The Global Programme to Eliminate Lymphatic Filariasis: Health Impact after 8 Years

Eric Ottesen, PJ Hooper, Mark Bradley, Gautam Biswas

Open access to full-text article (PDF)

Abstract

Background: In its first 8 years, the Global Programme to Eliminate Lymphatic Filariasis (GPELF) achieved an unprecedentedly rapid scale-up: >1.9 billion treatments with anti-filarial drugs (albendazole, ivermectin, and diethylcarbamazine) were provided via yearly mass drug administration (MDA) to a minimum of 570 million individuals living in 48 of the 83 initially identified LF-endemic countries.

Methodology: To assess the health impact that this massive global effort has had, we analyzed the benefits accrued first from preventing or stopping the progression of LF disease, and then from the broader anti-parasite effects (‘beyond-LF’ benefits) attributable to the use of albendazole and ivermectin. Projections were based on demographic and disease prevalence data from publications of the Population Reference Bureau, The World Bank, and the World Health Organization.

Result: Between 2000 and 2007, the GPELF prevented LF disease in an estimated 6.6 million newborns who would otherwise have acquired LF, thus averting in their lifetimes nearly 1.4 million cases of hydrocele, 800,000 cases of lymphedema and 4.4 million cases of subclinical disease. Similarly, 9.5 million individuals—previously infected but without overt manifestations of disease—were protected from developing hydrocele (6.0 million) or lymphedema (3.5 million). These LF-related benefits, by themselves, translate into 32 million DALYs (Disability Adjusted Life Years) averted. Ancillary, ‘beyond-LF’ benefits from the >1.9 billion treatments delivered by the GPELF were also enormous, especially because of the >310 million treatments to the children and women of childbearing age who received albendazole with/without ivermectin (effectively treating intestinal helminths, onchocerciasis, lice, scabies, and other conditions). These benefits can be described but remain difficult to quantify, largely because of the poorly defined epidemiology of these latter infections.

Conclusion: The GPELF has earlier been described as a ‘best buy’ in global health; this present tally of attributable health benefits from its first 8 years strengthens this notion considerably.

Determinants of Success in National Programs to LF Eliminate Lymphatic Filariasis

Dominique Kyelem, Gautam Biswas, Moses Bockarie, Mark Bradley, Maged El-Setouhy, Peter Fischer, Ralph Henderson, James Kazura, Patrick Lammie, Sammy Njenga, Eric Ottesen, Kapa Ramaiah, Frank Richards, Gary Weil, Steven Williams

Open access to full-text article (PDF)

Abstract

The Global Programme to Eliminate Lymphatic Filariasis (GPELF) was launched in 2000. To understand why some national programs have been more successful than others, a panel of individuals with expertise in LF elimination efforts met to assess available data from programs in 8 countries. The goal was to identify: 1) the factors determining success for national LF elimination programs (defined as the rapid, sustained reduction in microfilaremia/ antigenemia after repeated mass drug administration [MDA]); 2) the priorities for operational research to enhance LF elimination efforts.

Of more than 40 factors identified, the most prominent were 1) initial level of LF endemicity; 2) effectiveness of vector mosquitoes; 3) MDA drug regimen; 4) population compliance.

Research important for facilitating program success was identified as either biologic (i.e., [1] quantifying differences in vectorial capacity; [2] identifying seasonal variations affecting LF transmission) or programmatic (i.e., [1] identifying quantitative thresholds, especially the population compliance levels necessary for success, and the antigenemia or microfilaremia prevalence at which MDA programs can stop with minimal risk of resumption of transmission; [2] defining optimal drug distribution strategies and timing; [3] identifying those individuals who are “persistently noncompliant” during MDAs, the reasons for this non-compliance and approaches to overcoming it).

While addressing these challenges is important, many key determinants of program success are already clearly understood; operationalizing these as soon as possible will greatly increase the potential for national program success.

One step forward, two steps back?
Assessing the impact of a missed MDA cycle in Haiti

Kimberly Y. Won, Madsen Beau de Rochars, Dominique Kyelem, Sandra J. Laney, Steven A. Williams, Thomas Streit, Patrick J. Lammie

Abstract

Lymphatic filariasis (LF) elimination programs face challenges in monitoring the impact of multiple rounds of mass drug administration (MDA) on transmission, particularly in settings where the regularity or quality of MDA may be affected by resource constraints. Annual mass treatment with diethylcarbamazine and albendazole began in Leogane, Haiti, in 2000 and has continued yearly, with the exception of 2006. In September 2007, as part of a multi-country research project designed to standardize and compare available diagnostic tools, we conducted surveys in two sentinel sites, Centre Ville and Masson Mathieu, in the Leogane area. Samples from each participant were examined for the presence of microfilaremia, antigenemia, and antifilarial antibody (Bm14). Since 2000, there has been a significant decrease of antigenemia in both sites as measured by immunochromatographic card test (ICT). From 2000 to 2005, ICT prevalence had dropped from 48.6% to 23.2% (p<0.001) in Centre Ville and from 36.8% to 8.2% (p<0.001) in Masson Mathieu. Because of an interruption of funds in 2006, there was no MDA in Leogane. In 2007, approximately two years after the most recent MDA, ICT prevalence increased to 31.5% in Centre Ville and 14.1% in Masson Mathieu, representing a significant recrudescence of infection in both areas. Furthermore, a total of 18 of 102 (17.6%) children <6 years old were found to be ICT positive, suggesting recent LF transmission. The potential for ongoing transmission was supported by finding both Bm14 and microfilaria-positive children. These data suggest that missed MDA cycles can be damaging to LF elimination programs, and that five or more rounds of MDA may not be enough to successfully interrupt transmission in highly endemic settings.

Evaluation of diagnostic tools for brugian filariasis elimination programs

Taniawati Supali, Rahmah Noordin, Felix Liauw, Heri Wibowo, Tajul A. Awang Mohd, Kimberly Y. Won, Peter U. Fischer, Gary J. Weil

Abstract

The Global Programme to Eliminate Lymphatic Filariasis uses mass drug administration (MDA) to reduce infection rates to levels that cannot sustain transmission. More information is needed to define endpoints for MDA programs and to determine effective methods for post-MDA surveillance. The GAELF Diagnostics Study Group is testing various surveillance tools in 8 LF-endemic areas. We now report the results of diagnostic assays in Brugia-endemic areas in Sabah, Malaysia and Alor, Indonesia which had undergone 3 to 5 years of MDA. Blood was collected from 1,000 residents and 350 school children at each site and tested for microfilaremia (MF) by microscopy (60 μl thick smear) and by a qPCR test for Brugia DNA. Antibodies to recombinant filarial antigens were detected with two rapid tests (Brugia Rapid, BR and PanLF, PL) and by ELISA (Bm14). Filariasis rates were higher in Sabah (Mf 2.5% by smear and 1.4% with 95% CI 0.7-2.3% by PCR; antibody rates 18% BR, 18% PL, 60% Bm14) than in Alor (Mf 0.5% by smear and 0.28% CI 0.05-0.82 by PCR; antibodies 3% BR, 7% PL, and 30% Bm14). Using the BM14 assay, antibody rates in children were comparable to those seen in community surveys. Rapid tests were less sensitive than Bm14 for detecting low antibody levels indicative of exposure, but detected antibodies in most Mf carriers. We also estimated filarial DNA rates in mosquito pools by qPCR. Anopheles and Mansonia vectors in Brugia-endemic areas are difficult to catch, so we used gravid traps to collect non-vector Culex mosquitoes, as previous studies showed that filarial DNA persists in non-vector species. Brugia DNA rates in mosquitoes were 0.18% (CI 0.09-0.31%) in Alor and 0.08% (0.02-0.19) in Sabah. DNA rates could be higher in vector species, but Culex xenomonitoring efficiently detected Brugia parasites in both study areas. Results suggest that residual filariasis rates are higher in Sabah than in Alor. Additional study is needed to determine the optimal use and cost effectiveness of these tools for documenting interruption of LF transmission and for post-MDA surveillance.