Control and elimination of lymphatic filariasis in Oceania: Prevalence, geographical distribution, mass drug administration, and surveillance in Samoa, 1998-2017

Lymphatic filariasis (LF) is a major public health problem globally and in the Pacific Region. The Global Programme to Eliminate LF has made great progress but LF is persistent and resurgent in some Pacific countries and territories. Samoa remains endemic for LF despite elimination efforts through multiple two-drug mass drug administrations (MDA) since 1965, including renewed elimination efforts started in 1999 under the Pacific Programme for Elimination of LF (PacELF). Despite eight rounds of national and two rounds of subnational MDA under PacELF, Samoa failed transmission assessment surveys (TAS) in all three evaluation units in 2017. In 2018, Samoa was the first to distribute countrywide triple-drug MDA using ivermectin, diethylcarbamazine (DEC), and albendazole. This paper provides a review of MDAs and historical survey results from 1998 to 2017 in Samoa and highlights lessons learnt from LF elimination efforts, including challenges and potential ways to overcome them to successfully achieve elimination.

A fatal case of Shiga toxin-producing Escherichia coli linked to a private drinking water supply

In May 2017, a fatal case of Shiga toxin-producing <i>Escherichia coli</i> (STEC) with haemolytic uremic syndrome was investigated by the Victorian Department of Health and Human Services and a local government authority. Investigation revealed the case used rainwater harvested from the roof of their home and stored in tanks as a private drinking water supply, despite the availability of a reticulated supply from the local water authority. <i>Escherichia coli</I> Stx1 and Stx2 genes were detected in a water sample collected from the private drinking water supply, consistent with those earlier identified in the case’s faecal sample. This case study highlights the potential risks of STEC infection from private drinking water supplies, the importance of proper maintenance of such supplies, and the preferable use of reticulated water supplies when available. It also demonstrated an effective collaboration between local and state government for an environmental public health investigation.

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

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.