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The Development of an Age-Structured Model for Trachoma Transmission Dynamics, Pathogenesis and Control

Title: The Development of an Age-Structured Model for Trachoma Transmission Dynamics, Pathogenesis and Control
Authors: Gambhir, M
Basanez, M-G
Burton, MJ
Solomon, AW
Bailey, RL
Holland, MJ
Blake, IM
Donnelly, CA
Jabr, I
Mabey, DC
Grassly, NC
Item Type: Journal Article
Abstract: Background: Trachoma, the worldwide leading infectious cause of blindness, is due to repeated conjunctival infection with Chlamydia trachomatis. The effects of control interventions on population levels of infection and active disease can be promptly measured, but the effects on severe ocular sequelae require long-term monitoring. We present an age-structured mathematical model of trachoma transmission and disease to predict the impact of interventions on the prevalence of blinding trachoma. Methodology/Principal Findings: The model is based on the concept of multiple reinfections leading to progressive conjunctival scarring, trichiasis, corneal opacity and blindness. It also includes aspects of trachoma natural history, such as an increasing rate of recovery from infection and a decreasing chlamydial load with subsequent infections that depend upon a (presumed) acquired immunity that clears infection with age more rapidly. Parameters were estimated using maximum likelihood by fitting the model to pre-control infection prevalence data from hypo-, meso- and hyperendemic communities from The Gambia and Tanzania. The model reproduces key features of trachoma epidemiology: 1) the age-profile of infection prevalence, which increases to a peak at very young ages and declines at older ages; 2) a shift in this prevalence peak, toward younger ages in higher force of infection environments; 3) a raised overall profile of infection prevalence with higher force of infection; and 4) a rising profile, with age, of the prevalence of the ensuing severe sequelae (trachomatous scarring, trichiasis), as well as estimates of the number of infections that need to occur before these sequelae appear. Conclusions/Significance: We present a framework that is sufficiently comprehensive to examine the outcomes of the A (antibiotic) component of the SAFE strategy on disease. The suitability of the model for representing population-level patterns of infection and disease sequelae is discussed in view of the individual processes leading to these patterns.
Issue Date: 16-Jun-2009
Date of Acceptance: 19-May-2009
URI: http://hdl.handle.net/10044/1/48814
DOI: https://dx.doi.org/10.1371/journal.pntd.0000462
ISSN: 1935-2735
Publisher: Public Library of Science
Journal / Book Title: PLOS Neglected Tropical Diseases
Volume: 3
Issue: 6
Copyright Statement: © 2009 Gambhir et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Sponsor/Funder: Medical Research Council (MRC)
Funder's Grant Number: G0600719B
Keywords: Science & Technology
Life Sciences & Biomedicine
Infectious Diseases
Parasitology
Tropical Medicine
PARASITOLOGY
TROPICAL MEDICINE
CHLAMYDIA-TRACHOMATIS
LYMPHATIC FILARIASIS
ENDEMIC POPULATION
BLINDING TRACHOMA
SCARRING TRACHOMA
NATURAL-HISTORY
MASS TREATMENT
INFECTION
RISK
POLYMORPHISMS
Adolescent
Adult
Age Factors
Aged
Aged, 80 and over
Anti-Bacterial Agents
Antibiotic Prophylaxis
Child
Child, Preschool
Chlamydia trachomatis
Female
Gambia
Humans
Male
Middle Aged
Models, Theoretical
Prevalence
Tanzania
Trachoma
Young Adult
06 Biological Sciences
11 Medical And Health Sciences
Publication Status: Published
Article Number: ARTN e462
Appears in Collections:Faculty of Medicine
Epidemiology, Public Health and Primary Care



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