To analyze the relationships between the currently used indicator for impact assessments - prevalence of the clincial sign TF - and the prevalence of infection and antibody among 1-9 year old children in hyperendemic districts prior to mass drug administration
The primary objective for this request is to evaluate the performance of the Biplex RDT in a cohort of 500 people previously tested for oncho and LF in 2014 (3-year follow up). The evaluation of the Biplex is an add-on to a study that will conduct a longitudinal follow up on a cohort of 500 people from the Tshopo Province. The primary outcomes are serology and clinical manifestations of onchocerciasis, This study also evaluates serology, parasitology and clinical manifestations for other filarial infections, mainly LF, Loa and Mansonella.
Preliminary Findings and Lessons Learned
This study built on an existing onchocerciasis longitudinal follow-up study in Banalia community, Tshopo province, DRC. The location is co-endemic for Oncho, LF, Loa loa and Mansonella perstans. 500 people previously tested in 2014 have been followed up and were retested in 2017. A total of 239, out of 500, agreed to participate in the follow-up activity and provided a blood specimen. Thirty percent were positive by skin snip, 3% were positive by FTS, 15% were found to have loa (thick blood film) and 41% had M. perstans. Ov16 ELISA testing found 67% positive, while the Biplex found 38% Ov16 positive. The sensitivity of the Ov16 biplex compared to the ELISA was 53%.
To field-test the Pgp3 lateral flow assay to compare data obtained in the field on the rapid test to that from DBS collected from the same individual tested on the Pgp3 multiplex bead array.
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.
Determine whether school-based TAS results in the same programmatic conclusion as a community-based TAS in EUs where school attendance is poor.
Preliminary Findings and Lessons Learned
This USAID project represents an innovative approach to resolve critical questions about the performance of the TAS and in particular, the question of how important 75% school attendance is to a valid TAS result. At its core, this study addresses the concern that LF (specifically antigenemia) could be associated with school attendance, which leads to the programmatic research question: does a school-based TAS result in the same programmatic conclusion as a community-based TAS in EUs where school attendance is poor? This study will lead to a better understanding of the validity of the TAS in programmatic settings where school attendance and/or reporting of school enrollment may be poor. It will also generate important results for the Haitian program that is looking to the TAS for guidance on stopping MDA in several EUs. The school- and community-based TAS were both conducted in a commune considered to be highly endemic (‘zone rouge’) at baseline. Both surveys passed the TAS, with only 1 ICT positive child identified in the school TAS and 4 ICT-positive children in the community-based TAS. The conclusion is that there appears to be no meaningful difference between school- and community-based TAS for stopping MDA decisions, even where school attendance is poor. This is the third LFSC/NTDSC study to return a null result -- perhaps it can now be considered a "non-issue" for LF.
Mass drug administration (MDA) programs have dramatically reduced lymphatic filariasis (LF) incidence in many areas around the globe, including Bangladesh. Post-treatment surveillance activities as recommended by WHO include repeated transmission assessment surveys (TAS) among children and ongoing surveillance to detect new foci of transmission and collect data on infection trends in the general population. The contribution of molecular xenomonitoring (MX, or detection of filarial DNA in mosquitoes) to confirm the interruption of transmission during the post-treatment surveillance phase has not been well defined. There is also a need to better understand the relationship between the prevalence of W. bancrofti DNA in mosquitoes and infection in humans.
Correlation of Xenomonitoring and LF-Antibody Responses as Measures of Transmission in American Samoa
Determine the utility of xenomonitoring and serological assessments for the detection of residual transmission
Field validation of sampling strategies for integrating STH surveys into Transmission Assessment Surveys (Haiti)
Field validation of sampling strategies for integrating STH surveys into Transmission Assessment Surveys (Tanzania)
Monitor recrudescence of STH after TAS to improve planning of STH programs and more effective use of STH drugs.