BackgroundBlinding trachoma, caused by the bacteria Chlamydia trachomatis, is a neglected tropical disease targeted for elimination by 2020. A major component of the elimination strategy is mass drug administration (MDA) with azithromycin. Currently, program decisions are made based on clinical signs of ocular infection, but we have been investigating the use of antibody responses for post-MDA surveillance. In a previous study, IgG responses were detected in children lacking clinical evidence of trachoma, suggesting that IgG responses represented historical infection. To explore the utility of serology for program evaluation, we compared IgG and IgA responses to trachoma antigens and examined changes in IgG and IgA post-drug treatment.MethodsDried blood spots and ocular swabs were collected with parental consent from 264 1–6 year olds in a single village of Kongwa District, central Tanzania. Each child also received an ocular exam for detection of clinical signs of trachoma. MDA was given, and six months later an additional blood spot was taken from these same children. Ocular swabs were analyzed for C. trachomatis DNA and antibody responses for IgA and total IgG were measured in dried bloods spots.ResultsBaseline antibody responses showed an increase in antibody levels with age. By age 6, the percentage positive for IgG (96.0%) was much higher than for IgA (74.2%). Antibody responses to trachoma antigens declined significantly six months after drug treatment for most age groups. The percentage decrease in IgA response was much greater than for IgG. However, no instances of seroreversion were observed.ConclusionsData presented here suggest that focusing on concordant antibody responses in children will provide the best serological surveillance strategy for evaluation of trachoma control programs.

BackgroundTrachoma is targeted for elimination by 2020. World Health Organization advises districts to undertake surveillance when follicular trachoma (TF) <5% in children 1–9 years and mass antibiotic administration has ceased. There is a question if other tools could be used for surveillance as well. We report data from a test for antibodies to C. trachomatis antigen pgp3 as a possible tool.MethodologyWe randomly sampled 30 hamlets in Kilosa district, Tanzania, and randomly selected 50 children ages 1–9 per hamlet. The tarsal conjunctivae were graded for trachoma (TF), tested for C. trachomatis infection (Aptima Combo2 assay: Hologic, San Diego, CA), and a dried blood spot processed for antibodies to C. trachomatis pgp3 using a multiplex bead assay on a Luminex 100 platform.Principal findingsThe prevalence of trachoma (TF) was 0.4%, well below the <5% indicator for re-starting a program. Infection was also low, 1.1%. Of the 30 hamlets, 22 had neither infection nor TF. Antibody positivity overall was low, 7.5% and increased with age from 5.2% in 1–3 year olds, to 9.3% in 7–9 year olds (p = 0.015). In 16 of the 30 hamlets, no children ages 1–3 years had antibodies to pgp3.ConclusionsThe antibody status of the 1–3 year olds indicates low cumulative exposure to infection during the surveillance period. Four years post MDA, there is no evidence for re-emergence of follicular trachoma.

Ocular infection with Chlamydia trachomatis can lead to trachoma, a leading infectious cause of blindness. Trachoma is targeted for elimination by 2020. Clinical grading for ocular disease is currently used for evaluating trachoma elimination programs, but serological surveillance can be a sensitive measure of disease transmission and provide a more objective testing strategy than clinical grading. We calculated the basic reproduction number from serological data in settings with high, medium, and low disease transmission based on clinical disease. The data showed a striking relationship between age seroprevalence and clinical data, demonstrating the proof-of-principle that age seroprevalence predicts transmission rates and therefore could be used as an indicator of decreased transmission of ocular trachoma.

Background Individuals who are sexually active may want to make a decision as to whether they are at risk for having a sexually transmitted infection (STI) such as Chlamydia trachomatis, Neisseria gonorrhoeae and Trichomonas vaginalis. Our goal was to develop and evaluate a simple self-taken sexual risk quiz for participants, ordering an online STI self-collection test kit to determine whether the score predicted infection status. Methods As part of the IWantTheKit programme for home sample self-collection for STIs, 2010–2013, the programme asked male and female users to voluntarily take a risk quiz. The six-question quiz was about risk behaviour and included an age question. Data analyses were stratified by gender as determined a priori. Scores 0–10 were stratified into risk groups for each gender based on similar risk score-specific STI prevalence. Retrospective analyses were performed to assess whether risk group predicted aggregate STI positivity. Urogenital/rectal mailed samples were tested by nucleic acid amplification tests. Results More females (N=836) than males (N=558) provided voluntary risk scores. The percentage of eligible participants who submitted scores was 43.9% for both females and males. There was a higher STI infection rate in females (14.0%) than in males (7.0%) for having any STI (p<0.001). Multivariate logistic analysis for females, which controlled for age and race, demonstrated that a higher risk score group independently predicted risk for having an STI (OR of 2.2 for risk scores 5–7 and 4.2 OR for scores of 8–10). For males, the multivariate model, which controlled for race, indicated that no risk score group was associated having an STI. Conclusions Results of a participant’s own sexual risk quiz score independently predicted STI positivity for women, but not for men. Further study of this simple risk quiz is required.