TUESDAY, Jan. 14, 2003 (HealthDayNews) -- In what represents a quarter century of work, scientists have found an unusually simple solution to the worldwide scourge of cholera: a piece of folded cloth.
A study in the new Proceedings of the National Academy of Sciences found that filtering drinking water through a sari cloth slashed new cholera cases by half.
Cholera, which is caused by the bacterium Vibrio cholerae, kills tens of thousands of people around the world each year and is often transmitted via contaminated drinking water.
"It's been long known that if you can control the quality of drinking water, you can eliminate epidemics," says Steven Blanke, associate professor of biology and biochemistry at the University of Houston.
Being able to do that has been the problem.
Rita Colwell, the lead author of the study and a professor of microbiology and molecular biology at the University of Maryland, discovered years ago that water plankton harbor the bacterium. In fact, in Bangladesh, where this study took place, the September-to-October plankton bloom is followed by cholera outbreaks.
"It is naturally occurring, so it occurred to us as we did these studies that we could help people in Bangladesh -- where I've done work for 25 years -- [and] that simply filtering out copepods [tiny, shrimp-like structures which are a type of plankton] should reduce cholera," says Colwell, who is also head of the National Science Foundation and who answered questions in New Zealand, where she was waiting for a delayed flight to Antarctica.
Because the copepod is 200 to 500 times larger than the bacterium, it is much more easily filtered, Blanke says.
Villagers in Bangladesh commonly use untreated water from ponds and rivers for drinking and other purposes. "The most straightforward way to get rid of the bacteria is boiling, but that is not always possible," Blanke says. Often fuel, especially firewood, is in short supply.
An electron microscope told the researchers that a sari cloth, folded four to eight times, could remove all zooplankton and most phytoplankton and the cholera-causing bacterium.
The researchers then set out to test the method in the field, namely in 65 villages in rural Bangladesh, representing a population of about 133,000. When the cloth was folded at least four times, the results were astounding: cholera was reduced by about half the historical average. When people did still get sick, the severity seemed to be less.
In another coup for low tech over high tech, the investigators found that a regular, used sari cloth was as effective as specially designed nylon filters.
"It was enormously successful and it can be implemented particularly in areas where you don't have enough fuel for boiling," Colwell says. "The method of choice is to boil water, but often they don't have the fuel. Women collect cow dung and dry it to use as fuel to cook meals."
The filtration process had another unforeseen benefit: Mothers reported that their children had less diarrhea.
In addition to being cheap and convenient, using an old sari or other type of cloth has the advantage of being easily adopted by villagers. Colwell says that when she first proposed this study, one of the reviewers expressed concern that men might not drink water that was filtered through women's clothing. In fact, the research team discovered that women had already been filtering water through folded cloth to remove flies and other visible detritus.
Some 90 percent of villagers complied with the study's instructions, which may have been because women could literally see that murky water, once filtered through the sari cloth, emerged clear.
"You show the women water not filtered and you can see things swimming," Colwell says. "You filter the water and it's quite clear, so they get it in a heartbeat. "
The researchers speculate that other types of material may be equally effective in other parts of the world. They're also undertaking research to see if the sari cloth can reduce the incidence of other diseases.
"This offers a potentially simple and inexpensive solution to a global problem," Blanke says. "It also showed, in part, that not only with cholera but perhaps with other diseases, solutions can be offered from understanding the basic ecology, the source of the disease and mechanisms of disease transmission."
What To Do
To learn more about cholera, visit the World Health Organization or the U.S. Centers for Disease Control and Prevention.
