AWWA WQTC63993

The occurrence of various species and genotypes of Cryptosporidium in raw waterrepresent both cumulative and point source impacts present within a watershed. Thisis further complicated by physical and hydro-geographical characteristics of thewaterway as well as the topography and land use patterns of the catchment area.Successful environmental risk assessment strategies need not only examine faecalimpacts, but must also incorporate comprehensive land use analysis. A study wascarried out in the Oldman River in Alberta, Canada where Cryptosporidium speciesand genotypes were monitored at three sites on a monthly basis for 1 year. Hostspecificity of Cryptosporidium and land use patterns were combined to track thesource of faecal contamination. The number of oocysts detected using US Environmental Protection Agency Method 1623 ranged from non-detectable to 1.9 oocysts per liter. The site furthestupstream had the fewest occurrences of Cryptosporidium oocysts with three samplingperiods positive at a rate of 0.02 oocysts per liter. Molecular forensic profiling ofCryptosporidium oocysts recovered from microscope slides of the two downstreamsites indicated that C. andersoni was the predominant species in the Oldman River.Source tracking methods along with land use analysis indicate cattle are likely to bethe largest contributor of Cryptosporidium to the river. C. baileyi occurred at bothdownstream sites in late summer and the fall, W13 genotype was detected at themiddle site over a period of 3 months, and genotype W16 was detected only once atthe most downstream site. Birds, skunks, raccoons and muskrats were suspected to bethe contributors of the sporadic occurrences of these species and genotypes. TheCryptosporidium species and genotypes present in the Oldman River pose little risk tohuman health. The study demonstrates the value of an integrated approach to riskassessment by combining occurrence monitoring, species identification and land useinto a more robust tool for source tracking faecal contamination. Includes 20 references, table, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2006

Number of Pages:

12

File Size:

1 file , 560 KB