Strain complex of Schistosoma japonicum in the mainland of China.

The present paper deals with studies on the characteristics of Schistosoma japonicum isolated from five localities in the mainland of China. The following items were observed and compared including morphometric data, susceptibility of six mammalian hosts, prepatent period, compatibility between larvae and snail hosts, size of hepatic granuloma produced by eggs, immunoreactions in experimental animals, sensitivity to praziquantel, SDS-PAGE protein pattern and its antigenicity analysis, DNA hybridization and genetic variation and differentiation by analysis with multilocus enzyme electrophoresis. By means of these multidisciplinary methods, from morphological to molecular level, the following conclusions may be drawn from our results. The evidence indicates firstly that S. japonicum in the mainland of China comprises a strain complex with several components of geographically distributed strains. At least four distinct strains exist, ie Yunnan, Guangxi, Sichuan and Anhui-Hubei. Characteristics of each strain are distinct and the results of these studies lead to discussion on the problem of the intraspecific and interstrain differentiation of S. japonicum in the mainland of China.