GPS-based fine-scale mapping surveys for schistosomiasis assessment: a practical introduction and documentation of field implementation

Lydia Trippler,Stefanie Knopp,Jan Hattendorf,Shaali Makame Ame,Mohammed Nassor Ali,Fatma Kabole,Said Mohammed Ali

doi:10.1186/s40249-021-00928-y

Abstract

BackgroundFine-scale mapping of schistosomiasis to guide micro-targeting of interventions will gain importance in elimination settings, where the heterogeneity of transmission is often pronounced. Novel mobile applications offer new opportunities for disease mapping. We provide a practical introduction and documentation of the strengths and shortcomings of GPS-based household identification and participant recruitment using tablet-based applications for fine-scale schistosomiasis mapping at sub-district level in a remote area in Pemba, Tanzania.MethodsA community-based household survey for urogenital schistosomiasis assessment was conducted from November 2020 until February 2021 in 20 small administrative areas in Pemba. For the survey, 1400 housing structures were prospectively and randomly selected from shapefile data. To identify pre-selected structures and collect survey-related data, field enumerators searched for the houses’ geolocation using the mobile applications Open Data Kit (ODK) and MAPS.ME. The number of inhabited and uninhabited structures, the median distance between the pre-selected and recorded locations, and the dropout rates due to non-participation or non-submission of urine samples of sufficient volume for schistosomiasis testing was assessed.ResultsAmong the 1400 randomly selected housing structures, 1396 (99.7%) were identified by the enumerators. The median distance between the pre-selected and recorded structures was 5.4 m. A total of 1098 (78.7%) were residential houses. Among them, 99 (9.0%) were dropped due to continuous absence of residents and 40 (3.6%) households refused to participate. In 797 (83.1%) among the 959 participating households, all eligible household members or all but one provided a urine sample of sufficient volume.ConclusionsThe fine-scale mapping approach using a combination of ODK and an offline navigation application installed on tablet computers allows a very precise identification of housing structures. Dropouts due to non-residential housing structures, absence, non-participation and lack of urine need to be considered in survey designs. Our findings can guide the planning and implementation of future household-based mapping or longitudinal surveys and thus support micro-targeting and follow-up of interventions for schistosomiasis control and elimination in remote areas.Trial registration ISRCTN, ISCRCTN91431493. Registered 11 February 2020, https://www.isrctn.com/ISRCTN91431493

Highlights

Fine-scale mapping of schistosomiasis to guide micro-targeting of interventions will gain importance in elimination settings, where the heterogeneity of transmission is often pronounced
To document the strengths and shortcomings of Global Position System (GPS)-based household identification and participant recruitment for fine-scale schistosomiasis mapping in a remote area in Africa, we evaluated the results of the community-based household survey once the data collection was completed
Distance between centroids and recorded geolocation of housing structures As indicated in Fig. 3, the median distance between the randomized centroids of the housing structures and the geolocation recorded by the enumerator when arriving at the housing structure was 5.4 m

Summary

Introduction

Fine-scale mapping of schistosomiasis to guide micro-targeting of interventions will gain importance in elimination settings, where the heterogeneity of transmission is often pronounced. Schistosomiasis is among the 20 neglected tropical diseases (NTDs) defined by the World Health Organization (WHO) and is endemic in 78 countries worldwide [1,2,3]. Great progress was made in schistosomiasis control [6, 7] In their new roadmap for neglected tropical diseases 2021–2030, the WHO set the global elimination of schistosomiasis as a public health problem and the validated absence of infection in humans in 25 among the 78 endemic countries as targets for 2030 [1]. Remain as pockets of high transmission with persistent or reoccurring high prevalence levels despite intense interventions [8, 12,13,14, 17,18,19,20]

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