Comparison of Three Mosquito Traps for Lymphatic Filariasis Molecular Xenomonitoring in American Samoa Villages

Lymphatic filariasis (LF) is a mosquito-borne disease caused by Wuchereria bancrofti, which is endemic in American Samoa. The effort to eliminate LF has been highly successful, and is now in the monitoring phase to ensure continued progress. One of the monitoring methods is molecular xenomonitoring (MX) using PCR to detect W. bancrofti DNA in mosquitoes. Currently MX uses BG Sentinel traps to collect the LF vector Aedes polynesiensis. But the BG Sentinel traps catch relatively few Ae. polynesiensis, and most of those captured have not yet fed on blood. Gravid traps target mosquitoes that have already fed on blood, and have been used to collect large numbers of Culex quinquefasciatus for MX where that species is a vector. Though Cx. quinquefasciatus is not an LF vector in American Samoa, parasite DNA can be detected in non-vectors as well as vectors. We hypothesize that gravid traps targeting Cx. quinquefasciatus is more efficient for MX than the BG Sentinel trap targeting Ae. polynesiensis. For our study, we compared two alternative gravid traps to the BG Sentinel trap. Two of each trap type were set in each of two villages and rotated daily in a Latin square design. The daily average catch rate for Ae. polynesiensis and Cx. quinquefasciatus were compared to assess the relative efficacy of the traps. If one or both gravid traps prove to be effective in capturing large numbers of Cx. quinquefasciatus, then they may provide a more efficient alternative to the BG Sentinel for LF MX in American Samoa

Attractiveness of Three Gravid Trap Infusions for Ovipositing Polynesian Tiger Mosquitoes (Aedes polynesiensis) in American Samoa

The Polynesian tiger mosquito, Aedes polynesiensis, is a carrier of filariasis, chikungunya and dengue in American Samoa. The most commonly used tool for monitoring Ae. polynesiensis is the BG Sentinel trap; however, this trap catches relatively few mosquitoes and targets females searching for a blood meal. Recently developed gravid traps targeting females that have already blood-fed and are searching for oviposition sites may be a better alternative. But results of the initial trials of these gravid traps using a weedy grass hay infusion lure were disappointing. This experiment evaluates two alternative infusions made from dried banana leaves and Bermuda grass hay. We hypothesize that the Bermuda grass or banana leaves infusion may be more attractive to Ae. polynesiensis than the weedy grass infusion. Ovicups containing weedy grass hay, dried banana leaves and Bermuda grass infusions were arranged in a randomized complete block design in mixed vegetation on the American Samoa Community College campus. After three days, the egg sheets were collected from the cups, the eggs hatched, and the larvae raised to fourth instar to identify the species. The experiment was repeated three times and the average eggs were compared to determine the most effective infusion. If either the banana leaves or the Bermuda grass infusion proves more attractive than the weedy grass hay infusion, use of the more effective infusion in the new gravid traps may improve their efficacy and provide a valuable new tool for future research and better management of this important disease vector