The O-150 PCR is based upon the amplification of a genus specific tandemly repeated DNA sequence present in the genome of Onchocerca parasites [22] . Thus, the standard O-150 PCR will amplify sequences present in all Onchocerca species, including Onchocerca ochengi, a cattle parasite that is sympatric with O. volvulus in sub-Saharan Africa. Currently, the O-150 PCR is made species or strain specific by modifying the amplification conditions to limit amplification to species specific members of the O-150 repeat family [23] or by the use of species or strain specific probes to detect the resulting amplicons [8] . However the oligonucleotide used in the capture assay (OVS2) has previously Table 3 . Cost analysis of silica adsorption and oligonucleotide capture assays.