title: Modelling the geographical distribution of soil-transmitted helminth infections in Bolivia.
abstract: BACKGROUND
  The prevalence of infection with the three common soil-transmitted helminths (i.e. Ascaris lumbricoides, Trichuris trichiura, and hookworm) in Bolivia is among the highest in Latin America. However, the spatial distribution and burden of soil-transmitted helminthiasis are poorly documented.
  
  
  METHODS
  We analysed historical survey data using Bayesian geostatistical models to identify determinants of the distribution of soil-transmitted helminth infections, predict the geographical distribution of infection risk, and assess treatment needs and costs in the frame of preventive chemotherapy. Rigorous geostatistical variable selection identified the most important predictors of A. lumbricoides, T. trichiura, and hookworm transmission.
  
  
  RESULTS
  Results show that precipitation during the wettest quarter above 400 mm favours the distribution of A. lumbricoides. Altitude has a negative effect on T. trichiura. Hookworm is sensitive to temperature during the coldest month. We estimate that 38.0%, 19.3%, and 11.4% of the Bolivian population is infected with A. lumbricoides, T. trichiura, and hookworm, respectively. Assuming independence of the three infections, 48.4% of the population is infected with any soil-transmitted helminth. Empirical-based estimates, according to treatment recommendations by the World Health Organization, suggest a total of 2.9 million annualised treatments for the control of soil-transmitted helminthiasis in Bolivia.
  
  
  CONCLUSIONS
  We provide estimates of soil-transmitted helminth infections in Bolivia based on high-resolution spatial prediction and an innovative variable selection approach. However, the scarcity of the data suggests that a national survey is required for more accurate mapping that will govern spatial targeting of soil-transmitted helminthiasis control.
authors.affiliation: Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland.
authors.forename: Frédérique
authors.initials: F
authors.lastname: Chammartin
authors.forename: Ronaldo G C
authors.initials: RG
authors.lastname: Scholte
authors.forename: John B
authors.initials: JB
authors.lastname: Malone
authors.forename: Mara E
authors.initials: ME
authors.lastname: Bavia
authors.forename: Prixia
authors.initials: P
authors.lastname: Nieto
authors.forename: Jürg
authors.initials: J
authors.lastname: Utzinger
authors.forename: Penelope
authors.initials: P
authors.lastname: Vounatsou
mesh_terms: D000293:Adolescent; D000818:Animals; D001196:Ascariasis / Q000453:epidemiology* / Q000635:transmission*; D001838:Bolivia / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D005260:Female; D006725:Hookworm Infections / Q000453:epidemiology* / Q000635:transmission*; D006801:Humans; D008297:Male; D015233:Models, Statistical; D015995:Prevalence; D019371:Topography, Medical; D014257:Trichuriasis / Q000453:epidemiology* / Q000635:transmission*