title: Geostatistical modelling of soil-transmitted helminth infection in Cambodia: do socioeconomic factors improve predictions?
abstract: Soil-transmitted helminth infections are intimately connected with poverty. Yet, there is a paucity of using socioeconomic proxies in spatially explicit risk profiling. We compiled household-level socioeconomic data pertaining to sanitation, drinking-water, education and nutrition from readily available Demographic and Health Surveys, Multiple Indicator Cluster Surveys and World Health Surveys for Cambodia and aggregated the data at village level. We conducted a systematic review to identify parasitological surveys and made every effort possible to extract, georeference and upload the data in the open source Global Neglected Tropical Diseases database. Bayesian geostatistical models were employed to spatially align the village-aggregated socioeconomic predictors with the soil-transmitted helminth infection data. The risk of soil-transmitted helminth infection was predicted at a grid of 1×1km covering Cambodia. Additionally, two separate individual-level spatial analyses were carried out, for Takeo and Preah Vihear provinces, to assess and quantify the association between soil-transmitted helminth infection and socioeconomic indicators at an individual level. Overall, we obtained socioeconomic proxies from 1624 locations across the country. Surveys focussing on soil-transmitted helminth infections were extracted from 16 sources reporting data from 238 unique locations. We found that the risk of soil-transmitted helminth infection from 2000 onwards was considerably lower than in surveys conducted earlier. Population-adjusted prevalences for school-aged children from 2000 onwards were 28.7% for hookworm, 1.5% for Ascaris lumbricoides and 0.9% for Trichuris trichiura. Surprisingly, at the country-wide analyses, we did not find any significant association between soil-transmitted helminth infection and village-aggregated socioeconomic proxies. Based also on the individual-level analyses we conclude that socioeconomic proxies might not be good predictors at an aggregated large-scale analysis due to their large between- and within-village heterogeneity. Specific information of both the infection risk and potential predictors might be needed to obtain any existing association. The presented soil-transmitted helminth infection risk estimates for Cambodia can be used for guiding and evaluating control and elimination efforts.
authors.affiliation: Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, PO Box, CH-4002 Basel, Switzerland; University of Basel, PO Box, CH-4003 Basel, Switzerland.
authors.forename: Dimitrios-Alexios
authors.initials: DA
authors.lastname: Karagiannis-Voules
authors.affiliation: Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, PO Box, CH-4002 Basel, Switzerland; University of Basel, PO Box, CH-4003 Basel, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Odermatt
authors.affiliation: Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, PO Box, CH-4002 Basel, Switzerland; University of Basel, PO Box, CH-4003 Basel, Switzerland.
authors.forename: Patricia
authors.initials: P
authors.lastname: Biedermann
authors.affiliation: Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, PO Box, CH-4002 Basel, Switzerland; University of Basel, PO Box, CH-4003 Basel, Switzerland; National Centre for Parasitology, Entomology and Malaria Control, Ministry of Health, Phnom Penh, Cambodia.
authors.forename: Virak
authors.initials: V
authors.lastname: Khieu
authors.affiliation: Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, PO Box, CH-4002 Basel, Switzerland; University of Basel, PO Box, CH-4003 Basel, Switzerland.
authors.forename: Fabian
authors.initials: F
authors.lastname: Schär
authors.affiliation: National Centre for Parasitology, Entomology and Malaria Control, Ministry of Health, Phnom Penh, Cambodia.
authors.forename: Sinuon
authors.initials: S
authors.lastname: Muth
authors.affiliation: Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, PO Box, CH-4002 Basel, Switzerland; University of Basel, PO Box, CH-4003 Basel, Switzerland.
authors.forename: Jürg
authors.initials: J
authors.lastname: Utzinger
authors.affiliation: Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, PO Box, CH-4002 Basel, Switzerland; University of Basel, PO Box, CH-4003 Basel, Switzerland. Electronic address: penelope.vounatsou@unibas.ch.
authors.forename: Penelope
authors.initials: P
authors.lastname: Vounatsou
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D002160:Cambodia / Q000453:epidemiology; D005260:Female; D006373:Helminthiasis / Q000453:epidemiology*; D006801:Humans; D008297:Male; D015995:Prevalence; D018570:Risk Assessment; D012307:Risk Factors; D012499:Sanitation; D012959:Socioeconomic Factors; D012987:Soil / Q000469:parasitology*; D062206:Spatial Analysis
chemical_list: D012987:Soil
keywords: Bayesian geostatistics; Cambodia; Risk mapping and prediction; Socioeconomic status; Soil-transmitted helminths; Southeast Asia