Amplification products were detected by PCR enzyme-linked immunosorbent assay (ELISA), essentially as previously described [10] . Briefly, 5 ml of each PCR reaction was bound to a streptavidin-coated ELISA plate, and the DNA strands denatured by treatment with alkali. The bound PCR fragments were then hybridized to a fluorescein-labeled O. volvulus-specific oligonucleotide probe (OVS2: 59-AATCTCAAAAAACGGGTACATA-FL-39), and the bound probe detected with an alkaline phosphataselabeled anti-fluorescein antibody (fragment FA; Roche Diagnostics). Bound antibody was detected using the ELISA amplification reagent (BluePhos) kit from KPL (Gaithersburg, USA) following the manufacturer's instructions. Color development was stopped by the addition of 100 ml AP stop solution, and the plates read in an ELISA plate reader set at 630 nm. Samples were scored positive if their optical density exceeded either the mean plus three standard deviations of ten negative control wells run in parallel or 0.1, whichever was greater.