Survey of Australian Waters for Cryptosporidium and Giardia

This report was produced for the Urban Water Research Association of Australia, a now discontinued research program.

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Survey of Australian Waters for Cryptosporidium and Giardia

Report No UWRAA 128

September 1998

 SYNOPSIS

A total of 191 raw water samples from 26 sites around Australia were concentrated by flocculation and analysed by flow cytometry for the occurrence of the protozoan parasites, Cryptosporidium and Giardia. Cryptosporidium oocysts were detected in 19.1% of samples, at numbers up to 30 oocysts per 10 litre sample. Giardia was detected less frequently, with 6.4% of samples being found positive, and numbers up to 20 cysts per 10 litre sample. Sites from catchments which had significant farming or recreation use had a higher probability of either parasite being detected. In addition, there were indications that sites from catchments in which land use was mainly farming had a higher incidence of Cryptosporidium oocysts, and those with mainly recreation use had higher incidence of Giardia cysts. Both parasites were found to be more prevalent at southerly latitudes, possibly due to the lower water temperature at these sites leading to increased persistence of oocysts and cysts in the environment. There was no strong correlation with the occurrence of either parasite and any water quality parameter, although turbidity (NTU) was a minor indicator of the occurrence of either parasite.

The effectiveness of the method (concentration by flocculation and analysis by flow cytometry) was tested by a quality control program which compared recoveries from several different sites, and of the effect of factors which might affect recovery rate. The method was found to be at least as good as other methods reported in the literature, with recoveries averaging close to 50% for both parasites. The major cause of losses and variations in recovery rate were shown to be due to undetermined factors during concentration step, possibly related to water quality.

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