Low Prevalence of Conjunctival Infection with Chlamydia trachomatis in a Treatment-Naïve Trachoma-Endemic Region of the Solomon Islands.
Trachoma is endemic in several Pacific Island states. Recent surveys across the Solomon Islands indicated that whilst trachomatous inflammation-follicular (TF) was present at levels warranting intervention, the prevalence of trachomatous trichiasis (TT) was low. We set out to determine the relationship between chlamydial infection and trachoma in this population.



We conducted a population-based trachoma prevalence survey of 3674 individuals from two Solomon Islands provinces. Participants were examined for clinical signs of trachoma. Conjunctival swabs were collected from all children aged 1-9 years. We tested swabs for Chlamydia trachomatis (Ct) DNA using droplet digital PCR. Chlamydial DNA from positive swabs was enriched and sequenced for use in phylogenetic analysis.



We observed a moderate prevalence of TF in children aged 1-9 years (n = 296/1135, 26.1%) but low prevalence of trachomatous inflammation-intense (TI) (n = 2/1135, 0.2%) and current Ct infection (n = 13/1002, 1.3%) in children aged 1-9 years, and TT in those aged 15+ years (n = 2/2061, 0.1%). Ten of 13 (76.9%) cases of infection were in persons with TF or TI (p = 0.0005). Sequence analysis of the Ct-positive samples yielded 5/13 (38%) complete (>95% coverage of reference) genome sequences, and 8/13 complete plasmid sequences. Complete sequences all aligned most closely to ocular serovar reference strains.



The low prevalence of TT, TI and Ct infection that we observed are incongruent with the high proportion of children exhibiting signs of TF. TF is present at levels that apparently warrant intervention, but the scarcity of other signs of trachoma indicates the phenotype is mild and may not pose a significant public health threat. Our data suggest that, whilst conjunctival Ct infection appears to be present in the region, it is present at levels that are unlikely to be the dominant driving force for TF in the population. This could be one reason for the low prevalence of TT observed during the study.
Clinical Research Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom.
Robert M R
RM
Butcher
Eye Department, Solomon Islands Ministry of Health and Medical Services, Honiara, Solomon Islands.
Oliver
O
Sokana
Eye Department, Solomon Islands Ministry of Health and Medical Services, Honiara, Solomon Islands.
Kelvin
K
Jack
Clinical Research Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom.|Sightsavers, Haywards Heath, United Kingdom.
Colin K
CK
Macleod
Clinical Research Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom.|Hospital for Tropical Diseases, University College London Hospitals, London, United Kingdom.
Michael E
ME
Marks
Primary Care Department, Lata Hospital, Lata, Santa Cruz, Solomon Islands.
Eric
E
Kalae
Primary Care Department, Lata Hospital, Lata, Santa Cruz, Solomon Islands.
Leslie
L
Sui
Bellona Rural Health Centre, Bellona, Solomon Islands.
Charles
C
Russell
Division of Infection & Immunity, Faculty of Medical Sciences, University College London, London, United Kingdom.
Helena J
HJ
Tutill
Division of Infection & Immunity, Faculty of Medical Sciences, University College London, London, United Kingdom.
Rachel J
RJ
Williams
Division of Infection & Immunity, Faculty of Medical Sciences, University College London, London, United Kingdom.
Judith
J
Breuer
Task Force for Global Health, Decatur, Georgia, United States of America.
Rebecca
R
Willis
Centre for Eye Research Australia, University of Melbourne, Royal Victorian Eye and Ear Hospital, Melbourne, Australia.
Richard T
RT
Le Mesurier
Clinical Research Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom.|Hospital for Tropical Diseases, University College London Hospitals, London, United Kingdom.
David C W
DC
Mabey
Clinical Research Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom.
Anthony W
AW
Solomon
Clinical Research Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom.
Chrissy H
CH
Roberts
D000293:Adolescent; D017677:Age Distribution; D002648:Child; D002675:Child, Preschool; D002692:Chlamydia trachomatis / Q000302:isolation & purification*; D016000:Cluster Analysis; D003430:Cross-Sectional Studies; D005191:Family Characteristics; D005260:Female; D006801:Humans; D007223:Infant; D016015:Logistic Models; D008297:Male; D008403:Mass Screening; D008542:Melanesia / Q000453:epidemiology; D010802:Phylogeny; D011795:Surveys and Questionnaires; D014141:Trachoma / Q000453:epidemiology*; D058457:Trichiasis / Q000453:epidemiology*