Genetic epidemiology of lymphatic filariasis in American Samoa after mass drug administration

Over 892 million people in 48 countries are at risk of infection by nematodes that cause lymphatic filariasis. As part the Global Programme to Eliminate Lymphatic Filariasis, mass drug administration is distributed communities until surveillance indicates rates below target prevalence thresholds. In some countries, including American Samoa, filariasis transmission persists despite years and/or has resurged after cessation. Nothing known about population genetics Wuchereria bancrofti worms Polynesia, or whether local persisting increasing due inadequate coverage, expansion from residual hotspots, reintroduction elsewhere, a combination. We extracted DNA microfilariae on blood slides collected during surveys 2014 and 2016, comprising 31 pools five 22 persons living eight villages. sequenced 1104 bp across three mitochondrial markers (ND4, COI, CYTB). quantified parasite genetic differentiation using variant calls estimated haplotypes principal components analysis, F-statistics, haplotype networks. Of variants called, all but were shared main island Tutuila, those previously described hotspot village, Fagali’i. Genotypic data did not support structure among regions villages although differences observed between Fagali’i 2016. Because frequency varied villages, these statistics suggested differentiation, consistent Finally, networks demonstrated Samoan sequence clusters related published sequences Papua New Guinea. These are, our knowledge, first reports W. variation Polynesia. The resurgent parasites circulating Samoa represent single population. This study step towards investigating how might inform strategies manage resurgence elimination