Chapter Two - Control and elimination of lymphatic filariasis in Oceania: Prevalence, geographical distribution, mass drug administration, and surveillance in Samoa, 1998–2017
Section snippets
Background
Lymphatic filariasis (LF) is a helminthic human disease transmitted by mosquito vectors. Three species of filarial worms exist worldwide: Wuchereria bancrofti, Brugia malayi and B. timori, which are transmitted by Anopheles, Aedes, Culex and Mansonia mosquitoes (WHO, 2020c). Lymphatic filariasis can lead to severe chronic disability and disfigurement, as a result of lymphoedema, including swollen limbs (elephantiasis) and hydrocoele (scrotal swelling) in men. Initial symptoms may take 5–10 years
Samoa
Samoa is a South Pacific nation comprising two main islands, Upolu and Savai'i, and six islets located approximately between 13 and 14 degree S and 172 degree W, with a land area of 2935 km2. The estimated population grew from 176,710 to 187,820 between the 2001 and 2011 censuses. At the most recent census in 2016, the population was estimated as 191,126, with 93% Samoan ethnicity (Samoa Bureau of Statistics, 2016a). The capital Apia is located on Upolu. There are four administrative regions with
Methods
Data were extracted from published and unpublished reports from 1998 to 2017. Site and village survey records (numbers tested and positive by ICT or Mf blood slide) and MDA coverages were extracted from PacELF reports, the 2003 and 2006 PacELF databooks (WHO WPRO, 2003, WHO WPRO, 2006a) and the PacELF Way book (WHO WPRO, 2006b). Survey sites were usually villages, but sometimes there were multiple survey sites in the same village. Information was extracted from documents held at the PacELF
Programme overview
The timeline of elimination activities (programme and policy events, surveys and MDAs implemented) is shown in Table 1. A (mapping) surveys using ICT antigen tests and Mf slides to determine baseline endemicity began in Samoa in 1998 and continued in 1999, providing data to support the policy that MDA was required everywhere in the country. MDAs under PacELF began in 1999, after the A survey was completed.
Timing and number of participants for blood and other surveys, and years of MDA
Discussion
The extensive and fine-detailed information on LF and its control programme in Samoa from 1998 to 2017 has not previously been carefully collated, evaluated, disseminated or used to best advantage. Information for this 20-year period is presented here to describe the control programme activities and strategies, document all the detailed survey results, and clarify the prevalence and geographical distribution of infection prevalence over time.
The data have some limitations, including the
Conclusions
There was a large reduction in Ag and Mf prevalence in Samoa between 1998 and 2004, likely due to the five rounds of MDA 1999–2003, but elimination thresholds were not reached. Prevalence apparently increased slightly from 2004 to 2007, and was not impacted by intermittent MDAs since then, resulting in a clear resurgence by 2017 as shown in nationwide TAS.
Samoa's MOH has devoted attention and resources in a comprehensive and organized LF MDA programme for many years. Although there was good
Acknowledgements
The Samoa LF programme during the period of study was supported by the Government of Samoa, PacELF/the WHO Division of Pacific Support in Suva Fiji, WHO Geneva, WHO Western Pacific Regional Office, the Australian Government through AusAID, the Secretariat of the Pacific Community, US Centers for Disease Control and Prevention, the Japanese Government, and Japan International Cooperation Agency. James Cook University provided technical support and advice through the WHO Collaborating Centre (CC)
References (73)
- et al.
The PacELF programme: will mass drug administration be enough?
Trends Parasitol.
(2002) - et al.
Measles epidemic in Samoa and other Pacific islands
Lancet Infect. Dis.
(2020) - et al.
Current Zika virus epidemiology and recent epidemics
Med. Mal. Infect.
(2014) - et al.
Distribution of vectors, transmission indices and microfilaria rates of subperiodic Wuchereria bancrofti in relation to village ecotypes in Samoa
Trans. R. Soc. Trop. Med. Hyg.
(1987) - et al.
Natural infection of Wuchereria bancrofti in Aedes (Stegomyia) polynesiensis and Aedes (Finlaya) samoanus in Samoa
Trans. R. Soc. Trop. Med. Hyg.
(1987) - et al.
Geofil: a spatially-explicit agent-based modelling framework for predicting the long-term transmission dynamics of lymphatic filariasis in American Samoa
Epidemics
(2019) - et al.
Burden of hydrocoele assessed from medical and surgical records in a lymphatic filariasis endemic country, Samoa
Trop. Med. Health
(2019) - et al.
Elimination of lymphatic filariasis as a public health problem from the Cook Islands
Trop. Med. Health
(2018) - et al.
Combining different diagnostic studies of lymphatic filariasis for risk mapping in Papua New Guinea: a predictive model from microfilaraemia and antigenaemia prevalence surveys
Trop. Med. Health
(2018) - et al.
The argument for integrating vector control with multiple drug administration campaigns to ensure elimination of lymphatic filariasis
Filaria J.
(2006)
Elimination of lymphatic filariasis as a public health problem in Niue under PacELF, 1999-2016
Trop. Med. Health
Filariasis vectors and their control in the South Pacific
Report of Samoa Mass Drug Administration for Lymphatic Filariasis Conducted on 25-27 November 2011
Summary Note
Transmission Assessment Survey 2017 and Soil Transmitted Helminthes Survey Report
Dengue Serotype 2 Outbreak in Samoa, 2017/2018
Lymphatic filariasis in Oceania
Demographic, socioeconomic and disease knowledge factors, but not population mobility, associated with lymphatic filariasis infection in adult workers in American Samoa in 2014
Parasit. Vectors
Evaluation of traps and lures for mosquito vectors and xenomonitoring of Wuchereria bancrofti infection in a high prevalence Samoan village
Parasit. Vectors
Entomology of the filariasis control programme in Samoa, Aedes polynesiensis and Ae. samoanus
Med. Entomol. Zool.
Overview of PacELF-the Pacific Programme for the Elimination of Lymphatic Filariasis
Trop. Med. Health
Wuchereria bancrofti filariasis control in Samoa before PacELF (Pacific Programme to Eliminate Lymphatic Filariasis)
Trop. Med. Health
Village Beautification shows Pacific the Way, Says Samoan Tourism Minister
Exploratory study investigating factors influencing mass drug administration (MDA) compliance for lymphatic filariasis in Samoa
Samoa Med. J.
Epidemiological assessment of continuing transmission of lymphatic filariasis in Samoa
Ann. Trop. Med. Parasitol.
The Global Programme to Eliminate Lymphatic Filariasis: history and achievements with special reference to annual single-dose treatment with diethylcarbamazine in Samoa and Fiji
Trop. Med. Health
Low-density microfilaraemia in subperiodic bancroftian filariasis in Samoa
Bull. World Health Organ.
The efficacy of annual single-dose treatment with diethylcarbamazine citrate against diurnally subperiodic bancroftian filariasis in Samoa
Bull. World Health Organ.
Epidemiology of subperiodic bancroftian filariasis in Samoa 8 years after control by mass treatment with diethylcarbamazine
Bull. World Health Organ.
Long-term efficacy of single-dose mass treatment with diethylcarbamazine citrate against diurnally subperiodic Wuchereria bancrofti: eight years' experience in Samoa
Bull. World Health Organ.
Seroprevalence and spatial epidemiology of Lymphatic Filariasis in American Samoa after successful mass drug administration
PLoS Negl. Trop. Dis.
Cited by (2)
Evaluating Molecular Xenomonitoring as a Tool for Lymphatic Filariasis Surveillance in Samoa, 2018–2019
2022, Tropical Medicine and Infectious Disease
- †
Current address: West Melbourne, VIC, Australia.
- ‡
Current address: Communicable Disease Control Branch, SA Health, Adelaide, SA, Australia.
- §
Current address: Mossman, QLD, Australia.
- ¶
Current address: Castle Hill, NSW, Australia.
- ||
Current address: Department of Environmental Biology and Medical Parasitology; College of Medicine, Hanyang University, Seoul, Republic of Korea.
- **
Current address: Portland, OR, United States.
- ††
Current address: Tokyo, Japan.