MOLECULAR CHARACTERIZATION OF BULINUS-GLOBOSUS AND B-NASUTUS ON ZANZIBAR, AND AN INVESTIGATION OF THEIR ROLES IN THE EPIDEMIOLOGY OF SCHISTOSOMA-HAEMATOBIUM

The ribosomal internal transcribed spacer (ITS) regions of both Bulinu s globosus and B. nasutus from Zanzibar were amplified and restricted with 6 enzymes. Restriction products were separated by polyacrylamide gel electrophoresis and visualized by ethidium bromide staining. Consi derable genetic variation was observed at 3 levels: (i) between specie s, (ii) among populations and (iii) among individuals. In addition, th e 18S ribosomal deoxyribonucleic acid gene was amplified from both spe cies and the products were also restricted with several enzymes. No va riation was detected. Nucleotide diversity of the ITS was estimated to be approximately 0.019 for both species and nucleotide divergence bet ween species was estimated to be 0.03. Restriction profiles differenti ated these snail species and may prove useful for identification purpo ses. Only B. globosus populations were found to be naturally infected with Schistosoma haematobium. From laboratory infection studies of pro geny snails, B. nasutus appeared to be refractory to S. haematobium, w hereas certain B. globosus populations were susceptible to laboratory challenge.