Microbial impact from human and animal faecal sources around the drinking water source Lake R\ue5dasj\uf6n

The magnitude of microbial hazards is known to vary highly over time, depending on the contamination sources and runoff during rainfalls. As the infection risk for different pathogens relate to their sources, an understanding of the relative impact of faecal matter from humans and animals is of high importance. For example, as cattle are known to be carriers of the parasitic protozoa Cryptosporidium parvum, tracking the transport of faecal matter from ruminants is valuable. Quantifying the relative impact of various faecal sources gives a basis for water management, especially in relation to control measures. Various microbial source tracking methods have been presented during recent years, and their usefulness in different regions such as in the Nordic countries needs to be tested. In Lake R\ue5dasj\uf6n at the Swedish west coast, positive detections of Cryptosporidium spp. in the raw water have indicated that parasite sources in the watershed may represent a human health risk related to drinking water. The aim of this study was therefore to assess the microbial impact from human and animal faecal sources around this lake, during baseline and rain event conditions, using microbial source tracking as a complement to the analysis of traditional indicators and parasites