Xenomonitoring of Wuchereria bancrofti and Dirofilaria immitis Infections in Mosquitoes from American Samoa: Trapping Considerations and a Comparison of Polymerase Chain Reaction Assays with Dissection

Entomologic monitoring of filarial infections, xenomonitoring, may have advantages in certain epidemiologic situations to assess the presence of infections in humans. Hemalum staining and dissection and polymerase chain reaction (PCR) were compared to determine the filarial infection status of Aedes (Stegomyia) mosquitoes in American Samoa. The overall prevalences of Wuchereria bancrofti and Dirofilaria immitis infections in Ae. polynesiensis were, respectively, 0.16% and 1.06% by dissection and 0.69% and 1.77% by PCR. Human filarial worm DNA rates in Aedes aegypti and Aedes upolensis were 1.16% and 0.38%, respectively. The results suggest that W. bancrofti transmission to humans may be continuing at low levels in some villages despite recent completion of 5 years of mass drug administration. PCR testing of mosquitoes collected using the BG-Sentinel traps represents a promising alternative to landing catches for assessing the transmission of filariasis in areas where Ae. polynesiensis and related species are the primary vectors.