Robin L. Bailey

Polymorphisms in Chlamydia trachomatis tryptophan synthase genes differentiate between genital and ocular isolates

We previously reported that laboratory reference strains of Chlamydia trachomatis differing in infection organotropism correlated with inactivating mutations in the pathogens tryptophan synthase (trpBA) genes. Here, we have applied functional genomics to extend this work and find that the paradigm established for reference serovars also applies to clinical isolates - specifically, all ocular trachoma isolates tested have inactivating mutations in the synthase, whereas all genital isolates encode a functional enzyme. Moreover, functional enzyme activity was directly correlated to IFN-gamma resistance through an indole rescue mechanism. Hence, a strong selective pressure exists for genital strains to maintain a functional synthase capable of using indole for tryptophan biosynthesis. The fact that ocular serovars (serovar B) isolated from the genital tract were found to possess a functional synthase provided further persuasive evidence of this association. These results argue that there is an important host-parasite relationship between chlamydial genital strains and the human host that determines organotropism of infection and the pathophysiology of disease. We speculate that this relationship involves the production of indole by components of the vaginal microbial flora, allowing chlamydiae to escape IFN-gamma-mediated eradication and thus establish persistent infection.

Azithromycin in control of trachoma

The new Global Initiative by the World Health Organization has an ambitious goal of eliminating blinding trachoma by 2020, twenty years into the next millennium. GET 2020 consists of a four-pronged strategy to reduce active trachoma through community-based antibiotic distribution and health education on face washing and environmental sanitation, and to reduce vision loss from trichiasis through provision of appropriate surgical services. The SAFE strategy – Surgery, Antibiotics, Face-washing, Environmental change – is currently being implemented or planned for five pilot countries where the antibiotic component will be based on the drug azithromycin under a donation programme by Pfizer, Inc. Azithromycin represents a breakthrough for the community-based, antibiotic treatment of ocular Chlamydia trachomatis infection. Trachoma is a community disease, which clusters in neighbourhoods and within families, children having the highest rates of disease.1 Treatment of a few cases in such a setting guarantees re-infection from familial or neighbourhood sources, unless the treatment is more widespread. Moreover, re-infection from extra-ocular sites can occur if only topical treatment is used,2 and re-infection from other people can occur if treatment of members of the community is not carried out at the same time. Previously, topical agents, such as tetracycline, have been the agents of choice. This was done due to the absence of systemic side effects in children (seen with oral tetracycline) and the high cost and lack of availability of oral erythromycin in many of these remote communities. However, topical tetracycline must be used every day for four to six weeks to be effective. It also stings, is messy to use, and results in blurred vision because of its oily base. Compliance (regular use of the prescribed medicine) with topical agents is typically quite poor.

Strategies for control of trachoma: observational study with quantitative PCR

BACKGROUND Antibiotics are an important part of WHOs strategy to eliminate trachoma as a blinding disease by 2020. At present, who needs to be treated is unclear. We aimed to establish the burden of ocular Chlamydia trachomatis in three trachoma-endemic communities in Tanzania and The Gambia with real-time quantitative PCR. METHODS Conjunctival swabs were obtained at examination from 3146 individuals. Swabs were first tested by the qualitative Amplicor PCR, which is known to be highly sensitive. In positive samples, the number of copies of omp1 (a single-copy C trachomatis gene) was measured by quantitative PCR. FINDINGS Children had the highest ocular loads of C trachomatis, although the amount of pooling in young age groups was less striking at the site with the lowest trachoma frequency. Individuals with intense inflammatory trachoma had higher loads than did those with other conjunctival signs. At the site with the highest prevalence of trachoma, 48 of 93 (52%) individuals with conjunctival scarring but no sign of active disease were positive for ocular chlamydiae. INTERPRETATION Children younger than 10 years old, and those with intense inflammatory trachoma, probably represent the major source of ocular C trachomatis infection in endemic communities. Success of antibiotic distribution programmes could depend on these groups receiving effective treatment.

Effect of fly control on trachoma and diar rhoea

BACKGROUND Domestic flies are accepted vectors of diarrhoea, but their role in trachoma transmission has never been quantified and no study has shown that fly control decreases the prevalence of trachoma. We assessed the effect of fly control on public health in a pilot study in Gambian villages. METHODS We studied two pairs of villages--one pair in the 1997 wet season, and one pair in the 1998 dry season. For each pair, deltamethrin was sprayed for 3 months to control flies in one village whilst the other was used as a control. Fly populations were monitored with traps. We surveyed trachoma at baseline and at 3 months, and collected daily data on diarrhoea in children aged between 3 months and 5 years. FINDINGS Fly control decreased numbers of muscid flies by around 75% in the intervention villages compared with controls. Trachoma prevalence was similar at baseline (wet season, prevalence in intervention village 8.8% vs control 12.2%; dry season, 18.0% vs 16.0%), but after 3 months of fly control there were 75% fewer new cases of trachoma in the intervention villages (wet season 3.7% vs 13.7%; dry season 10.0% vs 18.9%; rate ratio and relative risk of pooled data 0.25 [adjusted 95% CI 0.09-0.64], p=0.003). There was 22% less childhood diarrhoea in the wet season (14% vs 19%, period prevalence ratio 0.78 [0.64-0.95], p=0.01), and 26% less diarrhoea in the dry season (6% vs 8%; 0.74 [0.34-1.59], p=0.60) compared with controls. INTERPRETATION Muscid flies are important vectors of trachoma and childhood diarrhoea in The Gambia. Deltamethrin spray is effective for fly control and may be useful for reducing trachoma and diarrhoea in some situations, but further research on sustainable fly-control methods is needed.

Role of flies and provision of latrines in trachoma control : cluster-randomised controlled trial.

BACKGROUND Eye-seeking flies have received much attention as possible trachoma vectors, but this remains unproved. We aimed to assess the role of eye-seeking flies as vectors of trachoma and to test provision of simple pit latrines, without additional health education, as a sustainable method of fly control. METHODS In a community-based, cluster-randomised controlled trial, we recruited seven sets of three village clusters and randomly assigned them to either an intervention group that received regular insecticide spraying or provision of pit latrines (without additional health education) to each household, or to a control group with no intervention. Our primary outcomes were fly-eye contact and prevalence of active trachoma. Frequency of child fly-eye contact was monitored fortnightly. Whole communities were screened for clinical signs of trachoma at baseline and after 6 months. Analysis was per protocol. FINDINGS Of 7080 people recruited, 6087 (86%) were screened at follow-up. Baseline community prevalence of active trachoma was 6%. The number of Musca sorbens flies caught from childrens eyes was reduced by 88% (95% CI 64-100; p<0.0001) by insecticide spraying and by 30% (7-52; p=0.04) by latrine provision by comparison with controls. Analysis of age-standardised trachoma prevalence rates at the cluster level (n=14) showed that spraying was associated with a mean reduction in trachoma prevalence of 56% (19-93; p=0.01) and 30% with latrines (-81 to 22; p=0.210) by comparison with the mean rate change in the controls. INTERPRETATION Fly control with insecticide is effective at reducing the number of flies caught from childrens eyes and is associated with substantially lower trachoma prevalence compared with controls. Such a finding is consistent with flies being important vectors of trachoma. Since latrine provision without health education was associated with a significant reduction in fly-eye contact by M sorbens, studies of their effect when combined with other trachoma control measures are warranted.

T helper type-1 (Th1)/Th2 profiles of peripheral blood mononuclear cells (PBMC); responses to antigens of Chlamydia trachomatis in subjects with severe trachomatous scarring

Increased stimulation of Th2 cytokines may contribute to the development of persistent ocular chlamydial infection, resulting in the blinding pathological changes of trachoma. Proliferation and cytokine production profiles of PBMC in response to stimulation with antigens of Chlamydia trachomatis were compared in 30 patients with severe conjunctival scarring due to trachoma and in 30 age‐, sex‐ and location‐matched controls. Interferon‐gamma (IFN‐γ) and IL‐4 were detected at the single‐cell level by ELISPOT assay. Transcription of the genes encoding IFN‐γ, IL‐4 and IL‐10 was detected in mRNA isolated from parallel cultures of PBMC using reverse transcriptase‐polymerase chain reaction (RT‐PCR). Incubation with the chlamydial heat shock protein (hsp)60 resulted in increased numbers of IL‐4‐producing cells in PBMC isolated from patients with scarring disease and increased secretion of IFN‐γ from PBMC of control subjects. Incubation with the chlamydial major outer membrane protein (MOMP) increased the number of IFN‐γ‐producing cells in the control group only. Messenger RNA encoding IL‐4 was only detected in PBMC of patients with scarring disease after in vitro stimulation with chlamydial antigens, but IFN‐γ mRNA and IL‐10 mRNA were also more frequently detected in this group. Thirty‐eight subjects were HLA‐DRB1 and ‐DQB1 typed. Associations were observed between certain HLA class II alleles and cellular immune responses to chlamydial antigens. No HLA associations were found with clinical status, and overall we found no evidence of strong associations and the type of immune response. These data are consistent with a role for Th2 cells and cytokines in the pathogenesis of trachomatous scarring.

Review of the evidence base for the 'F' and 'E' components of the SAFE strategy for trachoma control.

Summary Community control of trachoma as a blinding disease is based on the SAFE strategy of Surgery, Antibiotic therapy, Facial cleanliness and Environmental improvement. Surgery and antibiotic therapy currently dominate most programmes. Blindness from trachoma results from frequent infections repeated over many years, so ultimate success requires the reduction of transmission. This is only likely to be sustainable through the F and E components of SAFE. Environmental improvement with access to water, enhanced hygiene and better sanitation reduces trachoma transmission and the blinding sequelae eventually disappear. Transmission routes and factors that cause this are not known and consequently no single specific tool for F and E is in place. Evidence from intervention studies shows that the promotion of face‐washing gave modest gains for intense effort and a pilot study showed that trachoma transmission was reduced in the absence of eye‐seeking flies. Other studies have shown that latrines and improved access to water are associated with a lower prevalence of active trachoma. There is likely to be a long‐term beneficial effect of a combination of improved water supplies, provision of latrines, facial hygiene promotion through established infrastructure and control of eye‐seeking flies. Each of these interventions offers additional public health and other benefits in its own right. Further research on the routes of transmission, the role of hygiene and means of sustainable fly control should be a priority.

The duration of human ocular Chlamydia trachomatis infection is age dependent

We studied the relationship between age and prevalence, duration and incidence of clinical and laboratory evidence of ocular Chlamydia trachomatis infection in a cohort of Gambian subjects examined bi-weekly for 6 months. The duration of disease and infection, estimated by stratified survival analysis, proportional hazards regression and Weibull modelling, was markedly age-dependent. The estimated median duration of disease was 13.2 weeks in 0-4-year-old subjects and 1.7 weeks in those age 15 and over. Adjustment for multiple infections, and for missing observations did not alter this trend. The cumulative incidence rate of disease was reduced threefold with age. More rapid disease resolution is the main source of reduction in prevalence of active trachoma and ocular C. trachomatis infection with age; disease incidence was reduced to a lesser extent. This age-dependent resolution may be effected by adaptive cellular immune mechanisms. Mechanisms responsible for natural immunity should receive appropriate emphasis in vaccine design.

Re-emergence of Chlamydia trachomatis infection after mass antibiotic treatment of a trachoma-endemic Gambian community: a longitudinal study.

BACKGROUND Community-wide mass antibiotic treatment is a central component of trachoma control. The optimum frequency and duration of treatment are unknown. We measured the effect of mass treatment on the conjunctival burden of Chlamydia trachomatis in a Gambian community with low to medium trachoma prevalence and investigated the rate, route, and determinants of re-emergent infection. METHODS 14 trachoma-endemic villages in rural Gambia were examined and conjunctival swabs obtained at baseline, 2, 6, 12, and 17 months. Mass antibiotic treatment with azithromycin was given to the community at baseline. C trachomatis was detected by qualitative PCR and individual infection load then estimated by real-time quantitative PCR. FINDINGS C trachomatis was detected in 95 (7%) of 1319 individuals at baseline. Treatment coverage was 83% of the population (1328 of 1595 people). The effect of mass treatment was heterogeneous. In 12 villages all baseline infections (34 [3%] of 1062 individuals) resolved, and prevalence (three [0.3%]) and infection load remained low throughout the study. Two villages (baseline infection: 61 [24%] of 257 individuals) had increased infection 2 months after treatment (74 [30%]), after extensive contact with other untreated communities. Subsequently, this value reduced to less than half of that before treatment (25 [11%]). INTERPRETATION Mass antibiotic treatment generally results in effective, longlasting control of C trachomatis in this environment. For low prevalence regions, one treatment episode might be sufficient. Infection can be reintroduced through contact with untreated populations. Communities need to be monitored for treatment failure and control measures implemented over wide geographical areas.

The burden of reproductive-organ disease in rural women in The Gambia, West Africa

BACKGROUND Data on the epidemiology of reproductive-organ morbidity are needed to guide effective interventions, to set health-care priorities, and to target future research. This study aimed to find out the prevalence of reproductive-organ disease in a sample of rural Gambian women. METHODS A questionnaire on reproductive health was administered by fieldworkers to women aged 15-54 years living in a rural area under demographic surveillance. A female gynaecologist questioned and examined the women (including speculum and bimanual pelvic examinations). Vaginal swabs were taken to test for Trichomonas vaginalis, Candida albicans, and bacterial vaginosis, cervical smears for cytology, cervical swabs for Chlamydia trachomatis PCR and Neisseria gonorrhoeae culture, and venous blood for haemoglobin, HIV, herpes simplex virus 2, and syphilis serology. FINDINGS 1348 (72.0%) of 1871 eligible women took part. Reproductive-organ symptoms were more likely to be reported to the gynaecologist (52.7% of women) than to the fieldworker (26.5%). Menstrual problems, abnormal vaginal discharge, and vaginal itching were the most commonly reported symptoms. A minority of women said they had sought health care for their symptoms. The frequencies of reproductive-organ morbidity were high: menstrual dysfunction 34.1% (95% CI 29.6-39.1), infertility 9.8% (8.2-11.6), reproductive-tract infections 47.3% (43.7-51.0), pelvic tenderness 9.8% ((7.0-13.5), cervical dysplasia 6.7% (5.2-8.4), masses 15.9% (12.5-20.1), and childbirth-related damage to pelvic structures 46.1% (40.1-52.3). 948 (70.3%) women had at least one reproductive-organ disorder. INTERPRETATION For these rural women, whose lives depend heavily on their reproductive function, reproductive-organ disease is a large burden. In inadequately resourced rural areas, with poor education, heavy agricultural and domestic labour, and limited access to quality health care, many women are not able to attain and maintain reproductive health and wellbeing.