Xenomonitoring

Xenomonitoring of black flies to confirm serologic threshold for onchocerciasis elimination mapping

To determine the appropriate serologic threshold(s) to be used to initiate MDA for onchocerciasis

Countries: Malawi
Diseases: Onchocerciasis

Developing a surveillance framework for the post-elimination phase of the lymphatic filariasis programme in Bangladesh

  • Can the micro-stratification of lymphatic filariasis (LF) transmission assessment surveys positive case and clinical case data be used to identify, map and monitor transmission hotspots as part of an enhanced endgame surveillance strategy?
  • Can targeted molecular xenomonitoring detect ongoing transmission [to the same extent as human surveillance] in defined LF transmission hotspots?

 

Countries: Bangladesh

Operational research to compare the confirmatory mapping tool and xenomonitoring indicator (infectivity rate of L3 of Wuchereria bancrofti) in Monrovia to assess the necessity to implement MDA

What is the most appropriate method to evaluate the presence of W. bancrofti transmission in urban conurbations to establish if MDA is necessary for LF elimination?

Countries: Liberia

Operational research to develop an M&E strategy to guide triple drug stopping decisions for lymphatic filariasis in Kenya

  • 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 has been reduced so that triple drug therapy with ivermectin, diethylcarbamazine, and albendazole (IDA) can be stopped with little risk of resurgence of transmission?
  • Can the use of a tailored social mobilization package be used to strengthen community and health system participation and achieve >80% coverage for IDA in Kenya?
Countries: Kenya

Operational research to develop an M&E strategy to guide triple drug stopping decisions for lymphatic filariasis in Samoa

  • 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?

 

Countries: Samoa

TAS Strengthening in American Samoa

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.

Countries: American Samoa

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

TAS Strengthening in Tanzania

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 Tanzania 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. Because the EU is also endemic for onchocerciasis, the new Ov16 monoplex RDT was used in the field. The Wb123 and Ov16 antibodies were assessed via ELISA in the NIMR lab in Tanga and the results will soon be compiled.  Xenomonitoring work to assess Culex and Anopheles mosquitoes, as well as black flies, 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.

Countries: Tanzania

Develop epidemiological and entomological methods to assess verification of transmission interruption of Onchocerciasis in Equatorial Guinea- Africa

After two decades of onchocerciasis control activities in Bioko island, transmission is expected to be interrupted. This study aims to demonstrate that WHO criteria to verify transmission interruption have been met. It also aims to standardize the reading of RDTs, particularly the FTS and Ov16, and reduce the potential for human error.

Preliminary Study Findings:

A cross-sectional study was conducted from September 2016 to January 2017. Participants were 5- to 9-year-old school children. Onchocerciasis/lymphatic Filariasis (LF, only in endemic districts) rapid diagnostic tests (RDTs) were performed. Blood spots were collected from RDT positive children and 10 percent of the RDT negatives to determine Ov16 and Wb123 IgG4 antibodies through enzyme-linked immunosorbent assay (ELISA). Skin snips were collected from RDT positives. Filarial detection was performed by PCR in positives and indeterminate sera. Black fly collection was carried out in traditional breeding sites. A total of 7,052 children, ranging from 5 to 9 years of age, were included in the study. Four children (0.06%) were Ov16 IgG4 RDT positives, but negative by ELISA Ov16, while 6 RDT negative children tested positive by ELISA. A total of 1,230 children from the Riaba and Baney districts were tested for LF. One child was Wb123 RDT positive (0.08%), but ELISA negative, while 3 RDT negative children were positive by Wb123 ELISA. All positive samples were negative by PCR for onchocerciasis and LF (in blood spot and skin snip). All fly collections and larval prospections in the traditional catching and prospection sites were negative.

Read more in Herrador et al.: https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0006471

Countries: Equatorial Guinea

Ongoing Post-treatment Surveillance for Lymphatic Filariasis in Bangladesh

To evaluate the utility of ongoing surveillance of adults in a post-treatment setting.

To determine if post-treatment surveillance of adults represents a more effective surveillance strategy than TAS or xenomonitoring.

 

Countries: Bangladesh

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