How Does the Proportion of Never Treatment Influence the Success of Mass Drug Administration Programs for the Elimination of Lymphatic Filariasis?

Background: Mass drug administration (MDA) is the cornerstone for the elimination of lymphatic filariasis (LF). The proportion of the population that is never treated (NT) is a crucial determinant of whether this goal is achieved within reasonable time frames.
Methods: Using 2 individual-based stochastic LF transmission models, we assess the maximum permissible level of NT for which the 1% microfilaremia (mf) prevalence threshold can be achieved (with 90% probability) within 10 years under different scenarios of annual MDA coverage, drug combination and transmission setting.
Results: For Anopheles-transmission settings, we find that treating 80% of the eligible population annually with ivermectin + albendazole (IA) can achieve the 1% mf prevalence threshold within 10 years of annual treatment when baseline mf prevalence is 10%, as long as NT <10%. Higher proportions of NT are acceptable when more efficacious treatment regimens are used. For Culex-transmission settings with a low (5%) baseline mf prevalence and diethylcarbamazine + albendazole (DA) or ivermectin + diethylcarbamazine + albendazole (IDA) treatment, elimination can be reached if treatment coverage among eligibles is 80% or higher. For 10% baseline mf prevalence, the target can be achieved when the annual coverage is 80% and NT ≤15%. Higher infection prevalence or levels of NT would make achieving the target more difficult.
Conclusions: The proportion of people never treated in MDA programmes for LF can strongly influence the achievement of elimination and the impact of NT is greater in high transmission areas. This study provides a starting point for further development of criteria for the evaluation of NT.
Competing Interests: Potential conflicts of interest . R. A. reports funding for their institution Imperial College from Leiden Labs, Gates Foundation, and CIFF, leadership roles with Flora and Fauna International, Chairman Oriole Global Health Ltd, and Trusted Banga Trust, and stock with GSK, AstraZeneca, Pfizer. L. E. C. reports funding paid to their institution from March to July 2023 from APW on strongyloidiasis control from WHO Geneva and subcontract on VL modeling for LSTM. K. G. reports that their salary is paid by the Bill & Melinda Gates Foundation “Filling the Gaps Grant” and USAID “Coalition for Operational Research on NTDs.” J. D. K. reports receiving grants from Bayer AG, Carter Center, Cytiva, EISAI Co Ltd, EMS Brazil, Fred Hollows Foundation, Fundacion Anesvad, Fundacion Mundo Sano, Gilead Sciences Inc, Glaxo Smith Kline, Johnson and Johnson Family of Companies, Contribution Fund, Inc, Merck & Co Inc, Merck KGAA, Merck Sharp & Dohme Corp., Novartis, Sanofi Aventis, The Task Force for Global Health, which receives an operating budget and research funds from Pfizerr Inc, the manufacturers of Zithromax (azithromycin) and Wellcome Trust. K. K. reports receiving support for attending meetings and/or travel from the NTD Modelling Consortium: Informing program decision-making (Bill and Melinda Gates Foundation). A. K. reports receiving consulting fees from the Coalition for Operational Research for NTDs and is a member of the Mectizan Expert Committee and received support for travel to the biannual meeting. P. D. reports support for travel from the Bill & Melinda Gates Foundation. M. G. B. reports grant jointly funded by the UK MRC and the UK Foreign Commonwealth & Development Office (FCDO) under the MRC/FCDO Concordat atreement, also part of the EDCPT2 program supported by the European Union. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.
(© The Author(s) 2024. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)