The global burden of trichiasis in 2016

Chlamydia plasmid-encoded protein Pgp2 is a replication initiator with a unique β-hairpin necessary for iteron-binding and plasmid replication

The virulence plasmid of the obligate intracellular bacterium Chlamydia encodes eight proteins. Among these, Pgp3 is crucial for pathogenicity, and Pgp4 functions as a transcriptional regulator of both plasmid and chromosomal genes. The remaining proteins, Pgp1, Pgp5, Pgp6, Pgp7, and Pgp8, are predicted to play various roles in plasmid replication or maintenance based on their amino acid sequences. However, the function of Pgp2 remains unknown, even though it is required for transformation. In this study, we utilized AlphaFold to predict the three-dimensional (3-D) structure of Chlamydia trachomatis Pgp2. Despite a lack of apparent sequence homology, the AlphaFold structure exhibited high similarity to experimentally determined structures of several plasmid replication initiators. Notably, Pgp2 features a unique β-hairpin motif near the DNA-binding domain, absent in other plasmid replication initiators with overall 3-D structures similar to Pgp2. This β-hairpin motif is also present in AlphaFold models of Pgp2s across all 13 Chlamydia species. To assess its significance, we engineered a plasmid lacking the 11 amino acids constituting the β-hairpin motif in C. trachomatis Pgp2. Although this deletion did not alter the overall structure of Pgp2, the mutated plasmid failed to transform plasmid-free C. trachomatis. These findings reveal that Pgp2 is a plasmid replication initiator, with the β-hairpin motif playing a critical role in binding to its cognate iteron sequences in the replication origin of the chlamydial plasmid.

Prevalence of Trachoma After Three Rounds of Antibiotic Mass Drug Administration in 13 Woredas of Gambella Region, Ethiopia

BACKGROUND

Following baseline surveys in 2013 and 2014, trachoma elimination interventions, including three rounds of azithromycin mass drug administration (MDA), were implemented in 13 woredas (administrative districts) of Gambella Regional State, Ethiopia. We conducted impact surveys to determine if elimination thresholds have been met or if additional interventions are required.

METHODS

Cross-sectional population-based surveys were conducted in 13 woredas of Gambella Regional State, combined into five evaluation units (EUs), 6─12 months after their last MDA round. A two-stage systematic (first stage) and random (second stage) sampling technique was used. WHO-recommended protocols were implemented with the support of Tropical Data. Household water, sanitation and hygiene (WASH) access was assessed.

RESULTS

The age-adjusted prevalence of trachomatous inflammation - follicular (TF) in 1-9-year-olds in the five EUs ranged from 0.3-19.2%, representing a general decline in TF prevalence compared to baseline estimates. The age- and gender-adjusted prevalence of trachomatous trichiasis (TT) unknown to the health system in those aged ≥ 15 years ranged from 0.47-3.08%. Of households surveyed, 44% had access to an improved drinking water source within a 30-minute return journey of the house, but only 3% had access to an improved latrine.

CONCLUSION

In two EUs, no further MDA should be delivered, and a surveillance survey should be conducted after two years without MDA. In one EU, one further round of MDA should be conducted followed by another impact survey. In two EUs, three further MDA rounds are required. Surgery, facial cleanliness and environmental improvement interventions are needed throughout the region.

Chlamydia plasmid-encoded protein Pgp2 is a replication initiator with a unique β-hairpin necessary for iteron-binding and plasmid replication

The virulence plasmid of the obligate intracellular bacterium Chlamydia encodes eight proteins. Among these, Pgp3 is crucial for pathogenicity, and Pgp4 functions as a transcriptional regulator of both plasmid and chromosomal genes. The remaining proteins, Pgp1, Pgp5, Pgp6, Pgp7, and Pgp8, are predicted to play various roles in plasmid replication or maintenance based on their amino acid sequences. However, the function of Pgp2 remains unknown, even though it is required for transformation. In this study, we utilized AlphaFold to predict the 3-dimensional (3-D) structure of C. trachomatis Pgp2. Despite a lack of apparent sequence homology, the AlphaFold structure exhibited high similarity to experimentally determined structures of several plasmid replication initiators. Notably, Pgp2 features a unique β-hairpin motif near the DNA-binding domain, absent in other plasmid replication initiators with overall 3-D structures similar to Pgp2. This β-hairpin motif was also present in AlphaFold models of Pgp2s across all 13 Chlamydia species. To assess its significance, we engineered a plasmid lacking the 11 amino acids constituting the β-hairpin motif in C. trachomatis Pgp2. Although this deletion did not alter the overall structure of Pgp2, the mutated plasmid failed to transform plasmid-free C. trachomatis. These findings reveal that Pgp2 is a plasmid replication initiator, with the β-hairpin motif playing a critical role in binding to its cognate iteron sequences in the replication origin of the chlamydial plasmid.

The prevention and management of postoperative trachomatous trichiasis: A systematic review

Among ocular infections, trachoma is the main cause of blindness. Repeated conjunctival Chlamydia trachomatis infections lead to trichiasis, corneal opacification, and visual impairment. Surgery is often needed to relieve discomfort and preserve vision; however, a high postoperative trachomatous trichiasis (PTT) rate has been observed in various settings. We wanted to know why, whether PTT rates could be reduced, and how to manage the PTT that occurs. We performed a search of the literature. Of 217 papers screened, 59 studies were identified for inclusion as potentially relevant, the majority having been excluded for not directly concerning PTT in humans. Preventing PTT is a major challenge. Only one published trial, the STAR trial in Ethiopia, has reported a cumulative PTT rate <10% one year after surgery. The literature on the management of PTT is sparse. Though no PTT management guidelines are available, high-quality surgery with a low rate of unfavorable outcomes for PTT patients is likely to require enhanced training of a smaller group of highly-skilled surgeons. Based on the surgical complexity and the authors' own experience, the pathway for patients suffering from PTT should be studied further for improvement.

Tropical Data: Approach and Methodology as Applied to Trachoma Prevalence Surveys

PURPOSE

Population-based prevalence surveys are essential for decision-making on interventions to achieve trachoma elimination as a public health problem. This paper outlines the methodologies of Tropical Data, which supports work to undertake those surveys.

METHODS

Tropical Data is a consortium of partners that supports health ministries worldwide to conduct globally standardised prevalence surveys that conform to World Health Organization recommendations. Founding principles are health ministry ownership, partnership and collaboration, and quality assurance and quality control at every step of the survey process. Support covers survey planning, survey design, training, electronic data collection and fieldwork, and data management, analysis and dissemination. Methods are adapted to meet local context and needs. Customisations, operational research and integration of other diseases into routine trachoma surveys have also been supported.

RESULTS

Between 29th February 2016 and 24th April 2023, 3373 trachoma surveys across 50 countries have been supported, resulting in 10,818,502 people being examined for trachoma.

CONCLUSION

This health ministry-led, standardised approach, with support from the start to the end of the survey process, has helped all trachoma elimination stakeholders to know where interventions are needed, where interventions can be stopped, and when elimination as a public health problem has been achieved. Flexibility to meet specific country contexts, adaptation to changes in global guidance and adjustments in response to user feedback have facilitated innovation in evidence-based methodologies, and supported health ministries to strive for global disease control targets.

Population Prevalence of Trachoma in Nine Rural Non-Indigenous Evaluation Units of Brazil

PURPOSE

To assess the contemporary prevalence of trachoma in Brazil's non-indigenous population, surveys of those thought to be at greatest risk of disease were conducted.

METHODS

Rural census tracts of non-indigenous population from nine mesoregions were selected to compose the survey evaluation units (EUs) by considering previously endemic municipalities at greatest risk of trachoma. In each of the nine EUs, we conducted a population-based prevalence survey. Every resident of selected households aged ≥ 1 year was examined for trachomatous inflammation - follicular (TF) and trachomatous trichiasis (TT). Additionally, data were collected on household-level access to water, sanitation, hygiene (WASH) and education.

RESULTS

A total of 27,962 individuals were examined across nine EUs. The age-adjusted TF prevalence in 1-9-year-olds was <5% in each EU. The age- and gender-adjusted prevalence of TT unknown to the health system in ≥15-year-olds was <0.2% in eight EUs; in one EU, it was 0.22%. The median number of households surveyed per EU with access to an improved drinking water source within a 30-minute roundtrip of the house was 66%. School attendance was >99% of surveyed children.

CONCLUSIONS

The prevalence of TF was well below the target for elimination as a public health problem in all EUs. Because EUs surveyed were selected to represent the highest-risk non-indigenous areas of the country, TF prevalence is unlikely to be ≥5% in non-indigenous populations elsewhere. In one EU, the prevalence of TT was above the target threshold for elimination. Further investigation and possibly improvement in TT surgical provision are required in that EU.

Effectiveness of Trachomatous Trichiasis Case-identification Approaches in Ethiopia

BACKGROUND

Trachoma control programs use multiple approaches to identify individuals with trachomatous trichiasis (TT). Evidence is limited regarding which approaches are most effective and cost-efficient.

METHODS

We evaluated the effectiveness of two TT case-identification approaches in Ethiopia: community mobilization to encourage self-referral for centralized screening and house-to-house screenings conducted by case finders. We compared the number of true cases found per 1000 population and costs associated with case identification under each approach, stratified by villages that received one or multiple screening visits.

RESULTS

We conducted screenings in 396 villages. In villages receiving one house-to-house visit, case finders identified 14,229 suspected cases, of whom 10,513 (73.9%) presented for TT confirmation. A median of 17.2% (interquartile range [IQR]: 9.1%-27.8%) of those presenting truly had TT (positive predictive value). In single-visit villages, the community mobilization approach yielded higher rates of confirmed cases than the house-to-house approach (1.5 [IQR: 1.1, 2.6] vs. 1.1 [IQR: 0.5, 1.9] cases per 1000 population), and the median cost of identifying a TT case was less ($5.59 vs. $31.18) using community mobilization than house-to-house. In multiple-visit villages, additional screening visits increased the median rate of confirmed cases to 2.5 per 1000 population in community mobilization villages, but the rate remained unchanged in house-to-house villages.

CONCLUSIONS

Community mobilization-based TT case finding had a higher yield than house-to-house, at a substantially lower cost. Future research should examine whether additional tools to aid case finders in their diagnosis increases case-finding efficiency and accuracy and whether TT prevalence and surgical program duration impact case-finding success.

Time trends and heterogeneity in the disease burden of trachoma, 1990-2019: a global analysis

PURPOSE

To evaluate the epidemiological trends and associated risk factors of disease burden due to trachoma.

METHODS

Data for the country-specific disability-adjusted life year (DALY) number, rate and age-standardised rate of trachoma together with related data of other common eye diseases were acquired from the Global Burden of Disease Study 2019 database. The Socio-Demographic Index (SDI), Human Development Index (HDI), inequality-adjusted HDI and other related indices were obtained from published data or publicly available databases. Regression analyses were conducted to evaluate the associations between potential risk factors and the age-standardised DALY burden of trachoma.

RESULTS

The global DALY burden due to trachoma decreased by 37% from 1990 to 2019 and decreased by 69.8% after adjusting for age and population growth, and, in available 1990-2019 data, had the greatest reduction in attributable DALYs of all common eye disease, with the others analysed being cataract, glaucoma, refractive disorders and age-related macular degeneration. Women had higher age-standardised DALY burden due to trachoma than men (p<0.001). The African region (p<0.001) had the heaviest burden among global regions. The age-standardised DALY rate was higher in countries with lower income (p<0.001) and lower SDI (p<0.001). Higher disease burden due to trachoma was associated with lower HDI (β=-48.102, 95% CI -86.888 to -9.316, p=0.016), lower SDI (β=-48.063, 95% CI -83.702 to -12.423, p<0.001) and lower expected years of schooling (β=-2.352, 95% CI -3.756 to -0.948, p=0.002).

CONCLUSIONS

The global disease burden due to trachoma decreased from 1990 to 2019 and it had the greatest reduction compared with other common eye diseases. Lower HDI, socioeconomic status and educational level were related to a higher national disease burden of trachoma. Our findings could provide necessary information for trachoma control and prevention.

Perceptions of ophthalmologists on the impact of trachoma in Egypt: a mixed-methods, nationwide survey

PURPOSE

Understanding the perception and practices of ophthalmologists for trachoma is important to develop interventions aimed at disease elimination in Egypt. The survey investigated: (1) the views and practice patterns of Egyptian ophthalmologists for trachoma and (2) the influence of geographic location, setting, and years of practice on ophthalmologists' perceptions.

METHODS

A questionnaire sent to ophthalmologists currently working in Egypt collected information on: (1) demographics, (2) caseload and practice patterns for trachoma, (3) 13 Likert scale questions regarding the current state of trachoma, and (4) two open-ended written response questions.

RESULTS

Of the 500 recipients, 194 ophthalmologists participated. 98% of the respondents reported seeing trachoma patients in their practice. 28.8% agreed that trachoma is currently an active health problem in Egypt, with ophthalmologists in public practice having significantly higher agreement scores compared to private practitioners (p = 0.030). Rural ophthalmologists were significantly more likely to agree that a targeted trachoma control program is needed in their location of practice compared to their urban counterparts (p < 0.001). Open-ended questions revealed recurrent themes, including the rural distribution of trachoma patients and the high volume of patients with corneal opacity.

CONCLUSION

Ophthalmologists' experiences with trachoma in Egypt differed based on practice setting, years in practice, and location, and the overall perception of the impact of the disease remains low. However, there was widespread agreement that trachoma is present in communities across the country. Practitioners in rural areas and in the public sector shared a disproportionate burden of the trachoma caseload. The perspectives of such ophthalmologists must be emphasized in decision-making related to trachoma interventions.

Exploring eye care pathways, patient priorities and economics in Pakistan: A scoping review and expert consultation study with thematic analysis

PURPOSE

As the prevalence of eye diseases increases, demand for effective, accessible and equitable eye care grows worldwide. This is especially true in lower and middle-income countries, which have variable levels of infrastructure and economic resources to meet this increased demand. In the present study we aimed to review the literature on eye care in Pakistan comprehensively, with a particular focus on eye care pathways, patient priorities and economics.

METHODS

A systematic scoping review was performed to identify literature relating to eye care in Pakistan. Searches of relevant electronic databases and grey literature were carried out. The results were analysed through a mixed methods approach encompassing descriptive numerical summary and thematic analysis. To consolidate results and define priority areas for future study, expert consultation exercises with key stakeholders were conducted using qualitative semi-structured interviews.

RESULTS

One hundred and thirty-two papers (published and unpublished) were included in the final review. The majority (n = 93) of studies utilised a quantitative design. Seven interlinked themes were identified: eye care pathways, burden of eye disease, public views on eye-related issues, workforce, barriers to uptake of eye care services, quality of eye care services and economic impact of blindness. Research priorities included investigating the eye care workforce, the quality and efficiency of current eye care services, eye care services available in rural Pakistan and the costs and benefits related to eye care provision and sustaining eye care programmes.

CONCLUSIONS

To the best of our knowledge, this is the first review to synthesise evidence from papers across the field relating to eye care in Pakistan. As such, this work provides new insights into the achievements of the national eye health programme, challenges in eye care in Pakistan and priority areas for future research.

Associated factors of the co-occurrence of trachoma and soil-transmitted helminthiases in children 1 to 9 years old in rural communities of the Amazon basin in Loreto Department, Peru: Results from a population-based survey

BACKGROUND

There is evidence of the occurrence of trachoma in Peru, and studies have shown that soil-transmitted helminthiases (STH) are affecting rural communities in the Amazon basin in Loreto Department. This study was done to estimate trachoma prevalence, STH prevalence, and the associated factors for both diseases in children aged 1-9 years in rural communities of Peru.

METHODOLOGY

A population-based cross-sectional survey was carried out in rural communities of Loreto. A standardized survey questionnaire with individual and household risk factors related to both diseases was used. Ocular examination was done for all participants aged one year and above, and eye swab samples were collected from children with follicular trachoma (TF). Anthropometric measurements, stool samples for STH, and blood samples for hemoglobin measurement were taken from children.

PRINCIPAL FINDINGS

TF prevalence was 7.74% (95% CI 5.08-11.63%), STH prevalence was 49.49% (95% CI 25.00-52.43%), and prevalence of co-occurrence of both diseases was 5.06% (95% CI 2.80-8.98%) in children aged 1-9 years. Being at age 3-8 years old (AOR = 6.76; 95% CI 1.346-33.947), have an unclean face (AOR = 24.64; 95% CI 6.787-89.444), and having been dewormed in the last six months (AOR = 2.47; 95% CI 1.106-5.514), were risk factors of TF. Being a female (AOR = 0.22; 95% CI 0.103-0.457) was associated with decreased odds of TF. Having been dewormed in the last six months (AOR = 0.30; 95% CI 0.139-0.628) was a preventative factor for STH. Risk factors for children with both diseases mirrored the findings for risk factors for individual diseases.

CONCLUSIONS

Neglected tropical diseases and associated risk factors overlap in communities living in vulnerable conditions in the Amazon basin of Peru. These findings support the need to implement integrated interventions, including mass drug administration, water, sanitation, and hygiene for both diseases in the study area.

Trachoma

Trachoma is a neglected tropical disease caused by infection with conjunctival strains of Chlamydia trachomatis. It can result in blindness. Pathophysiologically, trachoma is a disease complex composed of two linked chronic processes: a recurrent, generally subclinical infectious-inflammatory disease that mostly affects children, and a non-communicable, cicatricial and, owing to trichiasis, eventually blinding disease that supervenes in some individuals later in life. At least 150 infection episodes over an individual's lifetime are needed to precipitate trichiasis; thus, opportunity exists for a just global health system to intervene to prevent trachomatous blindness. Trachoma is found at highest prevalence in the poorest communities of low-income countries, particularly in sub-Saharan Africa; in June 2021, 1.8 million people worldwide were going blind from the disease. Blindness attributable to trachoma can appear in communities many years after conjunctival C. trachomatis transmission has waned or ceased; therefore, the two linked disease processes require distinct clinical and public health responses. Surgery is offered to individuals with trichiasis and antibiotic mass drug administration and interventions to stimulate facial cleanliness and environmental improvement are designed to reduce infection prevalence and transmission. Together, these interventions comprise the SAFE strategy, which is achieving considerable success. Although much work remains, a continuing public health problem from trachoma in the year 2030 will be difficult for the world to excuse.

A New Surgical Technique for Postoperative Trachomatous Trichiasis

INTRODUCTION

The World Health Organization has identified management of postoperative trichiasis (PTT) as one of the key remaining areas of focus needed to eliminate blinding trachoma as a public health problem. We developed the Bevel-Rotation Advancement Procedure (B-RAP) to treat individuals who need repeat trichiasis surgery.

METHODS

Scarring caused by trichiasis surgery can cause the eyelid to become thick and distorted, making repeat surgery more difficult. To minimize eyelid thickness following B-RAP, a beveled incision of the tarsus is made allowing a marginal rotation of the eyelash fragment. Dissection between the anterior and posterior lamellae above the beveled incision and removal of scar tissue allows the marginal rotation to be combined with a posterior lamellar advancement to treat severely scarred eyelids with PTT and eyelid contour abnormalities (ECAs).

RESULTS

Two surgeons performed B-RAP on 44 eyelids of 30 patients with PTT. The number of prior trachomatous trichiasis (TT) surgeries ranged from 2 to more than 4. At the 3-6 months postoperative visit, 37 eyelids (84%) had no recurrence of PTT. Three eyelids had central lashes touching; the remaining eyelids with recurrent PTT had nasal and temporal lashes touching. Fifteen eyelids (34%) had ECAs, but only 1 was severe.

CONCLUSIONS

B-RAP was developed considering the altered eyelid anatomy found in the postsurgical eyelid with TT. Thinning of the eyelash fragment and removal of postoperative scar tissue improves the ability to advance and stabilize the eyelash fragment after external rotation. B-RAP shows promise as a procedure for improving outcomes of repeat trichiasis surgery.

GrgA overexpression inhibits Chlamydia trachomatis growth through sigma66- and sigma28-dependent mechanisms

The obligate intracellular bacterium Chlamydia trachomatis is an important human pathogen with a biphasic developmental cycle comprised of an infectious elementary body (EB) and a replicative reticulate body (RB). Whereas σ66, the primary sigma factor, is necessary for transcription of most chlamydial genes throughout the developmental cycle, σ28 is required for expression of some late genes. We previously showed that the Chlamydia-specific transcription factor GrgA physically interacts with both of these sigma factors and activates transcription from σ66- and σ28-dependent promoters in vitro. Here, we investigated the organismal functions of GrgA. We show that overexpression of GrgA slows EB-to-RB conversion, decreases RB proliferation, and reduces progeny EB production. In contrast, overexpression of a GrgA variant without the σ28-binding domain shows significantly less severe inhibitory effects, while overexpression of a variant without the σ66-binding domain demonstrates no adverse effects. These findings indicate that GrgA plays important roles in the expression regulation of both σ66-dependent genes and σ28-dependent genes during the chlamydial developmental cycle.

Detecting extra-ocular Chlamydia trachomatis in a trachoma-endemic community in Ethiopia: Identifying potential routes of transmission

BACKGROUND

Trachoma elimination efforts are hampered by limited understanding of Chlamydia trachomatis (Ct) transmission routes. Here we aimed to detect Ct DNA at non-ocular sites and on eye-seeking flies.

METHODS

A population-based household survey was conducted in Oromia Region, Ethiopia. Ocular and non-ocular (faces, hands, clothing, water containers and sleeping surfaces) swabs were collected from all individuals. Flies were caught from faces of children. Flies, ocular swabs and non-ocular swabs were tested for Ct by quantitative PCR.

RESULTS

In total, 1220 individuals in 247 households were assessed. Active trachoma (trachomatous inflammation-follicular) and ocular Ct were detected in 10% and 2% of all-ages, and 21% and 3% of 1-9-year-olds, respectively. Ct was detected in 12% (95% CI:8-15%) of tested non-ocular swabs from ocular-positive households, but in none of the non-ocular swabs from ocular-negative households. Ct was detected on 24% (95% CI:18-32%) of flies from ocular-positive households and 3% (95% CI:1-6%) of flies from ocular-negative households.

CONCLUSION

Ct DNA was detected on hands, faces and clothing of individuals living in ocular-positive households suggesting that this might be a route of transmission within Ct infected households. In addition, we detected Ct on flies from ocular-positive households and occasionally in ocular-negative households suggesting that flies might be a vector for transmission within and between Ct infected and uninfected households. These potential transmission routes may need to be simultaneously addressed to suppress transmission.