Quantitative Microbial Risk Assessment of Drinking Water Quality to Predict the Risk of Waterborne Diseases in Primary-School Children

Abstract

Primary-school children in low- and middle-income countries are often deprived of microbiologically safe water and sanitation, often resulting in a high prevalence of gastrointestinal diseases and poor school performance. We used Quantitative Microbial Risk Assessment (QMRA) to predict the probability of infection in schoolchildren due to consumption of unsafe school water. A multistage random-sampling technique was used to randomly select 425 primary schools from ten districts of Sindh, Pakistan, to produce a representative sample of the province. We characterized water supplies in selected schools. Microbiological testing of water resulted in inputs for the QMRA model, to estimate the risks of infections to schoolchildren. Groundwater (62%) and surface water (38%) were identified as two major sources of drinking water in the selected schools, presenting varying degrees of health risks. Around half of the drinking-water samples were contaminated with Escherichia coli (49%), Shigella spp. (63%), Salmonella spp. (53%), and Vibrio cholerae (49%). Southern Sindh was found to have the highest risk of infection and illness from Campylobacter and Rotavirus. Central and Northern Sindh had a comparatively lower risk of waterborne diseases. Schoolchildren of Karachi were estimated to have the highest probability of illness per year, due to Campylobacter (70%) and Rotavirus (22.6%). Pearson correlation was run to assess the relationship between selected pathogens. V. cholerae was correlated with Salmonella spp., Campylobacter, Rotavirus, and Salmonella spp. Overall, the risk of illness due to the bacterial infection (E. coli, Salmonella spp., V. cholerae, Shigella, and Campylobacter) was high. There is a dire need for management plans in the schools of Sindh, to halt the progression of waterborne diseases in school-going children.

Health Risks and Potential Sources of Contamination of Groundwater Used by Public Schools in Vhuronga 1, Limpopo Province, South Africa

“…E. coli , Salmonella typhimurium , and Shigella are also some of the well-known causes of gastrointestinal diseases all over the world [ 33 ], constituting a major threat to public health. The study managed to pinpoint risks associated with groundwater consumption based on short-term data, as was similarly done in other published studies, such as Machdar et al [ 19 ] and Ahmed et al [ 21 ].…”

“…The highest ingested doses for E. coli and Salmonella typhimurium were from S8, while S4 and S7 had the highest doses of Shigella flexneri . The ingested doses for E. coli , Salmonella, and Shigella obtained by [ 21 ] in northern and central Sindh districts in India where 64–94% of schools rely on groundwater ranged from 3.31–92.5, 19.8–189.6, and 35.2–480 CFU/day, respectively. The ingested doses obtained in this study are lower than those obtained by [ 21 ].…”

“…Maximum risks of illness per year were 31.19, 30.37, and 29.31% for E. coli , Salmonella typhimurium , and Shigella flexneri , respectively. Ahmed et al [ 21 ] reported annual risks of infection of 97.9–100%, 100%, and 80.9–100%, while risks of illness were 34.9–35, 45, and 28.3–35.0, for E. coli , Salmonella typhimurium , and Shigella flexneri , respectively. These were higher than annual risks of infections and illness obtained in this study.…”

“…The average dose ingested was calculated by multiplying the consumed volume of water per day by the recorded average value of the enumerated pathogen for the three sampling periods. The consumed volume of water of 1 liter per day per child was adopted, following Ahmed [ 21 ].…”

“… is the probability of annual infection, n is the number of days of exposure in a year, P ill is the probability of illness, and P ill/in the probability of illness per infection. P ill/in values were obtained from Ahmed [ 21 ]. The risks of infection per day was calculated using values for the months of August, September, and October 2018, while the risks of infection per year were calculated based on average values for the three-month period.…”