Defining Persistent Hotspots: Areas That Fail to Decrease Meaningfully in Prevalence after Multiple Years of Mass Drug Administration with Praziquantel for Control of Schistosomiasis.

Nupur Kittur,Carl H Campbell,Daniel G Colley,Annette Olsen,Pascal Magnussen,Charles H King,Safari Kinung’Hi,Sue Binder

doi:10.4269/ajtmh.17-0368

Abstract

.Preventive chemotherapy with praziquantel for schistosomiasis morbidity control is commonly done by mass drug administration (MDA). MDA regimen is usually based on prevalence in a given area, and effectiveness is evaluated by decreases in prevalence and/or intensity of infection after several years of implementation. Multiple studies and programs now find that even within well-implemented, multiyear, annual MDA programs there often remain locations that do not decline in prevalence and/or intensity to expected levels. We term such locations “persistent hotspots.” To study and address persistent hotspots, investigators and neglected tropical disease (NTD) program managers need to define them based on changes in prevalence and/or intensity. But how should the data be analyzed to define a persistent hotspot? We have analyzed a dataset from an operational research study in western Tanzania after three annual MDAs using four different approaches to define persistent hotspots. The four approaches are 1) absolute percent change in prevalence; 2) percent change in prevalence; 3) change in World Health Organization guideline categories; 4) change (absolute or percent) in both prevalence and intensity. We compare and contrast the outcomes of these analyses. Our intent is to show how the same dataset yields different numbers of persistent hotspots depending on the approach used to define them. We suggest that investigators and NTD program managers use the approach most suited for their study or program, but whichever approach is used, it should be clearly stated so that comparisons can be made within and between studies and programs.

Highlights

Global efforts to control morbidity due to schistosomiasis were codified by the World Health Assembly (WHA) Resolution 54.191 in 2001
When we defined a persistent hotspot as a place with a 30% or less decrease in prevalence, 37 of the 74 schools/villages (50%) met this criterion (Figure 1)
It is obvious that a location that started below 30% prevalence could not decrease its prevalence value more than 30% and would be automatically called a persistent hotspot under Approach 1

Summary

Introduction

Global efforts to control morbidity due to schistosomiasis were codified by the World Health Assembly (WHA) Resolution 54.191 in 2001 Since these efforts have largely rested on preventive chemotherapy (PC) with praziquantel (PZQ), often delivered through mass drug administration (MDA) either in school-based or community-wide programs.[2,3,4] These programs have often been implemented by national neglected tropical disease (NTD) control programs partnered with different enabling organizations through bilateral arrangements. As increasing numbers of national NTD control programs have scaled-up MDA, and major PZQ supplies (both donated and purchased) have been announced and provided, the WHA has approved two more resolutions (WHA 65.21 and 66.12) in 2012 and 2014, respectively,[5,6] that urge programs, where appropriate, to move from the goal of morbidity control to the extended goal of elimination of schistosomiasis as a public health problem, with the eventual objective of interrupting schistosomiasis transmission. It is only when a program or study “goes to scale,” and

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Conclusion