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

Hedtke, Shannon M., Zendejas-Heredia, Patsy A., Graves, Patricia M., Sheridan, Sarah, Sheel, Meru, Fuimaono, Saipale D., Lau, Colleen L., and Grant, Warwick N. (2021) Genetic epidemiology of lymphatic filariasis in American Samoa after mass drug administration. International Journal for Parasitology, 51 (2-3). pp. 137-147.

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

Item ID: 66307
Item Type: Article (Research - C1)
ISSN: 1879-0135
Keywords: Lymphatic filariasis; American Samoa; Wuchereria bancrofti; Population genetics; Mass drug administration
Copyright Information: © 2020 The Authors. Published by Elsevier Ltd on behalf of Australian Society for Parasitology. This is an open access article under the CC BY-NC-ND license (
Funders: UNICEF/UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases (TDR)), La Trobe University (LTU), PRISM, Australian National Health and Medical Research Council (NHMRC), Australian Institute of Tropical Health and Medicine (AITHM), University of Queensland (UQ), Coalition for Operational Research on Neglected Tropical Diseases (CORNTD)
Projects and Grants: TDR B80153, TDR B80149, LTU Asia Research Grant, LTU Understanding Disease Research Focus Area Start-Up Grant, NHMRC Fellowship 1109035, AITHM #13122014, UQ 2127835
Date Deposited: 04 Mar 2021 02:50
FoR Codes: 42 HEALTH SCIENCES > 4202 Epidemiology > 420202 Disease surveillance @ 34%
45 INDIGENOUS STUDIES > 4516 Pacific Peoples health and wellbeing > 451605 Pacific Peoples epidemiology @ 33%
32 BIOMEDICAL AND CLINICAL SCIENCES > 3207 Medical microbiology > 320704 Medical parasitology @ 33%
SEO Codes: 20 HEALTH > 2003 Provision of health and support services > 200303 Health surveillance @ 50%
20 HEALTH > 2005 Specific population health (excl. Indigenous health) > 200599 Specific population health (excl. Indigenous health) not elsewhere classified @ 50%
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