Detection of active schistosome infection by cell-free circulating DNA of Schistosoma japonicum in highly endemic areas in Sorsogon Province, the Philippines.

The current status of schistosomiasis in highly endemic areas is difficult to determine by ovum detection because of the superficially low parasite load after mass drug administration, whereas the parasite transmission rates are still high. Cell-free parasite DNA is fragments of parasite-derived DNA existing in the host's body fluids. We conducted population-based studies to test the presence of cell-free schistosome DNA in endemic areas of Sorsogon Province, the Philippines. Schistosome DNA in the serum and urine of Kato-Katz (KK)-positive subjects was detected by PCR (100% sensitivity). Schistosome DNA was also detected from KK-negative subjects (9/22 serum and 10/41 urine samples). Schistosome DNA was found to be network echogenic pattern (NW)-positive (serum 53.3%, urine 42.9%) or NW-negative (serum 25.5%, urine 20.8%) and enzyme-linked immunosorbent assay (ELISA)-positive (serum 47.1%, urine 40%) or ELISA-negative (serum 33.3%, urine 13.3%). These results indicate that cell-free schistosome DNA is a promising diagnostic marker for active schistosome infection in the case of light infection.