BOX 4-4A Multidisciplinary Approach to Prevent Cholera

Dr. Rita Colwell, now at the University of Maryland, and her colleagues have studied transmission dynamics of cholera in the Bangladeshi villages for more than 20 years (see, for example, Colwell et al., 2003). While surveillance figures for cholera are not exact due to under-reporting by many countries, lack of standard case definitions, and lack of surveillance technologies, there were at least 131,943 cholera cases in 52 countries in 2005, resulting in over 2,000 deaths (WHO, 2006). Cholera emergence and reemergence continues to challenge health authorities, particularly in African nations. The 2008 outbreak of cholera in Zimbabwe led to over 26,000 documented cases including 1,518 deaths (WHO, 2008). Over the past two decades, the knowledge base has been developed to show that one of the key components of the transmission cycle for the cholera bacterium is a planktonic copepod. Specifically, the copepod plays a major role in the multiplication, survival, and transmission of the Vibrio cholerae bacterium.

Dr. Colwell and her team devised and tested a simple intervention to filter out particles larger than 20 microns, including copepods, from drinking water. The intervention relied on folded sari cloth, which is used for women’s attire and is readily available in all villages. Pilot studies showed the best filtering occurred by folding a particular mesh of sari cloth four or more times. Between September 1999 and July 2002, 65 villages of rural Bangladesh were introduced to the filtering technique. More than 130,000 individuals took part in the study, which resulted in a 48 percent reduction of cholera compared with the control (Colwell et al., 2003).

Dr. Colwell recounts (personal communication to author, April 2008) that health researchers were skeptical about uptake of the filtering technique during the study itself since the expectation was that men would not accept water filtered through women’s sari cloth. In partnership with social scientists, the team soon discovered that men had already devised a similar filtering strategy as part of their own process in making fermented drinks. Anecdotal evidence shows that there were no obstacles in social acceptance of the filtered water.

It might be expected that this simple intervention would be widely and sustainably in place in the 65 villages, and that it would have been adopted by others. In fact this was the case, in that the “control” villages were found to filter their water when a study of sustainability of the method was done five years later. It was found that the filtration frequently employed less than the required four or more folds. If a continuing education and training effort had been provided, reduction in illness and even deaths would have been enhanced. Even so, it was observed that a “herd effect” occurred in that those not filtering their water benefited by a lower cholera rate if they lived within a village where filtration was practiced.

From: 4, Addressing Risk for Waterborne Disease

Cover of Global Issues in Water, Sanitation, and Health
Global Issues in Water, Sanitation, and Health: Workshop Summary.
Institute of Medicine (US) Forum on Microbial Threats.
Washington (DC): National Academies Press (US); 2009.
Copyright © 2009, National Academy of Sciences.

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