Spatial clustering of high load ocular Chlamydia trachomatis infection in trachoma: a cross-sectional population-based study

• Published in: Pathogens and disease 2017-07, Vol.75 (5)
• Main Authors: Last, Anna, Burr, Sarah, Alexander, Neal, Harding-Esch, Emma, Roberts, Chrissy H., Nabicassa, Meno, Cassama, Eunice Teixeira da Silva, Mabey, David, Holland, Martin, Bailey, Robin
• Format: Article
• Language: English
• Subjects: Archipelagoes; Bacteria; Bacterial Load; Blindness; Chlamydia; Chlamydia trachomatis; Chlamydia trachomatis - isolation & purification; Cluster Analysis; Clustering; Clusters; Communities; Conjunctiva - microbiology; Cross-Sectional Studies; Eye diseases; Geostatistics; Guinea-Bissau - epidemiology; Infections; Polymerase Chain Reaction; Population studies; Population-based studies; Sexually transmitted diseases; Spatial Analysis; Spatial distribution; STD; Surveillance; Topography, Medical; Trachoma; Trachoma - epidemiology; Trachoma - microbiology; Trachoma - pathology
• ISSN: 2049-632X; 2049-632X
• DOI: 10.1093/femspd/ftx050

Abstract Chlamydia trachomatis (Ct) is the most common cause of bacterial sexually transmitted infection and infectious cause of blindness (trachoma) worldwide. Understanding the spatial distribution of Ct infection may enable us to identify populations at risk and improve our understanding of Ct transmission. In this study, we sought to investigate the spatial distribution of Ct infection and the clinical features associated with high Ct load in trachoma-endemic communities on the Bijagós Archipelago (Guinea Bissau). We collected 1507 conjunctival samples and corresponding detailed clinical data during a cross-sectional population-based geospatially representative trachoma survey. We used droplet digital PCR to estimate Ct load on conjunctival swabs. Geostatistical tools were used to investigate clustering of ocular Ct infections. Spatial clusters (independent of age and gender) of individuals with high Ct loads were identified using local indicators of spatial association. We did not detect clustering of individuals with low load infections. These data suggest that infections with high bacterial load may be important in Ct transmission. These geospatial tools may be useful in the study of ocular Ct transmission dynamics and as part of trachoma surveillance post-treatment, to identify clusters of infection and thresholds of Ct load that may be important foci of re-emergent infection in communities. We identified clusters of high load Ct infections suggesting that high load infections may be important in transmission, which may have implications in trachoma elimination strategies and surveillance.