Circulating Anodic Antigen (CAA): A Highly Sensitive Diagnostic Biomarker to Detect Active Schistosoma Infections-Improvement and Use during SCORE

Flow-S: A Field-Deployable Device with Minimal Hands-On Effort to Concentrate and Quantify Schistosoma Circulating Anodic Antigen (CAA) from Large Urine Volumes

A laboratory-based lateral flow (LF) test that utilizes up-converting reporter particles (UCP) for ultrasensitive quantification of Schistosoma circulating anodic antigen (CAA) in urine is a well-accepted test to identify active infection. However, this UCP-LF CAA test requires sample pre-treatment steps not compatible with field applications. Flow, a new low-cost disposable, allows integration of large-volume pre-concentration of urine analytes and LF detection into a single field-deployable device. We assessed a prototype Flow-Schistosoma (Flow-S) device with an integrated UCP-LF CAA test strip, omitting all laboratory-based steps, to enable diagnosis of active Schistosoma infection in the field using urine. Flow-S is designed for large-volume (5-20 mL) urine, applying passive paper-based filtration and antibody-based CAA concentration. Samples tested for schistosome infection were collected from women of reproductive age living in a Tanzania region where S. haematobium infection is endemic. Fifteen negative and fifteen positive urine samples, selected based on CAA levels quantified in paired serum, were analyzed with the prototype Flow-S. The current Flow-S prototype, with an analytical lower detection limit of 1 pg CAA/mL, produced results correlated with the laboratory-based UCP-LF CAA test. Urine precipitates occurred in frozen banked samples and affected accurate quantification; however, this should not occur in fresh urine. Based on the findings of this study, Flow-S appears suitable to replace the urine pre-treatment required for the laboratory-based UCP-LF CAA test, thus allowing true field-based applications with fresh urine samples. The urine precipitates observed with frozen samples, though less important given the goal of testing fresh urines, warrant additional investigation to evaluate methods for mitigation. Flow-S devices permit testing of pooled urine samples with applications for population stratified testing. A field test with fresh urine samples, a further optimized Flow-S device, and larger statistical power has been scheduled.

Schistosome infection among pregnant women in the rural highlands of Madagascar: A cross-sectional study calling for public health interventions in vulnerable populations

INTRODUCTION

Schistosomiasis is a parasitic infection highly prevalent in sub-Saharan Africa (SSA) with Madagascar being among the countries with highest burden of the disease worldwide. Despite WHO recommendations, suggesting treatment of pregnant women after the first trimester, this group is still excluded from Mass Drug Administration programs. Our study, had the objective to measure the prevalence of schistosome infection among pregnant women in Madagascar in order to inform public health policies for treatment in this vulnerable population.

METHODS

Women were recruited for this cross-sectional study between April 2019 and February 2020 when attending Antenatal Care Services (ANCs) at one of 42 included Primary Health Care Centers. The urine-based upconverting reporter particle, lateral flow (UCP-LF) test detecting circulating anodic antigen was used for the detection of schistosome infections. To identify factors associated with the prevalence of schistosome infection crude and adjusted prevalence ratios and 95% CIs were estimated using mixed-effect Poisson regression.

RESULTS

Among 4,448 participating women aged between 16 and 47 years, the majority (70.4%, 38 n = 3,133) resided in rural settings. Overall, the prevalence of schistosome infection was 55.9% (n = 2486, CI 95%: 53.3-58.5). A statistically significant association was found with age group (increased prevalence in 31-47 years old, compared to 16-20 years old (aPR = 1.15, CI 95%: 1.02-1.29) and with uptake of antimalaria preventive treatment (decreased prevalence, aPR = 0.85, CI 95%: 0.77-0.95). No other associations of any personal characteristics or contextual factors with schistosome infection were found in our multivariate regression analysis.

DISCUSSION AND CONCLUSION

The high prevalence of schistosome infection in pregnant women supports the consideration of preventive schistosomiasis treatment in ANCs of the Malagasy highlands. We strongly advocate for adapting schistosomiasis programs in highly endemic contexts. This, would contribute to both the WHO and SDGs agendas overall to improving the well-being of women and consequently breaking the vicious cycle of poverty perpetuated by schistosomiasis.

Consensus definitions in imported human schistosomiasis: a GeoSentinel and TropNet Delphi study

Terminology in schistosomiasis is not harmonised, generating misunderstanding in data interpretation and clinical descriptions. This study aimed to achieve consensus on definitions of clinical aspects of schistosomiasis in migrants and returning travellers. We applied the Delphi method. Experts from institutions affiliated with GeoSentinel and TropNet, identified through clinical and scientific criteria, were invited to participate. Five external reviewers revised and pilot-tested the statements. Statements focusing on the definitions of acute or chronic; possible, probable, or confirmed; active; and complicated schistosomiasis were managed through REDCap and replies managed in a blinded manner. Round 1 mapped the definitions used by experts; subsequent rounds were done to reach consensus, or quantify disagreement, on the proposed statements. Data were analysed with percentages, medians, and IQRs of a 5-point Likert scale. The study was terminated on the basis of consensus or stability-related and time-related criteria. 28 clinicians and scientists met the criteria for experts. 25 (89%) of 28 experts replied to Round 1, 18 (64%) of 28 to Round 2, 19 (68%) of 28 to Round 3, and 21 (75%) of 28 to at least two rounds. High-level consensus (79-100% agreement and IQRs ≤1) was reached for all definitions. Consensus definitions will foster harmonised scientific and clinical communication and support future research and development of management guidelines for schistosomiasis.

Accuracy and precision of dried urine spot method for the detection of Schistosoma mansoni circulating cathodic antigens in resource-limited settings

BACKGROUND

The World Health Organization recommends the use of Schisto point-of-care circulating cathodic antigens (Schisto POC-CCA) for screening of Schistosoma mansoni as it offers better sensitivity than microscopy. However, there are limitation facing the use of this method including timely availability of the test cassettes. The aim of this study was to determine the reliability of dried urine spot (DUS) method for collection of urine and detection of S. mansoni using Schisto POC-CCA cassettes in a resource-limited settings.

METHODS

A cross-sectional study was conducted between October and November 2022 among 250 primary school children in Sengerema District, northwestern Tanzania. S. mansoni CCA was detected in filter paper-based DUS, liquid urine using DUS Schisto POC-CCA (index), and direct urine Schisto POC-CCA (comparator) methods respectively. S. mansoni eggs in stool were detected using duplicate Kato-Katz (KK) method. The measures of accuracy were computed and compared between the index and comparator methods. The strength of agreement between inter-raters precisions was tested using Cohen's kappa (k).

RESULTS

This study revealed S. mansoni prevalence rates of 28.8%, 54.0% and 50.8% by duplicate KK, direct urine Schisto POC-CCA and DUS Schisto POC-CCA methods respectively. The mean intensity of infection among infected participants was 86.3 eggs per gram of stool (EPG) ranging from 12.0 EPG to 824.0 EPG. The sensitivity of DUS Schisto POC-CCA and direct urine Schisto POC-CCA was 94.44% (95% CI: 89.15-99.74%) and 97.22% (95% CI: 93.43-100.00%) respectively. The DUS Schisto POC-CCA method had slightly higher specificity (66.85%) than direct urine Schisto POC-CCA method (63.48%). The accuracy of the DUS Schisto POC-CCA was found to be slightly high (74.80%, 95% CI: 68.94-79.06%) compared to that of direct urine Schisto POC-CCA (73.20%, 95% CI: 67.25-78.59%). There was good agreement between two laboratory technologists who performed the DUS Schisto POC-CCA method on similar samples (k = 0.80, 95% CI: 0.59-0.95).

CONCLUSIONS

The DUS Schisto POC-CCA method had comparable S. mansoni detection accuracy to direct urine Schisto POC-CCA. This suggests that the method could be a potential alternative to direct urine Schisto POC-CCA for screening S. mansoni in resource-limited situations.

Validation of artificial intelligence-based digital microscopy for automated detection of Schistosoma haematobium eggs in urine in Gabon

INTRODUCTION

Schistosomiasis is a significant public health concern, especially in Sub-Saharan Africa. Conventional microscopy is the standard diagnostic method in resource-limited settings, but with limitations, such as the need for expert microscopists. An automated digital microscope with artificial intelligence (Schistoscope), offers a potential solution. This field study aimed to validate the diagnostic performance of the Schistoscope for detecting and quantifying Schistosoma haematobium eggs in urine compared to conventional microscopy and to a composite reference standard (CRS) consisting of real-time PCR and the up-converting particle (UCP) lateral flow (LF) test for the detection of schistosome circulating anodic antigen (CAA).

METHODS

Based on a non-inferiority concept, the Schistoscope was evaluated in two parts: study A, consisting of 339 freshly collected urine samples and study B, consisting of 798 fresh urine samples that were also banked as slides for analysis with the Schistoscope. In both studies, the Schistoscope, conventional microscopy, real-time PCR and UCP-LF CAA were performed and samples with all the diagnostic test results were included in the analysis. All diagnostic procedures were performed in a laboratory located in a rural area of Gabon, endemic for S. haematobium.

RESULTS

In study A and B, the Schistoscope demonstrated a sensitivity of 83.1% and 96.3% compared to conventional microscopy, and 62.9% and 78.0% compared to the CRS. The sensitivity of conventional microscopy in study A and B compared to the CRS was 61.9% and 75.2%, respectively, comparable to the Schistoscope. The specificity of the Schistoscope in study A (78.8%) was significantly lower than that of conventional microscopy (96.4%) based on the CRS but comparable in study B (90.9% and 98.0%, respectively).

CONCLUSION

Overall, the performance of the Schistoscope was non-inferior to conventional microscopy with a comparable sensitivity, although the specificity varied. The Schistoscope shows promising diagnostic accuracy, particularly for samples with moderate to higher infection intensities as well as for banked sample slides, highlighting the potential for retrospective analysis in resource-limited settings.

TRIAL REGISTRATION

NCT04505046 ClinicalTrials.gov.

Transcriptome analysis of peripheral blood of Schistosoma mansoni infected children from the Albert Nile region in Uganda reveals genes implicated in fibrosis pathology

Over 290 million people are infected by schistosomes worldwide. Schistosomiasis control efforts focus on mass drug treatment with praziquantel (PZQ), a drug that kills the adult worm of all Schistosoma species. Nonetheless, re-infections have continued to be detected in endemic areas with individuals living in the same area presenting with varying infection intensities. Our objective was to characterize the transcriptome profiles in peripheral blood of children between 10-15 years with varying intensities of Schistosoma mansoni infection living along the Albert Nile in Uganda. RNA extracted from peripheral blood collected from 44 S. mansoni infected (34 high and 10 low by circulating anodic antigen [CAA] level) and 20 uninfected children was sequenced using Illumina NovaSeq S4 and the reads aligned to the GRCh38 human genome. Differential gene expression analysis was done using DESeq2. Principal component analysis revealed clustering of gene expression by gender when S. mansoni infected children were compared with uninfected children. In addition, we identified 14 DEGs between S. mansoni infected and uninfected individuals, 56 DEGs between children with high infection intensity and uninfected individuals, 33 DEGs between those with high infection intensity and low infection intensity and no DEGs between those with low infection and uninfected individuals. We also observed upregulation and downregulation of some DEGs that are associated with fibrosis and its regulation. These data suggest expression of fibrosis associated genes as well as genes that regulate fibrosis in S. mansoni infection. The relatively few significant DEGS observed in children with schistosomiasis suggests that chronic S. mansoni infection is a stealth infection that does not stimulate a strong immune response.

Variants of IL6, IL10, FCN2, RNASE3, IL12B and IL17B loci are associated with Schistosoma mansoni worm burden in the Albert Nile region of Uganda

BACKGROUND

Individuals genetically susceptible to high schistosomiasis worm burden may contribute disproportionately to transmission and could be prioritized for control. Identifying genes involved may guide development of therapy.

METHODOLOGY/PRINCIPAL FINDINGS

A cohort of 606 children aged 10-15 years were recruited in the Albert Nile region of Uganda and assessed for Schistosoma mansoni worm burden using the Up-Converting Particle Lateral Flow (UCP-LF) test detecting circulating anodic antigen (CAA), point-of-care Circulating Cathodic Antigen (POC-CCA) and Kato-Katz tests. Whole genome genotyping was conducted on 326 children comprising the top and bottom 25% of worm burden. Linear models were fitted to identify variants associated with worm burden in preselected candidate genes. Expression quantitative trait locus (eQTL) analysis was conducted for candidate genes with UCP-LF worm burden included as a covariate. Single Nucleotide Polymorphism loci associated with UCP-LF CAA included IL6 rs2066992 (OR = 0.43, p = 0.0006) and rs7793163 (OR = 2.0, p = 0.0007); IL21 SNP kgp513476 (OR 1.79, p = 0.0025) and IL17B SNP kgp708159 (OR = 0.35, p = 0.0028). A haplotype in the IL10 locus was associated with lower worm burden (OR = 0.53, p = 0.015) and overlapped SNPs rs1800896, rs1800871 and rs1800872. Significant haplotypes (p<0.05, overlapping significant SNP) associated with worm burden were observed in IL6 and the Th17 pathway IL12B and IL17B genes. There were significant eQTL in the IL6, IL5, IL21, IL25 and IFNG regions.

CONCLUSIONS

Variants associated with S. mansoni worm burden were in IL6, FCN2, RNASE3, IL10, IL12B and IL17B gene loci. However only eQTL associations remained significant after Bonferroni correction. In summary, immune balance, pathogen recognition and Th17 pathways may play a role in modulating Schistosoma worm burden. Individuals carrying risk variants may be targeted first in allocation of control efforts to reduce the burden of schistosomiasis in the community.

Dried urine spot method for detection of Schistosoma mansoni circulating cathodic antigen in resource-limited settings: a proof of concept study

Background

Among the challenges in schistosomiasis surveillance and mapping surveys is the lack of a sensitive diagnostic method especially in low transmission setting. Currently, the WHO recommends the use point-of-care circulating cathodic antigen (Schisto POC-CCA) tests for surveillance and mapping of intestinal schistosomiasis. However, Schisto POC-CCA test has its drawbacks, one of which is the timely availability of test kits. One approach to overcoming this challenge is to develop a low-cost sampling method that allows for the collection and transport of urine specimens even in resource-limited settings.

Objective

To develop a simple and efficient method for the collection and detection of Schistosoma mansoni (S. mansoni) CCA using urine spotted onto filter paper.

Methodology

To develop a dried urine spot (DUS) method, various dried matrix extraction parameters were tested and optimized using predesigned steps. The parameters include the size of filter paper (determined by the number of punches), volume of solvents, and type of solvent. Moreover, we optimized the incubation conditions (time and temperature). Urine and stool specimens to conduct the experiments were collected from volunteer fishermen in Mwanza and this project staff. Data were entered into the Microsoft Excel spreadsheet and IBM Statistical Package for the Social Sciences, version 20 for analysis.

Results

The optimal results were obtained when the procedure was run under the following conditions: Five punches of filter paper containing DUS were dissolved in 150 µl of distilled water and incubated at room temperature for 24 hours in an Eppendorf tube. More than 93% of the assays performed under these conditions produced results that were either comparable to or significantly better than the standard method.

Conclusion

This study demonstrates the feasibility of collecting urine specimen (DUS) using filter paper and detecting Schistosoma CCA from DUS specimen using the Schisto POC-CCA cassette test.

Performance evaluation of the AiDx multi-diagnostic automated microscope for the detection of schistosomiasis in Abuja, Nigeria

In this research, we report on the performance of automated optical digital detection and quantification of Schistosoma haematobium provided by AiDx NTDx multi-diagnostic Assist microscope. Our study was community-based, and a convenient sampling method was used in 17 communities in Abuja Nigeria, based on the disease prevalence information extracted from the baseline database on schistosomiasis, NTD Division, of the Federal Ministry of Health. At baseline, samples from 869 participants were evaluated of which 358 (34.1%) tested S. haematobium positive by the reference diagnostic standard. Registered images from the fully automated (autofocusing, scanning, image registration and processing, AI image analysis and automatic parasite count) AiDx assist microscope were analyzed. The Semi automated (autofocusing, scanning, image registration & processing and manual parasite count) and the fully automated AiDx Assist showed comparable sensitivities and specificities of [90.3%, 98%] and [89%, 99%] respectively. Overall, estimated egg counts of the semi-automated & fully automated AiDx Assist correlated significantly with the egg counts of conventional microscopy (r = 0.93, p ≤ 0.001 and r = 0.89, p ≤ 0.001 respectively). The AiDx Assist device performance is consistent with requirement of the World Health Organization diagnostic target product profile for monitoring, evaluation, and surveillance of Schistosomiasis elimination Programs.

The long road to schistosomiasis elimination in Zanzibar: A systematic review covering 100 years of research, interventions and control milestones

Zanzibar is among the few places in sub-Saharan Africa where interruption of Schistosoma transmission seems an achievable goal. Our systematic review identifies and discusses milestones in schistosomiasis research, control and elimination efforts in Zanzibar over the past 100 years. The search in online databases, libraries, and the World Health Organization Archives revealed 153 records published between May 1928 and August 2022. The content of records was summarised to highlight the pivotal work leading towards urogenital schistosomiasis elimination and remaining research gaps. The greatest achievement following 100 years of schistosomiasis interventions and research is undoubtedly the improved health of Zanzibaris, exemplified by the reduction in Schistosoma haematobium prevalence from>50% historically down to<5% in 2020, and the absence of severe morbidities. Experiences from Zanzibar have contributed to global schistosomiasis guidelines, whilst also revealing challenges that impede progression towards elimination. Challenges include: transmission heterogeneity requiring micro-targeting of interventions, post-treatment recrudescence of infections in transmission hotspots, biological complexity of intermediate host snails, emergence of livestock Schistosoma species complicating surveillance whilst creating the risk for interspecies hybridisation, insufficient diagnostics performance for light intensity infections and female genital schistosomiasis, and a lack of acceptable sanitary alternatives to freshwater bodies. Our analysis of the past revealed that much can be achieved in the future with practical implementation of integrated interventions, alongside operational research. With continuing national and international commitments, interruption of S. haematobium transmission across both islands is within reach by 2030, signposting the future demise of urogenital schistosomiasis across other parts of sub-Saharan Africa.

Schistosoma mansoni infection alters the host pre-vaccination environment resulting in blunted Hepatitis B vaccination immune responses

Schistosomiasis is a disease caused by parasitic flatworms of the Schistosoma spp., and is increasingly recognized to alter the immune system, and the potential to respond to vaccines. The impact of endemic infections on protective immunity is critical to inform vaccination strategies globally. We assessed the influence of Schistosoma mansoni worm burden on multiple host vaccine-related immune parameters in a Ugandan fishing cohort (n = 75) given three doses of a Hepatitis B (HepB) vaccine at baseline and multiple timepoints post-vaccination. We observed distinct differences in immune responses in instances of higher worm burden, compared to low worm burden or non-infected. Concentrations of pre-vaccination serum schistosome-specific circulating anodic antigen (CAA), linked to worm burden, showed a significant bimodal distribution associated with HepB titers, which was lower in individuals with higher CAA values at month 7 post-vaccination (M7). Comparative chemokine/cytokine responses revealed significant upregulation of CCL19, CXCL9 and CCL17 known to be involved in T cell activation and recruitment, in higher CAA individuals, and CCL17 correlated negatively with HepB titers at month 12 post-vaccination. We show that HepB-specific CD4+ T cell memory responses correlated positively with HepB titers at M7. We further established that those participants with high CAA had significantly lower frequencies of circulating T follicular helper (cTfh) subpopulations pre- and post-vaccination, but higher regulatory T cells (Tregs) post-vaccination, suggesting changes in the immune microenvironment in high CAA could favor Treg recruitment and activation. Additionally, we found that changes in the levels of innate-related cytokines/chemokines CXCL10, IL-1β, and CCL26, involved in driving T helper responses, were associated with increasing CAA concentration. This study provides further insight on pre-vaccination host responses to Schistosoma worm burden which will support our understanding of vaccine responses altered by pathogenic host immune mechanisms and memory function and explain abrogated vaccine responses in communities with endemic infections.

Emerging biomedical tools for biomarkers detection and diagnostics in schistosomiasis

Schistosomiasis is a neglected disease that strikes many people from tropical and subtropical countries where there are not satisfactory sanitation and wide access to clean water. Schistosoma spp., the causative agents of schistosomiasis, exhibit a quite complex life cycle that involves two hosts (humans and snails, respectively, the definitive and the intermediate), and five evolutive forms: cercariae (human infective form), schistosomula, adult worms, eggs, and miracidia. The techniques to diagnose schistosomiasis still have various limitations, mainly regarding low-intensity infections. Although various mechanisms associated with schistosomiasis have already been evidenced, there is still a need to fulfill the comprehension of this disease, especially to prospect for novel biomarkers to improve its diagnosis. Developing methods with more sensitivity and portability to detect the infection is valuable to reach schistosomiasis control. In this context, this review has gathered information not only on schistosomiasis biomarkers but also on emerging optical and electrochemical tools proposed in selected studies from about the last ten years. Aspects of the assays regarding the sensibility, specificity, and time needed for detecting diverse biomarkers are described. We hope this review can guide future developments in the field of schistosomiasis, contributing to improving its diagnosis and eradication.

Sensitivity and specificity of human point-of-care circulating cathodic antigen (POC-CCA) test in African livestock for rapid diagnosis of schistosomiasis: A Bayesian latent class analysis

Schistosomiasis is a major neglected tropical disease (NTD) affecting both humans and animals. The morbidity and mortality inflicted upon livestock in the Afrotropical region has been largely overlooked, in part due to a lack of validated sensitive and specific tests, which do not require specialist training or equipment to deliver and interpret. As stressed within the recent WHO NTD 2021-2030 Roadmap and Revised Guideline for schistosomiasis, inexpensive, non-invasive, and sensitive diagnostic tests for livestock-use would also facilitate both prevalence mapping and appropriate intervention programmes. The aim of this study was to assess the sensitivity and specificity of the currently available point-of-care circulating cathodic antigen test (POC-CCA), designed for Schistosoma mansoni detection in humans, for the detection of intestinal livestock schistosomiasis caused by Schistosoma bovis and Schistosoma curassoni. POC-CCA, together with the circulating anodic antigen (CAA) test, miracidial hatching technique (MHT) and organ and mesentery inspection (for animals from abattoirs only), were applied to samples collected from 195 animals (56 cattle and 139 small ruminants (goats and sheep) from abattoirs and living populations) from Senegal. POC-CCA sensitivity was greater in the S. curassoni-dominated Barkedji livestock, both for cattle (median 81%; 95% credible interval (CrI): 55%-98%) and small ruminants (49%; CrI: 29%-87%), than in S. bovis-dominated Richard Toll ruminants (cattle: 62%; CrI: 41%-84%; small ruminants: 12%, CrI: 1%-37%). Overall, sensitivity was greater in cattle than in small ruminants. Small ruminants POC-CCA specificity was similar in both locations (91%; CrI: 77%-99%), whilst cattle POC-CCA specificity could not be assessed owing to the low number of uninfected cattle surveyed. Our results indicate that, whilst the current POC-CCA does represent a potential diagnostic tool for cattle and possibly for predominantly S. curassoni-infected livestock, future work is needed to develop parasite- and/or livestock-specific affordable and field-applicable diagnostic tests to enable determination of the true extent of livestock schistosomiasis.

Visual diagnosis of female genital schistosomiasis in Zambian women from hand-held colposcopy: agreement of expert image review and association with clinical symptoms

Background: Female genital schistosomiasis (FGS) can occur in  S. haematobium infection and is caused by egg deposition in the genital tract. Confirming a diagnosis of FGS is challenging due to the lack of a diagnostic reference standard. A 2010 expert-led consensus meeting proposed visual inspection of the cervicovaginal mucosa as an adequate reference standard for FGS diagnosis. The agreement of expert human reviewers for visual-FGS has not been previously described. Methods: In two Zambian communities, non-menstruating, non-pregnant, sexually-active women aged 18-31 years participating in the HPTN 071 (PopART) Population-Cohort were enrolled in a cross-sectional study. Self-collected genital swabs and a urine specimen were collected at a home visit; trained midwives performed cervicovaginal lavage (CVL) and hand-held colposcopy at a clinic visit.  S. haematobium eggs and circulating anodic antigen (CAA) were detected from urine. Two senior physicians served as expert reviewers and independently diagnosed visual-FGS as the presence of sandy patches, rubbery papules or abnormal blood vessels in cervicovaginal images obtained by hand-held colposcopy. PCR-FGS was defined as  Schistosoma DNA detected by real-time PCR in any genital specimen (CVL or genital swab).  Results: Of 527 women with cervicovaginal colposcopic images, 468/527 (88.8%) were deemed interpretable by Reviewer 1 and 417/527 (79.1%) by Reviewer 2. Visual-FGS was detected in 35.3% (165/468) of participants by expert review of colposcopic images by Reviewer 1 and in 63.6% (265/417) by Reviewer 2. Cohen's kappa statistic for agreement between the two reviewers was 0.16, corresponding to "slight" agreement. The reviewers made concordant diagnoses in 38.7% (204/527) participants (100 negative, 104 positive) and discordant diagnoses in 31.8% (168/527) participants. Conclusions: The unexpectedly low level of correlation between expert reviewers highlights the imperfect nature of visual diagnosis for FGS based on cervicovaginal images. This finding is a call to action for improved point-of-care diagnostics for female genital schistosomiasis.

UCP-LF and other assay methods for schistosome circulating anodic antigen between 1978 and 2022

Detection of circulating anodic antigen (CAA) is known for its high sensitivity in diagnosing schistosomiasis infection, even in low-prevalence settings. The Up-Converting Phosphor-Lateral Flow (UCP-LF) assay developed in 2008 presented greater sensitivity than other assay methods in use for CAA detection. Our study aims to comprehensively review all studies conducted in this area and thus generate informed conclusions on the potential for adopting the UCP-LF assay for diagnosing this important yet neglected tropical disease. Using the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines, we generated search criteria to capture all studies in English journals available in the Scopus and PubMed databases on 20 December 2022. A total of 219 articles were identified, and 84 that met the inclusion criteria were retrieved and eventually included in the study. Twelve different assay methods were identified with a noteworthy transition from enzyme-linked immunosorbent assay (ELISA) to the UCP-LF assay, a laboratory-based assay that may be applicable as a point-of-care (POC) diagnostic test for schistosomiasis. Reducing the time, cost, and dependence on specialized laboratory skills and equipment, especially relating to the trichloroacetic acid extraction step and centrifugation in the UCP-LF CAA assay may go a long way to aid its potential as a POC tool. We also propose the development of a CAA-specific aptamer (short protein/antigen-binding oligonucleotide) as a possible alternative to monoclonal antibodies in the assay. UCP-LF has great potential for POC application.

CRISPR-assisted test for Schistosoma haematobium

Schistosomiasis is a major neglected tropical disease targeted for elimination as a public health issue by 2030, however there is an urgent need for more sensitive and specific diagnostic tests suitable to resource-limited settings. Here we developed CATSH, a CRISPR-assisted diagnostic test for Schistosoma haematobium, utilising recombinase polymerase amplification, Cas12a-targeted cleavage and portable real-time fluorescence detection. CATSH showed high analytical sensitivity, consistent detection of a single parasitic egg and specificity for urogenital Schistosoma species. Thanks to a novel CRISPR-compatible sample preparation developed using simulated urine samples containing parasitic eggs, CATSH had a sample-to-result within 2 h. The components of CATSH can be lyophilised, reducing cold chain dependence and widening access to lower and middle-income countries. This work presents a new application of CRISPR diagnostics for highly sensitive and specific detection of parasitic pathogens in remote areas and could have a significant impact on the elimination of neglected tropical diseases.

Schistosoma mansoni infection alters the host pre-vaccination environment resulting in blunted Hepatitis B vaccination immune responses

The impact of endemic infections on protective immunity is critical to inform vaccination strategies. In this study, we assessed the influence of Schistosoma mansoni infection on host responses in a Ugandan fishing cohort given a Hepatitis B (HepB) vaccine. Concentrations of schistosome-specific circulating anodic antigen (CAA) pre-vaccination showed a significant bimodal distribution associated with HepB titers, which were lower in individuals with high CAA. We established that participants with high CAA had significantly lower frequencies of circulating T follicular helper (cTfh) subpopulations pre- and post-vaccination and higher regulatory T cells (Tregs) post-vaccination. Polarization towards higher frequencies of Tregs: cTfh cells can be mediated by changes in the cytokine environment favoring Treg differentiation. In fact, we observed higher levels of CCL17 and soluble IL-2R pre-vaccination (important for Treg recruitment and development), in individuals with high CAA that negatively associated with HepB titers. Additionally, alterations in pre-vaccination monocyte function correlated with HepB titers, and changes in innate-related cytokines/chemokine production were associated with increasing CAA concentration. We report, that by influencing the immune landscape, schistosomiasis has the potential to modulate immune responses to HepB vaccination. These findings highlight multiple Schistosoma -related immune associations that could explain abrogated vaccine responses in communities with endemic infections.

Author Summary

Schistosomiasis drives host immune responses for optimal pathogen survival, potentially altering host responses to vaccine-related antigen. Chronic schistosomiasis and co-infection with hepatotropic viruses are common in countries where schistosomiasis is endemic. We explored the impact of Schistosoma mansoni ( S. mansoni ) infection on Hepatitis B (HepB) vaccination of individuals from a fishing community in Uganda. We demonstrate that high schistosome-specific antigen (circulating anodic antigen, CAA) concentration pre-vaccination, is associated with lower HepB antibody titers post-vaccination. We show higher pre-vaccination levels of cellular and soluble factors in instances of high CAA that are negatively associated with HepB antibody titers post-vaccination, which coincided with lower frequencies of circulating T follicular helper cell populations (cTfh), proliferating antibody secreting cells (ASCs), and higher frequencies of regulatory T cells (Tregs). We also show that monocyte function is important in HepB vaccine responses, and that high CAA is associated with alterations in the early innate cytokine/chemokine microenvironment. Our findings suggest that in individuals with high CAA and likely high worm burden, schistosomiasis creates and sustains an environment that is polarized against optimal host immune responses to the vaccine, which puts many endemic communities at risk for infection against HepB and other diseases that are preventable by vaccines.

A review on innovative optical devices for the diagnosis of human soil-transmitted helminthiasis and schistosomiasis: from research and development to commercialization

Diagnosis of soil-transmitted helminth (STH) and schistosome infections relies largely on conventional microscopy which has limited sensitivity, requires highly trained personnel and is error-prone. Rapid advances in miniaturization of optical systems, sensors and processors have enhanced research and development of digital and automated microscopes suitable for the detection of these diseases in resource-limited settings. While some studies have reported proof-of-principle results, others have evaluated the performance of working prototypes in field settings. The extensive commercialization of these innovative devices has, however, not yet been achieved. This review provides an overview of recent publications (2010–2022) on innovative field applicable optical devices which can be used for the diagnosis of STH and schistosome infections. Using an adapted technology readiness level (TRL) scale taking into account the WHO target product profile (TPP) for these diseases, the developmental stages of the devices were ranked to determine the readiness for practical applications in field settings. From the reviewed 18 articles, 19 innovative optical devices were identified and ranked. Almost all of the devices (85%) were ranked with a TRL score below 8 indicating that, most of the devices are not ready for commercialization and field use. The potential limitations of these innovative devices were discussed. We believe that the outcome of this review can guide the end-to-end development of automated digital microscopes aligned with the WHO TPP for the diagnosis of STH and schistosome infections in resource-limited settings.

Visual diagnosis of female genital schistosomiasis in Zambian women from hand-held colposcopy: agreement of expert image review

Female genital schistosomiasis (FGS) can occur in S. haematobium infection and is caused by parasite egg deposition in the genital tract. Confirming a diagnosis of FGS is challenging due to the lack of a diagnostic reference standard. A 2010 expert-led consensus meeting proposed visual inspection of the cervicovaginal mucosa as an adequate reference standard for FGS diagnosis. The agreement of expert human reviewers for visual-FGS has not been previously described. Methods: In two Zambian communities, non-menstruating, non-pregnant, sexually-active women aged 18-31 years participating in the HPTN 071 (PopART) Population-Cohort were enrolled in a cross-sectional study. Self-collected genital swabs and a urine specimen were collected at a home visit; trained midwives performed CVL and hand-held colposcopy at a clinic visit. S. haematobium eggs and circulating anodic antigen (CAA) were detected from urine. Two expert reviewers independently diagnosed visual-FGS as the presence of sandy patches, rubbery papules or abnormal blood vessels in digital cervicovaginal images obtained by hand-held colposcopy. PCR-FGS was defined as Schistosoma DNA detected by real-time PCR in any genital specimen (CVL or genital swab). Results: Of 527 women with cervicovaginal colposcopic images, 468/527 (88.8%) were deemed interpretable by Reviewer 1 and 417/527 (79.1%) by Reviewer 2. Visual-FGS was detected in 35.3% (165/468) of participants by expert review of colposcopic images by Reviewer 1 and in 63.6% (265/417) by Reviewer 2. Cohen's kappa statistic for agreement between the two expert reviewers was 0.16, corresponding to "slight" agreement. The reviewers made concordant diagnoses in 38.7% (204/527) participants (100 negative, 104 positive) and discordant diagnoses in 31.8% (168/527) participants. Conclusions: The unexpectedly low level of correlation between expert reviewers highlights the imperfect nature of visual diagnosis for FGS based on cervicovaginal images obtained with a hand-held colposcope. This finding is a call to action for improved point-of-care diagnostics for female genital schistosomiasis.

Limited efficacy of repeated praziquantel treatment in Schistosoma mansoni infections as revealed by highly accurate diagnostics, PCR and UCP-LF CAA (RePST trial)

BACKGROUND

Most studies assessing praziquantel (PZQ) efficacy have used relatively insensitive diagnostic methods, thereby overestimating cure rate (CR) and intensity reduction rate (IRR). To determine accurately PZQ efficacy, we employed more sensitive DNA and circulating antigen detection methods.

METHODOLOGY

A sub-analysis was performed based on a previously published trial conducted in children from Côte d'Ivoire with a confirmed Schistosoma mansoni infection, who were randomly assigned to a standard (single dose of PZQ) or intense treatment group (4 repeated doses of PZQ at 2-week intervals). CR and IRR were estimated based on PCR detecting DNA in a single stool sample and the up-converting particle lateral flow (UCP-LF) test detecting circulating anodic antigen (CAA) in a single urine sample, and compared with traditional Kato-Katz (KK) and point-of-care circulating cathodic antigen (POC-CCA).

PRINCIPAL FINDINGS

Individuals positive by all diagnostic methods (i.e., KK, POC-CCA, PCR, and UCP-LF CAA) at baseline were included in the statistical analysis (n = 125). PCR showed a CR of 45% (95% confidence interval (CI) 32-59%) in the standard and 78% (95% CI 66-87%) in the intense treatment group, which is lower compared to the KK results (64%, 95% CI 52-75%) and 88%, 95% CI 78-93%). UCP-LF CAA showed a significantly lower CR in both groups, 16% (95% CI 11-24%) and 18% (95% CI 12-26%), even lower than observed by POC-CCA (31%, 95% CI 17-35% and 36%, 95% CI 26-47%). A substantial reduction in DNA and CAA-levels was observed after the first treatment, with no further decrease after additional treatment and no significant difference in IRR between treatment groups.

CONCLUSION/SIGNIFICANCE

The efficacy of (repeated) PZQ treatment was overestimated when using egg-based diagnostics (i.e. KK and PCR). Quantitative worm-based diagnostics (i.e. POC-CCA and UCP-LF CAA) revealed that active Schistosoma infections are still present despite multiple treatments. These results stress the need for using accurate diagnostic tools to monitor different PZQ treatment strategies, in particular when moving toward elimination of schistosomiasis.

CLINICAL TRIAL REGISTRATION

www.clinicaltrials.gov, NCT02868385.

The Presence of Hemoglobin in Cervicovaginal Lavage Is Not Associated With Genital Schistosomiasis in Zambian Women From the BILHIV Study

Background

Female genital schistosomiasis (FGS) occurs when Schistosoma haematobium eggs are deposited in reproductive tissue. Female genital schistosomiasis in the cervical mucosa is associated with increased vascularity. If FGS is associated with the presence of hemoglobin in cervicovaginal lavage (CVL), the use of urinary reagent strips to detect hemoglobin in CVL could supplement FGS diagnosis.

Methods

Nonmenstruating, nonpregnant, sexually active women aged 18-31 participating in the HPTN 071 (PopART) Population-Cohort were invited in 2 Zambian communities. Genital self-swabs and a urine specimen were collected at a home visit, and CVL and hand-held colposcopy were performed at a midwife led clinic visit. Urinary reagent strips were used to identify hemoglobin in CVL. Eggs and circulating anodic antigen (CAA) were detected from urine. Visual-FGS was defined as the presence of sandy patches, rubbery papules, or abnormal blood vessels. Polymerase chain reaction (PCR)-FGS was defined as Schistosoma deoxyribonucleic acid detected by real-time PCR on CVL or cervical or vaginal swab.

Results

Of 209 women with home genital swabs and companion CVL specimens, 66% (138 of 209) had detectable CVL hemoglobin, 13.4% (28 of 209) had PCR-defined FGS, and 17.2% (36 of 209) had visual-FGS. Active Schistosoma infection, diagnosed by CAA or urine microscopy, was present in 21.0% (44 of 209) participants. Active Schistosoma infection (P = .4), PCR-FGS (P = 0.7), and visual-FGS (P = 0.3) were not associated with CVL hemoglobin presence. Results did not differ in subgroups with high infection burden (cycle threshold < 35 or 2-3 positive genital PCR).

Conclusions

Polymerase chain reaction-FGS, visual-FGS, and active Schistosoma infection were not associated with the presence of CVL hemoglobin. Further research is needed to establish accessible community-based FGS diagnostics.

Establishing and Integrating a Female Genital Schistosomiasis Control Programme into the Existing Health Care System

Female genital schistosomiasis (FGS) is a complication of Schistosoma haematobium infection, and imposes a health burden whose magnitude is not fully explored. It is estimated that up to 56 million women in sub-Saharan Africa have FGS, and almost 20 million more cases will occur in the next decade unless infected girls are treated. Schistosomiasis is reported throughout the year in South Africa in areas known to be endemic, but there is no control programme. We analyze five actions for both a better understanding of the burden of FGS and reducing its prevalence in Africa, namely: (1) schistosomiasis prevention by establishing a formal control programme and increasing access to treatment, (2) introducing FGS screening, (3) providing knowledge to health care workers and communities, (4) vector control, and (5) water, sanitation, and hygiene. Schistosomiasis is focal in South Africa, with most localities moderately affected (prevalence between 10% and 50%), and some pockets that are high risk (more than 50% prevalence). However, in order to progress towards elimination, the five actions are yet to be implemented in addition to the current (and only) control strategy of case-by-case treatment. The main challenge that South Africa faces is a lack of access to WHO-accredited donated medication for mass drug administration. The establishment of a formal and funded programme would address these issues and begin the implementation of the recommended actions.

Diagnosis of Schistosomiasis without a Microscope: Evaluating Circulating Antigen (CCA, CAA) and DNA Detection Methods on Banked Samples of a Community-Based Survey from DR Congo

Detection of Schistosoma eggs in stool or urine is known for its low sensitivity in diagnosing light infections. Alternative diagnostics with better sensitivity while remaining highly specific, such as real-time PCR and circulating antigen detection, are progressively used as complementary diagnostic procedures but have not yet replaced microscopy. This study evaluates these alternative methods for the detection of Schistosoma infections in the absence of microscopy. Schistosomiasis presence was determined retrospectively in 314 banked stool and urine samples, available from a previous survey on the prevalence of taeniasis in a community in the Democratic Republic of the Congo, using real-time PCR, the point-of-care circulating cathodic antigen (POC-CCA) test, as well as the up-converting particle lateral flow circulating anodic antigen (UCP-LF CAA) test. Schistosoma DNA was present in urine (3%) and stool (28%) samples, while CCA (28%) and CAA (69%) were detected in urine. Further analysis of the generated data indicated stool-based PCR and the POC-CCA test to be suitable diagnostics for screening of S. mansoni infections, even in the absence of microscopy. A substantial proportion (60%) of the 215 CAA-positive cases showed low antigen concentrations, suggesting that even PCR and POC-CCA underestimated the “true” number of schistosome positives.

A review of the genetic determinants of praziquantel resistance in Schistosoma mansoni: Is praziquantel and intestinal schistosomiasis a perfect match?

Schistosomiasis is a neglected tropical disease (NTD) caused by parasitic trematodes belonging to the Schistosoma genus. The mainstay of schistosomiasis control is the delivery of a single dose of praziquantel (PZQ) through mass drug administration (MDA) programs. These programs have been successful in reducing the prevalence and intensity of infections. Due to the success of MDA programs, the disease has recently been targeted for elimination as a public health problem in some endemic settings. The new World Health Organization (WHO) treatment guidelines aim to provide equitable access to PZQ for individuals above two years old in targeted areas. The scale up of MDA programs may heighten the drug selection pressures on Schistosoma parasites, which could lead to the emergence of PZQ resistant schistosomes. The reliance on a single drug to treat a disease of this magnitude is worrying should drug resistance develop. Therefore, there is a need to detect and track resistant schistosomes to counteract the threat of drug resistance to the WHO 2030 NTD roadmap targets. Until recently, drug resistance studies have been hindered by the lack of molecular markers associated with PZQ resistance. This review discusses recent significant advances in understanding the molecular basis of PZQ action in S. mansoni and proposes additional genetic determinants associated with PZQ resistance. PZQ resistance will also be analyzed in the context of alternative factors that may decrease efficacy within endemic field settings, and the most recent treatment guidelines recommended by the WHO.

Untargeted serum metabolomic profiling for early detection of Schistosoma mekongi infection in mouse model

Mekong schistosomiasis is a parasitic disease caused by blood flukes in the Lao People’s Democratic Republic and in Cambodia. The standard method for diagnosis of schistosomiasis is detection of parasite eggs from patient samples. However, this method is not sufficient to detect asymptomatic patients, low egg numbers, or early infection. Therefore, diagnostic methods with higher sensitivity at the early stage of the disease are needed to fill this gap. The aim of this study was to identify potential biomarkers of early schistosomiasis using an untargeted metabolomics approach. Serum of uninfected and S. mekongi-infected mice was collected at 2, 4, and 8 weeks post-infection. Samples were extracted for metabolites and analyzed with a liquid chromatography-tandem mass spectrometer. Metabolites were annotated with the MS-DIAL platform and analyzed with Metaboanalyst bioinformatic tools. Multivariate analysis distinguished between metabolites from the different experimental conditions. Biomarker screening was performed using three methods: correlation coefficient analysis; feature important detection with a random forest algorithm; and receiver operating characteristic (ROC) curve analysis. Three compounds were identified as potential biomarkers at the early stage of the disease: heptadecanoyl ethanolamide; picrotin; and theophylline. The levels of these three compounds changed significantly during early-stage infection, and therefore these molecules may be promising schistosomiasis markers. These findings may help to improve early diagnosis of schistosomiasis, thus reducing the burden on patients and limiting spread of the disease in endemic areas.

Identification of a linear B-cell epitope on the Schistosoma japonicum saposin protein, SjSAP4: Potential as a component of a multi-epitope diagnostic assay

Background

Schistosoma japonicum is one of three major species of blood flukes causing schistosomiasis, a disease, which continues to be a major public health issue in the Philippines. SjSAP4, a member of a multigene family of saposin-like proteins, is a recognized immunodiagnostic biomarker for schistosomiasis japonica. This study aimed to identify linear B-cell epitopes on SjSAP4 and to validate their potential as components of a multi-epitope assay for the serological diagnosis of schistosomiasis japonica.

Methodology

SjSAP4-derived peptides were expressed as GST-peptide-fused proteins and these were Western blot probed with human serum samples from S. japonicum Kato-Katz (KK)-positive individuals and uninfected controls. A core epitope was further identified by Western blotting through probing a series of truncated peptides with the schistosomiasis patient sera. The diagnostic performance of the core epitope-containing peptides and the full-length SjSAP4 was evaluated by enzyme-linked immunosorbent assay (ELISA) using a panel of sera collected from subjects resident in a schistosomiasis-endemic area of the Philippines.

Main findings

As a result of the peptide mapping, one peptide (P15) was found to be highly immunogenic in the KK-positive individuals. We subsequently showed that -S¹⁶³QCSLVGDIFVDKYLD¹⁷⁸- is a core B-cell epitope of P15. Subsequent ELISAs incorporating SjSAP4, SjSAP4-Peptide and SjSP-13V2-Peptide showed a sensitivity of 94.0%, 46.0% and 74.0%, respectively, and a specificity of 97.1%, 100% and 100%, respectively. Notably, complementary recognition of the B-cell epitopes (SjSAP4-Peptide and SjSP-13V2-Peptide) was observed in a subset of the KK-positive individuals. A dual epitope-ELISA (SjSAP4-Peptide + SjSP-13V2-Peptide-ELISA) showed a diagnostic sensitivity of 84.0% and a specificity of 100%.

Conclusions/Significance

In this study, -S¹⁶³QCSLVGDIFVDKYLD¹⁷⁸- was identified as a dominant linear B-cell epitope on SjSAP4. This peptide and the complementary recognition of other B-cell epitopes using sera from different KK-positive individuals can provide the basis of developing a multi-epitope assay for the serological diagnosis of schistosomiasis.

The recent road map (2021–2030) released by WHO for controlling or eliminating neglected tropical diseases (NTDs) highlights diagnostics as a major focus. Development and deployment of accurate, affordable and field-friendly diagnostics/surveillance tools will be crucial for the control and elimination of schistosomiasis. Multi-epitope chimeric antigens, constructed based on linear B-cell epitopes identified from highly antigenic antigens, may achieve not only an equivalent or superior diagnostic performance compared to the parent immunogens but also exhibit more optimal physicochemical properties. However, to date, only a limited number of linear B-cell epitopes have been identified for the serological diagnosis of schistosomiasis. In this study, we identified a linear B-cell epitope (-S¹⁶³QCSLVGDIFVDKYLD¹⁷⁸-) on SjSAP4, a recognized immunodiagnostic biomarker for schistosomiasis japonica, and validated its potential as a component of a multi-epitope assay for the serological diagnosis of schistosomiasis japonica. Notably, differential recognition of B-cell epitopes (SjSAP4-Peptide and SjSP-13V2-Peptide) was observed in a subset of subjects positive by the Kato-Katz technique for the disease. A dual epitope-ELISA (SjSAP4-Peptide + SjSP-13V2-Peptide-ELISA) showed a superior diagnostic performance (84.0% sensitivity and 100% specificity) than individual-epitope ELISAs. The findings in this study provide support for the development of multi-epitope antigen-based diagnostics for schistosomiasis.

High prevalence of Schistosoma mansoni infection and stunting among school age children in communities along the Albert-Nile, Northern Uganda: A cross sectional study

BACKGROUND

Knowing the prevalence of schistosomiasis is key to informing programmes to control and eliminate the disease as a public health problem. It is also important to understand the impact of infection on child growth and development in order to allocate appropriate resources and effort to the control of the disease.

METHODS

We conducted a survey to estimate the prevalence of schistosomiasis among school aged children in villages along the Albert-Nile shore line in the district of Pakwach, North Western Uganda. A total of 914 children aged between 10-15 years were screened for Schistosoma mansoni using the POC-CCA and Kato Katz (KK) techniques. The infection intensities were assessed by POC-CCA and KK as well as CAA tests. The KK intensities were also correlated with POC-CCA and with CAA intensity. Anthropometric measurements were also taken and multivariate analysis was carried out to investigate their association with infection status.

RESULTS

The prevalence of schistosomiasis using the POC-CCA diagnostic test was estimated at 85% (95% CI: 83-87), being highest amongst children living closer to the Albert-Nile shoreline. Visual scoring of the POC-CCA results was more sensitive than the Kato Katz test and was positively correlated with the quantified infection intensities by the CAA test. The majority of the children were underweight (BMI<18.5), and most notably, boys had significantly lower height for age (stunting) than girls in the same age range (p < 0.0001), but this was not directly associated with S. mansoni infection.

CONCLUSION

High prevalence of S. mansoni infection in the region calls for more frequent mass drug administration with praziquantel. We observed high levels of stunting which was not associated with schistosomiasis. There is a need for improved nutrition among the children in the area.

Research on Schistosomiasis in the Era of the COVID-19 Pandemic: A Bibliometric Analysis

The objectives of this work are to check whether the COVID-19 pandemic affected the research on schistosomiasis, to provide an insight into the most productive countries and journals and the most cited publications, and to analyse any association between the total publications of countries and a set of socio-economic and demographic factors. Based on PRISMA methodology, we used the Scopus database to search for articles published between 1 January 2020 and 26 March 2022. VOSviewer was used to generate the co-authorship and the co-occurrence networks, and Spearman’s rank correlation was applied to study associations. A total of 1988 articles were included in the study. Although we found that the year-wise distribution of publications suggests no impact on schistosomiasis research, many resources have been devoted to research on COVID-19, and the Global Schistosomiasis Alliance revealed the main activities for eradication of schistosomiasis had been affected. The most productive country was the United States of America. The articles were mainly published in PLoS Neglected Tropical Diseases. The most prolific funding institution was the National Natural Science Foundation of China. The total publications per country were significantly correlated with population, GERD, and researchers per million inhabitants, but not with GDP per capita and MPM.

Performance of a rapid immuno-chromatographic test (Schistosoma ICT IgG-IgM) for detecting Schistosoma-specific antibodies in sera of endemic and non-endemic populations

Background

Schistosomiasis, an acute and chronic parasitic disease caused by human pathogenic Schistosoma species, is a neglected tropical disease affecting more than 220 million people worldwide.

For diagnosis of schistosomiasis, stool and urine microscopy for egg detection is still the recommended method, however sensitivity of these methods is limited. Therefore, other methods like molecular detection of DNA in stool, detection of circulating cathodic antigen in urine or circulating anodic antigen in urine and serum, as well as serological tests have gained more attention. This study examines the sensitivity and specificity of a rapid diagnostic test based on immunochromatography (Schistosoma ICT IgG-IgM, LD Bio, Lyon, France) for simultaneous detection of specific IgG and IgM antibodies in serum, against Schistosoma spp. in endemic and non-endemic populations.

Methodology/Principal findings

Frozen banked serum samples from patients with confirmed schistosomiasis, patients with other helminth infections, patients with seropositive rheumatoid arthritis and healthy blood donors were used to assess the sensitivity and the specificity of the Schistosoma ICT IgG-IgM rapid diagnostic test.

The test showed a sensitivity of 100% in patients with parasitologically confirmed schistosomiasis, irrespective of the species (S. mansoni, S. haematobium, S. japonicum, S. mekongi). In healthy blood donors and patients with rheumatoid factor positive rheumatoid arthritis from Europe, specificity was 100%. However, in serum samples of patients with other tissue invasive helminth infections, the test showed some cross-reactivity, resulting in a specificity of 85%.

Conclusion/Significance

With its high sensitivity, the Schistosoma ICT IgG-IgM rapid diagnostic test is a suitable screening test for detection of Schistosoma specific antibodies, including S. mekongi. However, in populations with a high prevalence of co-infection with other tissue invasive helminths, positive results should be confirmed with other diagnostic assays due to the test’s imperfect specificity.

The Road to Elimination: Current State of Schistosomiasis Research and Progress Towards the End Game

The new WHO Roadmap for Neglected Tropical Diseases targets the global elimination of schistosomiasis as a public health problem. To date, control strategies have focused on effective diagnostics, mass drug administration, complementary and integrative public health interventions. Non-mammalian intermediate hosts and other vertebrates promote transmission of schistosomiasis and have been utilized as experimental model systems. Experimental animal models that recapitulate schistosomiasis immunology, disease progression, and pathology observed in humans are important in testing and validation of control interventions. We discuss the pivotal value of these models in contributing to elimination of schistosomiasis. Treatment of schistosomiasis relies heavily on mass drug administration of praziquantel whose efficacy is comprised due to re-infections and experimental systems have revealed the inability to kill juvenile schistosomes. In terms of diagnosis, nonhuman primate models have demonstrated the low sensitivity of the gold standard Kato Katz smear technique. Antibody assays are valuable tools for evaluating efficacy of candidate vaccines, and sera from graded infection experiments are useful for evaluating diagnostic sensitivity of different targets. Lastly, the presence of Schistosomes can compromise the efficacy of vaccines to other infectious diseases and its elimination will benefit control programs of the other diseases. As the focus moves towards schistosomiasis elimination, it will be critical to integrate treatment, diagnostics, novel research tools such as sequencing, improved understanding of disease pathogenesis and utilization of experimental models to assist with evaluating performance of new approaches.

Female Genital Schistosomiasis Lesions Explored Using Circulating Anodic Antigen as an Indicator for Live Schistosoma Worms

Background

In areas where reinfection with schistosomiasis is rampant, it is not known if the lesions of Female Genital Schistosomaisis are a consequence of live worms, or caused by dead ova. Live schistosome worms regurgitate Circulating Anodic Antigen (CAA). We sought to explore the association between the different lesions of FGS (grainy sandy patches, homogenous yellow patches, rubbery papules and abnormal blood vessels) and the presence of live worms as indicated by S. haematobium-derived CAA in blood.

Materials and Methods

In this cross-sectional study, rural high schools were randomly selected from Ilembe, uThungulu and Ugu Districts on the East Coast of South Africa, KwaZulu-Natal Province. Serum samples for CAA analysis were collected from 246 female learners aged 16 - 23 years. Uncorrected chi-square and odds ratio with 95% confidence interval (CI) were used to evaluate the null hypothesis.

Results

CAA was positive in 82/246 (33%) of the participants. Sandy patches were found in 123 (50%) of the study population. Grainy sandy patches were significantly associated with CAA even after controlling for age (Adjusted Odds Ratio (AOR) 4.2, 95% CI 2.3 - 7.9, p &lt; 0.001). Likewise, abnormal blood vessels were associated with CAA (AOR 3.0, 95% CI 1.5-4.5, p = 0.001) whereas homogenous yellow patches were not associated with CAA (p = 0.57). Rubbery papules were not found in this study population.

Conclusion

Grainy sandy patches and abnormal blood vessels are found more commonly in women who harbour live Schistosoma haematobium worms whilst homogenous yellow patches may indicate chronic tissue damage due to dead ova.

National mapping of schistosomiasis, soil-transmitted helminthiasis and anaemia in Yemen: Towards better national control and elimination

BACKGROUND

Schistosomiasis (SCH) and soil-transmitted helminthiasis (STH) are known to be endemic in Yemen. However, the distribution of both diseases had not previously been assessed by a well-structured national mapping study covering all governorates. The main aim of this study was, therefore, to map the prevalence of SCH and STH in Yemen in order to better inform implementation of effective national control and elimination interventions. The assessment of the distribution of anaemia was also included as a well-known consequence of infection with both SCH and STH. Secondarily, the study aimed to provide a broad indication of the impact of large-scale treatment on the distribution of infection.

METHODOLOGY AND PRINCIPAL FINDINGS

To achive these aims, 80,432 children (10-14 years old) from 2,664 schools in 332 of Yemen's 333 districts were included, in 2014, into this national cross-sectional survey. Countrywide, 63.3% (210/332) and 75.6% (251/332) of districts were found to be endemic for SCH and STH respectively. More districts were affected by intestinal than urogenital SCH (54.2% and 31.6% respectively). SCH infection was mostly mild and moderate, with no districts reporting high infection. One quarter (24.4%) of Yemeni districts had high or moderate levels of Ascaris lumbricoides infection. Infection with Trichuris trichiura was the second most common STH (44.9% of districts infected) after A. lumbricoides (68.1%). Hookworm was the least prevalent STH (9.0%). Anaemia was prevalent in 96.4% of districts; it represented a severe public health problem (prevalence ≥ 40%) in 26.5% of districts, and a mild to moderate problem in two thirds of the districts (33.7% and 36.1% respectively).

CONCLUSION

This study provided the first comprehensive mapping of SCH, STH, and anaemia across the country. This formed the basis for evaluating and continuing the national control and elimination programme for these neglected tropical diseases in Yemen.

Validation of the isothermal Schistosoma haematobium Recombinase Polymerase Amplification (RPA) assay, coupled with simplified sample preparation, for diagnosing female genital schistosomiasis using cervicovaginal lavage and vaginal self-swab samples

BACKGROUND

Female genital schistosomiasis (FGS) is a neglected and disabling gynecological disease that can result from infection with the parasitic trematode Schistosoma haematobium. Accurate diagnosis of FGS is crucial for effective case management, surveillance and control. However, current methods for diagnosis and morbidity assessment can be inaccessible to those at need, labour intensive, costly and unreliable. Molecular techniques such as PCR can be used to reliably diagnose FGS via the detection of Schistosoma DNA using cervicovaginal lavage (CVL) samples as well as lesser-invasive vaginal self-swab (VSS) and cervical self-swab samples. PCR is, however, currently unsuited for use in most endemic settings. As such, in this study, we assessed the use of a rapid and portable S. haematobium recombinase polymerase amplification (Sh-RPA) isothermal molecular diagnostic assay, coupled with simplified sample preparation methodologies, to detect S. haematobium DNA using CVL and VSS samples provided by patients in Zambia.

METHODOLOGY/PRINCIPAL FINDINGS

VSS and CVL samples were screened for FGS using a previously developed Sh-RPA assay. DNA was isolated from VSS and CVL samples using the QIAamp Mini kit (n = 603 and 527, respectively). DNA was also isolated from CVL samples using two rapid and portable DNA extraction methods: 1) the SpeedXtract Nucleic Acid Kit (n = 223) and 2) the Extracta DNA Tissue Prep Kit (n = 136). Diagnostic performance of the Sh-RPA using VSS DNA extacts (QIAamp Mini kit) as well as CVL DNA extracts (QIAamp Mini kit, SpeedXtract Nucleic Acid Kit and Extracta DNA Tissue Prep Kit) was then compared to a real-time PCR reference test. Results suggest that optimal performance may be achieved when the Sh-RPA is used with PuVSS samples (sensitivity 93.3%; specificity 96.6%), however no comparisons between different DNA extraction methods using VSS samples could be carried out within this study. When using CVL samples, sensitivity of the Sh-RPA ranged between 71.4 and 85.7 across all three DNA extraction methods when compared to real-time PCR using CVL samples prepared using the QIAamp Mini kit. Interestingly, of these three DNA extraction methods, the rapid and portable SpeedXtract method had the greatest sensitivity and specificity (85.7% and 98.1%, respectively). Specificity of the Sh-RPA was >91% across all comparisons.

CONCLUSIONS/SIGNIFICANCE

These results supplement previous findings, highlighting that the use of genital self-swab sampling for diagnosing FGS should be explored further whilst also demonstrating that rapid and portable DNA isolation methods can be used to detect S. haematobium DNA within clinical samples using RPA. Although further development and assessment is needed, it was concluded that the Sh-RPA, coupled with simplified sample preparation, shows excellent promise as a rapid and sensitive diagnostic tool capable of diagnosing FGS at the point-of-care in resource-poor schistosomiasis-endemic settings.

Characterisation of tetraspanins from Schistosoma haematobium and evaluation of their potential as novel diagnostic markers

Schistosoma haematobium is the leading cause of urogenital schistosomiasis and it is recognised as a class 1 carcinogen due to the robust association of infection with bladder cancer. In schistosomes, tetraspanins (TSPs) are abundantly present in different parasite proteomes and could be potential diagnostic candidates due to their accessibility to the host immune system. The large extracellular loops of six TSPs from the secretome (including the soluble excretory/secretory products, tegument and extracellular vesicles) of S. haematobium (Sh-TSP-2, Sh-TSP-4, Sh-TSP-5, Sh-TSP-6, Sh-TSP-18 and Sh-TSP-23) were expressed in a bacterial expression system and polyclonal antibodies were raised to the recombinant proteins to confirm the anatomical sites of expression within the parasite. Sh-TSP-2, and Sh-TSP-18 were identified on the tegument, whereas Sh-TSP-4, Sh-TSP-5, Sh-TSP-6 and Sh-TSP-23 were identified both on the tegument and internal tissues of adult parasites. The mRNAs encoding these TSPs were differentially expressed throughout all schistosome developmental stages tested. The potential diagnostic value of three of these Sh-TSPs was assessed using the urine of individuals (stratified by infection intensity) from an endemic area of Zimbabwe. The three Sh-TSPs were the targets of urine IgG responses in all cohorts, including individuals with very low levels of infection (those positive for circulating anodic antigen but negative for eggs by microscopy). This study provides new antigen candidates to immunologically diagnose S. haematobium infection, and the work presented here provides compelling evidence for the use of a biomarker signature to enhance the diagnostic capability of these tetraspanins.

Schistosoma haematobium, the leading cause of urogenital schistosomiasis, affects millions of people worldwide. Infection with this parasite is associated with different clinical complications such as squamous cell carcinoma and genital malignancy in women. Despite its importance, there is a lack of sensitive and specific diagnostics that support control and elimination initiatives against this devastating disease. Herein, we have characterised six molecules belonging to the tetraspanin family of membrane proteins, providing details about their relative expression during parasite’s development and their localization in adult forms of S. haematobium. Furthermore, we have characterised the antibody responses against three of these molecules in urine from infected human subjects from an endemic area, providing compelling evidence for the use of these molecules to diagnose urogenital schistosomiasis.

Mass spectrometric and glycan microarray-based characterization of the filarial nematode Brugia malayi glycome reveals anionic and zwitterionic glycan antigens

Millions of people worldwide are infected with filarial nematodes, responsible for lymphatic filariasis (LF) and other diseases causing chronic disablement. Elimination programs have resulted in a substantial reduction of the rate of infection in certain areas creating a need for improved diagnostic tools to establish robust population surveillance and avoid LF resurgence. Glycans from parasitic helminths are emerging as potential antigens for use in diagnostic assays. However, despite its crucial role in host–parasite interactions, filarial glycosylation is still largely, structurally, and functionally uncharacterized. Therefore, we investigated the glycan repertoire of the filarial nematode Brugia malayi. Glycosphingolipid and N-linked glycans were extracted from several life-stages using enzymatic release and characterized using a combination of MALDI-TOF-MS and glycan sequencing techniques. Next, glycans were purified by HPLC and printed onto microarrays to assess the host anti-glycan antibody response. Comprehensive glycomic analysis of B. malayi revealed the presence of several putative antigenic motifs such as phosphorylcholine and terminal glucuronic acid. Glycan microarray screening showed a recognition of most B. malayi glycans by immunoglobulins from rhesus macaques at different time points after infection, which permitted the characterization of the dynamics of anti-glycan immunoglobulin G and M during the establishment of brugian filariasis. A significant level of IgG binding to the parasite glycans was also detected in infected human plasma, while IgG binding to glycans decreased after anthelmintic treatment. Altogether, our work identifies B. malayi glycan antigens and reveals antibody responses from the host that could be exploited as potential markers for LF.

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Antigenic B. malayi N-linked and GSL glycans were structurally defined.

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IgG/IgM is induced to a subset of B. malayi glycans upon infection of rhesus macaques.

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Preferential IgG response to B. malayi glycans observed in chronically infected humans.

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Marked drop of anti-glycan IgG following treatment of individuals with anthelminthic.

A cluster randomized controlled trial for assessing POC-CCA test based praziquantel treatment for schistosomiasis control in pregnant women and their young children: study protocol of the freeBILy clinical trial in Madagascar

Background

Mass drug administration (MDA) of praziquantel is one of the main control measures against human schistosomiasis. Although there are claims for including pregnant women, infants and children under the age of 5 years in high-endemic regions in MDA campaigns, they are usually not treated without a diagnosis. Diagnostic tools identifying infections at the primary health care centre (PHCC) level could therefore help to integrate these vulnerable groups into control programmes. freeBILy (fast and reliable easy-to-use-diagnostics for eliminating bilharzia in young children and mothers) is an international consortium focused on implementing and evaluating new schistosomiasis diagnostic strategies. In Madagascar, the study aims to determine the effectiveness of a test-based schistosomiasis treatment (TBST) strategy for pregnant women and their infants and children up until the age of 2 years.

Methods

A two-armed, cluster-randomized, controlled phase III trial including 5200 women and their offspring assesses the impact of TBST on child growth and maternal haemoglobin in areas of medium to high endemicity of Schistosoma mansoni. The participants are being tested with the point of care-circulating cathodic antigen (POC-CCA) test, a commercially available urine-based non-invasive rapid diagnostic test for schistosomiasis. In the intervention arm, a POC-CCA-TBST strategy is offered to women during pregnancy and 9 months after delivery, for their infants at 9 months of age. In the control arm, study visit procedures are the same, but without the POC-CCA-TBST procedure. All participants are being offered the POC-CCA-TBST 24 months after delivery. This trial is being integrated into the routine maternal and child primary health care programmes at 40 different PHCC in Madagascar’s highlands. The purpose of the trial is to assess the effectiveness of the POC-CCA-TBST for controlling schistosomiasis in young children and mothers.

Discussion

This trial assesses a strategy to integrate pregnant women and their children under the age of 2 years into schistosomiasis control programmes using rapid diagnostic tests. It includes local capacity building for clinical trials and large-scale intervention research.

Trial registration

Pan-African Clinical Trial Register PACTR201905784271304. Retrospectively registered on 15 May 2019

Excretion patterns of Schistosoma mansoni antigens CCA and CAA by adult male and female worms, using a mouse model and ex vivo parasite cultures

Assays which enable the detection of schistosome gut-associated circulating anodic (CAA) and cathodic (CCA) antigen in serum or urine are increasingly used as a diagnostic tool for schistosome infection. However, little is known about the production and clearance of these circulating antigens in relation to the sex and reproductive maturity of the parasite. Here we describe CAA and CCA excretion patterns by exploring a mouse model after exposure to 36 male-only, female-only and mixed (male/female) Schistosoma mansoni cercariae. We found that serum and urine CAA levels, analysed at 3 weeks intervals, peaked at 6 weeks post-infection. Worms recovered after perfusion at 14 weeks were cultured ex vivo. Male parasites excreted more circulating antigens than females, in the mouse model as well as ex vivo. In mixed infections (supporting egg production), serum CAA levels correlated to the number of recovered worms, whereas faecal egg counts or Schistosoma DNA in stool did not. No viable eggs and no inflammation were seen in the livers from mice infected with female worms only. Ex vivo, CAA levels were higher than CCA levels. Our study confirms that CAA levels reflect worm burden and allows detection of low-level single-sex infections.

Association of Female Genital Schistosomiasis With the Cervicovaginal Microbiota and Sexually Transmitted Infections in Zambian Women

BACKGROUND

The cervicovaginal microbiota, including sexually transmitted infections (STIs), have not been well described in female genital schistosomiasis (FGS).

METHODS

Women (aged 18-31, sexually active, nonpregnant) were invited to participate at the final follow-up of the HPTN 071 (PopART) Population Cohort in January-August 2018. We measured key species of the cervicovaginal microbiota (Lactobacillus crispatus, L. iners, Gardnerella vaginalis, Atopobium vaginae, and Candida) and STIs (Chlamydia trachomatis, Neisseria gonorrhoeae, Trichomonas vaginalis, and Mycoplasma genitalium) using quantitative PCR (qPCR). We evaluated associations of the microbiota and STI presence and concentration with FGS (qPCR-detected Schistosoma DNA in any of 3 genital specimens).

RESULTS

The presence and concentration of key cervicovaginal species did not differ between participants with (n = 30) or without FGS (n = 158). A higher proportion of participants with FGS had T. vaginalis compared with FGS-negative women (P = .08), with further analysis showing that T. vaginalis was more prevalent among women with ≥2 Schistosoma qPCR-positive genital specimens (50.0%, 8/16) than among FGS-negative women (21.5%, 34/158; P = .01).

CONCLUSIONS

We found weak evidence of an association between the presence of T. vaginalis and FGS, with a stronger association in women with a higher-burden FGS infection. Additional research is needed on potential between-parasite interactions, especially regarding HIV-1 vulnerability.

Improving the diagnosis and management of acute schistosomiasis with antibody, antigen and molecular techniques: lessons from a cluster of six travellers

Different diagnostic tests were evaluated in a cluster of six European travellers with acute schistosomiasis (AS) acquired in Mozambique. Adult worm and soluble egg antibodies, circulating anodic antigen (CAA) and DNA detection allowed early confirmation of AS. CAA permitted monitoring treatment response and Sm1-7 polymerase chain reaction allowed identification of Schistosoma mansoni complex.

Context-Specific Procedures for the Diagnosis of Human Schistosomiasis – A Mini Review

Schistosomiasis is a parasitic disease caused by trematode blood flukes of the genus Schistosoma, affecting over 250 million people mainly in the tropics. Clinically, the disease can present itself with acute symptoms, a stage which is relatively more common in naive travellers originating from non-endemic regions. It can also develop into chronic disease, with the outcome depending on the Schistosoma species involved, the duration and intensity of infection and several host-related factors. A range of diagnostic tests is available to determine Schistosoma infection, including microscopy, antibody detection, antigen detection using the Point-Of-Care Circulating Cathodic Antigen (POC-CCA) test and the Up-Converting Particle Lateral Flow Circulating Anodic Antigen (UCP-LF CAA) test, as well as Nucleic Acid Amplification Tests (NAATs) such as real-time PCR. In this mini review, we discuss these different diagnostic procedures and explore their most appropriate use in context-specific settings. With regard to endemic settings, diagnostic approaches are described based on their suitability for individual diagnosis, monitoring control programs, determining elimination as a public health problem and eventual interruption of transmission. For non-endemic settings, we summarize the most suitable diagnostic approaches for imported cases, either acute or chronic. Additionally, diagnostic options for disease-specific clinical presentations such as genital schistosomiasis and neuro-schistosomiasis are included. Finally, the specific role of diagnostic tests within research settings is described, including a controlled human schistosomiasis infection model and several clinical studies. In conclusion, context-specific settings have different requirements for a diagnostic test, stressing the importance of a well-considered decision of the most suitable diagnostic procedure.

Association between cervical dysplasia and female genital schistosomiasis diagnosed by genital PCR in Zambian women

BACKGROUND

Female genital schistosomiasis (FGS) is a neglected tropical gynaecological disease that affects millions of women in sub-Saharan Africa (SSA). FGS is caused by Schistosoma haematobium, a parasitic carcinogen involved in the pathogenesis of squamous cell carcinoma of the bladder. Cervical cancer incidence and mortality are highest in SSA, where pre-cancerous cervical dysplasia is often detected on screening with visual inspection with acetic acid (VIA). There are no studies evaluating the association between VIA positivity and FGS diagnosed by genital PCR.

METHODS

Women were recruited from the Bilharzia and HIV (BILHIV) study in Zambia a community-based study comparing genital self-sampling to provider obtained cervicovaginal-lavage for the diagnosis of FGS in women aged 18-31. FGS was defined as positive Schistosoma DNA from any genital PCR. Urogenital schistosomiasis diagnostics included urine circulating anodic antigen, urine microscopy and portable colposcopy. Participants were offered cervical cancer screening using VIA at Livingstone Central Hospital. Associations of PCR confirmed FGS and other diagnostics with VIA positivity were assessed using multivariable logistic regression.

RESULTS

VIA results were available from 237 BILHIV participants. A positive Schistosoma PCR in any genital specimen was detected in 14 women (5.9%), 28.6% (4/14) of these women had positive VIA compared to 9.0% without PCR evidence of schistosome infection (20/223). Schistosoma PCR positivity in any genital specimen was strongly associated with VIA positivity (OR: 6.08, 95% CI: 1.58-23.37, P = 0.02).

CONCLUSIONS

This is the first study to find an association between FGS and positive VIA, a relationship that may be causal. Further longitudinal studies are needed.

Female Genital Schistosomiasis and HIV-1 Incidence in Zambian Women: A Retrospective Cohort Study

Background

Female genital schistosomiasis (FGS) has been associated with prevalent HIV-1. We estimated the incidence of HIV-1 infection in Zambian women with and without FGS.

Methods

Women (aged 18–31, nonpregnant, sexually active) were invited to participate in this study in January–August 2018 at the final follow-up of the HPTN 071 (PopART) Population Cohort. HIV-1-negative participants at enrollment (n = 492) were included in this analysis, with testing to confirm incident HIV-1 performed in HPTN 071 (PopART). The association of incident HIV-1 infection with FGS (Schistosoma DNA detected by polymerase chain reaction [PCR] in any genital specimen) was assessed with exact Poisson regression.

Results

Incident HIV-1 infections were observed in 4.1% (20/492) of participants. Women with FGS were twice as likely to seroconvert as women without FGS but with no statistical evidence for a difference (adjusted rate ratio, 2.16; 95% CI, 0.21–12.30; P = .33). Exploratory analysis suggested an association with HIV-1 acquisition among women with ≥2 positive genital PCR specimens (rate ratio, 6.02; 95% CI, 0.58–34.96; P = .13).

Conclusions

Despite higher HIV seroconversion rates in women with FGS, there was no statistical evidence of association, possibly due to low power. Further longitudinal studies should investigate this association in a setting with higher schistosomiasis endemicity.

Five-Year Follow-Up on the Prevalence and Intensity of Infections of Schistosoma mansoni in a Hard-to-Reach District of Madagascar

Schistosomiasis is a major public health problem in Madagascar. The WHO recommends preventive chemotherapy by mass drug administration (MDA) with praziquantel as the primary approach to control Schistosoma mansoni-related morbidity in endemic populations, alongside complementary interventions such as health education. The impact of annual MDA and health education programs was assessed in the hard-to-reach Marolambo district of eastern Madagascar, an area endemic for S. mansoni. Repeated cross-sectional studies undertaken 2015-2019 examined between 300 and 381 school-aged children (aged 5-14 years) annually. The prevalence and infection intensity of S. mansoni were assessed by urine-circulating cathodic antigen (CCA) dipsticks and coproscopy using Kato-Katz (KK) methodologies. After four rounds of annual MDA, a reduction in S. mansoni prevalence was seen in CCA (93.9% in year 1-87.7% in year 5; P = 0.007) and KK (73.9% in year 1-59.4% in year 5; P < 0.0001). The prevalence of heavy-intensity infections roughly halved from 23.7% to 10.1% (P < 0.0001), and the mean intensity of infection fell by 55.0% (480.2-216.3 eggs per gram of feces). A malacological survey found Biomphalaria pfeifferi snail intermediate hosts in multiple water contact sites including rice paddies, streams, and Nosivolo River. Despite reductions in infection prevalence and intensity, schistosomiasis still poses a significant public health challenge in Marolambo district. Twice yearly MDA cycles and/or community-wide MDA are suggested to better reduce infections. Expanding health education, improving standards of water, sanitation and hygiene, and attention on snail-related control will also be important, especially in rice paddy irrigated areas.

Early diagnosis and follow-up of acute schistosomiasis in a cluster of infected Belgian travellers by detection of antibodies and circulating anodic antigen (CAA): A diagnostic evaluation study

BACKGROUND

In order to evaluate the diagnostic value of schistosome circulating anodic antigen (CAA) detection, serum and urine CAA-levels were determined in a single cluster of 34 Belgian tourists at three timepoints within a period of 14 weeks following proven Schistosoma exposure in South Africa and compared with two in-house antibody assays.

METHODS

Samples were collected 4-5 and 7-8 weeks post-exposure and subsequently 5-6 weeks following praziquantel treatment. Schistosoma antibodies were detected by an adult worm antigen-immunofluorescence assay (AWA-IFA) and a soluble egg antigen-enzyme-linked immunosorbent assay (SEA-ELISA), while CAA concentrations were determined by the Up-Converting reporter Particle labelled Lateral Flow (UCP-LF) test.

RESULTS

Antibodies were detected in 25/34 (73%) travellers pre-treatment and in 27/34 (79%) post-treatment, with the AWA-IFA showing better performance than the SEA-ELISA. Pre-treatment, CAA was detected in 13/34 (38%) and 33/34 (97%) of the travellers in urine and serum, respectively. Post-treatment, all except one traveller became serum CAA negative. This in contrast to the detected antibodies, as well as the previously reported diagnostic results of this cluster.

CONCLUSIONS

The UCP-LF CAA serum assay has been demonstrated as the most sensitive method for the diagnosis of early Schistosoma infections and post-treatment monitoring in travellers.

Evaluation of microscopy, serology, circulating anodic antigen (CAA), and eosinophil counts for the follow-up of migrants with chronic schistosomiasis: a prospective cohort study

Background

An accurate test for the diagnosis and post-treatment follow-up of patients with schistosomiasis is needed. We assessed the performance of different laboratory parameters, including the up-converting reporter particle technology lateral flow assay to detect circulating anodic antigen (UCP-LF CAA), for the post-treatment follow-up of schistosomiasis in migrants attending a dedicated outpatient clinic in a non-endemic country.

Methods

Routine anti-Schistosoma serology results and eosinophil counts were obtained of patients with positive urine/stool microscopy and/or PCR (confirmed cases) or only positive serology (possible cases), and at least one follow-up visit at 6 (T6) or 12 (T12) months after praziquantel treatment. All sera samples were tested with the UCP-LF CAA assay.

Results

Forty-eight patients were included, 23 confirmed and 25 possible cases. The percentage seropositivity and median antibody titers did not change significantly during follow-up. UCP-LF CAA was positive in 86.9% of confirmed and 20% of possible cases. The percentage positivity and median CAA levels decreased significantly post-treatment, with only two patients having positive CAA levels at T12.

Conclusions

The UCP-LF CAA assay proved useful for the diagnosis of active infection with Schistosoma spp. and highly valuable for post-treatment monitoring in migrants, encouraging the development of a commercial test.

Cervicovaginal Immune Activation in Zambian Women With Female Genital Schistosomiasis

HIV-1 infection disproportionately affects women in sub-Saharan Africa, where areas of high HIV-1 prevalence and Schistosoma haematobium endemicity largely overlap. Female genital schistosomiasis (FGS), an inflammatory disease caused by S. haematobium egg deposition in the genital tract, has been associated with prevalent HIV-1 infection. Elevated levels of the chemokines MIP-1α (CCL-3), MIP-1β (CCL-4), IP-10 (CXCL-10), and IL-8 (CXCL-8) in cervicovaginal lavage (CVL) have been associated with HIV-1 acquisition. We hypothesize that levels of cervicovaginal cytokines may be raised in FGS and could provide a causal mechanism for the association between FGS and HIV-1. In the cross-sectional BILHIV study, specimens were collected from 603 female participants who were aged 18–31 years, sexually active, not pregnant and participated in the HPTN 071 (PopART) HIV-1 prevention trial in Zambia. Participants self-collected urine, and vaginal and cervical swabs, while CVLs were clinically obtained. Microscopy and Schistosoma circulating anodic antigen (CAA) were performed on urine. Genital samples were examined for parasite-specific DNA by PCR. Women with FGS (n=28), defined as a positive Schistosoma PCR from any genital sample were frequency age-matched with 159 FGS negative (defined as negative Schistosoma PCR, urine CAA, urine microscopy, and colposcopy imaging) women. Participants with probable FGS (n=25) (defined as the presence of either urine CAA or microscopy in combination with one of four clinical findings suggestive of FGS on colposcope-obtained photographs) were also included, for a total sample size of 212. The concentrations of 17 soluble cytokines and chemokines were quantified by a multiplex bead-based immunoassay. There was no difference in the concentrations of cytokines or chemokines between participants with and without FGS. An exploratory analysis of those women with a higher FGS burden, defined by ≥2 genital specimens with detectable Schistosoma DNA (n=15) showed, after adjusting for potential confounders, a higher Th2 (IL-4, IL-5, and IL-13) and pro-inflammatory (IL-15) expression pattern in comparison to FGS negative women, with differences unlikely to be due to chance (p=0.037 for IL-4 and p<0.001 for IL-5 after adjusting for multiple testing). FGS may alter the female genital tract immune environment, but larger studies in areas of varying endemicity are needed to evaluate the association with HIV-1 vulnerability.

Specificity of the Point-of-Care Urine Strip Test for Schistosoma Circulating Cathodic Antigen (POC-CCA) Tested in Non-Endemic Pregnant Women and Young Children

The point-of-care urine based strip test for the detection of circulating cathodic antigen (POC-CCA) in schistosome infections is a frequently used tool for diagnosis and mapping of Schistosoma mansoni in school-aged children. Because of its ease of use, the test is increasingly applied to adults and preschool-aged children (PSAC), but its performance has not been specifically evaluated in these target groups. Recent observations have raised concerns about possible reduced specificity, in particular in pregnant women (PW) and PSAC. We thus explored specificity of the POC-CCA urine strip test (Rapid Medical Diagnostics, Pretoria, South Africa) in a non-endemic, nonexposed population of 47 healthy nonpregnant adults (NPAs), 52 PW, and 58 PSAC. A total of 157 urines were tested with POC-CCA, of which five (10.6%) NPAs, 17 (32.7%) PW, and 27 (46.5%) PSAC were positive. The highest scores were found in the youngest babies, with an infant of 9 months being the oldest positive case. On measuring pH, it appeared that all POC-CCA strongly positive urines were acidic (pH range 5-5.5), whereas addition of pH-neutral buffer to a subsample reversed the false positivity. We conclude that the POC-CCA test has reduced specificity in PW and infants younger than 9 months, but that the false positivity might be eliminated by modifications in the buffers used in the test.

SCORE Operational Research on Moving toward Interruption of Schistosomiasis Transmission

As part of its diverse portfolio, the Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) included two cluster-randomized trials evaluating interventions that could potentially lead to interruption of schistosomiasis transmission (elimination) in areas of Africa with low prevalence and intensity of infection. These studies, conducted in Zanzibar and Côte d’Ivoire, demonstrated that multiyear mass drug administration (MDA) with praziquantel failed to interrupt the transmission of urogenital schistosomiasis, even when provided biannually and/or supplemented by small-scale implementation of additional interventions. Other SCORE activities related to elimination included a feasibility and acceptability assessment of test–treat–track–test–treat (T5) strategies and mathematical modeling. Future evaluations of interventions to eliminate schistosomiasis should recognize the difficulties inherent in conducting randomized controlled trials on elimination and in measuring small changes where baseline prevalence is low. Highly sensitive and specific diagnostic tests for use in very low–prevalence areas for schistosomiasis are not routinely available, which complicates accurate measurement of infection rates and assessment of changes resulting from interventions in these settings. Although not encountered in these two studies, as prevalence and intensity decrease, political and community commitment to population-wide MDA may decrease. Because of this potential problem, SCORE developed and funded the T5 strategy implemented in Egypt, Kenya, and Tanzania. It is likely that focal MDA campaigns, along with more targeted approaches, including a T5 strategy and snail control, will need to be supplemented with the provision of clean water and sanitation and behavior change communications to achieve interruption of schistosome transmission.

SCORE Studies on the Impact of Drug Treatment on Morbidity due to Schistosoma mansoni and Schistosoma haematobium Infection

The Schistosomiasis Consortium for Operational Research (SCORE) was funded in 2008 to improve the evidence base for control and elimination of schistosomiasis—better understanding of the systemic morbidities experienced by children in schistosomiasis-endemic areas and the response of these morbidities to treatment, being essential for updating WHO guidelines for mass drug administration (MDA) in endemic areas. This article summarizes the SCORE studies that aimed to gauge the impact of MDA-based treatment on schistosomiasis-related morbidities. Morbidity cohort studies were embedded in the SCORE’s larger field studies of gaining control of schistosomiasis in Kenya and Tanzania. Following MDA, cohort children had less undernutrition, less portal vein dilation, and increased quality of life in Year 5 compared with baseline. We also conducted a pilot study of the Behavioral Assessment System for Children (BASC-2) in conjunction with the Kenya gaining control study, which demonstrated beneficial effects of treatment on classroom behavior. In addition, the SCORE’s Rapid Answers Project performed systematic reviews of previously available data, providing two meta-analyses related to morbidity. The first documented children’s infection-related deficits in school attendance and achievement and in formal tests of learning and memory. The second showed that greater reductions in egg output following drug treatment correlates significantly with reduced odds of most morbidities. Overall, these SCORE morbidity studies provided convincing evidence to support the use of MDA to improve the health of school-aged children in endemic areas. However, study findings also support the need to use enhanced metrics to fully assess and better control schistosomiasis-associated morbidity.

Schistosomiasis Consortium for Operational Research and Evaluation (SCORE): Its Foundations, Development, and Evolution

The Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) was established in late 2008 to conduct operational research that would inform practices related to the control and elimination of schistosomiasis. This article traces SCORE’s beginnings and underpinnings. These include an emphasis on openness and contributing to the development of a cohesive schistosomiasis control community, building linkages between researchers and national programs, and focusing on answering questions that will help Neglected Tropical Disease program managers to better control and eliminate schistosomiasis. It describes the development and implementation of SCORE’s multiple projects. SCORE began by drawing on advice from a broad range of experts by holding wide-ranging meetings that informed the priorities and protocols for SCORE research. SCORE’s major efforts included large, multicountry field studies comparing multiple strategies for mass drug administration with praziquantel, assessment of approaches to elimination, evaluation of a point-of-care assay for field mapping Schistosoma mansoni, and increasing the sensitivity of a laboratory-based diagnostic. SCORE also supported studies on morbidity due to schistosomiasis, quantification of vector snails and the detection of schistosome infections in snails, and changes in schistosome population genetics under praziquantel drug pressure. SCORE data and specimens are archived and will remain available for future research. Although much remains to be carried out, our hope is that through the already published articles and SCORE results described in this supplement, we will have provided a body of evidence to assist policy makers in the development of judicious guidelines for the control and elimination of schistosomiasis.