Mapping Strategies

As countries experience success in expanding programs targeting NTDs and meeting initial programmatic goals, new targets require more precise and thorough efforts to identify remaining populations in need of treatment. Therefore, there is a need to develop strategies to improve the quality of information on the geographic distribution of these infections.

• For onchocerciasis, the shift in program goals from control to elimination has necessitated the development of new mapping strategies for areas that were previously not thought to need intervention. New mapping strategies are also required to support implementation decisions in areas where co-endemicity with Loa loa infection may inhibit safe implementation of MDA.

• For schistosomiasis, changes in program targets require mapping at a finer scale to improve the precision of decisions to implement MDA.

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Added 22 September 2021

TAS Strengthening in American Samoa

Australian National University (ANU),
American Samoa Community College
Lymphatic filariasis
Research question

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.

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