Differentiation of schistosomes by species, strain, and sex by using cloned DNA markers.

We have detected species, strain, and sex-specific genetic markers for the genus Schistosoma by Southern blot analysis of its DNA using cloned DNA segments of the Schistosoma mansoni ribosomal gene as probes. Restriction analysis of DNA from eight different strains of S. mansoni, from Africa and the Caribbean, revealed that the predominant or major DNA fragment containing the ribosomal gene unit was the same in each but that low copy number or minor fragments containing the gene varied. It was shown that the detection of these minor fragments could serve as the basis for both strain differentiation and the analysis of individual differences within a strain. Analysis of the parents and progeny of a genetic cross revealed sex-linked markers and suggested that these markers are inherited in a Mendelian fashion. DNAs from the species Schistosoma haematobium and Schistosoma japonicum were also analyzed. Differences in the length of the major repeating unit of the ribosomal gene served to distinguish each species. Furthermore, an array of minor bands was detected in each species, suggesting that strains of S. haematobium and S. japonicum could be differentiated in the same manner as S. mansoni strains.