Characterising spatial patterns of neglected tropical disease transmission using integrated sero-surveillance in Northern Ghana

Background

As prevalence decreases in pre-elimination settings, identifying the spatial distribution of remaining infections to target control measures becomes increasingly challenging. By measuring multiple antibody responses indicative of past exposure to different pathogens, integrated serological surveys enable simultaneous characterisation of residual transmission of multiple pathogens.

Methodology/Principal findings

Here, we combine integrated serological surveys with geostatistical modelling and remote sensing-derived environmental data to estimate the spatial distribution of exposure to multiple diseases in children in Northern Ghana. The study utilised the trachoma surveillance survey platform (cross-sectional two-stage cluster-sampled surveys) to collect information on additional identified diseases at different stages of elimination with minimal additional cost. Geostatistical modelling of serological data allowed identification of areas with high probabilities of recent exposure to diseases of interest, including areas previously unknown to control programmes. We additionally demonstrate how serological surveys can be used to identify areas with exposure to multiple diseases and to prioritise areas with high uncertainty for future surveys. Modelled estimates of cluster-level prevalence were strongly correlated with more operationally feasible metrics of antibody responses.

Conclusions/Significance

This study demonstrates the potential of integrated serological surveillance to characterise spatial distributions of exposure to multiple pathogens in low transmission and elimination settings when the probability of detecting infections is low.

Surveillance for peri-elimination trachoma recrudescence: Exploratory studies in Ghana

Introduction

To date, eleven countries have been validated as having eliminated trachoma as a public health problem, including Ghana in 2018. Surveillance for recrudescence is needed both pre- and post-validation but evidence-based guidance on appropriate strategies is lacking. We explored two potential surveillance strategies in Ghana.

Methodology/principal findings

Amongst randomly-selected communities enrolled in pre-validation on-going surveillance between 2011 and 2015, eight were identified as having had trachomatous-inflammation follicular (TF) prevalence ≥5% in children aged 1–9 years between 2012 and 2014. These eight were re-visited in 2015 and 2016 and neighbouring communities were also added (“TF trigger” investigations). Resident children aged 1–9 years were then examined for trachoma and had a conjunctival swab to test for Chlamydia trachomatis (Ct) and a dried blood spot (DBS) taken to test for anti-Pgp3 antibodies. These investigations identified at least one community with evidence of probable recent Ct ocular transmission. However, the approach likely lacks sufficient spatio-temporal power to be reliable.

A post-validation surveillance strategy was also evaluated, this reviewed the ocular Ct infection and anti-Pgp3 seroprevalence data from the TF trigger investigations and from the pre-validation surveillance surveys in 2015 and 2016. Three communities identified as having ocular Ct infection >0% and anti-Pgp3 seroprevalence ≥15.0% were identified, and along with three linked communities, were followed-up as part of the surveillance strategy. An additional three communities with a seroprevalence ≥25.0% but no Ct infection were also followed up (“antibody and infection trigger” investigations). DBS were taken from all residents aged ≥1 year and ocular swabs from all children aged 1–9 years. There was evidence of transmission in the group of communities visited in one district (Zabzugu-Tatale). There was no or little evidence of continued transmission in other districts, suggesting previous infection identified was transient or potentially not true ocular Ct infection.

Conclusions/significance

There is evidence of heterogeneity in Ct transmission dynamics in northern Ghana, even 10 years after wide-scale MDA has stopped. There is added value in monitoring Ct infection and anti-Ct antibodies, using these indicators to interrogate past or present surveillance strategies. This can result in a deeper understanding of transmission dynamics and inform new post-validation surveillance strategies. Opportunities should be explored for integrating PCR and serological-based markers into surveys conducted in trachoma elimination settings.

The goal for trachoma programmes is elimination of trachoma as a public health problem. This means that ongoing low-level eye-to-eye transmission of the causative bacterium, Chlamydia trachomatis (Ct), is acceptable. Countries need to implement a suitable surveillance system to identify any return to higher transmission levels. The best methodology for doing this is not known. We first explored the approach used by Ghana in its standard programme, which involved monitoring a limited number of randomly selected communities for evidence of active (inflammatory) trachoma visible in children’s eyes on examination by trained observers. Although this strategy led to identification of at least one community that had probably had recent Ct transmission, the approach is unlikely to consistently identify places where return to higher levels of transmission is a risk. We also explored using information on infection (detected in eye swabs) and antibodies to Ct (detected in the blood) to identify communities at risk. We found evidence of both persistent eye-to-eye Ct transmission and areas where infection was transient and has now gone away. We conclude that the use of infection and antibody data for surveillance of trachoma appears promising.

Operational adaptations of the trachoma pre-validation surveillance strategy employed in Ghana: a qualitative assessment of successes and challenges

BACKGROUND

In 2009 Ghana began to design a trachoma pre-validation surveillance plan, based on then-current WHO recommendations. The plan aimed to identify active trachoma resurgence and identify and manage trichiasis cases, through both active and passive surveillance approaches. This paper outlines and reviews the adaptations made by Ghana between 2011 and 2016. The assessment will provide a learning opportunity for a number of countries as they progress towards elimination status.

METHODS

A mixed methods approach was taken, comprising in-depth interviews and documents review. Between January and April 2016, 20 in-depth interviews were conducted with persons involved in the operationalisation of the trachoma surveillance system from across all levels of the health system. A three-tier thematic coding framework was developed using a primarily inductive approach but also allowed for a more iterative approach, which drew on aspects of grounded theory.

RESULTS

During the operationalisation of the Ghana surveillance plan there were a number of adaptations (as compared to the WHO recommendations), these included: (i) Inclusion of surveillance of active trachoma in the passive surveillance approach, as compared to trichiasis alone. Issues with case identification, challenges in implementation coverage and a non-specific reporting structure hampered effectiveness; (ii) Random selection and increase in number of sites selected for the active surveillance component. This likely lacked the spatiotemporal power to be able to identify recrudescence in a timely manner; (iii) Targeted trichiasis door-to-door case searches, led by ophthalmic nurses. An effective methodology to identify trichiasis cases but resource intensive; (iv) A buddy system between ophthalmic nurses to support technical skills in an elimination setting where it is difficult to attain diagnostic and surgical skills, due to a lack of cases. The strategy did not take into account the loss of proficiency within experienced personnel.

CONCLUSIONS

Ghana developed a comprehensive surveillance system that exceeded the WHO recommendations but issues with sensitivity and specificity likely led to an inefficient use of resources. Improved targeted surveillance strategies for identification of recrudescence and trichiasis case searches, need to be evaluated. Strategies must address the contextual changes that arise because of transmission decline, such as loss of surgical skills.

Serological and PCR-based markers of ocular Chlamydia trachomatis transmission in northern Ghana after elimination of trachoma as a public health problem

BACKGROUND

Validation of elimination of trachoma as a public health problem is based on clinical indicators, using the WHO simplified grading system. Chlamydia trachomatis (Ct) infection and anti-Ct antibody responses (anti-Pgp3) have both been evaluated as alternative indicators in settings with varying levels of trachoma. There is a need to evaluate the feasibility of using tests for Ct infection and anti-Pgp3 antibodies at scale in a trachoma-endemic country and to establish the added value of the data generated for understanding transmission dynamics in the peri-elimination setting.

METHODOLOGY/PRINCIPAL FINDINGS

Dried blood spots for serological testing and ocular swabs for Ct infection testing (taken from children aged 1-9 years) were integrated into the pre-validation trachoma surveys conducted in the Northern and Upper West regions of Ghana in 2015 and 2016. Ct infection was detected using the GeneXpert PCR platform and the presence of anti-Pgp3 antibodies was detected using both the ELISA assay and multiplex bead array (MBA). The overall mean cluster-summarised TF prevalence (the clinical indicator) was 0.8% (95% CI: 0.6-1.0) and Ct infection prevalence was 0.04% (95%CI: 0.00-0.12). Anti-Pgp3 seroprevalence using the ELISA was 5.5% (95% CI: 4.8-6.3) compared to 4.3% (95%CI: 3.7-4.9) using the MBA. There was strong evidence from both assays that seropositivity increased with age (p<0.001), although the seroconversion rate was estimated to be very low (between 1.2 to 1.3 yearly events per 100 children).

CONCLUSIONS/SIGNIFICANCE

Infection and serological data provide useful information to aid in understanding Ct transmission dynamics. Elimination of trachoma as a public health problem does not equate to the absence of ocular Ct infection nor cessation in acquisition of anti-Ct antibodies.

Impact of low vision services on the quality of life of low vision patients in Ghana

Patients’ perspectives on the impact of clinical interventions have been recognised as critical elements in patient care. Quality-of-life instruments are designed to measure these perspectives. We used the National Eye Institute’s 25-item Visual Function Questionnaire (NEI VFQ) to measure the impact of optical low vision devices on the quality of life of 22 low vision patients who obtained and were using low vision devices from a secondary low vision clinic in the Eastern Region, Ghana. The study employed a pre- and post-intervention technique. We found statistically significant improvements in measured visual acuity and NEI VFQ scores in 8 of the 10 domains evaluated. We conclude that optical low vision devices have a positive impact on the quality of life of low vision patients in Ghana.Keywords: low vision; quality of life; visual acuity; visual impairment; Ghana

Serological and immunochemical specificity of a human autoanti-Gerbich-like antibody

An 85-year-old male with cardiac failure secondary to anaemia had an apparent anti-Ge2 (Ge = Gerbich) in his serum which did not agglutinate his own red cells even though they were Ge-positive in tests with alloanti-Ge. The direct antiglobulin test was negative; however, an antibody with apparent anti-Ge2 specificity was eluted from his red cells. The patient's autoantibody was shown in immunoblotting experiments to react with an antigenic determinant on beta-sialoglycoprotein. This case illustrates that an autoanti-Ge can masquerade as an alloantibody, thereby complicating antibody identification, and implies that the immunochemical specificity of autoanti-Ge2 is different from that of alloanti-Ge2.