The impact of an 8-year mass drug administration programme on prevalence, intensity and co-infections of soil-transmitted helminthiases in Burundi

Ortu, Giuseppina; Assoum, Mohamad; Wittmann, Udo; Knowles, Sarah C. L.; Clements, Michelle N.; Ndayishimiye, Onésime; Basáñez, María‐Gloria; Lau, Colleen L.; Clements, Archie C. A.; Fenwick, Alan; Magalhães, Ricardo J. Soares

doi:10.1186/s13071-016-1794-9

Cited by 24 publications

(42 citation statements)

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“…Helminth parasites cause some of the world's most important neglected tropical diseases [1][2][3]. Morbidity attributed to soil-transmitted helminths (STHs; Ascaris lumbricoides, Trichuris trichiura, Ancylostoma duodenale and Necator americanus) and trematodes (genus Schistosoma) is widespread in impoverished areas with limited access to clean water and sanitation [4,5].…”

Section: Introductionmentioning

confidence: 99%

Parasite associations predict infection risk: incorporating co-infections in predictive models for neglected tropical diseases

et al. 2020

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Background: Schistosomiasis and infection by soil-transmitted helminths are some of the world's most prevalent neglected tropical diseases. Infection by more than one parasite (co-infection) is common and can contribute to clinical morbidity in children. Geostatistical analyses of parasite infection data are key for developing mass drug administration strategies, yet most methods ignore co-infections when estimating risk. Infection status for multiple parasites can act as a useful proxy for data-poor individual-level or environmental risk factors while avoiding regression dilution bias. Conditional random fields (CRF) is a multivariate graphical network method that opens new doors in parasite risk mapping by (i) predicting co-infections with high accuracy; (ii) isolating associations among parasites; and (iii) quantifying how these associations change across landscapes. Methods: We built a spatial CRF to estimate infection risks for Ascaris lumbricoides, Trichuris trichiura, hookworms (Ancylostoma duodenale and Necator americanus) and Schistosoma mansoni using data from a national survey of Rwandan schoolchildren. We used an ensemble learning approach to generate spatial predictions by simulating from the CRF's posterior distribution with a multivariate boosted regression tree that captured non-linear relationships between predictors and covariance in infection risks. This CRF ensemble was compared against single parasite gradient boosted machines to assess each model's performance and prediction uncertainty. Results: Parasite co-infections were common, with 19.57% of children infected with at least two parasites. The CRF ensemble achieved higher predictive power than single-parasite models by improving estimates of co-infection prevalence at the individual level and classifying schools into World Health Organization treatment categories with greater accuracy. The CRF uncovered important environmental and demographic predictors of parasite infection probabilities. Yet even after capturing demographic and environmental risk factors, the presences or absences of other parasites were strong predictors of individual-level infection risk. Spatial predictions delineated high-risk regions in need of anthelminthic treatment interventions, including areas with higher than expected co-infection prevalence. Conclusions: Monitoring studies routinely screen for multiple parasites, yet statistical models generally ignore this multivariate data when assessing risk factors and designing treatment guidelines. Multivariate approaches can be instrumental in the global effort to reduce and eventually eliminate neglected helminth infections in developing countries.

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Section: Introductionmentioning

confidence: 99%

Parasite associations predict infection risk: incorporating co-infections in predictive models for neglected tropical diseases

et al. 2020

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“…From 2007 until 2014, SCI supported an MDA programme in Burundi [ 5 ], primarily targeting school-aged children (SAC) and pregnant women. In 2007, a pilot longitudinal study was launched in 12 schools, followed in 2008 by an extension study, in which an additional 19 schools across the country were added [ 6 ]. The longitudinal study aimed to assess the impact of MDA on STH control in Burundi, and found that the overall prevalence of STH infection was statistically significantly reduced over the programme’s duration.…”

Section: Introductionmentioning

confidence: 99%

“…The study found that predictive prevalence mapping was indeed an effective tool for guiding MDA implementation to maximise deworming efficiency [ 5 ]. However, the impact of successive (annual) MDA rounds on the spatiotemporal variation of prevalence of STH infections such as the ensuing 8-year MDA programme in Burundi [ 6 ] has not been investigated. In our previous study, we found that disruption in the delivery of MDA, for example as a result of social unrest, may have contributed to the observed rebound in STH infection prevalence [ 6 ].…”

Section: Introductionmentioning

confidence: 99%

Spatiotemporal distribution and population at risk of soil-transmitted helminth infections following an eight-year school-based deworming programme in Burundi, 2007–2014

et al. 2017

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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.Electronic supplementary materialThe online version of this article (10.1186/s13071-017-2505-x) contains supplementary material, which is available to authorized users.

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“…Resurgence of infection may still occur quickly in locations where transmission intensity is high and the infectious reservoir has not been sustainably depleted. For example, Ortu et al 2016 report that a single year of missed treatment led STH resurgence back to baseline levels in an MDA programme for STH in Burundi where the dominant species was A. lumbricoides [21]. In a systematic review and meta-analysis of re-infection with STH after MDA, Jia et al 2012 found that re-infection between treatments occurs quickly.…”

Section: Discussionmentioning

confidence: 99%

Deworming Women of Reproductive Age During Adolescence and Pregnancy: What is the Impact on Morbidity From Soil-transmitted Helminths Infection?

Vegvari

Giardina

Bajaj

et al. 2020

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Background: Soil-transmitted helminths (STHs) are a major cause of poor health in low- and middle-income countries. In particular, hookworm is known to cause anaemia in children and women of reproductive age (WRA). One goal of the World Health Organization’s (WHO) 2030 roadmap for neglected tropical diseases is to reduce STH-related morbidity in WRA. As a minimal intervention the WHO recommends deworming adolescent girls annually during human papilloma virus vaccination programmes and women of reproductive age (WRA) during pregnancy and lactation. These routine interventions are low cost can be implemented even from the most basic health services in endemic countries. In this study we use a cohort model to investigate the potential impact on STH-related morbidity in WRA.Results: We find that annual deworming of adolescent girls reduces morbidity in a similar way treatment programmes for pre-school-age and school-age children (pSAC and SAC). Treatment of WRA during pregnancy and lactation on its own has a small but significant effect on morbidity although it does not achieve the morbidity target (<2% moderate-to-high intensity infections) in this age group. However, depending on the age-intensity profile of infection, which may vary geographically, and assumptions on the density-dependence of egg production by fertilised female worms, continued school-based treatment may be able to reduce the force of infection acting on WRA, both through an indirect effect on the overall population based force of infection and via reducing the burden of infection as children age and move into the WRA age classes. As a result, morbidity in WRA may be eliminated.Conclusion: While deworming during pregnancy and lactation does not achieve the morbidity target in WRA and its efficacy may vary by setting, it is still expected to be beneficial for maternity and child health. Monitoring of any WRA-based intervention is recommended to evaluate its effectiveness.

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The impact of an 8-year mass drug administration programme on prevalence, intensity and co-infections of soil-transmitted helminthiases in Burundi

Cited by 24 publications

References 32 publications

Parasite associations predict infection risk: incorporating co-infections in predictive models for neglected tropical diseases

Parasite associations predict infection risk: incorporating co-infections in predictive models for neglected tropical diseases

Spatiotemporal distribution and population at risk of soil-transmitted helminth infections following an eight-year school-based deworming programme in Burundi, 2007–2014

Deworming Women of Reproductive Age During Adolescence and Pregnancy: What is the Impact on Morbidity From Soil-transmitted Helminths Infection?

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