Positive-case follow up for lymphatic filariasis after a transmission assessment survey in Haiti

Abstract

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.

A nationwide epidemiological and geodemographic analysis of lymphatic filariasis in Ecuador: a neglected and often forgotten disease in Ecuador

“…Within the Americas, more than 12.5 million people are assumed to be at risk of this infection, most of them from Haiti and Brazil ( 8 , 9 ). While filariasis is endemic in Brazil, Haiti, Guyana and the Dominican Republic, other countries in the region suffer from this disease, which almost always goes unnoticed ( 8 ).…”

“…Within the Americas, more than 12.5 million people are assumed to be at risk of this infection, most of them from Haiti and Brazil ( 8 , 9 ). While filariasis is endemic in Brazil, Haiti, Guyana and the Dominican Republic, other countries in the region suffer from this disease, which almost always goes unnoticed ( 8 ). Most cases of LF worldwide are caused by the presence of the filarial nematode called Wuchereria bancrofti , followed by the Brugia malayi and Brugia timori species ( 10 , 11 ).…”

A game-theoretic model of lymphatic filariasis prevention

“…In 2000, WHO launched its Global Programme to Eliminate Lymphatic Filariasis (GPELF) as a public health problem [ 3 ]. The primary strategy for LF control and elimination is the WHO recommended preventive chemotherapy [ 4 ]. The entire population at risk is treated by mass drug administration (MDA) for at least five consecutive years.…”

“…At the same time, GPELF set new goals for the new NTD Road Map (2021-2030) that include reduction to 0 of the total population requiring MDA and 100% of endemic countries implement post-MDA or post-validation surveillance [ 3 ]. MDA has already ended and was successful in Dominican Republic [ 5 ] but it was not so successful in Haiti [ 4 ] and American Samoa [ 6 ]. It is therefore important to plan ahead and estimate what can happen at the end of MDA.…”

Reducing the Antigen Prevalence Target Threshold for Stopping and Restarting Mass Drug Administration for Lymphatic Filariasis Elimination: A Model-Based Cost-effectiveness Simulation in Tanzania, India and Haiti

“…For example, in certain regions, particularly where Culex mosquito is the main transmitting vector, there are difficulties in attaining [ 7 ] and maintaining the goals of the program [ 8 , 9 ], possibly due to higher transmission efficiency by this vector [ 10–12 ]. There is also evidence of ongoing transmission in Culex areas that have passed the TAS, including in Sri Lanka [ 13 ] and Haiti [ 14 ], possibly due to the vector's increased competence [ 15–18 ]. One approach being considered to circumvent this problem is a reduction in the upper 95% CI of the threshold to <1% Ag prevalence (representing a critical cutoff of <7 antigen-positive children).…”