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Report 5 of 5: Safe
Saris - Bangladesh
Introduction
Waterborne diseases are spread primarily via water, but secondary infection is caused by organisms excreted in faeces which are subsequently ingested by a new host through cross-contamination. They are also spread by food, especially raw or inadequately cooked food. The poor suffer high risk from waterborne infections as they tend to be undernourished, lack proper sanitation facilities and have little access to medicine. Children and the elderly are especially vulnerable because their immune systems are either undeveloped or heavily challenged.
For developing countries, fighting disease is a struggle, both to find the money to pay for treatment and to make necessary changes in infrastructure to prevent diseases from becoming epidemics or endemic, that is, always present. Cholera is a major illness in many developing countries and is caused by bacteria, called Vibrio cholerae that live in water environments. The present vaccine for cholera is, at best, only 50 to 60 per cent effective in preventing clinical illness. It does not control the spread of the disease and it is not economical for people in Bangladesh where cholera is endemic because of the cost, including requirement for refrigeration, etc.
People drinking safe water are at risk of contracting cholera if they continue to use pond or river water, where the cholera bacteria are present, for bathing, cooking, washing fruit, vegetables, and utensils. Therefore, both the provision of safe drinking water and the safe disposal of human excreta are priorities for public health. All human faeces contain large numbers of bacteria and, without good sanitation systems, excreta including those pathogens, enter water via faeces. This is a serious problem when people are suffering from watery diarrhoea, such as cholera.
Cholera
The bacterium that causes cholera is known as "Vibrio cholerae"and enters the body of those who drink water from places where the vibrio lives. Once the vibrios pass the stomach and enter into the small intestine, they multiply and may release a toxin which causes severe diarrhoea and vomiting. This results in the victim becoming severely dehydrated, which, in many cases, causes death unless the fluids being lost are replaced.
The bacteria are normally found associated with free swimming, tiny, microscopic shrimp-like animals called copepods. Each copepod carries thousands of cholera bacteria in its gut and on its surfaces, and ingesting a small number of these creatures containing the cholera bacteria when drinking or eating uncooked food, such as fresh fruit or salad, can cause cholera. Plankton blooms occur in spring and autumn in Bangladesh and each bloom is invariably followed by an outbreak of cholera.
One person with cholera can excrete enough bacteria each day that, theoretically, could infect up to 10 million people. It is, therefore, essential to separate the disposal of excreta from water used for drinking. This is usually carried out on a small scale by building latrines or septic tanks where the excreta is contained and prevented from seeping into nearby watercourses.
Decontaminating drinking water
Water can be sterilised by boiling, but this is not a feasible method because wood for fuel is extremely scarce in Bangladesh and many other developing countries. Tests of water samples showed that filtering out the copepods can remove the bacteria. Therefore, rather than making the effort to kill the copepods and bacteria in the water to be drunk, it is cost-effective to remove them first, before drinking.
Thus, by providing a suitable filtration method to eliminate the bacteria to the people of Bangladesh, it may be possible to minimise the number of cholera victims. In 1998, there were about 1,000 people entering the cholera hospital in Dhaka every day who were affected by the disease. Although cholera can never be eradicated because the bacterium is part of the natural environment, and there is currently no effective vaccine available, the disease can be controlled by using filtration systems that make water safer to drink.
The sari
A sari is a rectangular piece of cloth measuring five to six metres in length. The style, colour and texture of the cloth varies and the traditional dress of Bangladesh women can be made from cotton, silk, or man-made materials. For centuries, the sari has been worn by millions of women throughout the Far East and, in Bangladesh, people have, for years, been using the sari to remove insects and extraneous particulate matter from sugar or molasses water, commonly used to make a local drinks. The sari is now being used in Bangladesh to filter drinking water in an attempt to reduce the occurrence of cholera.
The sari as a filtration tool
The beauty of the sari material is that it is thin and readily available in all villages in Bangladesh. To filter the water effectively, the sari needs to be folded between four and eight times. The folded cloth is then wrapped over the pot used to collect drinking water from ponds or rivers. After the water has been collected, the sari is removed from the pot, unfolded, and rinsed in water and then air dried in the sun for a couple of hours to decontaminate it. This is sufficient to kill bacteria trapped in the material but in the monsoon seasons, an inexpensive disinfectant can be used to decontaminate the material.
Sari material is excellent for filtration purposes and as saris are found in every household in Bangladesh, this method is affordable, even for the poorest of the poor. Laboratory tests have shown that, by filtering water through four layers of sari material, 99% of the bacteria attached to and inside the copepods, as well as other matter, can be removed and, thereby, reduce the infectious dose of cholera vibrios present in the water. This is because the tiny bacteria are attached to the much larger plankton and particles so they can be filtered out easily when the plankton and particles are removed. This means that the chances of consuming a large enough dose of bacteria to cause cholera are dramatically reduced. Four to eight layers of cloth turned out to be the optimum number – any more folds can cause clogging and do not improve filtration efficiency significantly.
The technique of using a sari to filter bacteria out of water can be successfully adopted in other parts of the world, using almost any material that is thin and dries quickly.
For further information, please contact:
Anwar Huq, Ph.D.
Research Associate Professor
Rita R. Colwell, Ph.D., D. Sc.
Professor
University of Maryland Biotechnology Institute
Columbus Centre
701 East Pratt Street
Baltimore, Maryland 21202, USA.
Tel: +1 410-234-8833/8886 (Dr. Huq) or +1 703-306-1000 (Prof. Dr. Colwell)
Fax: +1 410-234-8873/8896 (Dr. Huq) or +1 703-306-0109 (Prof. Dr. Colwell)
E-mail: huq@umbi.umd.edu
E-mail: colwell@umbi.umd.edu |
Intermediate Technology Development Group would like to thank Rita Colwell and Anwar Huq from the University of Maryland and Peter Coles for producing the original information on safe saris.
This document is an output from a project funded by the UK Department for International Development (DFID) for the benefit of developing countries. The views expressed are not necessarily those of the DFID.
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