Estimating the burden of acute gastrointestinal illness due toGiardia, Cryptosporidium, Campylobacter, E. coliO157 and norovirus associated with private wells and small water systems in Canada

Abstract

SUMMARYWaterborne illness related to the consumption of contaminated or inadequately treated water is a global public health concern. Although the magnitude of drinking water-related illnesses in developed countries is lower than that observed in developing regions of the world, drinking water is still responsible for a proportion of all cases of acute gastrointestinal illness (AGI) in Canada. The estimated burden of endemic AGI in Canada is 20·5 million cases annually – this estimate accounts for under-reporting and under-diagnosis. About 4 million of these cases are domestically acquired and foodborne, yet the proportion of waterborne cases is unknown. There is evidence that individuals served by private systems and small community systems may be more at risk of waterborne illness than those served by municipal drinking water systems in Canada. However, little is known regarding the contribution of these systems to the overall drinking water-related AGI burden in Canada. Private water supplies serve an estimated 12% of the Canadian population, or ~4·1 million people. An estimated 1·4 million (4·1%) people in Canada are served by small groundwater (2·6%) and surface water (1·5%) supplies. The objective of this research is to estimate the number of AGI cases attributable to water consumption from these supplies in Canada using a quantitative microbial risk assessment (QMRA) approach. This provides a framework for others to develop burden of waterborne illness estimates for small water supplies. A multi-pathogen QMRA of Giardia, Cryptosporidium, Campylobacter, E. coli O157 and norovirus, chosen as index waterborne pathogens, for various source water and treatment combinations was performed. It is estimated that 103 230 AGI cases per year are due to the presence of these five pathogens in drinking water from private and small community water systems in Canada. In addition to providing a mechanism to assess the potential burden of AGI attributed to small systems and private well water in Canada, this research supports the use of QMRA as an effective source attribution tool when there is a lack of randomized controlled trial data to evaluate the public health risk of an exposure source. QMRA is also a powerful tool for identifying existing knowledge gaps on the national scale to inform future surveillance and research efforts.

Estimating the Relative Role of Various Subcategories of Food, Water, and Animal Contact Transmission of 28 Enteric Diseases in Canada

“…Attribution to municipal water systems was divided based on the size of population serviced by the municipal system: large municipal systems (>1000 population served, 13.3% of total waterborne cases) and small municipal systems (<1000 population served, 23.1%). Size is used as a proxy of level of treatment, resources available to support treatment adoption, and operator training (Murphy et al , 2015 ).…”

“…Food subcategories in this study were based on Centers for Disease Control and Prevention guidelines for outbreak reporting (Painter et al ., 2009 ), used in previous elicitations (Hoffmann et al ., 2006 ; Havelaar et al ., 2008 ; Davidson et al ., 2011 ). Waterborne subcategories were differentiated by source water (recreational, bottled, private well, municipal groundwater, municipal surface water, and municipal ground water under the influence of surface water [GUDI]) and size of system (municipal system > or <10,000 population serviced) (Murphy et al , 2015 ). Animal contact subcategories included exposure to wildlife, or domestic or farm animals.…”

Non food-related risk factors of campylobacteriosis in Canada: a matched case-control study

“…Beyond foodborne exposure, this limited number of Canadian case-control studies indicate that contact with animals and water are two important exposures to Campylobacter , and that better quantification is necessary for attributing human campylobacteriosis to source. Although Canada has one of the safest drinking water supplies in the world, sources of drinking water can still become contaminated through agricultural run-off, wastewater treatment effluent and wildlife [ 11 ].…”

A QMRA Framework for Sanitation Treatment Decisions

“…Norovirus genogroup II (NoV GII) was selected as a model virus for this example, because NoV was attributed as causing the most waterborne disease cases in developed countries (Murphy et al, 2016;Gibney et al, 2017), and it has been the most significant cause of gastroenteritis outbreaks among enteric viruses over the world (Katayama and Vinje, 2017). However, any model virus can be selected at this step, if its dose-response has been successfully established and the datasets of its concentration in untreated wastewater have been accumulated.…”