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  • Title: Bacterial indicators of risk of diarrhoeal disease from drinking-water in the Philippines.
    Author: Moe CL, Sobsey MD, Samsa GP, Mesolo V.
    Journal: Bull World Health Organ; 1991; 69(3):305-17. PubMed ID: 1893505.
    Abstract:
    Inadequate measures of water quality have been used in many studies of the health effects associated with water supplies in developing countries. The present 1-year epidemiological-microbiological study evaluated four bacterial indicators of tropical drinking-water quality (faecal coliforms, Escherichia coli, enterococci and faecal streptococci) and their relationship to the prevalence of diarrhoeal disease in a population of 690 under-2-year-olds in Cebu, Philippines. E. coli and enterococci were better predictors than faecal coliforms of the risk of waterborne diarrhoeal disease. Methods to enumerate E. coli and enterococci were less subject to interference from the thermotolerant, non-faecal organisms that are indigenous to tropical waters. Little difference was observed between the illness rates of children drinking good quality water (less than 1 E. coli per 100 ml) and those drinking moderately contaminated water (2-100 E. coli per 100 ml). Children drinking water with greater than 1000 E. coli per 100 ml had significantly higher rates of diarrhoeal disease than those drinking less contaminated water. This threshold effect suggests that in developing countries where the quality of drinking-water is good or moderate other transmission routes of diarrhoeal disease may be more important; however, grossly contaminated water is a major source of exposure to faecal contamination and diarrhoeal pathogens. Data on 690 to 0-20 month old infants who lived in metropolitan Cebu, the Philippines and microbiological data were used to examine the association between bacteria levels in drinking water and the prevalence of diarrhea in order to evaluate 4 bacterial indicators of tropical drinking water quality. Escherichia coli and enterococci were found to be better predictors of diarrhea risk than fecal coliforms and maybe fecal streptococci. Diarrhea prevalence for children who consumed good quality water (1 E. coli/100 ml-WHO standard) was roughly equivalent to that of children who consumed medium quality water (2-100 E. coli/100 ml). In fact, water containing up to 1000 E. coli/100 ml did not increase the risk of diarrhea. Grossly contaminated water (1000 E. coli/100 ml) had a significantly higher rate of diarrhea that good and moderate water (15% vs. 9%; p=.002), however. The threshold effect of indicator risk could account for these findings. This effect occurred for the other 3 bacterial indicators as well. When controlling the density of the indicator organisms, the type of water source did not significantly affect the risk of diarrhea. But, when controlling for the type of water source, density was a significant predictor of risk. Apparently the pathogens infected the children via other transmission routes. In fact, significant determinants of diarrhea for 0-12 month old urban infants included poor water quality, poor excreta disposal practices, poor food hygiene, and crowding. Breastfeeding had a strong protective effect against diarrhea. It is concluded that low cost improvements to very contaminated water supplies and concurrent improvements in sanitation and hygiene are more cost effective than providing high quality water without improvements in sanitation and hygiene.
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