A research about filtering out Cholera with cloth

Forcing water through a simple filter made from the cloth of old saris can reduce cholera cases by about half, according to a study of rural villages in Bangladesh where cholera is a major health problem.

Researchers suggest that the sari filters may also reduce other gastrointestinal illness.

The study, appearing this week in The Proceedings of the National Academy of Sciences, compared the effects of filtering pond or river water through modern nylon mesh and through old, much-washed sari cloth and found that the sari solution was better.

''Sari cloth is cheaper, and we found that it is much more effective than the nylon mesh,'' said Dr. Rita R. Colwell, a professor of microbiology at the University of Maryland at College Park, an author of the study. ''The nylon costs only a few dollars a year, but a few dollars can be a week's wages in these Bangladesh villages.''

Dr. Colwell said researchers had discovered in laboratory studies that most of the cholera bacteria in ponds, rivers and other standing water was attached to the gut of a copepod, (pronounced KO-puh-pod), a type of tiny zooplankton found in standing water.

When people drink unfiltered water, she said, they swallow the copepods and introduce cholera bacteria into their systems. As the germ multiplies, it releases a toxin that causes extreme diarrhea and cramping.

Filtering the copepod, Dr. Colwell said, reduced the cholera rate by at least half. She said there was also evidence that other germs were removed because women in the villages with sari-filtered water said there was less diarrhea and other digestive problems.

In modern hospitals, cholera is easily controlled, but without treatment it kills 50 to 80 percent of those infected. It is most lethal for children under 5 and for the elderly.

Dr. Colwell noted that the rural Bangladesh villages where the filter system was tested are many hours from good medical care.

Dr. John Mekalanos, a cholera expert at the Harvard Medical School, said Dr. Colwell and her co-authors ''have made a major contribution to the control of cholera'' by demonstrating an easy way for rural third world people to protect themselves from a major health problem.

''It could make a big difference in the region and elsewhere in the world,'' Dr. Mekalanos said.

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