Discovering, Defining, and Summarizing Persistent Hotspots in SCORE Studies.

Nupur Kittur,Carl H Campbell,Joseph R Mwanga,Rosemary M Musuva,Stefanie Knopp,Ye Shen,Daniel G Colley,Ryan E Wiegand,Maurice R Odiere,Sultani H Matendechero,Sue Binder,Safari M Kinung’Hi

doi:10.4269/ajtmh.19-0815

Abstract

.The Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) conducted large field studies on schistosomiasis control and elimination in Africa. All of these studies, carried out in low-, moderate-, and high-prevalence areas, resulted in a reduction in prevalence and intensity of Schistosoma infection after repeated mass drug administration (MDA). However, in all studies, there were locations that experienced minimal or no decline or even increased in prevalence and/or intensity. These areas are termed persistent hotspots (PHS). In SCORE studies in medium- to high-prevalence areas, at least 30% of study villages were PHS. There was no consistent relationship between PHS and the type or frequency of intervention, adequacy of reported MDA coverage, and prevalence or intensity of infection at baseline. In a series of small studies, factors that differed between PHS and villages that responded to repeated MDA as expected included sources of water for personal use, sanitation, and hygiene. SCORE studies comparing PHS with villages that responded to MDA suggest the potential for PHS to be identified after a few years of MDA. However, additional studies in different social-ecological settings are needed to develop generalizable approaches that program managers can use to identify and address PHS. This is essential if goals for schistosomiasis control and elimination are to be achieved.

Highlights

The Schistosomiasis Consortium for Operational Research and Evaluation (SCORE; https://score.uga.edu) portfolio included several studies with multiyear mass drug administration (MDA) interventions for control and elimination of schistosomiasis.[1]
There was no consistent relationship between persistent hotspots (PHS) and the type or frequency of intervention, adequacy of reported MDA coverage, and prevalence or intensity of infection at baseline
In a series of small studies, factors that differed between PHS and villages that responded to repeated MDA as expected included sources of water for personal use, sanitation, and hygiene

Summary

INTRODUCTION

The Schistosomiasis Consortium for Operational Research and Evaluation (SCORE; https://score.uga.edu) portfolio included several studies with multiyear mass drug administration (MDA) interventions for control and elimination of schistosomiasis.[1]. We used Year 1 (baseline) and Year 3 (after two MDAs) data from gaining control studies in Kenya and Tanzania to assess the performance of six modeling approaches to predicting PHS at Year 5 (final evaluation).[10] Both of these studies took place in villages near Lake Victoria, where Schistosoma mansoni is endemic. The Kenya gaining control study results were assessed for hotspots[11] with spatial scan statistics,[12] using SaTScan For purposes of this analysis, a hotspot was identified by determining if schistosomiasis prevalence or intensity in SCORE study villages was randomly distributed over the study area. A growing body of literature promotes an approach using model-based geostatistics and exceedance probabilities for a given threshold to define hotspots.[13,14] This approach is not dependent on the sample size of the study and allows the program to set a threshold and determine hotspot boundaries rather than to have the statistical algorithm and hypothesis testing determine the appropriate bounds

FACTORS CONTRIBUTING TO PHS

Findings

Definition of PHS