustainable Alternatives to DDT in Vector Management”, will take place in 40 countries in Africa, the eastern Mediterranean, and central Asia. It has 40 million dollars in funding from the GEF and hopes to achieve a 30 percent reduction in DDT application by 2014 and a DDT-free world by 2020.

The projects will be launched over the next year and will last five years. The integrated vector management strategy on which the projects are based was pioneered in a project that took place from 2003 to 2008 across 202 communities in seven Central American countries and Mexico.

Communities that had relied for 50 years on spraying DDT onto water bodies to prevent malaria began to use more decentralised, participatory approaches such as planting oak and other mosquito-repellent trees, draining stagnant water ditches, utilising larvae-eating fish, and fitting doors and windows with mesh screens.

Inventories of DDT and other persistent organic pesticides were also developed and stockpiles are to be eliminated, said Carter.

These non-chemical techniques, along with local-management strategies, helped cut cases of malaria by 60 percent in the participating communities, and their use will be expanded to new communities under this project.

“Mexico was at the front lines of malaria in the Americas, so pushing back a bit wasn’t hard,” said Lines. “The difficulty will come in Africa where transmission is 1,000 to 10,000 times greater – that is, the frequency with which people get bit – so non-chemical methods used in Africa will need to be much stronger.”

As is recognised in the Stockholm Convention, alternatives to DDT are not for everybody. South Africa was one of the first countries to use DDT in fighting malaria, and was able to quickly reduce the areas affected. When alternative insecticides were used, however, the malaria-carrying mosquitoes became resistant.

Mosquitoes in southern Africa have never really become resistant to DDT, according to Lines. Resistance, rather, has been a problem in Indonesia, parts of India, and Zanzibar and other parts of Africa where mosquito populations are relatively isolated.

“The southern African [mosquito] population is regularly washed through with other continental populations so resistance is diluted,” he said. “If you were to deprive South Africa of using DDT they would be in trouble.”

It is hoped, however, that simultaneous progress can be made toward both a reduction in DDT use and a reduction in cases of malaria, eventually leading to a sustainable way of fighting malaria. The goal is to “produce a level of control as good as if you were using DDT – that’s the point of the programme,” Lines said.

In a statement released by the organisations involved in the programmes, Achim Steiner, executive director of the U.N. Environment Programme, called DDT “a chemical rooted in the scientific knowledge and simplistic options of a previous age” and called for new and sustainable solutions “that meet the genuine health and environmental aspirations of a 21st century society.”

There are complicated tradeoffs between the risks of using DDT in malaria control and the risks of not using it. The effects of DDT-use are felt worldwide, says Lines, even in the Arctic – far away from its places of application – while malaria is a very localised risk.

Still, he says, for some populations “the health risks of DDT would have to be really quite severe to outweigh the benefits it provides in preventing malaria.”

As regards the Central American programmes, “the local populations in the demonstration sites were supportive and participated in project related activities as they were being undertaken,” Carter told IPS. “I think the test is whether that enthusiasm will continue now that the project has ended.”

Speaking more generally, Lines said, “On the one hand, people in the villages where the work takes place do tend to be the ones who ask the difficult questions like ‘Is this good for my baby?’ – more so than the ministers of health – but they are also enthusiastic about using environmentally-safe methods.”

“Countries have been moving away from DDT partly for environmental reasons but mostly because more easily operational methods become available,” he said. “There still are places, however, where DDT is most cost-effective.”

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