Abstract
The estimated burden of endemic acute gastrointestinal illness (AGI) annually in Canada is 20·5 million cases. Approximately 4 million of these cases are domestically acquired and foodborne, yet the proportion of waterborne cases is unknown. A number of randomized controlled trials have been completed to estimate the influence of tap water from municipal drinking water plants on the burden of AGI. In Canada, 83% of the population (28 521 761 people) consumes tap water from municipal drinking water plants serving >1000 people. The drinking water-related AGI burden associated with the consumption of water from these systems in Canada is unknown. The objective of this research was to estimate the number of AGI cases attributable to consumption of drinking water from large municipal water supplies in Canada, using data from four household drinking water intervention trials. Canadian municipal water treatment systems were ranked into four categories based on source water type and quality, population size served, and treatment capability and barriers. The water treatment plants studied in the four household drinking water intervention trials were also ranked according to the aforementioned criteria, and the Canadian treatment plants were then scored against these criteria to develop four AGI risk groups. The proportion of illnesses attributed to distribution system events vs. source water quality/treatment failures was also estimated, to inform the focus of future intervention efforts. It is estimated that 334 966 cases (90% probability interval 183 006-501 026) of AGI per year are associated with the consumption of tap water from municipal systems that serve >1000 people in Canada. This study provides a framework for estimating the burden of waterborne illness at a national level and identifying existing knowledge gaps for future research and surveillance efforts, in Canada and abroad.
Highlights
Enteric illness is largely underreported, and existing Canadian national and provincial surveillance systems for enteric illness often do not discriminate between infections caused by food, animal contact, person-to-person, environmental, or drinking water transmission, for sporadic cases
The Canadian drinking water systems were divided into four categories (Table 8) to facilitate ranking against the randomized controlled trials (RCTs) results and the development of the model: (1) Systems ranking 416·9 percentile for source water treatment and 49·3 percentile for distribution systems (1·4 million people) – poorest quality
The consumption of municipal tap water from systems serving >1000 people may be responsible for an estimated 334 966 acute gastrointestinal illness (AGI) cases annually (90% probability interval (PI) 183 066-501 026) in Canada, which accounts for roughly 1·7% of all AGI from all causes
Summary
Enteric illness is largely underreported, and existing Canadian national and provincial surveillance systems for enteric illness often do not discriminate between infections caused by food, animal contact, person-to-person, environmental, or drinking water transmission, for sporadic cases. M. Murphy and others community on a surface water source (Canada) [1, 2]. Murphy and others community on a surface water source (Canada) [1, 2] These randomized controlled trials (RCTs) estimated that 0·126 and 0·0388 AGI cases per person per year, respectively, were attributable to drinking water. RCTs performed in the United States and Australia suggest between 0 and 0·0145 AGI cases/person per year may be attributable to tap water consumption from municipal systems [3,4,5]
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