What Is Needed to Eradicate Lymphatic Filariasis? A Model-Based Assessment on the Impact of Scaling Up Mass Drug Administration Programs

Abstract

BackgroundLymphatic filariasis (LF) is a neglected tropical disease for which more than a billion people in 73 countries are thought to be at-risk. At a global level, the efforts against LF are designed as an elimination program. However, current efforts appear to aim for elimination in some but not all endemic areas. With the 2020 goal of elimination looming, we set out to develop plausible scale-up scenarios to reach global elimination and eradication. We predict the duration of mass drug administration (MDA) necessary to reach local elimination for a variety of transmission archetypes using an existing model of LF transmission, estimate the number of treatments required for each scenario, and consider implications of rapid scale-up.MethodologyWe have defined four scenarios that differ in their geographic coverage and rate of scale-up. For each scenario, country-specific simulations and calculations were performed that took into account the pre-intervention transmission intensity, the different vector genera, drug regimen, achieved level of population coverage, previous progress toward elimination, and potential programmatic delays due to mapping, operations, and administration.Principal FindingsOur results indicate that eliminating LF by 2020 is unlikely. If MDA programs are drastically scaled up and expanded, the final round of MDA for LF eradication could be delivered in 2028 after 4,159 million treatments. However, if the current rate of scale-up is maintained, the final round of MDA to eradicate LF may not occur until 2050.Conclusions/SignificanceRapid scale-up of MDA will decrease the amount of time and treatments required to reach LF eradication. It may also propel the program towards success, as the risk of failure is likely to increase with extended program duration.

Economic performance and cost-effectiveness of using a DEC-salt social enterprise for eliminating the major neglected tropical disease, lymphatic filariasis

“…We used the total costs of implementing each strategy until LF elimination (crossing below the 1% mf threshold) is achieved to investigate the cost effectiveness of either strategy. The total costs and effectiveness of using MDA at 65% and 80% coverages and supplying DEC salt at 65%, 80% and the actual coverages given in Table 4, were evaluated and compared via calculations of the average cost effectiveness ratio [10,41–47]. With respect to DEC salt, we also conducted the analysis using three different net costs of salt production per person per year as recorded in Table 5: (i) average of the net cost of salt produced per person calculated for the years 2018-2020, i.e., US$0.57 per person/year, (ii) average of the net cost of salt per person for the years 2021-2023, i.e., US$0.3 per person/year, and (iii) average of the net cost of salt per person for the years 2025-2027, i.e., US$0.025 per person/year.…”

Global elimination of lymphatic filariasis

“…9 A principal consideration for the optimisation of elimination strategies, particularly in resource-constrained settings, is the cost-effectiveness of innovative interventions that integrate new diagnostic methods and treatment of lymphatic filariasis in the context of economic constraints and logistical barriers. Since drugs for the lymphatic filariasis programme are donated by manufacturers, 11 and scale-up and geographical expansion of mass drug administration are cost-effective for eradication of lymphatic filariasis, 12 we anticipate that the marginal benefits of the triple-drug regimen as a replacement for double-drug treatment would further improve the cost-effectiveness of mass drug administration strategies. With only 4 years remaining before the 2020 target, rapid scale-up of mass drug administration and prompt decisions about the implementation of alternative strategies, such as biannual mass drug administration and triple-drug therapy, are imperative to interrupting lymphatic filariasis transmission in all countries.…”

Continental-Scale, Data-Driven Predictive Assessment of Eliminating the Vector-Borne Disease, Lymphatic Filariasis, in Sub-Saharan Africa by 2020

“…We then use the discovered local models in conjunction with LF intervention data assembled for each relevant endemic country to highlight how such a system can be used to investigate the emergent policy questions germane to the elimination of this highly debilitating disease from this important endemic continent, viz., (1) which countries are on course to meet the LF elimination target year of 2020, (2) which are unlikely to meet this goal, and (3) which remedial strategies are best suited to enhance disruption of parasite transmission most effectively in the latter case. We also contrast the findings with those resulting from recently conducted national-level intervention modeling work [1][2][3][4][5]12] by focusing on two themes: (1) the importance of constraining model parameters to reflect the complexity of subgrid transmission heterogeneities with multiple localized input data and (2) the need for addressing such heterogeneous transmission dynamics for minimizing aggregation error when making coarse-scale predictions.…”

“…Recently, there has been increasing interest in assessing the prospects of currently applied and proposed nationwide interventions for achieving the global elimination or control of the major preventable helminthic diseases, ranging from soil-transmitted helminthiases to schistosomiasis, onchocerciasis, and lymphatic filariasis (LF) [1][2][3][4][5]. Partly, this is in response to the urgent policy demands for more accurate scientific information for determining if the roadmap set by the World Health Organization (WHO), based on sustaining and expanding drug access programs, will accomplish the elimination or control of these neglected tropical diseases (NTDs) by the target year of 2020 [6].…”

“…In essence, this approach assumes that employing models parameterized at point-support spatial scales, i.e., using parameters and model structures originally defined from data collected at a few spatial sites, invariantly across a region is valid for mimicking regional-scale parasite population dynamics [13][14][15]. More recently, approaches that use global grid-based parameter search methods for calibrating transmission models against either mean national-level infection values or a range of subgrid values within countries have been applied for undertaking these modeling investigations [1][2][3][4][5]. While these studies have provided important strategic insights into the impacts of intervention options on likely timelines to parasite elimination, an implicit assumption behind these methods is stability and stationarity in the fine-scale pattern-process relationships used to develop the transmission models [13,14,[16][17][18].…”