AWWA WQTC65882

Cryptosporidium contamination of drinking water systems continues to be a public health issue for the drinking water industry. The current US Environmental Protection Agency (USEPA) methods for detecting Cryptosporidium in water (USEPA Method 1623) provides information on the presence or absence of oocysts, but gives no information on the isolate or whether the oocysts are infectious. A recent study using cell culture combined with polymerase chain reaction (PCR) detected infectious oocysts in 1.4% of 1,690 treated drinking water samples collected from 82 surface water treatment plants. As a follow-up to this earlier study, 3 assays combining cell culture with various infection detection methods were evaluated in 2 laboratories to assess sensitivity, reliability, and accuracy (frequency of false positives and false negatives). The infectivity detection methods were immunofluorescence microscopy (IFA), PCR, and reverse transcriptase-PCR (RT-PCR) combined with post-detection genotyping. The most reliable assay will be used to test 1000L treated drinking water samples from participating utilities for the presence of infectious Cryptosporidium oocysts. Includes 24 references, tables, figure.