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The environmental distribution of Giardia spp. and Cryptosporidium spp. is dependent upon human, agricultural, and wildlife sources. The significance of each source with regard to the presence of parasites in the environment is unknown. This 2-year study examined parasite prevalence in human sewage influent, wildlife, and agricultural sources associated with the North Saskatchewan River Basin in Alberta, Canada. Fecal samples were collected from cow-calf, dairy, and hog operations in the watershed area. Sewage-treatment facilities were sampled bimonthly during the 2-year study, and wildlife scat was collected at locations along tributaries of the North Saskatchewan River. All samples were analyzed for the presence of Giardia and Cryptosporidium, using sucrose-gradient separation followed by immunofluorescent microscopy. Giardia and Cryptosporidium were detected in all three sources. The lowest prevalence of both Giardia (3.28%) and Cryptosporidium (0.94%) was found in wildlife, with 6 of 19 species testing positive. Sewage influent had the highest prevalence of Giardia (48.80%) and Cryptosporidium parvum-like oocysts (5.42%); however, the concentration of both parasites was minimal compared with the concentration detected in cattle feces. Cow-calf sources contained the highest concentration of Giardia (mean 5800/g feces, P < 0.01), and dairy sources contained the highest concentration of C. parvum-like oocysts (mean 295/g feces, P < 0.01). Although prevalence and concentration are higher in cattle feces than in sewage, the Giardia and Cryptosporidium in animal manure do not have direct access to water draining into the North Saskatchewan River. PCR-based characterization of rDNA from isolates of Cryptosporidium collected from Alberta human, pig, calf, mature steer, dog, cat, and beaver hosts revealed distinct genetic differences that may reflect host specificity.

Recent studies in Alberta have shown that agriculture can impact surface water quality with elevated levels of nutrients and bacteria. However, there is limited information available to determine if agriculture in cold climates is a significant source of waterborne pathogens to surface waters. High levels of Cryptosporidium spp. and Giardia spp. in the raw drinking water supply at Edmonton, Alberta in 1997 led to the development of a three-year research project to identify sources of these parasites in a large northern river basin. Sources targeted for investigation include municipal sewage effluent, agriculture and wildlife. The collaborative research project, initiated in 1998, includes water monitoring and parasite prevalence surveys. Water quality monitoring in the North Saskatchewan River Basin is being conducted on the major tributaries between Rocky Mountain House and the City of Edmonton; on sewage effluent and source drinking water supplies in rural communities and on the river in the City of Edmonton. The prevalence of parasites in agricultural operations and wildlife in the basin is also being surveyed. Cryptosporidium spp. and Giardia spp. levels found in the major tributaries in the NSR basin are highly variable and tend to be influenced by the type of watershed (forested versus agricultural), the time of year of runoff and the patterns of runoff. Municipal sewage effluent is a source of Cryptosporidium spp. and Giardia to the NSR with effluent from sewage treatment lagoons having the highest concentrations of both parasites. This unique research initiative brings together various departments of provincial and federal governments, academic institutions, industry and the agricultural community to determine the sources of waterborne parasites in a large river basin. The project will conclude March 3, 2001.

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