Genotypes of Cryptosporidium in Sydney's Catchments

Intensive monitoring for CryptosporidiulIl in source waters has been ongoing in Sydney since the Sydney Water Crisis in August 1998. Three separate C,yptosporidhllll contamination 'events' have been detected in the water supply catchments since the Crisis. Duplicate water samples from these events were analysed for Cryptosporiditllll by immuno-fluorescence assay (IFA), polymerase chain reaction (PCR) and malachite green. The PCR technique confirmed the presence of Oyptosporidhllll parvlIlIl in more than 70% of the samples that tested positive by IFA. C. paMl11l type II or 'cattle' genotype was the only Cryptosporidilllll strain identified by PCR. This study demonstrated that combining the quantification afforded by the IFA method and the genetic specificity from PCR analysis assists in understanding both the public health risk and the source of Cryptosporidilll1l in drinking water supplies. An apparent lack of sensitivity in the PCR analysis compared to IF A may be related to storage time before PCR analysis and warrants further attention.