POOL SCREEN POLYMERASE CHAIN REACTION FOR ESTIMATING THE PREVALENCE OF ONCHOCERCA VOLVULUS INFECTION IN SIMULIUM DAMNOSUM SENSU LATO: RESULTS OF A FIELD TRIAL IN AN AREA SUBJECT TO SUCCESSFUL VECTOR CONTROL

Abstract. Detection of infective parasites in the vector population can be an early indicator of recrudescence in areas freed of new cases of onchocerciasis. However, dissection of vector black flies is inefficient in areas subject to effective control. Recently, a polymerase chain reaction (PCR)–based assay has been used to detect a single Oncho-cerca volvulus–infected black fly in pools containing large numbers of uninfected flies. This method had not been validated on wild-caught black flies in an area subject to effective vector control. Here, we report a method of restricting the pool screen PCR assay to infectious parasites and the results of a field test in an area subject to long-term vector control. The prevalence of infection determined by dissection did not differ from that determined by pool screen PCR. The results suggest that the PCR assay may be a useful tool for epidemiologic surveillance for O. volvulus infection. One of the major challenges of the Onchocerciasis Control Program (OCP) in West Africa is to place the 11 participat-ing countries in a position to be able to take over its residual activities when the program comes to an end in 2002. At that time, epidemiologic surveillance and ivermectin treat-ment will remain the residual activities to be implemente