Spatial and temporal propagation of Cryptosporidium and Giardia at various scales in a drinking water reservoir

Cryptosporidium and Giardia are emergent protozoan parasites of faecal origin causing diarrhoeal diseases throughout the world. Their impact on public health is closely linked to the management of water resources and both pathogens are continuously released in the environment by punctual and diffuse faecal pollution sources. With the amendment of the Water Safety Plans published by the World Health Organization in 2005, the assessment of the public health risk associated with the presence of both parasites has extended to watershed scale. In Luxembourg, the Upper-Sûre reservoir provides 50% of the population of the country with drinking water. The presence of both Cryptosporidium and Giardia in surface water within the catchment area has been documented earlier. The aim of this study was therefore to understand the propagation of both protozoans within the catchment area over time and space. Integrated into a risk assessment-based approach, the results are intended for establishing an efficient monitoring strategy. Currently, no such strategy is available for water utilities. Though it is a crucial tool for improving the management of drinking water resources because it should alert responsible authorities in case of high contamination risk and prevent from possible waterborne outbreaks