We discuss the experience of some Pacific island countries in introducing the new WHO-recommended treatment protocol for lymphatic filariasis-a triple-drug therapy composed of ivermectin, diethylcarbamazine, and albendazole. The successful rollout of the new treatment protocol was dependent on strong partnerships among these countries' ministries of health, WHO, and other stakeholders. Effective communication among these partners allowed for lessons learned to cross borders and have a positive impact on the experiences of other countries. We also describe various challenges confronted during this process and the ways these countries overcame them.

BACKGROUND: Lymphatic filariasis (LF) has been targeted for global elimination as a public health problem since 1997. The primary strategy to interrupt transmission is annual mass drug administration (MDA) for ≥5 years. The transmission assessment survey (TAS) was developed as a decision-making tool to measure LF antigenemia in children to determine when MDA in a region can be stopped. The objective of this study was to investigate potential sampling strategies for follow-up of LF-positive children identified in TAS to detect evidence of ongoing transmission. METHODOLOGY/PRINCIPLE FINDINGS: Nippes Department in Haiti passed TAS 1 with 2 positive cases and stopped MDA in 2015; however, 8 positive children were found during TAS 2 in 2017, which prompted a more thorough assessment of ongoing transmission. Purposive sampling was used to select the closest 50 households to each index case household, and systematic random sampling was used to select 20 households from each index case census enumeration area. All consenting household members aged ≥2 years were surveyed and tested for circulating filarial antigen (CFA) using the rapid filarial test strip and for Wb123-specific antibodies using the Filaria Detect IgG4 ELISA. Among 1,927 participants, 1.5% were CFA-positive and 4.5% were seropositive. CFA-positive individuals were identified for 6 of 8 index cases. Positivity ranged from 0.4-2.4%, with highest positivity in the urban commune Miragoane. Purposive sampling found the highest number of CFA-positives (17 vs. 9), and random sampling found a higher percent positive (2.4% vs. 1.4%). CONCLUSIONS/SIGNIFICANCE: Overall, both purposive and random sampling methods were reasonable and achievable methods of TAS follow-up in resource-limited settings. Both methods identified additional CFA-positives in close geographic proximity to LF-positive children found by TAS, and both identified strong signs of ongoing transmission in the large urban commune of Miragoane. These findings will help inform standardized guidelines for post-TAS surveillance.

Lymphatic filariasis is a debilitating and disfiguring mosquitoborne parasitic disease. As part of the Global Programme to Eliminate Lymphatic Filariasis, the World Health Organization (WHO) recommends at least five rounds of annual mass drug administration (MDA) in areas with endemic disease to reduce incidence and prevalence (1). Onward transmission is expected to end once community prevalence falls below 1% (1). | | American Samoa, located in the southern Pacific Ocean, is the only U.S. territory with evidence of ongoing lymphatic filariasis transmission. After 7 years of MDA (2000–2006), the prevalence of lymphatic filariasis antigenemia in American Samoa declined from 16.5% to 2.3%, and MDA was stopped (2,3). In 2016, a household survey among 2,507 participants revealed that the prevalence of antigenemia had rebounded to 6.2%, and transmission was ascertained to be widespread across the territory (4). MDA was resumed in 2018 using a novel three-drug regimen of ivermectin, diethylcarbamazine, and albendazole, which has been shown to more effectively clear filarial larvae from the blood than the standard two-drug treatment of albendazole with diethylcarbamazine or ivermectin alone (5,6). This WHO-recommended three-drug regimen is anticipated to accelerate progress toward global elimination goals in areas without other filarial infections that would contraindicate the use of diethylcarbamazine (onchocerciasis) or ivermectin (loiasis).

Since 1950, the global urban population grew from 746 million to almost 4 billion and is expected to reach 6.4 billion by mid-century. Almost 90% of this increase will take place in Asia and Africa and disproportionately in urban slums. In this context, concerns about the amplification of several neglected tropical diseases (NTDs) are warranted and efforts towards achieving effective mass drug administration (MDA) coverage become even more important. This narrative review considers the published literature on MDA implementation for specific NTDs and in-country experiences under the ENVISION and END in Africa projects to surface features of urban settings that challenge delivery strategies known to work in rural areas. Discussed under the thematics of governance, population heterogeneity, mobility and community trust in MDA, these features include weak public health infrastructure and programs, challenges related to engaging diverse and dynamic populations and the limited accessibility of certain urban settings such as slums. Although the core components of MDA programs for NTDs in urban settings are similar to those in rural areas, their delivery may need adjustment. Effective coverage of MDA in diverse urban populations can be supported by tailored approaches informed by mapping studies, research that identifies context-specific methods to increase MDA coverage and rigorous monitoring and evaluation.