IMA World Health

Lymphatic Filariasis Positive-Case Follow-up After TAS 2 in Haiti

To identify the sampling strategy for positive case follow-up after TAS 2 and TAS 3 that optimizes the chances of correctly identifying evidence of ongoing transmission, while saving program resources.

Countries: Haiti

Field Validation of Wb123 monoplex, Haiti

To compare the performance of antigen (FTS) and antibody (Wb123 monoplex) tools in programmatic settings (TAS).

Preliminary Findings and Lessons Learned

The goal of this study is to compare the performance of antigen (FTS) and antibody (Wb123 monoplex, Wb123 ELISA, multiplex) tools in programmatic settings (TAS). In order to strengthen the existing TAS platform we need to better understand which diagnostic indicator(s) are best-suited for making programmatic decisions. The TAS was conducted in Trou de Nord and Plaisance EUs.  Both EUs passed the TAS, but positive FTS were identified (4 and 2, respectively). However the Wb123 RDT found ZERO positive children, of the over 2000 tested. While the Wb123 ELISA testing is still ongoing, this initial result agrees with findings from other studies, all of which suggest that the Wb123 RDT is too insensitive a tool to be of programmatic use.

Countries: Haiti

TAS Strengthening in Haiti

To evaluate strategies to improve the sensitivity of the TAS for detecting evidence of recent lymphatic filariasis transmission in an evaluation unit (EU). The TAS Strengthening Study in Haiti is designed to assess additional indicators that may be added to the current TAS platform in order to strengthen the resulting stopping or surveillance decisions. A comprehensive analysis will be conducted to understand the correlation between antigen and antibody in adults and children with the mosquito data. A spatial analysis looking at microfoci of infection will also be conducted.  Xenomonitoring work to assess Culex mosquitoes will be conducted in the same sites as the human sampling. 

Preliminary Findings and Lessons Learned

The ultimate goal of this study is to strengthen the existing TAS platform so that the programs can be more confident with their stopping and surveillance decisions.   In order to strengthen the existing TAS platform we need to better understand which target population(s) and diagnostic indicator(s) are best-suited for identifying areas with persistent transmission that is not expected to cease on its own, knowing that the answer may vary according the primary vector and stage of the program.  In the selected sites a community-based TAS was conducted using the standard sampling of 6-7 year olds while a community TAS (individuals >8 years) was conducted concurrently.  All samples were tested via FTS and DBS (for Wb123 ELISA).  In these same communities a molecular xenomonitoring study will take place and the mosquitoes will be tested for filarial DNA to relate back to the human specimens.  To date human sampling has been completed in all sites and laboratory analysis of the specimens is complete. Mosquito collection has been completed in Haiti and Tanzania and the PCR analysis has been completed in Haiti and is planned for Tanzania (pending the arrival of a new PCR machine).  In American Samoa xenomonitoring has been delayed due to weather conditions and arbovirus outbreaks; work is expected to commence spring 2018.

Countries: Haiti