Novel real-time PCr for detection of Schistosoma japonicum in stool

Chemotherapy has been used on a large scale in countries where the blood fluke Schistosoma japonicum is endemic. This has led to a lower intensity of infections and consequently lower diagnostic values of commonly used diagnostic tests like serology and Kato-Katz stool smear. We designed a novel real-time PCR method for detection of S. japonicum in stool samples. Further, we evaluated different versions of an inexpensive, non-commercial extraction method, ROSE, as well as the commercial QIAamp DNA Stool Mini Kit. PCR primer sequences were designed targeting the mitochondrial NADH dehydrogenase I gene. Bovine serum albumin was added to the DNA extracts and SYBR Green was used for detection. The PCR method was evaluated with non-infected stool samples spiked with S. japonicum eggs. It demonstrated high sensitivity, even in samples containing a single egg. The two extraction methods were equally effective. The PCR was specific for S. japonicum when tested against other Schistosoma species, Trichuris trichiura, hookworm and Taenia sp. We conclude that this novel real-time PCR, in combination with either ROSE or QIAamp DNA Stool Mini Kit extraction, is a sensitive and specific tool for diagnosing S. japonicum in human stool samples.