WHO reverses policy, recommends use of DDT to control malaria
Source: Earthtimes.org
Date: 18 September 2006
Author: Geoffrey Lewis
The World Health Organization, reversing an earlier policy, has now approved the use indoors of long-banned insecticide DDT in the fight against mosquitoes that spread malaria.
WASHINGTON: The World Health Organization, reversing an earlier policy, has now approved the use indoors of long-banned insecticide DDT in the fight against mosquitoes that spread malaria.
WHO said DDT should be used widely across Africa and Asia to kill the mosquitoes that carry the malarial parasite, which causes the disease that kills more than a million people a year, 800,000 of them young children in Africa.
Dr Arata Kochi, who leads WHO's global malaria program, told a news conference Friday one of the best tools against malaria is indoor residual house spraying and of the dozen pesticides the organization has approved as safer for house spraying, the most effective has been found to be DDT. He said enhanced use of DDT is essential in reviving the flagging international campaign to control the disease
For around $5 a house, indoor spraying of DDT is the most viable tool in the control of the diseases, he added.
DDT had been commonly used in the 1930s as an agricultural insecticide. However, its adverse effect on the health of people came to be revealed in a book by biologist and ecologist Rachel Carson in 1992. Carson said DDT entered the food chain and killed wildlife and also posed a serious threat to humans.
Later, in 1969, the National Cancer Institute too announced that DDT could cause cancer and the U.S. imposed a federal ban on its use in 1972.
Dr Kochi said the most substantive change in WHO's guidelines on the use of insecticides would extend the reach of the strategy. Until now, the agency had recommended indoor spraying of insecticides in areas of seasonal or episodic transmission of malaria, but it is now advocating it where continuous, intense transmission of the disease causes the most deaths.
According to WHO records, there are 17 African countries using at least some indoor spraying of insecticides to combat malaria. Only 10 of them use DDT — Eritrea, Madagascar, Ethiopia, Swaziland, South Africa, Mauritius, Mozambique, Zimbabwe, Namibia and Zambia.
Richard Tren, director of Africa Fighting Malaria, said residual spraying of the insecticide in houses acted like a huge mosquito net over the houses.
He said the environmental impact associated with spraying insecticides -- whether it is DDT or other insecticides -- indoors is minimal and negligible. The science is very clear that there are no harmful human effects, he added.
The new policy at WHO had its toll. Dr Allan Schapira, a senior member of the WHO malaria team, who most recently oversaw the organization's approach to insecticide spraying, quit last week. He, however, declined to comment on his reasons, saying they were professional. His successor at WHO, Pierre Guillet, a medical entomologist, said Schapira left because he was uncomfortable with the new approach on insecticide spraying.
Meanwhile, a non-profit group, Beyond Pesticides, opposed WHO's new policy, saying a dependence on pesticides like DDT causes greater long-tem problems than those that are being addressed in the short-term.
Dr Kochi clarified at the news conference that the endorsement is only for once- or twice-yearly spraying of the pesticide on the inside walls of dwellings, especially mud and thatched huts. When used that way, it acts both as an insect repellent and as an insecticide against the female mosquito, when it lands on the wall to digest its meal.
While widespread agricultural use of DDT has led to the thinning of bird eggshells and the steep decline in the population of some species, as a weapon in malaria control it is undisputed. Its spraying is known to have helped eradicate or greatly reduce malaria in North America, southern Europe, North Africa and the Middle East in the decades after World War II. It continues to be used indoors in a few countries.
A study in Zambia in 2000 found that when all houses in a neighborhood were sprayed with DDT, malaria incidence fell 35 per cent compared with years when none was sprayed.
DDT is one of 12 chemicals to be phased out globally under the Stockholm Convention on Persistent Organic Pollutants, substances that are both toxic and persist in the environment. WHO itself had evolved a plan of action for reducing reliance on DDT to control malaria in countries where it was used.
Developed during World War II, DDT, the abbreviation for dicholoro-diphenyl-trichloroethane, had been described as a "miracle" for its effectiveness in combating malaria, typhus and other insect-born diseases.