Modelling the geographical distribution of soil-transmitted helminth infections in Bolivia

Chammartin, Frédérique; Scholte, Ronaldo Guilherme Carvalho; Malone, John B.; Bavia, Mara E; Nieto, Prixia; Utzinger, Jürg; Vounatsou, Penelope

doi:10.1186/1756-3305-6-152

Cited by 62 publications

(68 citation statements)

References 47 publications

(54 reference statements)

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“…Our findings are also in contrast with the prevalence of STHs estimated recently by a geostatistical model for school-age children of the Hernando Siles province (A. lumbricoides, 55%; hookworm, 6%) and Cordillera province (A. lumbricoides, 29%; hookworm, 23%), [20] as well as the estimated prevalence (35%) of STHs for Bolivia (IDB, PAHO/WHO, Sabin Vaccine Institute) [21].…”

Section: Discussioncontrasting

confidence: 99%

Intestinal parasitic infections and associated epidemiological drivers in two rural communities of the Bolivian Chaco

Macchioni

Segundo

Totino

et al. 2016

J Infect Dev Ctries

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Introduction: In 2013 a coproparasitological survey was carried out in two rural communities of the Bolivian Chaco to determine the prevalence of intestinal parasitic infections (IPIs) and to investigate on possible infection drivers through a questionnaire interview. Methodology: Faecal samples were examined by microscopy. Samples positive for Entamoeba histolytica complex and Blastocystis were molecularly examined to identify the species/subtypes involved. Results: The overall infection rate was 86%, identical in both communities and mostly due to protozoa. Soil-transmitted helminths were detected in <3% of children and adults. Discussion: The protozoa detected, including Blastocystis subtypes, indicate faecal contamination of the environment by both humans (as confirmed by the presence of Hymenolepis nana) and animals. Nested-PCR identified E. histolytica, thus signalling the possible occurrence of invasive amoebosis. Lack of safe water, environmental contamination, poor sanitation and hygiene, shared by both communities, are the main drivers of IPIs. In addition, unlike gender and socioeconomic factors, childhood (only for some species), crowding and cohabitation with animals proved to be further significant protozoon infection risk factors. Conclusions: These results highlight the need for the promotion of access to clean water, improved sanitation and better hygiene, thus reducing the frequency of preventive chemotherapy for STHs while continuing to monitor the population for possible recrudescence.

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Section: Discussioncontrasting

confidence: 99%

Intestinal parasitic infections and associated epidemiological drivers in two rural communities of the Bolivian Chaco

Macchioni

Segundo

Totino

et al. 2016

J Infect Dev Ctries

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“…trichiura infection prevalence with increasing elevation was also found by other authors [30–33]. This effect is likely due to decreasing temperature at higher altitudes, which might negatively affect the development of T .…”

Section: Discussionsupporting

confidence: 80%

Trichuris trichiura infection and its relation to environmental factors in Mbeya region, Tanzania: A cross-sectional, population-based study

Manz

Clowes²,

Kroidl

et al. 2017

PLoS ONE

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BackgroundThe intestinal nematode Trichuris trichiura is among the most common causes of human infectious disease worldwide. As for other soil-transmitted nematodes, its reproductive success and thus prevalence and intensity of infection in a given area strongly depend on environmental conditions. Characterization of the influence of environmental factors can therefore aid to identify infection hot spots for targeted mass treatment.MethodologyWe analyzed data from a cross-sectional survey including 6234 participants from nine distinct study sites in Mbeya region, Tanzania. A geographic information system was used to combine remotely sensed and individual data, which were analyzed using uni- and multivariable Poisson regression. Household clustering was accounted for and when necessary, fractional polynomials were used to capture non-linear relationships between T. trichiura infection prevalence and environmental variables.Principal findingsT. trichiura infection was restricted to the Kyela site, close to Lake Nyasa with only very few cases in the other eight sites. The prevalence of T. trichiura infection in Kyela was 26.6% (95% confidence interval (CI) 23.9 to 29.6%). Multivariable models revealed a positive association of infection with denser vegetation (prevalence ratio (PR) per 0.1 EVI units = 2.12, CI 1.28 to 3.50) and inverse associations with rainfall (PR per 100 mm = 0.54, CI 0.44 to 0.67) and elevation (PR per meter = 0.89, CI 0.86 to 0.93) while adjusting for age and previous worm treatment. Slope of the terrain was modelled non-linearly and also showed a positive association with T. trichiura infection (p-value p<0.001).Conclusion/SignificanceHigher prevalences of T. trichiura infection were only found in Kyela, a study site characterized by denser vegetation, high rainfall, low elevation and flat terrain. But even within this site, we found significant influences of vegetation density, rainfall, elevation and slope on T. trichiura infection. The inverse association of rainfall with infection in Kyela is likely due to the fact, that rainfall in this site is beyond the optimum conditions for egg development. Our findings demonstrate that use of remotely sensed environmental data can aid to predict high-risk areas for targeted helminth control.

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“…Bayesian geostatistical stochastic search variable selection (SSVS) was performed to explore all possible models within a geostatistical framework and select the most important predictors for P. falciparum infection [35, 36]. In addition, a parameter expanded normal mixture of inverse gamma (peNMIG) prior parameterization was used to address the oversampling of the categorical variables around zero that can arise with more traditional parameterizations [37]).…”

Section: Methodsmentioning

confidence: 99%

Spatial mapping and prediction of Plasmodium falciparum infection risk among school-aged children in Côte d’Ivoire

et al. 2016

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BackgroundIn Côte d’Ivoire, malaria remains a major public health issue, and thus a priority to be tackled. The aim of this study was to identify spatially explicit indicators of Plasmodium falciparum infection among school-aged children and to undertake a model-based spatial prediction of P. falciparum infection risk using environmental predictors.MethodsA cross-sectional survey was conducted, including parasitological examinations and interviews with more than 5,000 children from 93 schools across Côte d’Ivoire. A finger-prick blood sample was obtained from each child to determine Plasmodium species-specific infection and parasitaemia using Giemsa-stained thick and thin blood films. Household socioeconomic status was assessed through asset ownership and household characteristics. Children were interviewed for preventive measures against malaria. Environmental data were gathered from satellite images and digitized maps. A Bayesian geostatistical stochastic search variable selection procedure was employed to identify factors related to P. falciparum infection risk. Bayesian geostatistical logistic regression models were used to map the spatial distribution of P. falciparum infection and to predict the infection prevalence at non-sampled locations via Bayesian kriging.ResultsComplete data sets were available from 5,322 children aged 5–16 years across Côte d’Ivoire. P. falciparum was the predominant species (94.5 %). The Bayesian geostatistical variable selection procedure identified land cover and socioeconomic status as important predictors for infection risk with P. falciparum. Model-based prediction identified high P. falciparum infection risk in the north, central-east, south-east, west and south-west of Côte d’Ivoire. Low-risk areas were found in the south-eastern area close to Abidjan and the south-central and west-central part of the country.ConclusionsThe P. falciparum infection risk and related uncertainty estimates for school-aged children in Côte d’Ivoire represent the most up-to-date malaria risk maps. These tools can be used for spatial targeting of malaria control interventions.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1775-z) contains supplementary material, which is available to authorized users.

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Modelling the geographical distribution of soil-transmitted helminth infections in Bolivia

Cited by 62 publications

References 47 publications

Intestinal parasitic infections and associated epidemiological drivers in two rural communities of the Bolivian Chaco

Intestinal parasitic infections and associated epidemiological drivers in two rural communities of the Bolivian Chaco

Trichuris trichiura infection and its relation to environmental factors in Mbeya region, Tanzania: A cross-sectional, population-based study

Spatial mapping and prediction of Plasmodium falciparum infection risk among school-aged children in Côte d’Ivoire

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