Isolation and characterization of form specific DNA sequences of O. volvulus.

Maintenance of the control of O. volvulus in Africa would be assisted by the development of assays to identify the origin of outbreaks of transmission within the controlled regions. The isolation of pFS-1, a DNA sequence specific for forest form O. volvulus, has suggested that it might be possible to develop such an assay based on form specific DNA probes. The isolation and characterization of pSS-1, a clone which hybridized preferentially to savannah form O. volvulus is described here. DNA sequence analysis demonstrated that pSS-1 was a representative of a highly repeated sequence family of O. volvulus. Comparison of the sequence of pSS-1 to other known examples of this family has identified a region of pSS-1, designated pSS-1BT, which appeared to be specific for savannah form O. volvulus. Tests of isolates from different areas demonstrated that the specificity of pFS-1 and pSS-BT were not confined to a small geographic region. However, the close relationship of pFS-1 and pSS-BT to less specific members of the repeat family means that their specificity and sensitivity are affected by small changes in the conditions under which they are used.