A new method was developed to detect viable Cryptosporidium parvum oocysts. For the excystation of viable C. parvum oocysts, Hank's Balanced Salt Solution with 1.5% taurocholic acid was used to excyst the oocysts, and nucleic acid binding membrane filters were used to recover chromosomal DNA from C. parvum sporozoites after DNA extraction with proteinase K. Polymerase chain reaction (PCR) method was applied to the final detection of the DNA extracted from excysted oocysts. For the PCR, a polythreonine gene region was targeted to amplify the C. parvum specific DNA. Amplified PCR product which was detected by agarose gel electrophoresis was confirmed by restriction enzyme digestion profiling and DNA sequencing. The method developed in this study is useful to detect viable C.parvum selectively. Therefore, this method is applicable to assessment of the actual infection risk of C. parvum and to evaluation of disinfection efficiency in the water supply systems.
