Malaria outbreak forces S. Africa to return to DDT

The insecticide, banned in most countries, is back after mosquitoes shrug off alternatives.

DDT for control of disease vectors is exempt from ban under Annex B of POP's Treaty

December 18, 2000

Knight Ridder Newspapers

JOZINI, South Africa - Malaria was pretty much under control in KwaZulu-Natal province five years ago. So health officials thought it was safe to stop using DDT, the notorious insecticide banned in most of the developed world.

Almost immediately, this semitropical region along the Indian Ocean saw a dramatic increase in the number of cases of malaria, which is transmitted by mosquitoes.

There are now nearly 10 times as many cases as in 1995. There were no malaria deaths five years ago. This year, the disease has killed more than 300 people in the province.

Health officials said they had no choice but to go back to DDT, even though the pesticide is widely blamed for environmental damage and is suspected of posing a health hazard.

"We have to use it. People are dying," said Bheki Qwabe, an environmental health officer who supervises 17 DDT- spraying teams that resumed work in May in northern KwaZulu-Natal. South Africa's experience with DDT was a main reason the pesticide received a reprieve under an international treaty negotiated this month to ban 12 toxic chemicals.

The treaty, scheduled to take effect in about five years, would immediately ban the production of nine of the "dirty dozen" chemicals that biodegrade slowly and have been linked to cancer, birth defects and other disorders. They include chlordane, dieldrin and hexachlorobenzene.

But DDT, whose perils were the subject of Rachel Carson's 1962 book, "Silent Spring", which catalyzed the modern environmental movement, was regarded as too useful in the fight against malaria to ban outright.

About 25 countries, including South Africa, would be allowed to use DDT under strict controls until a safer solution is found.

DDT, which stands for dichlorodiphenyltrichloroethane, is produced only in Mexico, India and China.

DDT's image has metamorphosed since health officials began raising alarms about a worldwide resurgence in malaria, which kills more people than any communicable disease except tuberculosis. The World Health Organization estimates that from 300 million to 500 million people are afflicted with malaria each year, and more than a million die, mostly children in rural Africa.

Although other insecticides are more expensive and less effective, DDT is unsurpassed as an affordable killer and repellent of mosquitoes.

"Malaria is a disease of the poor," said Jotham Mthembu, the malaria coordinator for the KwaZulu-Natal Department of Health. "DDT can help Africa."

Health officials in South Africa emphasize that they use DDT judiciously, only spraying the chemical on residential structures where humans are vulnerable to mosquitoes at night, when the species that carries the malaria parasite prefers to feed on warm- blooded creatures.

South Africa, where thousands of tons of DDT were introduced into the environment by airplane crop-dusters, long ago banned agricultural use of the compound.

In the United States, such campaigns to eradicate insects led to the near extermination of several species of birds of prey, including the bald eagle and the peregrine falcon.

The chemical became so pervasive that it was found in the breast milk of nursing mothers.

"Now we are more target-oriented," Mthembu said. "We don't just go berserk and throw DDT everywhere."

Last week, one of the provincial health department crews moved from house to house in a steamy, rural area on the coastal plain near Mozambique, where several malaria cases were recently reported.

The work crews, wearing blue overalls and protective paper masks, applied the sweet-smelling aerosol [note: DDT for malaria control is applied as a wettable powder mixed in ordinary water in a compressed air sprayer, not as an aerosol. The compressed air sprayer uses a mechanism similar to a bicycle air pump to create the pressure] from hand-pumped tanks on the mud-and-stick walls and grass roofs of the traditional Zulu dwellings.

The crews apply about 2 grams of pesticide per square yard, which leaves a light white coating. It is effective for up to a year.

"When they spray, the mosquitoes go away," said Muzi Tembe, a retired woman in her 60s.

She and her family sat on the ground, surrounded by their chickens and their possessions, which they had removed from their huts to make way for the spray.

Tembe said her family members had no fears that the DDT would threaten their health.

"We're happy they're spraying," she said.

When health officials stopped using DDT in 1995, they switched to a biodegradable pyrethroid, a synthetic insecticide based on the pyrethrum flower.

Last year, health officials noted that malaria cases failed to decline in June during the onset of the southern hemisphere winter.

Then entomologists in KwaZulu identified the Anopheles funestus mosquito, a species adept at carrying malaria parasites that had been eradicated in South Africa in the 1950s. It was resistant to pyrethroids.

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