Spatiotemporal distribution and population at risk of soil-transmitted helminth infections following an eight-year school-based deworming programme in Burundi, 2007\u20132014

Mohamad Assoum,Giuseppina Ortu,Ricardo J Soares Magalhães,Maria-Gloria Basáñez,Alan Fenwick,Archie C A Clements,Colleen Lau,Kate Halton

doi:10.1186/s13071-017-2505-x

Abstract

BackgroundInvestigating the effect of successive annual deworming rounds on the spatiotemporal distribution of infection prevalence and numbers at risk for soil-transmitted helminths (STHs) can help identify communities nearing elimination and those needing further interventions. In this study, we aim to quantify the impact of an 8-year mass drug administration (MDA) programme (from 2007 to 2014) on the spatiotemporal distribution of prevalence of STH infections and to estimate the number of school-aged children infected with STHs in Burundi.MethodsDuring annual longitudinal school-based surveys in Burundi between 2007 and 2011, STH infection and anthropometric data for a total of 40,656 children were collected; these data were supplemented with data from a national survey conducted in 2014. Bayesian model based geostatistics (MBG) were used to generate predictive prevalence maps for each STH species and year. The numbers of children at-risk of infection per district between 2008 and 2014 were estimated as the product of the predictive prevalence maps and population density maps.ResultsOverall, the degree of spatial clustering of STH infections decreased between 2008 and 2011; in 2014 the geographical clusters of all STH infections reappeared. The reduction in prevalence was small for Ascaris lumbricoides and Trichuris trichiura in the centre and central north of the country. Our predictive prevalence maps for hookworm indicate a reduction in prevalence along the periphery of the country. The predicted number of children infected with any STH species decreased substantially between 2007 and 2011, but in 2014 there was an increase in the predicted number of children infected with A. lumbricoides and T. trichiura. In 2014, the districts with the highest predicted number of children infected with A. lumbricoides, T. trichiura and hookworms were Kibuye district (n = 128,903), Mabayi district (n = 35,302) and Kiremba (n = 87,511), respectively.ConclusionsWhile the MDA programme in Burundi resulted in a reduction in STH prevalence, this reduction was spatiotemporally heterogeneous, with some pockets of high prevalence remaining, suggesting that treatment coverage and complementary interventions should be evaluated to improve impact.

Highlights

Investigating the effect of successive annual deworming rounds on the spatiotemporal distribution of infection prevalence and numbers at risk for soil-transmitted helminths (STHs) can help identify communities nearing elimination and those needing further interventions
Initial univariate analyses demonstrated that Land surface temperature (LST) and elevation were highly correlated, with a Pearson’s correlation coefficient of 0.9
The P-value and Akaike information criterion (AIC) scores for LST was lower than the P-value for elevation and for that reason elevation was excluded from the multivariable analysis

Summary

Introduction

Investigating the effect of successive annual deworming rounds on the spatiotemporal distribution of infection prevalence and numbers at risk for soil-transmitted helminths (STHs) can help identify communities nearing elimination and those needing further interventions. We aim to quantify the impact of an 8-year mass drug administration (MDA) programme (from 2007 to 2014) on the spatiotemporal distribution of prevalence of STH infections and to estimate the number of school-aged children infected with STHs in Burundi. Reductions in prevalence of infection and associated morbidity can be achieved by successive mass drug administration (MDA). It has been argued that to further control and reach elimination targets, MDA campaigns would need to be integrated with water, sanitation and hygiene (WASH) programmes [3]. Morbidity control through long-standing MDA programmes can be undermined by geographical disparities in drug coverage and drug efficacy and by socioeconomic conditions that limit the access and adequate utilisation of water and sanitation infrastructure [4]

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