Molecular Ecology (2005) 14, 839–849 doi: 10.1111/j.1365-294X.2005.02443.x © 2005 Blackwell Publishing Ltd Blackwell Publishing, Ltd. An insight into the genetic variation of Schistosoma japonicum in mainland China using DNA microsatellite markers JAYA SHRIVASTAVA,*† BAO ZHEN QIAN,*‡ GILEAN MCVEAN * and JOANNE P. WEBSTER *† *Peter Medawar Building for Pathogen Research, University of Oxford, South Parks Road, Oxford OX1 3SY, UK, †Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College, Norfolk Place, London, W2 1PG. UK, ‡Institute of Bioengineering, Zhejiang Academy of Medical Sciences, Zhejiang, PR China Abstract This study presents the first microsatellite investigation into the level of genetic variation among Schistosoma japonicum from different geographical origins. S. japonicum isolates were obtained from seven endemic provinces across mainland China: Zhejiang ( Jiashan County), Anhui (Guichi County), Jiangxi (Yongxiu County), Hubei (Wuhan County), Hunan (Yueyang area), Sichuan 1 (Maoshan County), Sichuan 2 (Tianquan County), Yunnan (Dali County), and also one province in the Philippines (Sorsogon). DNA from 20 indi- viduals from each origin were screened against 11 recently isolated and characterized S. japonicum microsatellites, and a set of nine loci were selected based on their polymorphic information content. High levels of polymorphism were obtained between and within population samples, with Chinese and Philippine strains appearing to follow different lineages, and with distinct branching between provinces. Moreover, across mainland China, genotype clustering appeared to be related to habitat type and /or intermediate host morph. These results highlight the suitability of microsatellites for population genetic studies of S. japonicum and suggest that there may be different strains of S. japonicum cir- culating in mainland China. Keywords: China, DNA microsatellites, habitat, population structure, Schistosoma japonicum, schistosomiasis Received 30 September 2004; revision accepted 29 November 2004 Introduction Schistosomiasis is one of the most crucial human parasitic diseases in the Far East, where it infects an estimated 2 million people (McGarvey et al. 1999). Of five major spe- cies of schistosomes that infect humans, Schistosoma japonicum is generally recognized as the most virulent partly because of its high egg production (Garcia 1976). Moreover, S. japonicum is the only schistosome for which zoonotic transmission is considered important (Nelson 1975), with over 40 species of wild and domesticated animals suspected to serve as reservoir hosts for the parasite. S. japonicum , however, remains the least investigated and understood of all the schistosome species (Hagan & Gryseels 1994). To gain an insight into the transmission and epidemiological processes of the disease, a detailed understanding of schistosome popula- tion genetic structure is important. Several workers using, for example, isozyme (Hope et al . 1995) and mitochondrial DNA (mtDNA) techniques (Bowles et al . 1993) have reported remarkable similarity at the genetic level, even between Chinese and Philippine S. japonicum populations. Sørensen and coworkers (Sørensen et al . 1999a,b) using variation in the NDI gene, were able to detect differences between S. japonicum populations, although they also could not conclusively detect variability at the intra- population level. Woodruff et al . (1987) concluded that S. japonicum may almost be isogenic, and Merelender et al . (1987) even raised the possibility that such homozygosity could be indicative of parthenogenetic reproduction. Gasser et al . (1996), in contrast, using the randomly ampli- fied polymorphic DNA (RAPD) technique, did detect Correspondence: Jaya Shrivastava, Fax: 020 74023927; E-mail: jaya.shrivastava@imperial.ac.uk The authors contributed equally to this work.