Spatial and temporal distribution of Cryptosporidium and Giardia in a drinking water resource: Implications for monitoring and risk assessment

• Published in: The Science of the total environment 2014-02, Vol.472, p.1023-1035
• Main Authors: Burnet, Jean-Baptiste, Penny, Christian, Ogorzaly, Leslie, Cauchie, Henry-Michel
• Format: Article
• Language: English
• Subjects: Applied sciences; Compartments; Continental surface waters; Cryptosporidiosis - epidemiology; Cryptosporidium; Cryptosporidium - growth & development; Drinking water; Drinking Water - parasitology; Drinking water and swimming-pool water. Desalination; Environmental Monitoring; Exact sciences and technology; Faecal indicators; Giardia; Giardia - growth & development; Giardiasis - epidemiology; Hydro-climatology; Land use; Microbial risk; Microorganisms; Natural water pollution; Parasites; Pollution; Risk Assessment; Rivers; Spatio-Temporal Analysis; Surface water; Water Resources - statistics & numerical data; Water Supply - statistics & numerical data; Water treatment and pollution; Waterborne parasites; Watersheds
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2013.10.083

Because of their significant public health impact, waterborne Cryptosporidium and Giardia have been monitored in surface water in order to assess microbial quality of water bodies used for drinking water production and/or for recreational purposes. In this context, sampling strategy is of key importance and should be representative enough to appropriately assess the related microbial risk. This, however, requires sound knowledge on the behaviour of both pathogens in water. In the present study, the spatial and temporal distribution of Cryptosporidium and Giardia was explored in the rural Upper-Sûre watershed used for drinking water production in Luxembourg. By subdividing it into three compartments including (i) sub-catchments, (ii) the Sûre River fed by the sub-catchments and (iii) the Upper-Sûre reservoir fed by the Sûre River, parasite distribution was assessed using sampling designs adapted to the hydro-dynamic characteristics of the respective compartments. Results highlighted the high spatial and temporal variability in parasite distribution at watershed scale, as well as the prevalence of Giardia over Cryptosporidium. Besides land use features and catchment characteristics, hydro-climatology appeared to be a major driver of parasite behaviour in the watershed. It introduced a seasonal trend in their occurrence, highest densities being detected during the wet season. Peaks of contamination triggered out by rainfall-induced runoff were further observed in the three compartments. In the Sûre River, Cryptosporidium and Giardia fluxes peaked at 109 and 1010 (oo)cysts.d−1, respectively, and were discharged into the drinking water reservoir, where they underwent a 2 to 3 log10 removal rate. Despite this, parasite fluxes entering the drinking water treatment plant were still high (106 to 107 (oo)cysts.d−1) and stressed on the need for improved watershed management upstream the water treatment barrier. The catchment-wide analysis described here constitutes a valuable tool for assessment of catchment microbial dynamics, especially within the framework of Water Safety Plans. •We investigated Cryptosporidium and Giardia distribution trends in a rural watershed.•Their distribution in water was heterogeneous over various spatial temporal scales.•Parasite fluxes (from 103 to 1011 (oo)cysts.day−1) varied with location and time.•Key drivers of parasite fluxes were rainfall, land use and catchment morphology.•Our study provides a methodology for catchment-wide study