SENSITIVITY OF A POLYMERASE CHAIN REACTION-BASED ASSAY TO DETECT ONCHOCERCA-VOLVULUS DNA IN SKIN BIOPSIES

A polymerase chain reaction (PCR) of a 150-bp tandem repeat of Onchoce rca volvulus (O-150) combined with Southern-blot hybridization to spec ies-specific DNA probes was employed for DNA detection. O-150 was ampl ified from parasites originating from Uganda, Benin, Cameroon, Liberia , Ghana, Burkina Faso, Mali, and Zaire and was successfully hybridized to digoxigenin-labeled oligonucleotides. To investigate the sensitivi ty of the PCR, 2 skin biopsies were taken from each of 227 persons fro m Uganda with proven O. volvulus infections but with low microfilaria (mf) densities due to ivermectin treatment. One biopsy was tested by P CR and the other was digested using collagenase to assess the total nu mber of mf. The PCR revealed 76.2% of the samples to be positive, and the collagenase method showed that 78.9% were positive, indicating sim ilar sensitivity for the two methods. It is probable that for both tec hniques the biopsy must contain at least one live mf or fragments of a dead mf. In this study, no free or circulating O. volvulus DNA could be detected in skin biopsies by PCR.