Associations between extreme precipitation and acute gastro-intestinal illness due to cryptosporidiosis and giardiasis in an urban Canadian drinking water system (1997–2009)

Abstract

Drinking water related infections are expected to increase in the future due to climate change. Understanding the current links between these infections and environmental factors is vital to understand and reduce the future burden of illness. We investigated the relationship between weekly reported cryptosporidiosis and giardiasis (n = 7,422), extreme precipitation (>90th percentile), drinking water turbidity, and preceding dry periods in a drinking water system located in greater Vancouver, British Columbia, Canada (1997-2009) using distributed lag non-linear Poisson regression models adjusted for seasonality, secular trend, and the effect of holidays on reporting. We found a significant increase in cryptosporidiosis and giardiasis 4-6 weeks after extreme precipitation. The effect was greater following a dry period. Similarly, extreme precipitation led to significantly increased turbidity only after prolonged dry periods. Our results suggest that the risk of cryptosporidiosis and giardiasis increases with extreme precipitation, and that the effects are more pronounced after a prolonged dry period. Given that extreme precipitation events are expected to increase with climate change, it is important to further understand the risks from these events, develop planning tools, and build resilience to these future risks.

Time series study of weather, water quality, and acute gastroenteritis at Water Safety Plan implementation sites in France and Spain

“…This study largely confirms the literature on drinking water-related gastrointestinal disease and contributors to health risks (Chhetri et al, 2017; Levy et al, 2016), while eliciting potential areas of site-specific management intervention. Precipitation, generally thought to be harmful, was inconsistently associated with acute gastroenteritis rates among sites, potentially due to differences in treatment processes and pollution sources.…”

“…Owing to connections between waterborne disease risk and climate patterns, risk management approaches should consider potential hazards posed by climate change (Bartram et al, 2017; Beaudeau et al, 2011; Chhetri et al, 2017; Howard et al, 2016; Levy et al, 2016). Of the three locations studied, location 5 is subject to the greatest projected climate change and social sensitivity to climate change, due in part to flash floods and urban heat island effects (European Commission, European Environment Agency, 2018).…”

Projected local rain events due to climate change and the impacts on waterborne diseases in Vancouver, British Columbia, Canada

“…Estimation of the future impact of climate change on the risk of cryptosporidiosis and giardiasis required two stages:1) Characterization of the exposure-outcome relationship between precipitation and disease through analysis of historical data (1997–2009) using distributed lag non-linear Poisson regression models; and 2) projection of the exposure-outcome relationship to future periods (2020–2099) using climate model predictions to derive expected annual numbers of cases under various climate change scenarios. The details of Stage 1 were described previously [15].…”

“…Several studies have reported that two important AGI, cryptosporidiosis and giardiasis, have seasonal variability and may therefore be affected by climate change [7–10]. Extreme precipitation events have been implicated in several waterborne AGI outbreaks [11–14] and in sporadic AGI [15]. Extreme precipitation may increase pathogen transfer from environmental reservoirs (e.g.…”

“…In a related previous study [15], we investigated the relationship between extreme precipitation events (defined as 7-day cumulative weekly precipitation exceeding the 90th percentile in the historical record), drinking water turbidity and cryptosporidiosis and giardiasis for an urban surface drinking water system (DWS) in Metro Vancouver, British Columbia, Canada. The study found that extreme precipitation led to significantly increased turbidity, and cryptosporidiosis and giardiasis risk and the risk was greater for precipitation following a dry period [15]. After the previous study period (1997–2009) this DWS installed filtration for two of its three surface water sources to increase the protection from both direct and indirect turbidity-causing events.…”