Old clothes cut cholera cases by half

Filtering water through old clothes, such as saris, can cut cases of cholera by half, according to new research into the disease in villages in Bangladesh.

The bacteria for the disease – which kills tens of thousands of people around the world every year – live in a symbiotic relationship with zooplankton. Researchers from Bangladesh and the University of Maryland in the US have found that by filtering water through at least four layers of old sari cloth the plankton can be removed.

“This is very simple, but it took 25 years to find out,” Anwar Huq of the Center of Marine Biotechnology at the University of Maryland, told edie. Huq grew up in Bangladesh, and remembers seeing people using old saris to filter homemade drinks. Nylon filters are also used in Africa to remove Guinea worm from drinking water, he explained. This lead Huq and his colleague, lead author of the study and Director of the National Science Foundation, Rita Colwell, to try using old cloth.

The researchers tested the effectiveness of both specially designed nylon filters and sari cloth in preventing new cholera cases in 65 Bangladesh villages between September 1999 and July 2002. The villagers using the sari cloth had around 50% of the historic average of new cases of the disease, and the nylon filters produced similar results, but had slightly higher numbers of new cholera cases.

Old saris work better than new saris, said Huq. This is because the threads in new cloth are much tighter, and consequently the pores between them are larger. In old saris, washing and use make the thread ‘mushy’, and the pores get smaller. Expensive saris have even tighter thread, making them even less suitable.

This is a good thing, as many people in Bangladesh villages would not be able to afford to buy new saris and then cut them up to make filters, pointed out Huq.

The next phase of Huq and Colwell’s research will be to see why there was a reduction in new cholera cases of only 50%. One reason could be that at times people travel to other villages that are not filtering their water and drinking water there, said Huq. When this has occurred villagers who would normally drink the filtered water have often contracted the disease the following day. The disease cannot be eradicated, he explained.

The researchers have been asked by aid workers in Africa and Brazil whether their local materials would have a similar effect. However, Huq points out that he could not know the answer unless he had tested other types of old cloth.

The results of the study are published in the latest edition of the Proceedings of the National Academies.

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