Toward Molecular Parasitologic Diagnosis: Enhanced Diagnostic Sensitivity for Filarial Infections in Mobile Populations

The diagnosis of filarial infections among individuals residing in areas where the disease is not endemic requires both strong clinical suspicion and expert training in infrequently practiced parasitological methods. Recently developed filarial molecular diagnostic assays are highly sensitive and specific but have limited availability and have not been closely evaluated for clinical use outside populations residing in areas of endemicity. In this study, we assessed the performance of a panel of real-time PCR assays for the four most common human filarial pathogens among blood and tissue samples collected from a cohort of patients undergoing evaluation for suspected filarial infections. Compared to blood filtration, real-time PCR was equally sensitive for the detection of microfilaremia due to Wuchereria bancrofti (2 of 46 samples positive by both blood filtration and PCR with no discordant results) and Loa loa (24 of 208 samples positive by both blood filtration and PCR, 4 samples positive by PCR only, and 3 samples positive by blood filtration only). Real-time PCR of skin snip samples was significantly more sensitive than microscopic examination for the detection of Onchocerca volvulus microfiladermia (2 of 218 samples positive by both microscopy and PCR and 12 samples positive by PCR only). The molecular assays required smaller amounts of blood and tissue than conventional methods and could be performed by laboratory personnel without specialized parasitology training. Taken together, these data demonstrate the utility of the molecular diagnosis of filarial infections in mobile populations.