Age-specific prevalence of anti-Pgp3 antibodies and severe conjunctival scarring in the Solomon Islands

Abstract

BackgroundTrachomatous trichiasis (TT) and ocular Chlamydia trachomatis (Ct) infection in the Solomon Islands are scarce, whereas trachomatous inflammation–follicular (TF) is prevalent.MethodsWe enrolled 1511 people aged ≥1 year from randomly selected households in 13 villages in which >10% of the population had TF prior to a single round of azithromycin MDA undertaken six months previously. Blood was collected from people of all ages to be screened for anti-Pgp3 antibodies. Photographs were collected from people of all ages for analysis of scarring severity.ResultsConjunctival scars were visible in 13.1% of photographs. Mild (p<0.0001) but not severe (p=0.149) scars increased in prevalence with age. Anti-Pgp3 antibody seroprevalence was 18% in 1–9 year olds, increased sharply around the age of sexual debut, and reached 69% in those over 25 years. Anti-Pgp3 seropositivity did not increase significantly between the ages of 1–9 years, and was not associated with scarring in children (p=0.472) or TF in children (p=0.581).ConclusionsSigns of trachoma are common in the Solomon Islands but occur frequently in individuals who have no serological evidence of prior ocular infection with Ct. WHO recommendations for directing MDA provision based on signs alone may not be suitable in this context.

Conjunctival transcriptome profiling of Solomon Islanders with active trachoma in the absence of Chlamydia trachomatis infection

“…The World Health Organization guidelines for implementing mass drug administration (MDA) are based largely on TF prevalence. We have previously argued that whilst the Solomon Islands has sufficiently prevalent clinical signs (TF) of trachoma to qualify for implementation of MDA, the prevalence of infection and trichiasis [ 3 , 5 ], as well as severe scarring and serological signs of prior infection [ 6 ] are all too low to suggest that clinical diagnosis with TF has the necessary specificity to be used as an indicator of need for intervention in this population. By showing that the transcriptional profile of TF ( Ct uninfected) cases in the Solomon Islands share some, but not all, the components of typical trachoma responses seen elsewhere, the current findings add to those of our previous studies to suggest that the majority of TF disease we observe there is not related to Ct .…”

“…Two years after the initial survey, all individuals in groups D and N were revisited by chance during a serological survey and were tested for evidence of prior Ct infections with an anti-Pgp3 ELISA test [ 5 ]. All members of groups D and N were seronegative at that time, suggesting that no member of either group had previously been infected with Ct .…”

“…We found that TF was not associated with Pgp3 seropositivity. These data suggested that the majority of TF cases that we identified were in individuals who were very unlikely to have ever been exposed to any form of Ct infection [ 5 ]. When we tested for the presence of several other infectious micro-organisms that are known to be able to cause symptoms of follicular inflammation ( Haemophilus influenzae , Streptococcus pneumoniae , Moraxella catarrhalis , Staphylococcus spp.…”

“…The grading of TF was conducted by graders trained to the same international standards as graders in other countries, giving us no reason to suspect the TF phenotype in the Solomon Islands is different to that in trachoma-endemic populations elsewhere in the world [ 3 ]. However, we observed very little TS in the Solomon Islands [ 5 ]. Therefore, an important question that emerges from our work is whether there are differences in the underlying immune response that could explain why, in the Solomon Islands, highly prevalent TF does not seem to be concurrent with the same burden of blinding sequelae of trachoma as in other countries.…”

Serology reflects a decline in the prevalence of trachoma in two regions of The Gambia

“…Around 26% of 1-9 year olds living there had TF, but Ct infection was very scarce at just 1.3%. Using a serological tool we showed that 53/66 (80%) of the cases of TF that we observed were in people who were serologically negative for prior Ct infection 8 . Clinical signs of trachoma were also a poor indicator for the need to deploy antimicrobials in Fiji, where the high prevalence of TT cases could be better explained by socio-epidemiological practices of eyelash depilation than by Ct infections 9 .…”