Short Report: Use of Ceramic Water Filtration in the Prevention of Diarrheal Disease: A Randomized Controlled Trial in Rural South Africa and Zimbabwe Martella du Preez,* Ronán M. Conroy, James A. Wright, Sibonginkosi Moyo, Natasha Potgieter, and Stephen W. Gundry Natural Resources and the Environment, CSIR, Pretoria, South Africa; Department of Epidemiology and Preventive Medicine, Royal College of Surgeons in Ireland; Department of Geography, University of Southampton, Southampton, United Kingdom; Research and Technical Services, Institute of Water and Sanitation Development, Harare, Zimbabwe; Natasha Potgieter, Department of Microbiology, University of Venda for Science and Technology, Thohoyandou, Venda, South Africa; Water and Environmental Management Research Centre, University of Bristol, Bristol, United Kingdom Abstract. To determine the effectiveness of ceramic filters in reducing diarrhea, we conducted a randomized con- trolled trial in Zimbabwe and South Africa, in which 61 of 115 households received ceramic filters. Incidence of non-bloody and bloody diarrhea was recorded daily over 6 months using pictorial diaries for children 24–36 months of age. Poisson regression was used to compare incidence rates in intervention and control households. Adjusted for source quality, intervention household drinking water showed reduced Escherichia coli counts (relative risk, 0.67; 95% CI, 0.50–0.89). Zero E. coli were obtained for drinking water in 56.9% of intervention households. The incidence rate ratio for bloody diarrhea was 0.20 (95% CI, 0.09–0.43; P < 0.001) and for non-bloody diarrhea was 0.17 (95% CI, 0.08–0.38; P < 0.001), indicating much lower diarrhea incidence among filter users. The results suggest that ceramic filters are effective in reducing diarrheal disease incidence. Many people living in developing countries are still reliant on water of poor quality. Figures reported in 2004 by the Joint Monitoring Program showed that, of a population of 734.6 million in sub-Saharan Africa, 56% had no access to a water supply. 1 In South Africa, 34% of households did not have access to a water supply in 2000. 2 For children younger than 5 years of age in South Africa, diarrhea is the third most important cause of death, after HIV/AIDS and low birth weight, representing 11% of all deaths in that age group. 3 Worldwide diarrheal disease is one of the leading causes of morbidity and mortality in developing countries, accounting for 21% of all deaths in children younger than 5 years old and a total of 2.5 million deaths per year. 4 The magnitude of the task of providing people without sustainable access to improved water supply with the ultimate option, piped water, in the near future has initiated studies into alternative technologies. Point of use interventions are fast becoming the preferred method for providing improved water quality 5 and consequently reduction in diarrheal dis- ease. 6,7 A meta-analysis 8 confirmed that point-of-use water treatment is more effective than had been previously thought. Among 37 treatment technologies reviewed for a variety of their characteristics, which included maintaining and improv- ing microbial water quality, health impact, and costs, gravity filtration using ceramic filters was indicated as one of the five most promising technologies. 9 When used appropriately, ce- ramic filters provide an immediate source of drinking water with reduced turbidity and up to 99.99% removal of bacteria and protozoan parasites. To our knowledge, there have been only four field trials published that document diarrhea reduction in households using ceramic filters. 7,10–12 A number of field trials using home-based chlorination methods, 13,14 various combinations of flocculation and chlorination, 15–17 and solar disinfec- tion 18–20 also documented the effectiveness of these water treatment methods for reduction of diarrhea incidence. How- ever, these trials and others did not differentiate between non-bloody and bloody diarrhea. Bloody diarrhea is often associated with shigellosis. Infec- tions associated with Shigella spp. comprise a considerable portion of the diarrheal burden of disease. The most recent report on the global burden of Shigella infections estimated the annual number of diarrheal episodes related to Shigella spp. to be 164.7 million, of which 163.2 million were in devel- oping countries. 21 Recent studies on the Asian continent showed that incidence of Shigella diarrhea is more ubiquitous in Asian impoverished populations than previously thought 22 and that the incidence is substantially underestimated in chil- dren and older people in impoverished communities. 23 Shi- gella infections are often, but not exclusively, 24 associated with bloody diarrhea and are also referred to as shigellosis or dysentery. 25 Except for ad hoc outbreaks that are reported in the literature, information on the prevalence and incidence of Shigella infections on the African continent is limited. To determine how effective point of use ceramic filtration is in preventing non-bloody diarrhea and bloody diarrhea, we conducted a controlled trial in two rural areas in southern Africa, assessing the incidence of non-bloody diarrhea and bloody diarrhea in children 24–36 months of age. Our study made use of pictorial diaries 26 that enabled distinguishing be- tween non-bloody diarrhea and bloody diarrhea and enu- meration of each. The study was conducted in two districts, Mutale in the Vhembe district, Limpopo province, South Africa, and the Zaka district, Masvingo province, Zimbabwe. The population of the Limpopo province was 5,227,432 in 2000, with a density of 43 persons/km 2 . 27 Forty percent of the population of 69,313 residing in the South African municipality of Mutale in 2001 had no access to sanitation. 28 The majority (53%) of the population used public standpipes, with a further 14% using rivers, dams, boreholes, and springs as sources of water. The Zaka district in Zimbabwe had a population of 184,814. 29 Forty-five percent of the population in the district had no access to protected water sources, and 70% had no access to any type of sanitation facility. 30 More recent 2002 * Address correspondence to Martella du Preez, Natural Resources and the Environment, CSIR, PO Box 395, Pretoria 0001, South Af- rica. E-mail: mdupreez@csir.co.za Am. J. Trop. Med. Hyg., 79(5), 2008, pp. 696–701 Copyright © 2008 by The American Society of Tropical Medicine and Hygiene 696