Molecular arguments for splitting of Schistosoma intercalatum, into two distinct species

The taxonomic status of the two known strains of Sckistosoma intercalatum, the Lower Guinea strain (originating from Edea, Cameroon) and the Zaire str ain (originating from Kinshasa, Democratic Republic of Congo, formerly Zair e) was examined using random amplified polymorphic DNA (RAPD) markers. Two additional species within the S. haematobium group, S. haematobium and S. m attheei, were included in the study. DNA was extracted from four male and f our female worms of each species and strain under investigation. In all, 13 primers gave reproducible and informative marker patterns; the monomorphic bands in all the males and females of each sample were scored, and 138 ban ds were included in the final analysis. Overall, 14 RAPD fragments were sha red by all the schistosomes studied, and 19 RAPD fragments were considered to be sex markers. Only 22% (20/91) of the RAPD fragments were shared betwe en S. intercalatum Zaire and S. intercalatum Cameroon. The mean values reco rded for the Nei and Li's genetic distances between S. haematobium and S. m attheei and between S. intercalatum Zaire and S. intercalatum Cameroon were 0.546 and 0.596, respectively. A principal component analysis and one-way analysis of variance (ANOVA/MANOVA) showed a significant separation between S. intercalatum Zaire and S. intercalatum Cameroon. The data support the h ypothesis that S. intercalatum Zaire and S. intercalatum Cameroon are disti nct species. Additional molecular-biology studies are in progress that invo lve the use of nuclear and mitochondrial markers to confirm the extent of t he genetic divergence prior to the establishment of final decision on the t axonomic status of the two strains of S. intercalatum.