January 30, 2021 is the second annual World NTD Day, a celebration set to mark the anniversary of the signing of the 2012 London Declaration on Neglected Tropical Diseases and the World Health Organization’s (WHO) 2020 road map on NTDs. Echoes of these historic, coalescing events are found in this year’s World NTD Day, which is celebrated two days after the official launch of WHO’s revised NTD road map.
The new road map, Ending the Neglected to Attain the Sustainable Development Goals: A road map for neglected tropical diseases 2021–2030, comes at a time when uncertainty still abounds. Covid-19 has delayed NTD activities, redirected scarce attention and resources, and has taken an incalculable toll on many lives. Yet the new roadmap reminds us that momentum is cyclical, that targets must often be revised, and that fighting against these diseases is an investment in more than just NTDs. With renewed energy, the new NTD road map acknowledges the significant progress made towards eliminating and controlling NTDs since 2012. It also addresses the challenges.
The below article, Achievements and challenges of lymphatic filariasis elimination in Sierra Leone, details recent progress towards eliminating LF in Sierra Leone. Despite significant progress towards eliminating LF in Sierra Leone, repeated pre-TAS failures have proven perplexing, especially given the prevailing WHO guidelines on annual mass treatment for LF. Regardless, it has led to greater understanding of the drivers of pre-TAS failures. With failure comes learning. These difficulties have generated a greater knowledge base, providing tools and best practices that can be replicated elsewhere.
With all that has been learned since 2012, the new road map prioritizes country ownership and calls for intensified cross cutting approaches with a bold vision for 2030. Beyond disease elimination, fighting against NTDs is central to Universal Health Coverage, the achievement of the Sustainable Development Goals, and the realization of concerted efforts across countries, global partners, and stakeholders to achieve a common goal. Recommitting to the new WHO road map means that on World NTD Day, and every day, we hope to #beatNTDs and #EndTheNeglect.
Achievements and challenges of lymphatic filariasis elimination in Sierra Leone
Bah YM, et al. (2020) PLoS Negl Trop Dis 14(12): e0008877. https://doi.org/10.1371/journal. pntd.0008877
Lymphatic filariasis (LF) is targeted for elimination as a public health problem in Sierra Leone, which reported some of the highest prevalence rates in all of Africa in the 1990s. Mapping conducted in 2005 showed that all fourteen districts were endemic for LF, including 12 districts which were co-endemic with onchocerciasis. Starting in 2006, community directed treatment with ivermectin (CDTI) began, using community drug distributors (CDDs) to provide medicines. By 2008, CDTI plus albendazole was scaled up to all 12 co-endemic districts. All districts were eligible to conduct pre-transmission assessment surveys (pre-TAS) in 2013, where eight out of 12 districts achieved the requisite mf prevalence to proceed with TAS1. The remaining districts required two additional rounds of quality MDA before repeating pre-TAS. However, the Ebola outbreak in Sierra Leone from 2014-2016 led to postpone of the TAS1, and additional rounds of MDA were performed in all districts. Ultimately, a total of 6-8 rounds of MDA have been conducted in all districts. The paper explores the results of the pre-TAS and TAS surveys subsequently conducted in 2017, identifying areas for improvement and the challenges for LF elimination in Sierra Leone.
TAS was conducted in 2017 in four evaluations units (eight districts) that passed pre-TAS in 2013. A school-based cluster survey was conducted, targeting school-aged children aged 6 – 7. The Survey Sample Builder was used to determine sample size and selection based on WHO guidelines.
Pre-TAS was conducted in four districts that failed pre-TAS in 2013, as well as the two districts in the Western Area. One sentinel sight and one spot check site were selected in each district except in Bombali district where an additional spot check site was selected. A convenience sample of 300 participants aged five and over were tested with filariasis test strips (FTS), and positive cases were confirmed with a second positive test. The confirmed FTS positive cases were sampled with midday and midnight blood and tested for with Mansonella perstans and Wuchereria bancrofti microfilariae respectively.
All districts reported effective epidemiological coverage rates of at least 65%. All four EUs/eight districts passed TAS, with all FTS positives falling below the critical cut-off values. All four districts that conducted the repeat pre-TAS failed to reach the threshold of <2% antigenemia prevalence required to qualify for TAS. For the pre-TAS in the two districts in the Western Area, Western Area Urban passed while the Western Area Rural failed.
In FTS positives, 9/236 persons were positive for W. bancrofti mf and 12 persons were positive for M. perstans mf. Six samples were positive for both parasites, six samples were positive for M. perstans mf and three samples were positive for W. bancrofti mf.
The four EUs/eight districts that passed TAS qualified for stopping LF MDA. The Western Area Urban qualified for conducted TAS1. Overall, five districts failed to reach the criteria for stopping LF MDA, and four districts failed twice despite the 6-8 rounds of MDA, with reportedly good coverage.
There were many potential reasons for why the five districts failed the pre-TAS, including very high baseline prevalence in the districts bordered with Guinea and Liberia, highly mobile populations, and vector competence. There may have been unsatisfactory MDA coverage at sub-district level, which may have been caused by community reluctance and non-compliance, insufficient social mobilization, the post-Ebola context, inaccurate denominators used for calculating coverage rates due to employment seeking migration, urbanization, and other drivers of rapid population change. Finally, reduced CDD participation and motivation may have weakened MDA quality.
Recommendations to improve MDA include improved social mobilization and supervision, syncing MDA treatment schedules with Guinea and Liberia to ensure treatment of migratory populations, involving participating of religious leaders and traditional healers, and researching the possible impact of M.perstans on LF diagnostic testing.