- The Washington Times - Monday, January 13, 2003

ARLINGTON, Va., Jan. 13 (UPI) — Research in Bangladesh has shown that cholera and other lethal waterborne diseases can be removed from drinking water with simple cloth filters, U.S. scientists reported Monday.

"This is a very low technology solution to a massive problem that even the most poverty-stricken developing country can implement," Rita Colwell, director of the National Science Foundation, told United Press International. "It's simple, but it's based on good science, and it saves lives."

Cholera ravages some 60 developing countries worldwide and kills thousands yearly. "The most vulnerable victims are children under the ages of five," Colwell said.

The disease is caused by a comma-shaped germ and leads to severe, dehydrating diarrhea. World Health Organization findings show 184,311 cases of cholera reported officially globally in 2001, and numbers likely are grossly underreported due to fear of consequences such as reduced tourism.

Colwell and NSF colleagues helped demonstrate some 25 years ago that cholera was spread via tainted water, not through human contact as previously thought. The bacterium lives symbiotically in crab-like animals known as copepods, where the germs help copepods digest food.

"Normally, all you have to do is boil the contaminated water," Colwell explained.

Unfortunately, firewood in rural villages in Bangladesh is costly and in short supply. Also, as many as half the wells drilled in the late 1960s in that country, which were supposed to help resolve its severe water pollution crisis, have been found to contain unacceptably high levels of arsenic.

It also is difficult to supply rural Bangladesh with large enough supplies of chlorine to purify the water, Colwell said, given the expense and lack of major highways. This means many in Bangladesh resort to surface water, risking cholera.

The researchers speculated that water filters could remove cholera germs. Although the microbes themselves are only about one-eighth the width of a human blood cell, the copepods they dwell in are 100 or more times larger, which cloth fibers should be able to strain.

Prior experiments revealed specially designed nylon fibers were effective filters against copepods, but Colwell and her team also discovered old folded clothes at least four layers thick were just as effective.

"The older the better, since the threads separate," Colwell said. Folded clothes eight layers thick would serve even better, though it naturally takes longer for the water to pour through, "and people could grow impatient and less likely they'd use the technique," she added.

Colwell and colleagues tested the cheap filters over an 18-month period with some 150,000 villagers in more than 50 villages in rural Bangladesh. They tried a number of different kinds of clothing, with scientists settling on cloth from saris — traditional woolen garments women wrap around themselves.

"The fact that they're not stitched means you can use them over and over again. Holes in stitched garments tend to get wider," Colwell said. There were initial fears that local men would consider water strained through women's garments as unclean, but it turned out sari cloth already was used to filter local sweetened yogurt drinks.

In findings published Jan. 13 in the online Proceedings of the National Academy of Sciences, the researchers found villagers trained to use sari cloth experienced about half the historic average of new cholera cases. Villagers who used the nylon filter actually experienced slightly more cholera cases.

In addition, villagers using the filters reported that cholera cases also were less severe.

"Cholera is dose dependent, and based on human volunteer experiments about 20 years ago, it's been found that as you reduce the numbers, you get mild diarrhea but not full-blown cholera," Colwell said.

Colwells' team hopes to continue the experiment to find out how much the filters reduce cholera symptoms. Filtered water also should require much less chlorine to cleanse, which could make it feasible to remove other dangerous waterborne illnesses in Bangladesh, such as salmonella, shigella and rotavirus.

Similar fabrics also could help fight cholera elsewhere in the world. "There's nothing more wonderful to be a scientist and have your science applied and make life better for people to save lives," Colwell said.

Harvard University medical researcher Richard Cash found these results "very important" and "very significant," in an e-mail from India.

"This has value in day-to-day living for many, and is particularly significant during the monsoon season when wells flood," he told UPI.

(Reported by Charles Choi, UPI Science News, in New York)

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