Background WHO's 2020 milestones for Chagas disease include having all endemic Latin American countries certified with no intradomiciliary Trypanosoma cruzi transmission, and infected patients under care. Evaluating the variation in historical exposure to infection is crucial for assessing progress and for understanding the priorities to achieve these milestones.
Methods Focusing on Colombia, all the available age-structured serological surveys (undertaken between 1995 and 2014) were searched and compiled. A total of 109 serosurveys were found, comprising 83 742 individuals from rural (indigenous and non-indigenous) and urban settings in 14 (out of 32) administrative units (departments). Estimates of the force-of-infection (FoI) were obtained by fitting and comparing three catalytic models using Bayesian methods to reconstruct temporal and spatial patterns over the course of three decades (between 1984 and 2014).
Results Significant downward changes in the FoI were identified over the course of the three decades, and in some specific locations the predicted current seroprevalence in children aged 0–5 years is <1%. However, pronounced heterogeneity exists within departments, especially between indigenous, rural and urban settings, with the former exhibiting the highest FoI (up to 66 new infections/1000 people susceptible/year). The FoI in most of the indigenous settings remain unchanged during the three decades investigated. Current prevalence in adults in these 15 departments varies between 10% and 90% depending on the dynamics of historical exposure.
Conclusions Assessing progress towards the control of Chagas disease requires quantifying the impact of historical exposure on current age-specific prevalence at subnational level. In Colombia, despite the evident progress, there is a marked heterogeneity indicating that in some areas the vector control interventions have not been effective, hindering the possibility of achieving interruption by 2020. A substantial burden of chronic cases remains even in locations where serological criteria for transmission interruption may have been achieved, therefore still demanding diagnosis and treatment interventions.
- chagas disease
- mathematical modelling
- cross-sectional survey
- control strategies
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Contributors ZMC carried out data collation, analysis and was responsible for write-up and drafts of the manuscript. PN oriented data analysis. PN, LC and MGB served as supervisors on the doctoral thesis, including this manuscript, contributed to conceiving and designing the analysis and writing the final draft. VMA, MV, JCD and GPH carried out field data collection, and assisted during various stages of this research. All authors read and approved the final version of the manuscript. ZMC is the corresponding author.
Funding This work was supported by the Departamento Administrativo Nacional de Ciencia y Tecnología de Colombia (COLCIENCIAS) through a grant for the research programme CHAGAS NETWORK ‘Unión Temporal Programa Nacional de Investigación para la Prevención, Control y Tratamiento Integral de la Enfermedad de Chagas en Colombia–RED CHAGAS’ (grant no. 380-2011, code 5014-537-30398). Also, ZMC receives a PhD scholarship from COLCIENCIAS (call 569). PN was supported by the Medical Research Council and the Health Protection Research Units of the National Institute for Health Research. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.
Disclaimer The views expressed and information contained in it is not necessarily those of or endorsed by the institutions or the supporters.
Competing interests None declared.
Patient consent Detail has been removed from this case description/these case descriptions to ensure anonymity. The editors and reviewers have seen the detailed information available and are satisfied that the information backs up the case the authors are making.
Ethics approval This study was approved by the Ethics Committee of the National Institute of Health in Colombia (Code CTIN N° 14-2011).
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement All data used in the paper have been made available in the supplementary material.
Collaborators Secretaría de Salud de Boyacá, Secretaría de Salud de Casanare, Secretaría de Salud de Santader, Secretaría de Salud de Guainía, Secretaría de Salud de Antioquia, Univerisdad del Magdalena, Universidad de Antioquia, Medicos Sin Fronteras, Universidad Antonio Nariño.
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