Progress towards global elimination of lymphatic filariasis
Authors: Joseph Kamgno, Hugues Nana Djeunga
Journal: The Lancet Global Health (2020)

In response to the burden of lymphatic filariasis—which was considered to be the second leading cause of permanent and long-term disability1WHOMonitoring and epidemiological assessment of mass drug administration in the global programme to eliminate lymphatic filariasis: a manual for national elimination programmes. World Health Organization, Geneva2011Google Scholar—WHO committed to eliminating lymphatic filariasis as a public health problem at the 50th World Health Assembly, in 1997. The Global Programme to Eliminate Lymphatic Filariasis (GPELF) was therefore created and launched its activities in 2000, with the core mission to coordinate control efforts to reach elimination of lymphatic filariasis by 2020. The GPELF proposed a comprehensive elimination strategy, including transmission interruption in endemic communities (by use of mass drug administration [MDA]) and implementation of interventions to prevent and manage lymphatic filariasis-associated disabilities (the so-called morbidity management and disability prevention [MMDP] strategy).1WHOMonitoring and epidemiological assessment of mass drug administration in the global programme to eliminate lymphatic filariasis: a manual for national elimination programmes. World Health Organization, Geneva2011Google Scholar The GPELF recognised the need to establish a process for external evaluation of the evidence for elimination and for official recognition of success, so they created the Regional Programme Review Group and the Strategic and Technical Advisory Group on Neglected Tropical Diseases to provide advice to endemic countries and evaluate country dossiers help accelerate progress towards control and elimination of targeted diseases, including lymphatic filariasis. In The Lancet Global Health, the Local Burden of Disease (LBD) 2019 Neglected Tropical Diseases Collaborators2Local Burden of Disease 2019 Neglected Tropical Diseases CollaboratorsThe global distribution of lymphatic filariasis, 2000–18: a geospatial analysis.Lancet Glob Health. 2020; 8: e1186-e1194Summary Full Text Full Text PDF PubMed Scopus (16) Google Scholar use Bayesian model-based geostatistics and time series methods to generate spatially continuous estimates, to report the progress towards elimination and identify geographic variation in the distribution of infection. Although the prevalence of lymphatic filariasis substantially declined—from 199 million individuals (95% uncertainty interval 174–234 million) in 2000, to 51 million individuals (43–63 million) in 2017 (that is after implementation of GPELF-recommended interventions)—not all areas will achieve the original 2020 goal, and this Article provides national programmes and implementing partners with indications on areas where local elimination might not be attained. The study predicted that in 2017, some countries in Central Africa (such as Chad) and West Africa (such as Ghana and Côte d'Ivoire) had a prevalence of lymphatic filariasis above 1% elimination threshold, probably because of high baseline prevalence or more recent programme initiation. These observations can provide insight into the actions needed to accelerate progress towards elimination. For example, it is largely documented that in central and west Africa, loiasis—another filarial infection—constitutes a barrier to elimination of lymphatic filariasis in areas of coendemicity.3Zouré HG Wanji S Noma M et al.The geographic distribution of Loa loa in Africa: results of large-scale implementation of the Rapid Assessment Procedure for Loiasis (RAPLOA).PLoS Negl Trop Dis. 2011; 5e1210Crossref PubMed Scopus (166) Google Scholar A twice-yearly albendazole regimen,4Pion SDS Chesnais CB Weil GJ Fischer PU Missamou F Boussinesq M Effect of 3 years of biannual mass drug administration with albendazole on lymphatic filariasis and soil-transmitted helminth infections: a community-based study in Republic of the Congo.Lancet Infect Dis. 2017; 17: 763-769Summary Full Text Full Text PDF PubMed Scopus (24) Google Scholar integrated with malaria vector control, or a test and not treat approach, developed and successfully tested on onchocerciasis,5Kamgno J Pion SD Chesnais CB et al.A test-and-not-treat strategy for onchocerciasis in Loa loa-endemic areas.N Engl J Med. 2017; 377: 2044-2052Crossref PubMed Scopus (75) Google Scholar could be explored to achieve elimination of lymphatic filariasis in central and west Africa; such a strategy, based on situation analysis, is one of the applications expected from this study. Diagnostic tools have regularly changed over the course of lymphatic filariasis elimination programmes. However, WHO recommended immunochromatographic tests—later replaced by the more sensitive filariasis test strips—in areas where Wuchereria bancrofti is endemic6Weil GJ Curtis KC Fakoli L et al.Laboratory and field evaluation of a new rapid test for detecting Wuchereria bancrofti antigen in human blood.Am J Trop Med Hyg. 2013; 89: 11-15Crossref PubMed Scopus (75) Google Scholar and Brugia Rapid in areas where Brugia spp is endemic for mapping, transmission assessment, and surveillance activities.1WHOMonitoring and epidemiological assessment of mass drug administration in the global programme to eliminate lymphatic filariasis: a manual for national elimination programmes. World Health Organization, Geneva2011Google Scholar Mapping and monitoring and evaluation exercises have been questioned because of a loss of sensitivity or cross-reactivity with ICT, especially in central and west Africa, where loiasis is coendemic.7Gounoue-Kamkumo R Nana-Djeunga HC Bopda J et al.Loss of sensitivity of immunochromatographic test (ICT) for lymphatic filariasis diagnosis in low prevalence settings: consequence in the monitoring and evaluation procedures.BMC Infect Dis. 2015; 15: 579Crossref PubMed Scopus (15) Google Scholar, 8Bakajika DK Nigo MM Lotsima JP et al.Filarial antigenemia and Loa loa night blood microfilaremia in an area without Bancroftian filariasis in the Democratic Republic of Congo.Am J Trop Med Hyg. 2014; 91: 1142-1148Crossref PubMed Scopus (39) Google Scholar Although the LBD 2019 Neglected Tropical Diseases Collaborators adjusted the estimates to account for the reliability of diagnostic tools, the question remains as to whether the available diagnostic tools can accurately be used to certify lymphatic filariasis elimination, and further proof of transmission interruption (eg, xenomonitoring) is necessary so that sites with residual infection and at risk of resurgence of transmission can be detected.9Subramanian S Jambulingam P Krishnamoorthy K et al.Molecular xenomonitoring as a post-MDA surveillance tool for global programme to eliminate lymphatic filariasis: field validation in an evaluation unit in India.PLoS Negl Trop Dis. 2020; 14e0007862Crossref PubMed Scopus (11) Google Scholar MMDP is largely neglected by almost all elimination programmes in endemic countries; therefore, the morbidity associated with lymphatic filariasis (hydrocele, lymphoedema, and elephantiasis) and management procedures are largely ignored and so is progress towards a better lifestyle for affected individuals. Although verification of the absence of transmission of lymphatic filariasis does not include MMDP, data on the burden of lymphatic filariasis and appropriate management are informative on the progress towards elimination,1WHOMonitoring and epidemiological assessment of mass drug administration in the global programme to eliminate lymphatic filariasis: a manual for national elimination programmes. World Health Organization, Geneva2011Google Scholar and programmes should be encouraged to implement MMDP concomitantly with MDA. Research and practice are oriented towards progress in interventions, transmission assessment surveys, and post-MDA surveillance for certification of lymphatic filariasis elimination. In 2012, the WHO neglected tropical diseases roadmap reconfirmed the target date for achieving elimination by 2020.10WHOAccelerating work to overcome the global impact of neglected tropical diseases—a roadmap for implementation. World Health Organization, Geneva2012Google Scholar It is obvious that this deadline cannot be met because some endemic countries are yet to complete mapping or launch MDA. The steps taken towards elimination vary by WHO region and area. The LBD 2019 Neglected Tropical Diseases Collaborators have succeeded in compiling and analysing these data globally and provide estimates to accelerate progress towards elimination. The study by LBD 2019 Neglected Tropical Diseases Collaborators provides valuable information to quantify the progress towards elimination of lymphatic filariasis and identify areas for which additional efforts are still needed. These efforts need to be concerted, wherever this debilitating disease is endemic, and by investigating subnational variation in the distribution of infection, LBD 2019 Neglected Tropical Diseases Collaborators clearly provide crucial insights. We declare no competing interests. The global distribution of lymphatic filariasis, 2000–18: a geospatial analysisAlthough the prevalence of lymphatic filariasis infection has declined since 2000, MDA is still necessary across large populations in Africa and Asia. Our mapped estimates can be used to identify areas where the probability of meeting infection thresholds is low, and when coupled with large uncertainty in the predictions, indicate additional data collection or intervention might be warranted before MDA programmes cease. Full-Text PDF Open Access