Daily Archives: 15 September 2006

WHO Endorses DDT Use Indoors

Saturday’s Washington Post reports:

The World Health Organization reversed a 30-year-old policy yesterday and declared its support for indoor use of the pesticide DDT to control mosquitoes in regions where malaria is a major health problem.

The Geneva-based WHO, which provides advice to many developing countries, believes the benefits of the long-acting pesticide far outweigh any health or environmental risk it may pose….

The endorsement is only for once- or twice-yearly spraying of the pesticide on the inside walls of dwellings, especially mud and thatched huts. Used that way, DDT functions as both an insect repellent and — when a blood-engorged female mosquito lands on the wall to digest its meal — an insecticide.

One application costs about $5. Most of that cost is labor, as it is sprayed on by professional applicators, and each packet of the pesticide must be strictly accounted for.

About 1 million people die each year of malaria, most of them African children under age 5. …

Numerous countries in southern Africa use DDT, but the compound is generally not used in central and west Africa, which have more intense malaria transmission, said Shiva Murugasampillay, a physician at WHO in Geneva.

DDT was the chief chemical villain of Rachel Carson’s book “Silent Spring,” whose publication in 1962 helped nurture the modern environmental movement. The chemical was banned in the United States in 1972, and its use worldwide fell steeply after that. It is no longer used in agriculture.

A study in Zambia in 2000 found that when all houses in a neighborhood were sprayed, malaria incidence fell 35 percent compared with years when none was sprayed.

Swaziland and Madagascar each had malaria epidemics after suspending DDT spraying, the latter’s outbreak killing more than 100,000 people from 1986 to 1988. Both epidemics were stopped when DDT spraying resumed.

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Escherichia coli O157:H7

Human stomachs are naturally full of E. coli bacteria. That’s something that gets lost in most news reports about the current outbreak.

A majority of the infections have occurred in Wisconsin, where 29 people so far have contracted the disease. Utah had 11 cases, and New York and Ohio each had seven, Acheson said.

Other states where the infection has occurred are California, Connecticut, Idaho, Indiana, Kentucky, Maine, Michigan, Minnesota, New Mexico, Nevada, Oregon, Pennsylvania, Tennessee, Virginia, Washington and Wyoming, Acheson said.

The outbreak is part of a problem in the U.S. food supply that affects about 100,000 to 150,000 people each year. The bacteria can be spread by insufficiently cooked meat, sprouts, lettuce, unpasteurized milk and juice or contact with sewage-contaminated water. The last outbreak involving spinach was in California in 2003.

The bacteria can cause low-grade fever, vomiting and diarrhea, often with bloody stool, the FDA said. Most healthy adults recover within a week, though some people develop serious kidney damage.

The subspecific strain that is now causing problems is O157:H7, the same one that affected thousands of schoolchildren in Japan ten years ago.

To determine the cause of a July 1996 outbreak of Escherichia coli O157:H7 among factory workers in Kyoto, Japan, we conducted cohort and case-control studies. Eating radish sprout salad during lunch at the factory cafeteria had been linked to illness. The sprouts were traced to four growers in Japan; one had been associated with an outbreak of E. coli O157:H7 among 6,000 schoolchildren in Sakai earlier in July.

UPDATE: See the story behind the killer spinach on Carl Zimmer’s science blog The Loom.

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