Monica Desai explains how researchers have found a short term solution to stopping transmission of cholera: filtering water through saris
Imagine you are a young child in London--you want a drink of water. You ask your mum, who turns on the tap, fills a glass with water, and hands it to you to drink. Now imagine that you are a young child in a rural village in Bangladesh. You want some water, so you ask your mum. Bottled water is safe but far too expensive. Boiling water is also safe, but fuel is too expensive. A water pump has not been built in your village--foreign funds haven't got here yet. So mum goes to the river and fills her water container--at least it's fresh and the water is flowing. The next day you have awful diarrhoea--it's like rice water. You are getting weak and dehydrated.
Every day we turn on our taps and drink clean water without a second thought. Many parts of the world, however, are not so fortunate to be able to do this. People may still drink water directly from the taps, or collect it from a well or river, but at a price. Clean water is a luxury. It may be touted as a basic human necessity and right, yet despite living in the 21st century, people still die in poorer countries because of dirty water. In 2000, 1.1 billion people (one sixth of the world's population) did not have access to clean water, most of them in Asia and Africa. Eighty per cent of diseases in the developing world have been attributed to lack of clean water and sanitation.1
The major killer
Why is this? Water from wells, rivers, and even centralised water systems in poorer countries is often full of dangerous organisms. The major killer in many countries is Vibrio cholerae. According to the World Health Organization, 58 countries officially reported cholera in 2001, contributing to almost 300 000 cases and 3000 deaths.2 This is a gross underestimation though, as a result of surveillance difficulties and fear of social and economic consequences. Some countries in Latin America are even experiencing cholera again after almost a century free from it.3
Cholera toxin kills by binding to chloride transporters in the gut lining and causing a secretory diarrhoea that causes dehydration, seriously affecting the very young and very old.
Cholera has been a major problem for a long time, so why has it not yet been overcome? Many methods that we advocate, such as vaccines, water pumps, boreholes, and boiling water are too expensive for many communities. In the long term, they are a great way of eradicating cholera, but they take a long time to implement and are expensive. In the short term, methods are needed to prevent deaths now.
Short term solution
So what is the solution? A recent study carried out in Bangladesh by Colwell and colleagues may provide a practical short term solution.4 Cholera in rivers lives in the gut of a zooplankton organism called a copepod. The copepod is important in the multiplication, survival, and transmission of cholera. In Bangladesh, this zooplankton thrives in the spring and summer, and cases of cholera soar. Richer households can use nylon filters to remove the zooplankton from their water effectively. Colwell and colleagues decided to use an alternative filter. They used old sari material folded four times as a filter and found that 99% of the V cholerae attached to zooplankton was removed. The sari filter was just as effective as, if not more so than, the nylon filter.
In countries such as Bangladesh, where cholera is endemic, this simple solution could provide a short term solution to the problem of cholera transmission. Old saris or similar material are easily found and cost nothing as they have already been used as clothes. The investigators found high compliance with and acceptance of the method, despite fears of cultural offence at using women's clothing.
So should we abandon well and pump projects and concentrate on encouraging the use of sari filters? Filtration of water still leaves some problems--people store water, so bacteria can still grow; V cholerae is not the only organism that causes morbidity and mortality in dirty water, and toxins such as arsenic have also been a problem. Filtration is therefore good in the short term, but is not a long term solution.
WHO says that access to clean water provides people with health, dignity, and economic power.1 We have a duty to encourage and provide both long and short term solutions for this basic human right.
