Abstract: Objective To establish a sensitive and specific PCR assay for detecting Schistosoma japonicum-infected Oncomelania hupensis. Methods Based on 18S-rRNA gene of S. japonicum， a PCR assay for detecting Onc-omelania snails infected with S. japonicum was established. The PCR product was sequenced， and the sensitivity， cross-reaction and mass detection experiments of PCR assay were performed. Results The location of PCR product for detecting Oncomelania snails infected with S. japonicum was similar to the target DNA， with a length of 469 bp and the same sequence as the target DNA. It was registered in GenBank （Accession No. DQ442999）. There was no PCR product for detecting uninfected snail. Experiments showed that the minimum DNA concentration of S. japoncium miracidium to be detected was 40 pg/μl. DNA from snail infected with single-tail cercaria could not be detected. The maximum dilution concentration of infected snail DNA pooled with uninfected snail DNA that could be detected was 1∶640. Conclusion The PCR assay for detecting S. japonicum-infected Oncomelania snails shows high sensitivity， specificity and effect of mass detection.

Key words: Schistosoma japonicum, Oncomelania hupensis, PCR, 18S-rRNA gene