Clinical signs of trachoma are prevalent among Solomon Islanders who have no persistent markers of prior infection with Chlamydia trachomatis

Abstract

The low population-prevalence of trachomatous trichiasis and high prevalence of trachomatous inflammation-follicular (TF) provide contradictory estimates of the magnitude of the public health threat from trachoma in the Solomon Islands. Improved characterisation of the biology of trachoma in the region may support policy makers as they decide what interventions are required. Here, age-specific profiles of anti-Pgp3 antibodies and conjunctival scarring were examined to determine whether there is evidence of ongoing transmission and pathology from ocular infection. A total of 1511 individuals aged ≥1 year were enrolled from randomly selected households in 13 villages in which >10% of children aged 1-9 years had TF prior to a single round of azithromycin mass drug administration undertaken six months previously. Blood was collected to be screened for antibodies to the antigen Pgp3. Tarsal conjunctival photographs were collected for analysis of scarring severity. Anti-Pgp3 seropositivity was 18% in 1-9 year olds, sharply increasing around the age of sexual debut to reach 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 TF (p=0.581) or scarring in children (p=0.472). Conjunctival scars were visible in 13.1% of photographs. Mild (p<0.0001) but not severe (p=0.149) scars increased in prevalence with age. Neither conjunctival scars nor lymphoid follicles were associated with antibodies to suggesting that they are unlikely to be a direct result of ocular infection Clinical signs of trachoma were prevalent in this population but were not indicative of the underlying rates of infection. The current World Health Organization guidelines for trachoma elimination indicated that this population should receive intervention with mass distribution of antibiotics, but the data presented here suggest that this may not have been appropriate.

Ocular Chlamydia trachomatis infection, anti-Pgp3 antibodies and conjunctival scarring in Vanuatu and Tarawa, Kiribati before antibiotic treatment for trachoma

“…Compared to previous population-based estimates of scar prevalence and severity, Tarawa is similar to areas with high ocular Ct infection prevalence, 33 and Vanuatu is similar to areas in Melanesia with low ocular Ct infection prevalence. 18 Ocular Ct infection was common in Tarawa, with almost 30% of the children aged 1-9 years having infection. The relationship between TF and ocular Ct infection in Tarawa resembles trachoma-endemic districts in sub-Saharan Africa.…”

The use of serology for trachoma surveillance: Current status and priorities for future investigation

“…Data reviewed at the meeting from multiple EUs of the Solomon Islands, Vanuatu, and Papua New Guinea suggest that moderately high levels of TF in these populations are not reflective of ongoing intense ocular Ct transmission: the prevalence of ocular Ct infection is very low, and there is no increase in seropositivity among 1-to 9-year-olds. However, in the Solomon Islands, the absolute prevalence of antibody positivity in 1-to 9-year-olds is higher than that seen in other areas with low-intensity ocular Ct transmission [36]. The Solomon Islands have a high prevalence of urogenital Ct infection in women of reproductive age [37], which might explain this finding, potentially related to exposure of newborns to urogenital strains at the time of delivery, or exposure of children to ocular infection with urogenital strains through poor parental hand hygiene.…”

A systematic review of historical and contemporary evidence of trachoma endemicity in the Pacific Islands

“…The authors considered this to be much lower than may have been expected in an area where TF was common [ 14 ]. A recent study found no association between severe scarring, classed using the FPC grading system [ 64 , 65 ], and age [ 66 ]. Seroepidemiological analyses also provided little evidence of ongoing intense transmission of infection [ 66 , 67 ].…”

“…A recent study found no association between severe scarring, classed using the FPC grading system [ 64 , 65 ], and age [ 66 ]. Seroepidemiological analyses also provided little evidence of ongoing intense transmission of infection [ 66 , 67 ]. Other pathogens ( Adenoviridae , coagulase-negative Staphylococcus , Haemophilus influenza , Moraxella catarrhalis , Staphylococcus pneumonia and Staphylococcus aureus ) were sought in these samples using PCR, but none appeared to have significant association with TF.…”