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 American Samoa 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 Aedes mosquitoes is underway.
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.
What is the effectiveness of appropriately dosed IDA in clearing microfilariae (Mf) from Mf positive people who (i) reported taking triple drug therapy with ivermectin, diethylcarbamazine, and albendazole (IDA) in August 2018, and (ii) did not report recently taking IDA.
This will be investigated by:
assessing the baseline (current) Mf presence and density before re/treatment with IDA, against which post-treatment Mf presence and density can be compared
assessing the peak plasma concentration levels of ivermectin, DEC and albendazole in treated Mf positive individuals to identify whether the recommended dosages of medications are sufficient for achieving effective plasma concentrations
assessing Mf clearance one week following directly observed IDA re/treatment
What is the indicator(s) and accompanying M&E strategy that enables country programs to determine when the risk of ongoing transmission of lymphatic filariasis (LF) has been reduced so that triple drug therapy with ivermectin, diethylcarbamazine, and albendazoe (IDA) can be stopped with little risk of resurgence of transmission?
To develop an M&E strategy that enables Samoa’s LF elimination program to determine when the risk of ongoing transmission of LF has been reduced so that IDA can be stopped with little risk of resurgence of transmission
What is the effectiveness of appropriately dosed IDA in clearing Mf from Mf positive people who (i) reported taking IDA in August 2018, and (ii) did not report recently taking IDA?