Prevalence and risk factors associated with lymphatic filariasis in American Samoa after mass drug administration

Coutts, Shaun P., King, Jonathan, Pa'au, Molisamoa, Fuimaono, Saipale, Roth, Joseph, King, Mary Rose, Lammie, Patrick J., Lau, Colleen L., and Graves, Patricia M. (2017) Prevalence and risk factors associated with lymphatic filariasis in American Samoa after mass drug administration. Tropical Medicine and Health, 45. 22. pp. 1-10.

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Background: In 2000, American Samoa had 16.5% prevalence of lymphatic filariasis (LF) antigenemia. Annual mass drug administration (MDA) was conducted using single-dose albendazole plus diethylcarbamazine from 2000 to 2006. This study presents the results of a 2007 population-based PacELF C-survey in all ages and compares the adult filarial antigenemia results of this survey to those of a subsequent 2010 survey in adults with the aim of improving understanding of LF transmission after MDA.

Results: The 2007 C-survey used simple random sampling of households from a geolocated list. In 2007, the overall LF antigen prevalence by immunochromatographic card test (ICT) for all ages was 2.29% (95% CI 1.66-3. 07). Microfilaremia prevalence was 0.27% (95% CI 0.09-0.62). Increasing age (OR 1.04 per year, 95% CI 1.02-1.05) was significantly associated with ICT positivity on multivariate analysis, while having ever taking MDA was protective (OR 0.39, 95% CI 0.16-0.96). The 2010 survey used a similar spatial sampling design. The overall adult filarial antigenemia prevalence remained relatively stable between the surveys at 3.32% (95% CI 2.44-4.51) by ICT in 2007 and 3.23 (95% CI 2.21-4.69) by Og4C3 antigen in 2010. However, there were changes in village-level prevalence. Eight village/village groupings had antigen-positive individuals identified in 2007 but not in 2010, while three villages/village groupings that had no antigen-positive individuals identified in 2007 had positive individuals identified in 2010.

Conclusions: After 7 years of MDA, with four rounds achieving effective coverage, a representative household survey in 2007 showed a decline in prevalence from 16.5 to 2.3% in all ages. However, lack of further decline in adult prevalence by 2010 and fluctuation at the village level showed that overall antigenemia prevalence at a broader scale may not provide an accurate reflection of ongoing transmission at the village level.

Item ID: 50509
Item Type: Article (Research - C1)
ISSN: 1349-4147
Keywords: lymphatic filariasis, American Samoa, prevalence, MDA, epidemiology, Wuchereria bancrofti, PacELF
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© The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.

Funders: United States Agency for International Development (USAID), Centers for Disease Control and Prevention (CDC), James Cook University (JCU), GlaxoSmithKline, National Health and Medical Research Council (NHMRC)
Projects and Grants: NHMRC Fellowship 1109035
Date Deposited: 20 Sep 2017 09:44
FoR Codes: 32 BIOMEDICAL AND CLINICAL SCIENCES > 3207 Medical microbiology > 320704 Medical parasitology @ 20%
32 BIOMEDICAL AND CLINICAL SCIENCES > 3202 Clinical sciences > 320211 Infectious diseases @ 40%
42 HEALTH SCIENCES > 4202 Epidemiology > 420202 Disease surveillance @ 40%
SEO Codes: 92 HEALTH > 9201 Clinical Health (Organs, Diseases and Abnormal Conditions) > 920109 Infectious Diseases @ 50%
92 HEALTH > 9204 Public Health (excl. Specific Population Health) > 920404 Disease Distribution and Transmission (incl. Surveillance and Response) @ 50%
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