The incidence of S. japonicum in the molluscan intermediate host, and in various wild and domestic mammals was known to be relatively high in the endemic area in Formosa. The apparent absence of schistosome infection in the human population needed further study. Stool examinations by the sedimentation method were done in seven villages in the Changhua endemic area. An examination of 12,591 stools from 4,197 persons did not reveal a definite positive case of S. japonicum infection. The intradermal test for schistosomiasis japonica on 2,562 persons in six villages where stool examinations had been done showed 8.4 per cent of positive reactors. The incidence of positive reactions was significantly less for women than for men. It was also significantly less for the age group 3 through 12 than for the higher age groups but there was no significant difference among the higher age groups.
Three stools were obtained from each person giving a positive reaction (214 persons) and re-examined for S. japonicum infection by the sedimentation, acidether, and hatching methods. No positive cases were found in examination of these stools. An explanation has been given for the apparent discrepancy in the results obtained from stool examinations and intradermal tests. All the evidence obtained in this study indicates that S. japonicum in Formosa is a non-human, zoophilic strain.
Medical Zoology Department, 406th Medical General Laboratory, U. S. Army, taking part in the intradermal test.