Disappearance of specific antibodies in patients with chronic schistosomiasis japonica by treatment with praziquantel

We tested effects of praziquantel, an antischistosomal compound, on clinical and immunological parameters of chronic schistosomiasis japonica. Two Japanese patients, who had high antibody titers to Schistosoma japonicum antigens but no fecal schistosome eggs or no or mild symptoms complained, were treated with praziquantel. Within two years after treatment, anti-schistosome antibodies in sera from the patients became negative in enzyme-linked immunosorbent assay. There was no significant alteration in cellular immunity to the parasite. Although S. japonicum infection is believed to have been eradicated in Japan, our present results seem to suggest the possibility that a few Japanese individuals, who have high anti-schistosome antibody, still harbor live parasites.