Bacterial indicators of risk of diarrhoeal disease from drinking-water in the Philippines

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.     

Outbreak of Norwalk virus in a Caribbean island resort: application of molecular diagnostics to ascertain the vehicle of infection

In 1998, an outbreak of gastroenteritis affected at least 448 persons including 122 staff at a resort hotel in Bermuda. A survey among staff indicated that gastroenteritis was associated with eating or drinking at the hotel (OR = 60, 95% CI = 2.4-15.1). Multiple specimens of drinking water had elevated faecal coliform levels and Escherichia coli present, suggestive of faecal contamination. Stools from 18 of the 19 persons with gastroenteritis that were tested were positive for genogroup-II Norwalk-like viruses (NLVs). RT-PCR analysis of a 31 specimen of water produced a genogroup-II NLV genome with a sequence identical to that of NLVs in the stools of three ill persons. This outbreak shows the value of new molecular diagnostics to link illness with a contaminated source through the use of sequence analysis. The risk of outbreaks such as these could be reduced in tourism dependent regions like Bermuda and the Caribbean by regular evaluation of data from the inspection and monitoring of drinking water supplies and waste water systems, by ensuring the chlorination of supplemental drinking water supplies and by establishing food-safety initiatives.     

Waterborne outbreak of gastroenteritis transmitted through the public water supply

INTRODUCTION: The chlorination of public water supplies has led researchers to largely discard drinking water as a potential source of gastroenteritis outbreaks. The aim of this study was to investigate an outbreak of waterborne disease associated with drinking water from public supplies. METHODS: A historical cohort study was carried out following notification of a gastroenteritis outbreak in Baqueira (Valle de Arán, Spain). We used systematic sampling to select 87 individuals staying at hotels and 67 staying in apartments in the target area.Information was gathered on four factors (consumption of water from the public water supply, sandwiches, water and food in the ski resorts) as well as on symptoms. We assessed residual chlorine in drinking water, analyzed samples of drinking water, and studied stool cultures from 4 patients. The risk associated with each water source and food type was assessed by means of relative risk (RR) and 95% confidence intervals (CI). RESULTS: The overall attack rate was 51.0% (76/149). The main symptoms were diarrhea 87.5%, abdominal pain 80.0%, nausea 50.7%, vomiting 30.3%, and fever 27.0%. The only factor associated with a statistically significant risk of disease was consumption of drinking water (RR = 11.0; 95% CI, 1.6-74.7). No residual chlorine was detected in the drinking water, which was judged acceptable. A problem associated with the location of the chlorinator was observed and corrected. We also recommended an increase in chlorine levels, which was followed by a reduction in the number of cases. The results of stool cultures of the four patients were negative for enterobacteria. CONCLUSIONS: This study highlights the potential importance of waterborne outbreaks of gastroenteritis transmitted through drinking water considered acceptable and suggests the need to improve microbiological research into these outbreaks (viruses and protozoa detection).     

Assessment of microbiological water quality and its relation to human health in Gaza Governorate, Gaza Strip

OBJECTIVE: To assess the contamination level of total and faecal coliforms in water wells and distribution networks, and their association with human health in Gaza Governorate, Gaza Strip. METHODS: Data were obtained from the Palestinian Ministry of Health on contamination of total and faecal coliforms in water wells and distribution networks, and on the incidence of water-related diseases in Gaza Governorate. An interview questionnaire was conducted with 150 residents of Gaza. RESULTS: The contamination level of total and faecal coliforms exceeded that of the World Health Organization (WHO) limit for water wells and networks. However, the contamination percentages in networks were higher than that in wells. Giardiasis was strongly correlated with faecal coliform contamination in water networks (r=0.7) compared with diarrhoeal diseases and hepatitis A (r=0.3 and 0.1, respectively). Diarrhoeal diseases were the highest self-reported diseases among interviewees in Gaza city. Such diseases were more prevalent among people using municipal water than people using desalinated water and water filtered at home for drinking (OR=1.6). Intermittent water supply and sewage flooding seemed to contribute largely to self-reported diseases. People in Gaza Strip have good knowledge on drinking water contamination, and this is reflected in good practice. CONCLUSIONS: Water quality has deteriorated in Gaza Strip. This may contribute to the prevalence of water-related diseases. Self-reported diseases among interviewees in Gaza City were associated with source of drinking water, intermittent water supply, sewage flooding and age of water, and wastewater networks.     

Estimates of endemic waterborne risks from community-intervention studies

The nature and magnitude of endemic waterborne disease are not well characterized in the United States. Epidemiologic studies of various designs can provide an estimate of the waterborne attributable risk along with other types of information. Community drinking water systems frequently improve their operations and may change drinking water treatment and their major source of water. In the United States, many of these treatment changes are the result of regulations promulgated under the Safe Drinking Water Act. A community-intervention study design takes advantage of these "natural" experiments to assess changes in health risks. In this paper, we review the community-intervention studies that have assessed changes in waterborne gastroenteritis risks among immunocompetent populations in industrialized countries. Published results are available from two studies in Australia, one study in the United Kingdom, and one study in the United States. Preliminary results from two other US studies are also available. Although the current information is limited, the risks reported in these community-intervention studies can help inform the national estimate of endemic waterborne gastroenteritis. Information is provided about endemic waterborne risks for unfiltered surface water sources and a groundwater under the influence of surface water. Community-intervention studies with recommended study modifications should be conducted to better estimate the benefits associated with improved drinking water treatment.     

Observational epidemiologic studies of endemic waterborne risks: cohort, case-control, time-series, and ecologic studies

Observational studies have assessed endemic waterborne risks in a number of countries. Time-series analyses associated increased water turbidity with increased gastroenteritis risks in several public water systems. Several cohort studies reported an increased risk of gastroenteritis in populations using certain public or individual water systems. Although several case-control studies found increased waterborne risks, they also found increased risks associated with other exposures. An increased risk of campylobacteriosis was associated with drinking untreated water from non-urban areas and some tap waters; other significant risks included contaminated poultry and foreign travel. Increased risks of cryptosporidiosis and giardiasis were associated with drinking water in some populations; other risk factors included foreign travel, day care exposures, and swimming. These observational studies provide evidence that some populations may be at an increased risk of endemic or sporadic illness from waterborne exposures, but not all studies found an increased risk. Differences in waterborne risks may be due to differences in water quality. System vulnerabilities and contamination likely differed in the areas that were studied. The information from these studies may help inform estimates of waterborne illness for the US population but is inadequate to estimate a population attributable risk.     

Aspects of health-related microbiology of the Subin, an urban river in Kumasi, Ghana

The aim of this study was to assess the influence of urban waste, sewage and other human centred activities on the microbiological quality of the river Subin, which flows through the metropolis of Kumasi, Ghana, and serves as drinking water for communities downstream. Three sites, Racecourse, Asafo and Asago, on the Subin were monitored over a year for total coliforms, faecal coliforms, enterococci and biochemical oxygen demand. Bacterial indicator numbers (geometric mean 100 ml(-1)) varied from 1.61 x 10(9) to 4.06 x 10(13) for total coliforms, 9.75 x 10(8) to 8.98 x 10(12) for faecal coliforms and 1.01 x 10(2) to 6.57 x 10(6) for enterococci. There was a consistent increase in bacterial loading as the river flows from the source (Racecourse) through Kumasi. Bacterial numbers were significantly (p < or = 0.05) higher during the rainy season compared with the dry (harmattan) season. The biochemical oxygen demand ranged from 8 mg l(-1) at the source of the river to 419 mg l(-1) at Asago; none of the sites achieved internationally accepted standards for water quality. The River Subin becomes grossly polluted as it flows through Kumasi and at Asago, a rural community downstream of Kumasi that abstracts water from the river for drinking, this probably contributes to the observed high levels of diarrhoeal disease.     

A randomized, blinded, controlled trial investigating the gastrointestinal health effects of drinking water quality

A double-blinded, randomized, controlled trial was carried out in in Melbourne, Australia, to determine the contribution of drinking water to gastroenteritis. Melbourne is one of the few major cities in the world that draws drinking water from a protected forest catchment with minimal water treatment (chlorination only). Six hundred families were randomly allocated to receive either real or sham water treatment units (WTUs) installed in their kitchen. Real units were designed to remove viruses, bacteria, and protozoa. Study participants completed a weekly health diary reporting gastrointestinal symptoms during the 68-week observation period. There were 2,669 cases of highly credible gastroenteritis (HCG) during the study (0.80 cases/person/year). The ratio of HCG episode rates for the real WTU group compared to the sham WTU group was 0.99 (95% confidence interval, 0.85-1.15, p = 0.85). We collected 795 fecal specimens from participants with gastroenteritis, and pathogens were not more significantly common in the sham WTU group. We found no evidence of waterborne disease in Melbourne. The application of this methodology to other water supplies will provide a better understanding of the relationship between human health and water quality.     

Microbiological standards for water and their relationship to health risk

Maintenance of the microbiological quality of water has been used as an important means of preventing waterborne disease throughout the twentieth century. The commonest microbiological tests done on water are for coliforms and Escherichia coli (or faecal coliform). This paper reviews the legislative and other guidance for microbial standards in drinking and bathing waters and considers evidence for the relationship between the microbiological quality of water and risk to human health. In the past measures of the microbiological quality of water correlated well with risks of acquiring gastrointestinal disease. More recent work suggests that gastrointestinal disease is more strongly associated with the presence of enterococci than of E. coli. New diseases such as cryptosporidiosis have been shown to cause outbreaks of waterborne disease when levels of conventional microbiological parameters are satisfactory. In response to this, and because of failure of prosecution in one outbreak, the United Kingdom (UK) Government has introduced new legislation that requires water providers to perform a risk assessment on their water treatment facilities and to implement continuous monitoring for cryptosporidium. A new European directive on drinking water has been introduced and legislation on cryptosporidium in drinking water has been proposed in the UK.     

Feasibility and efficacy of in-home water chlorination in rural North-eastern Brazil

The purpose of this study was to assess the feasibility, acceptability and effect of an in-home water chlorination programme in a rural village. Previous studies at this site showed high levels of faecal coliforms in household water, high diarrhoea rates in children, and enterotoxigenic Escherichia coli and rotaviruses were the most common pathogens isolated from patients. Household water came from a pond and was stored in clay pots. No homes had sanitary facilities. A blind, cross-over trial of treatment of household water with inexpensive hypochlorite by a community health worker was carried out over 18 weeks among 20 families. Water in the clay pots was sampled serially, and symptom surveillance was done by medical students. The programme was generally acceptable to the villagers and no change in water use patterns were apparent. The mean faecal coliform level in the chlorinated water was significantly less than in the placebo treated samples (70 vs 16000 organisms/dl, P less than 0.001). People living in houses receiving placebo treatment had a mean of 11.2 days of diarrhoea per year, and the highest rate of 36.7 was among children less than 2 years old. Diarrhoea rates were not significantly different among the participants while exposed to water treated with hypochlorite. We conclude that a low-cost programme of this type, which utilizes community resources, is logistically feasible, appears to be culturally acceptable in this setting, and can result in a marked reduction in water contamination. The lack of effect on diarrhoea rates suggests that improvement in water quality may affect morbidity only when other variables relating to faecal-oral agent transmission are ameliorated at the same time.     

Feasibility and efficacy of in-home water chlorination in rural North-eastern Brazil.

The purpose of this study was to assess the feasibility, acceptability and effect of an in-home water chlorination programme in a rural village. Previous studies at this site showed high levels of faecal coliforms in household water, high diarrhoea rates in children, and enterotoxigenic Escherichia coli and rotaviruses were the most common pathogens isolated from patients. Household water came from a pond and was stored in clay pots. No homes had sanitary facilities. A blind, cross-over trial of treatment of household water with inexpensive hypochlorite by a community health worker was carried out over 18 weeks among 20 families. Water in the clay pots was sampled serially, and symptom surveillance was done by medical students. The programme was generally acceptable to the villagers and no change in water use patterns were apparent. The mean faecal coliform level in the chlorinated water was significantly less than in the placebo treated samples (70 vs 16000 organisms/dl, P less than 0.001). People living in houses receiving placebo treatment had a mean of 11.2 days of diarrhoea per year, and the highest rate of 36.7 was among children less than 2 years old. Diarrhoea rates were not significantly different among the participants while exposed to water treated with hypochlorite. We conclude that a low-cost programme of this type, which utilizes community resources, is logistically feasible, appears to be culturally acceptable in this setting, and can result in a marked reduction in water contamination. The lack of effect on diarrhoea rates suggests that improvement in water quality may affect morbidity only when other variables relating to faecal-oral agent transmission are ameliorated at the same time.     

Water - health relationships in developing countries: a case study in Tulkarem district in Palestine

This study focuses on quantitative and qualitative determinants of drinking water in the Tulkarem district of Palestine, and the effect of water pollution on the health of its inhabitants. Five hundred drinking water samples were obtained from the records of the Public Health Department/Ministry of Health (MoH) at Tulkarem district for the year 1999, which were collected from different sources in the district. The samples were examined for free chlorine residual concentration, total coliforms and faecal coliforms. Data of water-related diseases was obtained from the records of public health clinics in the district. Many of the examined samples were unacceptable according to the Palestinian and WHO standards. It was found that (60.6%) of the samples have concentrations of free chlorine residual less than 0.2 ppm, which is the minimum concentration, recommended by WHO. Out of these samples, 34% and 9.2% were contaminated with total coliforms and faecal coliforms respectively. It was obvious that the prevalence of water-related diseases is much higher in the areas with contaminated or nonchlorinated drinking water than in other areas.     

Microbiological assessment of private drinking water supplies in Co. Cork, Ireland

The microbiological quality of 75 private drinking water supply boreholes in Co. Cork, Ireland was assessed in order to determine the incidence of contamination and the potential pathways of such contamination. Microbiological analysis was carried out using the membrane filtration technique for the recovery of thermotolerant (faecal) coliforms. The sanitary protection of the supplies was evaluated by means of systematic inspections and subsequent qualitative sanitary risk assessment. Almost a quarter of all supplies investigated (24%, n = 18) was found positive for thermotolerant coliforms. Weather conditions had a significant impact on microbiological water quality, increasing both contamination incidence and gross contamination frequency. Over half of the supplies had nine or more sanitary hazards and most had rudimentary sanitary protection measures at the head of the borehole. These low sanitary protection measures suggest that boreholes can pose a significant hazard to valuable groundwater resources by providing direct contamination routes.     

Preventing diarrhoea with household ceramic water filters: assessment of a pilot project in Bolivia

In an attempt to prevent diarrhoea in a rural community in central Bolivia, an international non-governmental organization implemented a pilot project to improve drinking water quality using gravity-fed, household-based, ceramic water filters. We assessed the performance of the filters by conducting a five-month randomized controlled trial among all 60 households in the pilot community. Water filters eliminated thermotolerant (faecal) coliforms from almost all intervention households and significantly reduced turbidity, thereby improving water aesthetics. Most importantly, the filters were associated with a 45.3% reduction in prevalence of diarrhoea among the study population (p = 0.02). After adjustment for household clustering and repeated episodes in individuals and controlling for age and baseline diarrhoea, prevalence of diarrhoea among the intervention group was 51% lower than controls, though the protective effect was only borderline significant (OR 0.49, 95% CI: 0.24, 1.01; p = 0.05). A follow-up survey conducted approximately 9 months after deployment of the filters found 67% being used regularly, 13% being used intermittently, and 21% not in use. Water samples from all regularly used filters were free of thermotolerant coliforms.     

Bladder cancer mortality reduction after installation of a tap-water supply system in an arsenious-endemic area in southwestern Taiwan

Arsenic has been well documented as the major risk factor for blackfoot disease (BFD), a unique peripheral vascular disease that was endemic in the southwestern coast of Taiwan, where residents had consumed high-arsenic artesian well water for more than 50 years. Long-term arsenic exposure has also been reported to be associated with bladder cancer mortality in a dose-response relationship. A tap water supply system was implemented in the early 1960s in the BFD endemic areas. Artesian well water was no longer used for drinking and cooking after the mid-1970s. The objective of this study is to examine whether bladder cancer mortality decreased after the improvement of the drinking water supply system through elimination of arsenic exposure from artesian well water. Standardized mortality ratios (SMRs) for bladder cancer were calculated for the BFD endemic area for the years 1971-2000. The study results show that mortality from bladder cancer declined gradually after the improvement of the drinking water supply system to eliminate arsenic exposure from artesian well water. Based on the reversibility criterion, this finding strengthened the likelihood of the observed association between arsenic exposure and bladder cancer being causal.     

Bacteria and disinfection byproducts in water from southern Mexico City

Disinfection byproducts and microorganisms present in drinking water may have deleterious effects on human health. The authors examined bacterial indicators (enterobacteria and Helicobacter pylori [H. pylori]), physicochemical parameters, and trihalomethane (THM) levels to conduct a water quality evaluation in Mexico City, where little is known about disinfection byproducts and microbial counts. Analyses were performed by standard membrane filtration for the enumeration of total coliforms, fecal coliforms, fecal streptococci, and Vibrio species. Other testing consisted of polymerase chain reaction (PCR) for H. pylori, physicochemical parameters by selective electrodes, and THMs by head-space with the use of a gas chromatograph. Indicator bacteria and enterobacteria were detected in 23% of samples, with significant differences between total coliforms, fecal coliforms, and fecal streptococci before and after chlorination. H. pylori was detected in 69% of samples prior to chlorination and 57% postchlorination. THM levels were < 200 microg/l. Chlorine concentrations ranged from < 0.05 mg/l to 35 mg/l. Disinfection at the well does not ensure good water quality for the Mexico City population. The next step will be the monitoring of water quality in the distribution system that supplies dwellings, as well as water obtained directly from the tap.     

Water supply, sanitation and diarrhoeal disease in Nicaragua: results from a case-control study

A case-control study of risk factors for child diarrhoeal disease was undertaken in a rural area of Nicaragua. Some 1229 children under the age of five were matched with an equal number of children of the same age presenting with other illnesses unrelated to water and sanitation. The main types of water supply were sampled at monthly intervals and tested for the presence of faecal coliforms in order to characterize their microbiological quality. In spite of marked differences in water quality between the different types of water supply, no relationship was found with diarrhoea morbidity. In contrast, there was a statistically significant association between water availability and diarrhoea morbidity. Children from homes with water supplies over 500 meters from the house had incidence rates of diarrhoea 34% higher than those of children from houses with their own water supply. Owning a latrine was not found to be significantly related to diarrhoea morbidity. A mother's level of schooling was inversely correlated with the frequency of diarrhoea in her children. A significant association was also found between the number of children under the age of five living in the house and the incidence of diarrhoea. These effects remained significant after controlling for confounding variables by conditional logistic regression.     

上海市饮水机污染状况及其影响因素分析

[目的]通过对普通饮水机和冰水机污染状况的调查及其影响因素的分析,对饮水机微生物污染的情况作出一个初步的评价,以便为将来改进和提高饮水机的卫生性能提供科学依据。[方法]随机选择188台普通饮水机和16台冰水机进行卫生学调查,分析调查因素与检出微生物指标之间的关系。[结果]普通饮水机常温龙头水细菌总数、总大肠菌群超标率分别为70.2%、11.2%,霉菌检出率为41.5%;冰水机低温龙头水细菌总数、总大肠菌群超标率分别为81.3%、12.5%,未检出霉菌。饮水机聪明座的霉菌污染与桶内水霉菌污染之间(r_s=0.427,P=0.007)、聪明座的霉菌污染与常温龙头水之间(r_s=0.464,P=0.003)存在等级相关关系。不同放置场所的饮水机常温龙头水总大肠菌群的检出率不同(x~2=14.669,P=0.047);饮水机上使用水的种类对常温龙头水霉菌的检出率有影响(x~2=16.441,P=0.001);桶装水的周转时间及饮水机的清洗频率对常温龙头水总大肠菌群的检出率有影响(分别为x~2=8.254,P=0.041和x~2= 11.348,P=0.010)。[结论]必须重视饮水机的微生物污染;改造饮水机的现有结构;加快桶装水的周转时间并增加清洗频率,正确清洗。     

Enterotoxigenic Escherichia coli in the domestic environment of a Malaysian village

The membrane-filter assay, GM1-ELISA, and DNA-DNA hybridization assay, were used to detect enterotoxigenic Escherichia coli (ETEC) in samples of water, weaning food, food preparation surface swabs, fingerprints of mothers, and the fingerprints and stools of children under 5 years of age, in 20 households in a Malaysian village. Weaning food and environmental samples were frequently contaminated by faecal coliforms, including ETEC. The membrane-filter assay detected and enumerated faecal coliforms and LT-ETEC in all types of water and weaning food samples. Highest concentrations of faecal coliforms and LT-ETEC were found in weaning food, followed by well-water, stored water and stored drinking water. The GM1-ELISA detected LT-ETEC in weaning food, food preparation surfaces, fingerprints and stool samples. The DNA-DNA hybridization assay detected a larger proportion of STa2-ETEC than the other toxotypes, either singly or in combination. All the assays in combination detected the presence of ETEC in all types of samples on at least one occasion in each household. It was not possible to classify households as consistently more or less contaminated with ETEC. On individual occasions it was possible to show a significant association of the presence of LT-ETEC between the fingerprints of children and their stools, fingerprints of mothers and children, and weaning food and the stools of the child consuming the food.     

某市首起水源污染引起的诺瓦克病毒胃肠炎暴发的调查

目的调查分析某市429人出现以呕吐为主的群发性急性胃肠炎的原因,探讨区县生活饮用水卫生监督对策。方法现场流行病学调查与现场卫生学进行调查,应用ELISA、RT-PCR法对病例及水样标本进行实验室检测。结果采集的水厂A出厂水、末梢水及生活污水水体标本中,RT-PCR法检出诺瓦克病毒核酸阳性;现场调查发现水源受排污口污水污染,水厂卫生管理情况较差,水处理工艺较落后。结论这是某市首起水源污染引起的诺瓦克病毒所致的急性胃肠炎暴发事件,提示卫生监督部门应重点加强基层生活饮用水水源水监管力度,加强出厂水与末梢水的监测,提高水厂卫生管理水平,改进区县水厂水处理工艺。