Currently, the accepted method for pool screening vector black flies to detect O. volvulus relies upon screening DNA prepared from fly pools with a PCR assay targeting a repeated sequence family (the O-150 repeat [6] ) specific for parasites of the genus Onchocerca. Algorithms have been developed that permit one to derive a point estimate of the prevalence of infection in the fly population (and an associated confidence interval) from the number of PCR positive pools and the number of flies contained in each pool [7] . Furthermore, because the infective stage of the parasite is the only form found in the black fly head capsule, separated pools of heads and bodies may be screened to obtain estimates of the prevalence of infective flies (flies with infective stages in their head) and the prevalence of infected flies (flies with immature larval stages in their bodies). This approach has been used to monitor transmission of O. volvulus in many foci of Latin America and Africa [8] [9] [10] [11] , as well as to certify the interruption of transmission in foci on both continents [5, [12] [13] [14] .