Improved sensitivity of the urine CAA lateral-flow assay for diagnosing active Schistosoma infections by using larger sample volumes

Capacities and needs of health care facilities for schistosomiasis diagnosis and management in elimination settings

BACKGROUND

Schistosomiasis is a debilitating neglected tropical disease endemic in sub-Saharan Africa. The role of health facilities in the prevention, diagnosis, control, and elimination of schistosomiasis is poorly documented. In a setting targeted for schistosomiasis elimination in Zanzibar, we assessed the prevalence of Schistosoma haematobium among patients seeking care in a health facility and investigated schistosomiasis-related knowledge of staff, and health facilities' capacities and needs for schistosomiasis diagnosis and management.

METHODS

We conducted a health facility-based mixed-method study on Pemba Island from June to August 2023. Patients aged ≥ 4 years seeking care in four health facilities were screened for S. haematobium infection using urine filtration and reagent strips. Those patients aged ≥ 10 years were additionally interviewed about signs and symptoms. Staff from 23 health facilities responded to a questionnaire assessing knowledge and practices. Ten staff participated in a focus group discussion (FGD) about capacities and needs for schistosomiasis diagnosis and management.

RESULTS

The prevalence of S. haematobium infection in patients attending the health facilities, as determined by the presence of eggs in urine, was 1.1% (8/712). Microhaematuria was detected in 13.3% (95/712) of the patients using reagent strips. Among patients responding to the questionnaire, pelvic pain, pain during sex, and painful urination were reported by 38.0% (237/623), 6.3% (39/623), and 3.2% (20/623), respectively. Among the health facility staff, 90.0% (44/49) and 87.8% (43/49) identified blood in urine and pelvic pain, respectively, as symptoms of urogenital schistosomiasis, 81.6% (40/49) and 93.9% (46/49) reported collecting a urine sample and pursuing a reagent strip test, respectively, for diagnosis, and 87.8% (43/49) administered praziquantel for treatment. The most reoccurring themes in the FGD were the need for more staff training about schistosomiasis, requests for diagnostic equipment, and the need to improve community response to schistosomiasis services in health facilities.

CONCLUSIONS

The prevalence of S. haematobium infection in patients seeking care in health facilities in Pemba is very low and similar to what has been reported from recent community-based cross-sectional surveys. The health facility staff had good schistosomiasis-related knowledge and practices. However, to integrate schistosomiasis patient management more durably into routine health facility activities, scalable screening pathways need to be identified and capacities need to be improved by regular staff training, and an unbroken supply of accurate point-of-care diagnostics and praziquantel for the treatment of cases.

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.

Baseline soil-transmitted helminth and schistosome infection in the Geshiyaro project, Ethiopia: A unique transmission interruption project using biometric fingerprinting for longitudinal individual analysis

BACKGROUND

The Geshiyaro project aims to assess the feasibility of interrupting transmission of soil-transmitted helminths (STH) and schistosome (SCH) infection in the Wolaita zone of southern Ethiopia through high coverage community-wide mass drug administration (MDA), in combination with improved water, sanitation, and hygiene services and behaviour change communication delivered through the existing health care infrastructure. To accurately measure treatment coverage a population census was conducted enrolling individuals with biometric fingerprinting and barcoded ID cards. This paper details the baseline census and parasitology surveys conducted before the start of any interventions.

METHODS

The census was conducted in five of the 15 Wolaita districts between October 2018 and December 2019, enrolling all consenting participants from every household. Simultaneously, a cross-sectional parasitology survey was conducted in 130 out of 361 randomly selected communities from all 15 districts, with 100 individuals across all age groups (infant to adult) per community providing stool and urine for analysis by duplicate Kato-Katz and a point-of-care circulating cathodic antigen (POC-CCA) to test for Schistosoma mansoni and STH, and microhaematuria and urine filtration for Schistosoma haematobium. Of the 130 communities, 30 were randomly selected for annual, longitudinal parasitological monitoring, with 150 randomly selected individuals from infant to adult providing two days of stool and urine samples for analysis by the same diagnostic tests per community.

RESULTS

In total 97,919 households participated in the baseline census enrolling 466,071 individuals, with parasitological data obtained from 10,785 people. At baseline, 15.5% were infected with at least one STH species, with Ascaris lumbricoides (9.5%), followed by hookworm (7.2%) and Trichuris trichiura (1.8%). Substantial heterogeneity in STH prevalence was observed between communities ranging from 0% to 61% where most infections were low intensity. Schistosoma mansoni infection was the dominant schistosome infection (0.85% by Kato-Katz and 13.3% by POC-CCA trace negative and 21.5% trace positive), with few Schistosoma haematobium infections identified (2.77% haematuria positive and 0.13% positive by urine filtration).

CONCLUSIONS

While the national control program in Ethiopia has made good progress in reducing prevalence of STH and SCH in Wolaita since it was launched in 2015, there remain areas of persistent infection suggesting the existence of environmental or behavioural risk factors that contribute to ongoing transmission. This project aims to identify the most efficient intervention strategies to reduce community burden and reach interruption of transmission.

Comparative assessment of the SjSAP4-incorporated gold immunochromatographic assay for the diagnosis of human schistosomiasis japonica

Background

Schistosomiasis, a disease caused by parasites of the genus Schistosoma, remains a global public health threat. This study aimed to validate the diagnostic performance of a recently developed gold immunochromatographic assay (GICA) for the detection of S. japonicum infection in a rural endemic area of the Philippines.

Methods

Human clinical samples were collected from 412 subjects living in Laoang and Palapag municipalities, Northern Samar, the Philippines. The presence of Schistosoma-specific antibodies in serum samples was tested with the SjSAP4-incorporated GICA strips and the results were converted to fully quantitative data by introducing an R value. The performance of the established GICA was further compared with other diagnostic tools, including the Kato-Katz (KK) technique, point-of-care circulating cathodic antigen (POC-CCA), droplet digital (dd) PCR, and enzyme-linked immunosorbent assays (ELISAs).

Results

The developed GICA strip was able to detect KK positive individuals with a sensitivity of 83.3% and absolute specificity. When calibrated with the highly sensitive faecal ddPCR assay, the immunochromatographic assay displayed an accuracy of 60.7%. Globally, the GICA assay showed a high concordance with the SjSAP4-ELISA assay. The schistosomiasis positivity rate determined by the GICA test was similar to those obtained with the SjSAP4-ELISA assay and the ddPCR assay performed on serum samples (SR_ddPCR), and was 2.3 times higher than obtained with the KK method.

Conclusion

The study further confirms that the developed GICA is a valuable diagnostic tool for detecting light S. japonicum infections and implies that this point-of-care assay is a viable solution for surveying endemic areas of low-intensity schistosomiasis and identifying high-priority endemic areas for targeted interventions.

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.

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.

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.

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.

Subclinical signs of podocyte injury associated with Circulating Anodic Antigen (CAA) in Schistosoma mansoni-infected patients in Brazil

BACKGROUND

The long-term effects of schistosomiasis on the glomerulus may contribute to the development of chronic kidney disease. This study aimed to investigate baseline Schistosoma mansoni-Circulating Anodic Antigen (CAA) levels and their association with kidney biomarkers related to podocyte injury and inflammation in long-term follow-up after praziquantel (PZQ) treatment.

METHODS

Schistosoma infection was diagnosed by detecting CAA in urine using a quantitative assay based on lateral flow using luminescent up-converting phosphor reporter particles. A cutoff threshold of 0.1 pg/mL CAA was used to diagnose Schistosoma infection (baseline) in a low-prevalence area in Ceará, Northeast, Brazil. Two groups were included: CAA-positive and CAA-negative individuals, both of which received a single dose of PZQ at baseline. Urinary samples from 55 individuals were evaluated before (baseline) and at 1, 2, and 3 years after PZQ treatment. At all time points, kidney biomarkers were quantified in urine and adjusted for urinary creatinine levels.

RESULTS

CAA-positive patients had increased baseline albuminuria and proteinuria and showed greater associations between kidney biomarkers. CAA levels correlated only with Vascular Endothelial Growth Factor (VEGF) (podocyte injury) levels. Increasing trends were observed for malondialdehyde (oxidative stress), monocyte chemoattractant protein-1 (inflammation marker), and VEGF. In the follow-up analysis, no relevant differences were observed in kidney biomarkers between the groups and different periods.

CONCLUSIONS

S. mansoni-infected individuals presented subclinical signs of glomerular damage that may reflect podocyte injury. However, no causal effect on long-term renal function was observed after PZQ treatment.

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.

Osmotic Processor for Enabling Sensitive and Rapid Biomarker Detection via Lateral Flow Assays

Urine is an attractive biospecimen for in vitro diagnostics, and urine-based lateral flow assays are low-cost devices suitable for point-of-care testing, particularly in low-resource settings. However, some of the lateral flow assays exhibit limited diagnostic utility because the urinary biomarker concentration is significantly lower than the assay detection limit, which compromises the sensitivity. To address the challenge, we developed an osmotic processor that statically and spontaneously concentrated biomarkers. The specimen in the device interfaces with the aqueous polymer solution via a dialysis membrane. The polymer solution induces an osmotic pressure difference that extracts water from the specimen, while the membrane retains the biomarkers. The evaluation demonstrated that osmosis induced by various water-soluble polymers efficiently extracted water from the specimens, ca. 5–15 ml/h. The osmotic processor concentrated the specimens to improve the lateral flow assays’ detection limits for the model analytes—human chorionic gonadotropin and SARS-CoV-2 nucleocapsid protein. After the treatment via the osmotic processor, the lateral flow assays detected the corresponding biomarkers in the concentrated specimens. The test band intensities of the assays with the concentrated specimens were very similar to the reference assays with 100-fold concentrations. The mass spectrometry analysis estimated the SARS-CoV-2 nucleocapsid protein concentration increased ca. 200-fold after the osmosis. With its simplicity and flexibility, this device demonstrates a great potential to be utilized in conjunction with the existing lateral flow assays for enabling highly sensitive detection of dilute target analytes in urine.

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.

Paper and thread as media for the frugal detection of urinary tract infections (UTIs)

Urinary tract infections (UTIs) make up a significant proportion of the global burden of disease in vulnerable groups and tend to substantially impair the quality of life of those affected, making timely detection of UTIs a priority for public health. However, economic and societal barriers drastically reduce accessibility of traditional lab-based testing methods for critical patient groups in low-resource areas, negatively affecting their overall healthcare outcomes. As a result, cellulose-based materials such as paper and thread have garnered significant interest among researchers as substrates for so-called frugal analytical devices which leverage the material's portability and adaptability for facile and reproducible diagnoses of UTIs. Although the field may be only in its infancy, strategies aimed at commercial penetration can appreciably increase access to more healthcare options for at-risk people. In this review, we catalogue recent advances in devices that use cellulose-based materials as the primary housing or medium for UTI detection and chart out trends in the field. We also explore different modalities employed for detection, with particular emphasis on their ability to be ported onto discreet casings such as sanitary products.

The praziquantel in preschoolers (PIP) trial: study protocol for a phase II PK/PD-driven randomised controlled trial of praziquantel in children under 4 years of age

BACKGROUND

Over 200 million individuals worldwide are infected with Schistosoma species, with over half of infections occurring in children. Many children experience first infections early in life and this impacts their growth and development; however praziquantel (PZQ), the drug used worldwide for the treatment of schistosomiasis, only has regulatory approval among adults and children over the age of four, although it is frequently used "off label" in endemic settings. Furthermore, pharmacokinetic/pharmacodynamics (PK/PD) evidence suggests the standard PZQ dose of 40 mg/kg is insufficient in preschool-aged children (PSAC). Our goal is to understand the best approaches to optimising the treatment of PSAC with intestinal schistosomiasis.

METHODS

We will conduct a randomised, controlled phase II trial in a Schistosoma mansoni endemic region of Uganda and a Schistosoma japonicum endemic region of the Philippines. Six hundred children, 300 in each setting, aged 12-47 months with Schistosoma infection will be randomised in a 1:1:1:1 ratio to receive either (1) 40 mg/kg PZQ at baseline and placebo at 6 months, (2) 40 mg/kg PZQ at baseline and 40 mg/kg PZQ at 6 months, (3) 80 mg/kg PZQ at baseline and placebo at 6 months, or (4) 80 mg/kg PZQ at baseline and 80 mg/kg PZQ at 6 months. Following baseline treatment, children will be followed up for 12 months. The co-primary outcomes will be cure rate and egg reduction rate at 4 weeks. Secondary outcomes include drug efficacy assessed by novel antigenic endpoints at 4 weeks, actively collected adverse events and toxicity for 12 h post-treatment, morbidity and nutritional outcomes at 6 and 12 months, biomarkers of inflammation and environmental enteropathy and PZQ PK/PD parameters.

DISCUSSION

The trial will provide valuable information on the safety and efficacy of the 80 mg/kg PZQ dose in PSAC, and on the impact of six-monthly versus annual treatment, in this vulnerable age group.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03640377 . Registered on 21 Aug 2018.

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.

Evaluation of Artesunate-mefloquine as a Novel Alternative Treatment for Schistosomiasis in African Children (SchistoSAM): protocol of a proof-of-concept, open-label, two-arm, individually-randomised controlled trial

INTRODUCTION

Alternative drugs and diagnostics are needed for the treatment and control of schistosomiasis. The exclusive use of praziquantel (PZQ) in mass drug administration programmes may result in the emergence of drug resistance. PZQ has little activity against Schistosoma larvae, thus reinfection remains a problem in high-risk communities. Furthermore, the insufficient sensitivity of conventional microscopy hinders therapeutic response assessment. Evaluation of artesunate-mefloquine (AM) as a Novel Alternative Treatment for Schistosomiasis in African Children (SchistoSAM) aims to evaluate the safety and efficacy of the antimalarial combination artesunate-mefloquine, re-purposed for the treatment of schistosomiasis, and to assess the performance of highly sensitive novel antigen-based and DNA-based assays as tools for monitoring treatment response.

METHODS AND ANALYSIS

The SchistoSAM study is an open-label, two-arm, individually randomised controlled non-inferiority trial, with a follow-up of 48 weeks. Primary school-aged children from the Richard Toll district in northern Senegal, an area endemic for Schistosoma mansoni and Schistosoma haematobium, are allocated to the AM intervention arm (3-day courses at 6-week intervals) or the PZQ control arm (single dose of 40 mg/kg). The trial's primary endpoints are the efficacy (cure rate (CR), assessed by microscopy) and safety (frequency and pattern of drug-related adverse events) of one AM course versus PZQ at 4 weeks after treatment. Secondary endpoints include (1) cumulative CR, egg reduction rate and safety after each additional course of AM, and at weeks 24 and 48, (2) prevalence and severity of schistosomiasis-related morbidity and (3) malaria prevalence, incidence and morbidity, both after 24 and 48 weeks. CRs and intensity reduction rates are also assessed by antigen-based and DNA-based diagnostic assays, for which performance for treatment monitoring is evaluated.

ETHICS AND DISSEMINATION

Ethics approval was obtained both in Belgium and Senegal. Oral assent from the children and signed informed consent from their legal representatives was obtained, prior to enrolment. The results will be disseminated in peer-reviewed journals and at international conferences.

TRIAL REGISTRATION NUMBER

NCT03893097; pre-results.

Enhancing the Sensitivity of Lateral Flow Immunoassay by Magnetic Enrichment Using Multifunctional Nanocomposite Probes

For lateral flow immunoassay (LFIA), it is an important challenge to enhance the detection sensitivity to the same level as polymerase chain reaction or enzyme-linked immunosorbent assay to make LFIA pervasive in the field of on-site environmental analysis. We recently demonstrated that the LFIA sensitivity is dramatically enhanced by using Pt-nanoparticle-latex nanocomposite beads (Pt-P2VPs) as probes for the detection of the influenza A (H1N1) antigen compared with using conventional Au colloids as probes. Here, to further enhance the LFIA sensitivity using Pt-P2VPs, superparamagnetic iron oxide nanoparticles (SPIONs) were chemically conjugated to Pt-P2VPs (Pt-P2VP@SPION) to give them magnetic separation capability (enrichment and/or purification). To investigate the effect of magnetic enrichment on the LFIA sensitivity in a sandwich format, the C-reactive protein (CRP) was chosen as a model analyte and anti-CRP antibody (CRPAb)-conjugated Pt-P2VP@SPION (Pt-P2VP@SPION-CRPAb) beads were used as probes. The visual limit of detection (LOD) of LFIA was successfully lowered by increasing the magnetic enrichment factor φ. The minimum LOD under the present experimental conditions was 0.08 ng/mL for φ = 40, which is 26-fold lower than that of the standard Au-nanoparticle-based LFIA. In theory, the LOD can be unlimitedly decreased by just increasing φ. However, the times required for both the antigen-antibody binding reaction and magnetic separation dramatically increase with φ. We also propose solutions to overcome this drawback.

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.

Effect of intensive treatment for schistosomiasis on immune responses to vaccines among rural Ugandan island adolescents: randomised controlled trial protocol A for the 'POPulation differences in VACcine responses' (POPVAC) programme

INTRODUCTION

Several licensed and investigational vaccines have lower efficacy, and induce impaired immune responses, in low-income versus high-income countries and in rural, versus urban, settings. Understanding these population differences is essential to optimising vaccine effectiveness in the tropics. We suggest that repeated exposure to and immunomodulation by chronic helminth infections partly explains population differences in vaccine response.

METHODS AND ANALYSIS

We have designed an individually randomised, parallel group trial of intensive versus standard praziquantel (PZQ) intervention against schistosomiasis, to determine effects on vaccine response outcomes among school-going adolescents (9-17 years) from rural Schistosoma mansoni-endemic Ugandan islands. Vaccines to be studied comprise BCG on day 'zero'; yellow fever, oral typhoid and human papilloma virus (HPV) vaccines at week 4; and HPV and tetanus/diphtheria booster vaccine at week 28. The intensive arm will receive PZQ doses three times, each 2 weeks apart, before BCG immunisation, followed by a dose at week 8 and quarterly thereafter. The standard arm will receive PZQ at week 8 and 52. We expect to enrol 480 participants, with 80% infected with S. mansoni at the outset.Primary outcomes are BCG-specific interferon-γ ELISpot responses 8 weeks after BCG immunisation and for other vaccines, antibody responses to key vaccine antigens at 4 weeks after immunisation. Secondary analyses will determine the effects of intensive anthelminthic treatment on correlates of protective immunity, on waning of vaccine response, on priming versus boosting immunisations and on S. mansoni infection status and intensity. Exploratory immunology assays using archived samples will enable assessment of mechanistic links between helminths and vaccine responses.

ETHICS AND DISSEMINATION

Ethics approval has been obtained from relevant ethics committes of Uganda and UK. Results will be shared with Uganda Ministry of Health, relevant district councils, community leaders and study participants. Further dissemination will be done through conference proceedings and publications.

TRIAL REGISTRATION NUMBER

ISRCTN60517191.

Effect of intermittent preventive treatment for malaria with dihydroartemisinin-piperaquine on immune responses to vaccines among rural Ugandan adolescents: randomised controlled trial protocol B for the 'POPulation differences in VACcine responses' (POPVAC) programme

INTRODUCTION

Drivers of lower vaccine efficacy and impaired vaccine-specific immune responses in low-income versus high-income countries, and in rural compared with urban settings, are not fully elucidated. Repeated exposure to and immunomodulation by parasite infections may be important. We focus on Plasmodium falciparum malaria, aiming to determine whether there are reversible effects of malaria infection on vaccine responses.

METHODS AND ANALYSIS

We have designed a randomised, double-blind, placebo-controlled, parallel group trial of intermittent preventive malaria treatment versus placebo, to determine effects on vaccine response outcomes among school-going adolescents (9 to 17 years) from malaria-endemic rural areas of Jinja district (Uganda). Vaccines to be studied comprise BCG vaccine on day 'zero'; yellow fever, oral typhoid and human papilloma virus vaccines at week 4; and tetanus/diphtheria booster vaccine at week 28. Participants in the intermittent preventive malaria treatment arm will receive dihydroartemisinin/piperaquine (DP) dosed by weight, 1 month apart, prior to the first immunisation, followed by monthly treatment thereafter. We expect to enrol 640 adolescents. Primary outcomes are BCG-specific interferon-γ ELISpot responses 8 weeks after BCG immunisation and for other vaccines, antibody responses to key vaccine antigens at 4 weeks after immunisation. In secondary analyses, we will determine effects of monthly DP treatment (versus placebo) on correlates of protective immunity, on vaccine response waning, on whether there are differential effects on priming versus boosting immunisations, and on malaria infection prevalence. We will also conduct exploratory immunology assays among subsets of participants to further characterise effects of the intervention on vaccine responses.

ETHICS AND DISSEMINATION

Ethics approval has been obtained from relevant Ugandan and UK ethics committees. Results will be shared with Uganda Ministry of Health, relevant district councils, community leaders and study participants. Further dissemination will be done through conference proceedings and publications.

TRIAL REGISTRATION NUMBER

Current Controlled Trials identifier: ISRCTN62041885.

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.

Fast and reliable easy-to-use diagnostics for eliminating bilharzia in young children and mothers: An introduction to the freeBILy project

Schistosoma antigen detection tests have a large potential for schistosomiasis control programs due to their ability to detect active and ongoing Schistosoma infections, their much higher sensitivity compared to microscopical methods, and the possibility to use non-invasive urine samples. Pregnant women and young children could especially benefit from affordable and easy-to-use antigen tests as inclusion of these vulnerable groups in mass drug administration campaigns will always require higher justification hurdles, especially in low to middle endemic regions with a higher proportion of individuals who are not infected and thus unnecessarily exposed to praziquantel. The overall objective of the 'fast and reliable easy-to-use diagnostics for eliminating bilharzia in young children and mothers' (freeBILy, www.freeBILy.eu) project is to thoroughly evaluate the point-of-care circulating cathodic antigen (POC-CCA) and the up-converting phosphor reporter particle, lateral flow circulating anodic antigen (UCP-LF CAA) urine strip tests to diagnose Schistosoma infections in pregnant women and young children and to assess their potential as a schistosomiasis control tool in test-and-treat strategies. The freeBILy project will generate valuable, evidence-based findings on improved tools and test-and-treat strategies to reduce the burden of schistosomiasis in pregnant women and young children.

Prospective, observational study to assess the performance of CAA measurement as a diagnostic tool for the detection of Schistosoma haematobium infections in pregnant women and their child in Lambaréné, Gabon: study protocol of the freeBILy clinical trial in Gabon

BACKGROUND

Schistosoma antigen detection in urine is a valuable diagnostic approach for schistosomiasis control programmes because of the higher sensitivity compared to parasitological methods and preferred sampling of urine over stool. Highly accurate diagnostics are important in low Schistosoma transmission areas. Pregnant women and young children could particularly benefit from antigen testing as praziquantel (PZQ) can be given to only confirmed Schistosoma cases. This prevents the unborn baby from unnecessary exposure to PZQ. We present here the protocol of a diagnostic study that forms part of the freeBILy project. The aim is to evaluate the accuracy of circulating anodic antigen (CAA) detection for diagnosis of Schistosoma haematobium infections in pregnant women and to validate CAA as an endpoint measure for anti-Schistosoma drug efficacy. The study will also investigate Schistosoma infections in infants.

METHODS

A set of three interlinked prospective, observational studies is conducted in Gabon. The upconverting phosphor lateral flow (UCP-LF) CAA test is the index diagnostic test that will be evaluated. The core trial, sub-study A, comprehensively evaluates the accuracy of the UCP-LF CAA urine test against a set of other Schistosoma diagnostics in a cross-sectional trial design. Women positive for S. haematobium will proceed with sub-study B and will be randomised to receive PZQ treatment immediately or after delivery followed by weekly sample collection. This approach includes comparative monitoring of CAA levels following PZQ intake and will also contribute further data for safety of PZQ administration during pregnancy. Sub-study C is a longitudinal study to determine the incidence of S. haematobium infection as well as the age for first infection in life-time.

DISCUSSION

The freeBILy trial in Gabon will generate a comprehensive set of data on the accuracy of the UCP-LF CAA test for the detection of S. haematobium infection in pregnant women and newborn babies and for the use of CAA as a marker to determine PZQ efficacy. Furthermore, incidence of Schistosoma infection in infants will be reported. Using the ultrasensitive diagnostics, this information will be highly relevant for Schistosoma prevalence monitoring by national control programs as well as for the development of medicaments and vaccines.

TRIAL REGISTRATION

The registration number of this study is NCT03779347 ( clinicaltrials.gov , date of registration: 19 December 2018).

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

The Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) was funded in 2008 to conduct research that would support country schistosomiasis control programs. As schistosomiasis prevalence decreases in many places and elimination is increasingly within reach, a sensitive and specific test to detect infection with Schistosoma mansoni and Schistosoma haematobium has become a pressing need. After obtaining broad input, SCORE supported Leiden University Medical Center (LUMC) to modify the serum-based antigen assay for use with urine, simplify the assay, and improve its sensitivity. The urine assay eventually contributed to several of the larger SCORE studies. For example, in Zanzibar, we demonstrated that urine filtration, the standard parasite egg detection diagnostic test for S. haematobium, greatly underestimated prevalence in low-prevalence settings. In Burundi and Rwanda, the circulating anodic antigen (CAA) assay provided critical information about the limitations of the stool-based Kato-Katz parasite egg-detection assay for S. mansoni in low-prevalence settings. Other SCORE-supported CAA work demonstrated that frozen, banked urine specimens yielded similar results to fresh ones; pooling of specimens may be a useful, cost-effective approach for surveillance in some settings; and the assay can be performed in local laboratories equipped with adequate centrifuge capacity. These improvements in the assay continue to be of use to researchers around the world. However, additional work will be needed if widespread dissemination of the CAA assay is to occur, for example, by building capacity in places besides LUMC and commercialization of the assay. Here, we review the evolution of the CAA assay format during the SCORE period with emphasis on urine-based applications.

Genital self-sampling compared with cervicovaginal lavage for the diagnosis of female genital schistosomiasis in Zambian women: The BILHIV study

BACKGROUND

Given the potentially causal association of female genital schistosomiasis (FGS) with HIV-1 infection, improved diagnostics are urgently needed to scale-up FGS surveillance. The BILHIV (bilharzia and HIV) study assessed the performance of home-based self-collection methods (cervical and vaginal swabs) compared to cervicovaginal lavage (CVL) for the detection of Schistosoma DNA by real-time polymerase chain reaction (PCR).

METHODS

Between January and August 2018, a consecutive series of female participants from the Population-Cohort of the previous HIV prevention trial HPTN 071 (PopART), resident in Livingstone, Zambia were invited to take part in BILHIV if they were 18-31 years old, non-pregnant and sexually active. Genital self-collected swabs and a urine specimen were obtained and a questionnaire completed at home visits. CVL was obtained at clinic follow-up.

RESULTS

603 women self-collected genital swabs. Of these, 527 women had CVL performed by a mid-wife during clinic follow-up. Schistosoma DNA was more frequently detected in genital self-collected specimens (24/603, 4.0%) compared to CVL (14/527, 2.7%). Overall, 5.0% (30/603) women had female genital schistosomiasis, defined as a positive PCR by any genital sampling method (cervical swab PCR, vaginal swab PCR, or CVL PCR) and 95% (573/603) did not have a positive genital PCR. The sensitivity of any positive genital self-collected swab against CVL was 57.1% (95% CI 28.9-82.3%), specificity 97.3% (95.5-98.5%). In a subset of participants with active schistosome infection, determined by detectable urine Circulating Anodic Antigen (CAA) (15.1%, 91/601), positive PCR (4.3%, 26/601), or positive microscopy (5.5%, 33/603), the sensitivity of any positive self-collected specimen against CVL was 88.9% (51.8-99.7%).

CONCLUSIONS

Genital self-sampling increased the overall number of PCR-based FGS diagnoses in a field setting, compared with CVL. Home-based sampling may represent a scalable alternative method for FGS community-based diagnosis in endemic resource limited settings.

Survey of Schistosomiasis in Saint Lucia: Evidence for Interruption of Transmission

Saint Lucia at one time had levels of schistosomiasis prevalence and morbidity as high as many countries in Africa. However, as a result of control efforts and economic development, including more widespread access to sanitation and safe water, schistosomiasis on the island has practically disappeared. To evaluate the current status of schistosomiasis in Saint Lucia, we conducted a nationally representative school-based survey of 8–11-year-old children for prevalence of Schistosoma mansoni infections using circulating antigen and specific antibody detection methods. We also conducted a questionnaire about available water sources, sanitation, and contact with fresh water. The total population of 8–11-year-old children on Saint Lucia was 8,985; of these, 1,487 (16.5%) provided urine for antigen testing, 1,455 (16.2%) provided fingerstick blood for antibody testing, and 1,536 (17.1%) answered the questionnaire. Although a few children were initially low positives by antigen or antibody detection methods, none could be confirmed positive by follow-up testing. Most children reported access to clean water and sanitary facilities in or near their homes and 48% of the children reported contact with fresh water. Together, these data suggest that schistosomiasis transmission has been interrupted on Saint Lucia. Additional surveys of adults, snails, and a repeat survey among school-age children will be necessary to verify these findings. However, in the same way that research on Saint Lucia generated the data leading to use of mass drug administration for schistosomiasis control, the island may also provide the information needed for guidelines to verify interruption of schistosomiasis transmission.

Improvement in Detection Limit for Lateral Flow Assay of Biomacromolecules by Test-Zone Pre-enrichment

Lateral flow assay (LFA) is one of the most prevalent commercially available techniques for point-of-care tests due to its simplicity, celerity, low cost and robust operation. However, conventional colorimetric LFAs have inferior limits of detection (LODs) compared to sophisticated laboratory-based assays. Here, we report a simple strategy of test-zone pre-enrichment to improve the LOD of LFA by loading samples before the conjugate pad assembly. The developed method enables visual LODs of miR-210 mimic and human chorionic gonadotropin protein, to be improved by 10–100 fold compared with a conventional LFA setup without introducing any additional instrument and reagent except for phosphate running buffer, while no obvious difference occurred for Aflatoxin B1 (AFB1). It takes about 6–8 min to enrich every 50 μL of sample diluted with phosphate running buffer, therefore we can get visual results within 20 min. We identified a parameter by modeling the entire process, the concentration of probe-analyte conjugate at test zone when signaling unit being loaded, to be important for the improvement of visual limit of detection. In addition, the test-zone pre-enrichment did not impair the selectivity when miR-210 mimic was adopted as target. Integrated with other optimization, amplification and modification of LFAs, the developed test-zone pre-enrichment method can be applied to further improve LOD of LFAs.

Screening of a library of recombinant Schistosoma mansoni proteins with sera from murine and human controlled infections identifies early serological markers

Background

Schistosomiasis is a major global health problem caused by blood-dwelling parasitic worms, which is currently tackled primarily by mass administration of the drug praziquantel. Appropriate drug treatment strategies are informed by diagnostics that establish the prevalence and intensity of infection, which, in regions of low transmission, should be highly sensitive.

Methods

To identify sensitive new serological markers of Schistosoma mansoni infections, we have compiled a recombinant protein library of parasite cell-surface and secreted proteins expressed in mammalian cells.

Results

Together with a time series of sera samples from volunteers experimentally infected with a defined number of male parasites, we probed this protein library to identify several markers that can detect primary infections with as low as 10 parasites and as early as 5 weeks postinfection.

Conclusions

These new markers could be further explored as valuable tools to detect ongoing and previous S mansoni infections, including in endemic regions where transmission is low.

Nationwide Remapping of Schistosoma mansoni Infection in Rwanda Using Circulating Cathodic Antigen Rapid Test: Taking Steps toward Elimination

The field standard for the detection of Schistosoma mansoni infection is Kato–Katz (KK), although it misses many active infections, especially light infections. In 2014, a reassessment of S. mansoni prevalence was conducted in Rwanda using the more sensitive point-of-care circulating cathodic antigen (POC-CCA) rapid assay. A total of 19,371 children from 399 schools were selected for testing for single urine CCA. Of these, 8,697 children from 175 schools were also tested with single stool double-slide KK. Samples from eight of these 175 schools were tested again with CCA and additionally with the highly specific and sensitive up-converting phosphor-lateral flow circulating anodic antigen (UCP-LF CAA) assay. Latent class analysis was applied to all four test results to assess sensitivity and specificity of POC-CCA and estimate the proportion of trace results from Rwanda likely to be true infections. The overall prevalence of S. mansoni infection in Rwanda when CCA trace results were considered negative was 7.4% (school interquartile range [IQR] 0–8%) and 36.1% (school IQR 20–47%) when trace was considered positive. Prevalence by KK was 2.0% with a mean intensity of infection of 1.66 eggs per gram. The proportion of active infections among children diagnosed with CCA trace was estimated by statistical analysis at 61% (Bayesian credibility interval: 50–72%). These results indicate that S. mansoni infection is still widespread in Rwanda and prevalence is much underestimated by KK testing. Circulating cathodic antigen is an affordable alternative to KK and more suitable for measuring S. mansoni prevalence in low-intensity regions.

Sensitive diagnostic tools and targeted drug administration strategies are needed to eliminate schistosomiasis

Although preventive chemotherapy has been instrumental in reducing schistosomiasis incidence worldwide, serious challenges remain. These problems include the omission of certain groups from campaigns of mass drug administration, the existence of persistent disease hotspots, and the risk of recrudescent infections. Central to these challenges is the fact that the diagnostic tools currently used to establish the burden of infection are not sensitive enough, especially in low-endemic settings, which results in underestimation of the true prevalence of active Schistosoma spp infections. This central issue necessitates that the current schistosomiasis control strategies recommended by WHO are re-evaluated and, possibly, adapted. More targeted interventions and novel approaches have been used to estimate the prevalence of schistosomiasis, such as establishing infection burden by use of precision mapping, which provides high resolution spatial information that delineates variations in prevalence within a defined geographical area. Such information is instrumental in guiding targeted intervention campaigns. However, the need for highly accurate diagnostic tools in such strategies is a crucial factor that is often neglected. The availability of highly sensitive diagnostic tests also opens up the possibility of applying strategies of sample pooling to reduce the cost of control programmes. To interrupt the transmission of, and eventually eliminate, schistosomiasis, better local targeting of preventive chemotherapy, in combination with highly sensitive diagnostic tools, is crucial.

A controlled human Schistosoma mansoni infection model to advance novel drugs, vaccines and diagnostics

Schistosomiasis treatment relies on the use of a single drug, praziquantel, which is insufficient to control transmission in highly endemic areas¹. Novel medicines and vaccines are urgently needed^2,3. An experimental human model for schistosomiasis could accelerate the development of these products. We performed a dose-escalating clinical safety trial in 17 volunteers with male Schistosoma mansoni cercariae, which do not produce eggs (clinicaltrials.gov NCT02755324), at the Leiden University Medical Center, the Netherlands. The primary endpoints were adverse events and infectivity. We found a dose-related increase in adverse events related to acute schistosomiasis syndrome, which occurred in 9 of 17 volunteers. Overall, 5 volunteers (all 3 of the high dose group and 2 of 11 of the medium dose group) reported severe adverse events. Worm-derived circulating anodic antigen, the biomarker of the primary infection endpoint, peaked in 82% of volunteers at 3-10 weeks following exposure. All volunteers showed IgM and IgG1 seroconversion and worm-specific cytokine production by CD4⁺ T cells. All volunteers were cured with praziquantel provided at 12 weeks after exposure. Infection with 20 Schistosoma mansoni cercariae led to severe adverse events in 18% of volunteers and high infection rates. This infection model paves the way for fast-track product development for treatment and prevention of schistosomiasis.

Non-typhoidal Salmonella intestinal carriage in a Schistosoma mansoni endemic community in a rural area of the Democratic Republic of Congo

BACKGROUND

Clinical observations and animal studies have suggested that Salmonella intestinal carriage is promoted by concurrent Schistosoma infection. The present study assessed association of Salmonella intestinal carriage and Schistosoma mansoni infection among individuals in a Schistosoma endemic area in sub-Saharan Africa.

METHODS

From November 2015 to March 2016, a cross-sectional community-wide study was conducted in Kifua II, a rural village in Kongo Central Province, Democratic Republic of Congo. Stool samples were collected and analyzed for Salmonella intestinal carriage (culture) and Schistosoma mansoni infection (Kato Katz microscopy with determination of egg load). Salmonella Typhimurium and Enteritidis isolates were assessed for genetic similarity with blood culture isolates obtained during the same period in a neighboring hospital using multi-locus variable-numbers tandem repeat analysis (MLVA).

RESULTS

A total of 1,108 participants were included (median age 15 years (IQR: 7-36), male-to-female ratio of 1:1.1). The overall prevalence of Schistosoma mansoni infection and non-typhoidal Salmonella carriage was 51.2% (95% CI: 48.2-54.1) and 3.4% (95% CI: 2.5-4.7) respectively, with 2.2% (95% CI: 1.5-3.2) of participants coinfected. The proportion of Salmonella carriage tended to be higher among Schistosoma mansoni infected participants compared to non-infected participants but this difference did not reach statistical significance (4.2% versus 2.6%, p = 0.132). However, the proportion of Salmonella carriage among participants with a heavy Schistosoma mansoni infection was significantly higher compared to those with a light and moderate infection (8.7% versus 3.2%, p = 0.012) and compared to Schistosoma mansoni negatives (8.7% versus 2.6%, p = 0.002). The 38 Salmonella isolates comprised five and four Enteritidis and Typhimurium serotypes respectively, the majority of them had MLVA types identical or similar to those observed among blood culture isolates.

CONCLUSION

Salmonella intestinal carriage was associated with a heavy intensity of Schistosoma mansoni infection. Further studies are needed to address causation.

Survey and Diagnostic Challenges after Transmission-Stop: Confirming Elimination of Schistosomiasis haematobium in Morocco

Clinical cases of Moroccan residents have been recorded since 2004, indicating successful interruption of transmission of S. haematobium infection at national level. The first national survey initiated in 2009 for Schistosomiasis haematobium among children born after 2004, applied diagnostic test was the HAMA-EITB, based on the Western blot technology, and molecular malacological diagnostic tools clearly confirm transmission stop. In 2015, a recent, small survey utilizing an HAI, ELISA tests and an ultrasensitive antigen test, FTCUP CAA, in a group of individual with a past history of infection. However, obviously follow-up surveys to prevent reemergency and for certification of the schistosomiasis elimination require vigilant diagnosis strategies. Here we discuss diagnosis story line in the national laboratory and challenges based on the available tools in relation to their clinical parameters (sensitivity/specificity; Sn/Sp), practicability and associated costs. When transmission stop has been achieved, survey cost and speed are likely to benefit from cost effective pooling strategies and ultrasensitive assays indicating active infection in all potential risk groups. Similarly molecular pooling strategies to monitor infections in the snail vectors.

Development of a recombinase polymerase amplification (RPA) fluorescence assay for the detection of Schistosoma haematobium

Background

Accurate diagnosis of urogenital schistosomiasis is vital for surveillance and control programmes. While a number of diagnostic techniques are available there is a need for simple, rapid and highly sensitive point-of-need (PON) tests in areas where infection prevalence and intensity are low. Recombinase Polymerase Amplification (RPA) is a sensitive isothermal molecular diagnostic technology that is rapid, portable and has been used at the PON for several pathogens.

Results

A real time fluorescence RPA assay (RT-ShDra1-RPA) targeting the Schistosoma haematobium Dra1 genomic repeat region was developed and was able to detect 1 fg of S. haematobium gDNA. Results were obtained within 10 minutes using a small portable battery powered tube scanner device that incubated reactions at 40 °C, whilst detecting DNA amplification and fluorescence over time. The assay’s performance was evaluated using 20 urine samples, with varying S. haematobium egg counts, from school children from Pemba Island, Zanzibar Archipelago, Tanzania. Prior to RPA analysis, samples were prepared using a quick crude field DNA extraction method, the Speed Extract Kit (Qiagen, Manchester, UK). Positive assay results were obtained from urine samples with egg counts of 1–926 eggs/10 ml, except for two samples, which had inconclusive results. These two samples had egg counts of two and three eggs/10 ml of urine.

Conclusions

The RT-ShDra1-RPA assay proved robust for S. haematobium gDNA detection and was able to amplify and detect S. haematobium DNA in urine samples from infected patients. The assay’s speed and portability, together with the use of crude sample preparation methods, could advance the rapid molecular diagnosis of urogenital schistosomiasis at the PON within endemic countries.

How can schistosome circulating antigen assays be best applied for diagnosing male genital schistosomiasis (MGS): an appraisal using exemplar MGS cases from a longitudinal cohort study among fishermen on the south shoreline of Lake Malawi

We provide an update on diagnostic methods for the detection of urogenital schistosomiasis (UGS) in men and highlight that satisfactory urine-antigen diagnostics for UGS lag much behind that for intestinal schistosomiasis, where application of a urine-based point-of-care strip assay, the circulating cathodic antigen (CCA) test, is now advocated. Making specific reference to male genital schistosomiasis (MGS), we place greater emphasis on parasitological detection methods and clinical assessment of internal genitalia with ultrasonography. Unlike the advances made in defining a clinical standard protocol for female genital schistosomiasis, MGS remains inadequately defined. Whilst urine filtration with microscopic examination for ova of Schistosoma haematobium is a convenient but error-prone proxy of MGS, we describe a novel low-cost sampling and direct visualization method for the enumeration of ova in semen. Using exemplar clinical cases of MGS from our longitudinal cohort study among fishermen along the shoreline of Lake Malawi, the portfolio of diagnostic needs is appraised including: the use of symptomatology questionnaires, urine analysis (egg count and CCA measurement), semen analysis (egg count, circulating anodic antigen measurement and real-time polymerase chain reaction analysis) alongside clinical assessment with portable ultrasonography.

Sensitivity enhancement in lateral flow assays: a systems perspective

Lateral flow assays (LFAs) are rapid, inexpensive, easy-to-manufacture and -use tests widely employed in medical and environmental applications, particularly in low resource settings. Historically, LFAs have been stigmatized as having limited sensitivity. However, as their global usage expands, extensive research has demonstrated that it is possible to substantially improve LFA sensitivity without sacrificing their advantages. In this critical review, we have compiled state-of-the-art approaches to LFA sensitivity enhancement. Moreover, we have organized and evaluated these approaches from a system-level perspective, as we have observed that the advantages and disadvantages of each approach have arisen from the integrated and tightly interconnected chemical, physical, and optical properties of LFAs.

Performance of an Ultra-Sensitive Assay Targeting the Circulating Anodic Antigen (CAA) for Detection of Schistosoma mansoni Infection in a Low Endemic Area in Brazil

Techniques with high sensitivity and specificity are required for an accurate diagnosis in low-transmission settings, where the conventional parasitological methods are insensitive. We determined the accuracy of an up-converting phosphor-lateral flow circulating anodic antigen (UCP-LF CAA) assay in urine and serum for Schistosoma mansoni diagnosis in low-prevalence settings in Ceará, Brazil, before and after praziquantel treatment. Clinical samples of a total of 258 individuals were investigated by UCP-LF CAA, point-of-care-circulating cathodic antigen (POC-CCA), soluble worm antigen preparation (SWAP)-ELISA and Kato-Katz (KK); a selection of 128 stools by real-time PCR technique. Three and 6-weeks after treatment, samples were collected and evaluated by detection Schistosoma circulating antigens (CAA and CCA). The UCP-LF CAA assays detected 80 positives (31%) with urine and 82 positives (31.8%) with serum. The urine POC-CCA and serum SWAP-ELISA assays detected 30 (11.6%) and 107 (40.7%) positives, respectively. The Kato-Katz technique revealed only 4 positive stool samples (1.6%). Among the 128 individuals with complete data records, 19 cases were identified by PCR (14.8%); Sensitivities and specificities of the UCP-LF CAA assays, determined versus a combined reference standard based on CCA/KK/PCR positivity, ranged from 60-68% to 68-77%, respectively. In addition only for comparative purposes, sensitivities of the different assays were determined vs. a comparative reference based on CAA/KK/PCR positivity, showing the highest sensitivity for the urine CAA assay (80%), followed by the serum CAA (70.9%), SWAP-ELISA (43.6%), PCR (34.5%), POC-CCA (29.1%), whilst triplicate Kato-Katz thick smears had a very low sensitivity (3.6%). CAA concentrations were higher in serum than in urine and were significantly correlated. There was a significant decrease in urine and serum CAA levels 3 and 6-weeks after treatment. The UCP-LF CAA assays revealed 33 and 28 S. mansoni-infected patients at the 3- and 6-week post-treatment follow-up, respectively. The UCP-LF CAA assays show high sensitivity for the diagnosis of S. mansoni in low-endemicity settings. It detects a considerably higher number of infections than microscopy, POC-CCA or PCR. Also it shows to be very useful for evaluating cure rates after treatment. Hence, the UCP-LF CAA assay is a robust and promising diagnostic approach in low-transmission settings.

Diagnosis of Schistosoma mansoni infections: what are the choices in Brazilian low-endemic areas?

The population of Brazil is currently characterised by many individuals harbouring low-intensity Schistosoma mansoni infections. The Kato-Katz technique is the diagnostic method recommended by the World Health Organization (WHO) to assess these infections, but this method is not sensitive enough in the context of low egg excretion. In this regard, potential alternatives are being employed to overcome the limits of the Kato-Katz technique. In the present review, we evaluated the performance of parasitological and immunological approaches adopted in Brazilian areas. Currently, the diagnostic choices involve a combination of strategies, including the utilisation of antibody methods to screen individuals and then subsequent confirmation of positive cases by intensive parasitological investigations.

Serological proteomic screening and evaluation of a recombinant egg antigen for the diagnosis of low-intensity Schistosoma mansoni infections in endemic area in Brazil

Background

Despite decades of use of control programs, schistosomiasis remains a global public health problem. To further reduce prevalence and intensity of infection, or to achieve the goal of elimination in low-endemic areas, there needs to be better diagnostic tools to detect low-intensity infections in low-endemic areas in Brazil. The rationale for development of new diagnostic tools is that the current standard test Kato-Katz (KK) is not sensitive enough to detect low-intensity infections in low-endemic areas. In order to develop new diagnostic tools, we employed a proteomics approach to identify biomarkers associated with schistosome-specific immune responses in hopes of developing sensitive and specific new methods for immunodiagnosis.

Methods and findings

Immunoproteomic analyses were performed on egg extracts of Schistosoma mansoni using pooled sera from infected or non-infected individuals from a low-endemic area of Brazil. Cross reactivity with other soil-transmitted helminths (STH) was determined using pooled sera from individuals uniquely infected with different helminths. Using this approach, we identified 23 targets recognized by schistosome acute and chronic sera samples. To identify immunoreactive targets that were likely glycan epitopes, we compared these targets to the immunoreactivity of spots treated with sodium metaperiodate oxidation of egg extract. This treatment yielded 12/23 spots maintaining immunoreactivity, suggesting that they were protein epitopes. From these 12 spots, 11 spots cross-reacted with sera from individuals infected with other STH and 10 spots cross-reacted with the negative control group. Spot number 5 was exclusively immunoreactive with sera from S. mansoni-infected groups in native and deglycosylated conditions and corresponds to Major Egg Antigen (MEA). We expressed MEA as a recombinant protein and showed a similar recognition pattern to that of the native protein via western blot. IgG-ELISA gave a sensitivity of 87.10% and specificity of 89.09% represented by area under the ROC curve of 0.95. IgG-ELISA performed better than the conventional KK (2 slides), identifying 56/64 cases harboring 1–10 eggs per gram of feces that were undiagnosed by KK parasitological technique.

Conclusions

The serological proteome approach was able to identify a new diagnostic candidate. The recombinant egg antigen provided good performance in IgG-ELISA to detect individuals with extreme low-intensity infections (1 egg per gram of feces). Therefore, the IgG-ELISA using this newly identified recombinant MEA can be a useful tool combined with other techniques in low-endemic areas to determine the true prevalence of schistosome infection that is underestimated by the KK method. Further, to overcome the complexity of ELISA in the field, a second generation of antibody-based rapid diagnostic tests (RDT) can be developed.

Schistosomiasis remains a serious global public health problem. Detecting parasite eggs in patient stool samples using the KK method is the standard diagnostic recommended by the World Health Organization (WHO) for infection by S. mansoni. As a result of intensive control strategies, many previously high-endemic areas are now considered low-endemic areas and the KK method does not function well in low-endemic areas and therefore cannot be considered the gold standard. Thus, a new emphasis on strategies to accurately diagnose low-intensity infections was outlined in a plan from the WHO focusing on elimination of disease as a public health problem. Successful diagnoses and treatment of infected individuals may result in eradication of low-burden transmitters and consequently contribute to interruption of disease transmission. In this regard, immunological techniques have proven to be more sensitive and promising for identifying low-intensity infections where KK may be negative. The identification of antigens is the initial step for developing new immunodiagnostic assays. In this study, we used sets of pooled human sera samples from controls with acute and chronic infections to identify new target antigens via proteomic screening. Using these approaches, we initially identified 12 different egg proteins in S. mansoni-infected individuals (acute and chronic phase). A single antigen, identified as MEA, was shown to be highly specific as this antigen was not recognized by sera from negative patients or patients infected with other STH. The recombinant MEA protein functioned in an ELISA as a highly sensitive and specific antigen to detect patient IgG-antibodies. Recombinant MEA performed significantly better to detect low-intensity infections (1 egg per gram of feces) than the KK method using 2 slides. Therefore, we were able to use a proteomic screening approach to identify a potential new candidate antigen for development of far more sensitive diagnostic assays. Further diagnostic assays employing the MEA could be useful tools on their own or in combination with other methods for diagnosis of schistosome infection in populations living in extreme low-intensity endemic areas of Brazil.

Inorganic Complexes and Metal-Based Nanomaterials for Infectious Disease Diagnostics

Infectious diseases claim millions of lives each year. Robust and accurate diagnostics are essential tools for identifying those who are at risk and in need of treatment in low-resource settings. Inorganic complexes and metal-based nanomaterials continue to drive the development of diagnostic platforms and strategies that enable infectious disease detection in low-resource settings. In this review, we highlight works from the past 20 years in which inorganic chemistry and nanotechnology were implemented in each of the core components that make up a diagnostic test. First, we present how inorganic biomarkers and their properties are leveraged for infectious disease detection. In the following section, we detail metal-based technologies that have been employed for sample preparation and biomarker isolation from sample matrices. We then describe how inorganic- and nanomaterial-based probes have been utilized in point-of-care diagnostics for signal generation. The following section discusses instrumentation for signal readout in resource-limited settings. Next, we highlight the detection of nucleic acids at the point of care as an emerging application of inorganic chemistry. Lastly, we consider the challenges that remain for translation of the aforementioned diagnostic platforms to low-resource settings.

Poly(amidoamine)-coated magnetic particles for enhanced detection of Schistosoma circulating anodic antigen in endemic urine samples

Accurate and sensitive point-of-care diagnostic tools are critical for schistosomiasis control and elimination. The existing ultrasensitive lateral flow assay for the detection of Schistosoma circulating anodic antigen (CAA) has demonstrated excellent sensitivity but is time-consuming and requires significant laboratory infrastructure that limits its applicability at the point of care. To address this challenge, we sought to develop an alternative sample preparation method to concentrate CAA from large-volume urine samples requiring little-to-no laboratory equipment. The developed method relies on electrostatic interactions between the negatively-charged CAA biomarker and positively-charged poly(amidoamine) (PAMAM) dendrimers functionalized to the surface of magnetic particles. After CAA capture on the surface of the PAMAM-functionalized magnetic beads, the supernatant was removed, and CAA was eluted into a small-volume, high-salt elution buffer. This concentrated eluate was subsequently applied to the existing lateral flow assay. The PAMAM-functionalized magnetic bead-based CAA concentration method was extensively characterized for its robustness, evaluated on a set of endemic urine samples, and compared to spin filter-based concentration methods. The novel bead-based sample preparation method used only disposable laboratory materials, resulted in a 200-fold improvement in CAA limits of detection, and performed just as well as infrastructure-intensive and high-cost spin filter methods. Additionally, the functionalized beads were robust to variations in sample pH and storage conditions. The PAMAM-functionalized magnetic bead-based CAA concentration method represents a promising step toward ultrasensitive schistosomiasis diagnosis at the point of care.

Repeated doses of Praziquantel in Schistosomiasis Treatment (RePST) - single versus multiple praziquantel treatments in school-aged children in Côte d'Ivoire: a study protocol for an open-label, randomised controlled trial

Background

Large scale administration of the anthelminthic drug praziquantel (PZQ) to at-risk populations is the cornerstone of schistosomiasis control, although persisting high prevalence of infections in some areas and growing concerns of PZQ resistance have revealed the limitations of this strategy. Most studies assessing PZQ efficacy have used relatively insensitive parasitological diagnostics, such as the Kato-Katz (KK) and urine-filtration methods, thereby overestimating cure rates (CRs). This study aims to determine the efficacy of repeated PZQ treatments against Schistosoma mansoni infection in school-aged children in Côte d’Ivoire using the traditional KK technique, as well as more sensitive antigen- and DNA-detection methods.

Methods

An open-label, randomised controlled trial will be conducted in school-aged children (5 to 18 years) from the region of Taabo, Côte d’Ivoire, an area endemic for S. mansoni. This 8-week trial includes four two-weekly standard doses of PZQ in the “intense treatment” intervention group and one standard dose of PZQ in the “standard treatment” control group. The efficacy of PZQ will be evaluated in stool samples using the KK technique and real-time PCR as well as in urine using the point-of-care circulating cathodic antigen test and the up-converting phosphor, lateral flow, circulating anodic antigen assay. The primary outcome of the study will be the difference in CR of intense versus standard treatment with PZQ on individuals with a confirmed S. mansoni infection measured by KK. Secondary outcomes include the difference in CR and intensity reduction rate between the intense and standard treatment groups as measured by the other diagnostic tests, as well as the accuracy of the different diagnostic tests, and the safety of PZQ.

Discussion

This study will provide data on the efficacy of repeated PZQ treatment on the clearance of S. mansoni as measured by several diagnostic techniques. These findings will inform future mass drug administration policy and shed light on position of novel diagnostic tools to evaluate schistosomiasis control strategies.

Trial registration

The study is registered at EudraCT (2016–003017-10, date of registration: 22 July 2016) and (NCT02868385, date of registration: 16 August 2016).

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3554-2) contains supplementary material, which is available to authorized users.

Refining Diagnosis of Schistosoma haematobium Infections: Antigen and Antibody Detection in Urine

Background: Traditional microscopic examination of urine or stool for schistosome eggs lacks sensitivity compared to measurement of schistosome worm-derived circulating antigens in serum or urine. The ease and non-invasiveness of urine collection makes urine an ideal sample for schistosome antigen detection. In this study several user-friendly, lateral-flow (LF) based urine assays were evaluated against a composite reference that defined infection as detection of either eggs in urine or anodic antigen in serum. Method: In a Tanzanian population with a S. haematobium prevalence of 40-50% (S. mansoni prevalence <2%), clinical samples from 44 women aged 18 to 35 years were analyzed for Schistosoma infection. Urine and stool samples were examined microscopically for eggs, and serum samples were analyzed for the presence of the anodic antigen. Urines were further subjected to a set of LF assays detecting (circulating) anodic (CAA) and cathodic antigen (CCA) as well as antibodies against soluble egg antigens (SEA) and crude cercarial antigen preparation (SCAP). Results: The urine LF anodic antigen assay utilizing luminescent upconverting reporter particles (UCP) confirmed its increased sensitivity when performed with larger sample volume. Qualitatively, the anodic antigen assay performed on 250 μL urine matched the performance of the standard anodic antigen assay performed on 20 μL serum. However, the ratio of anodic antigen levels in urine vs. serum of individual patients varied with absolute levels always higher in serum. The 10 μL urine UCP-LF cathodic antigen assay correlated with the commercially available urine POC-CCA (40 μL) test, while conferring better sensitivity with a quantitative result. Urinary antibodies against SEA and SCAP overlap and correlate with the presence of urinary egg and serum anodic antigen levels. Conclusions: The UCP-LF anodic antigen assay using 250 μL of urine is an expedient user-friendly assay and a suitable non-invasive alternative to serum-based antigen testing and urinary egg detection. Individual biological differences in the clearance process of the circulating antigens are thought to explain the observed high variation in the type and level of antigen (anodic or cathodic) measured in urine or serum. Simultaneous detection of anodic and cathodic antigen may be considered to further increase accuracy.

Urogenital schistosomiasis elimination in Zanzibar: accuracy of urine filtration and haematuria reagent strips for diagnosing light intensity Schistosoma haematobium infections

Background

Urine filtration and microhaematuria reagent strips are basic standard diagnostic methods to detect urogenital schistosomiasis. We assessed their accuracy for the diagnosis of light intensity infections with Schistosoma haematobium as they occur in individuals living in Zanzibar, an area targeted for interruption of transmission.

Methods

Urine samples were collected from children and adults in surveys conducted annually in Zanzibar from 2013 through 2016 and examined with the urine filtration method to count S. haematobium eggs and with the reagent strip test (Hemastix) to detect microhaematuria as a proxy for infection. Ten percent of the urine filtration slides were read twice. Sensitivity was calculated for reagent strips, stratified by egg counts reflecting light intensity sub-groups, and kappa statistics for the agreement of urine filtration readings.

Results

Among the 39,207 and 18,155 urine samples examined from children and adults, respectively, 5.4% and 2.7% were S. haematobium egg-positive. A third (34.7%) and almost half (46.7%) of the egg-positive samples from children and adults, respectively, had ultra-low counts defined as 1–5 eggs per 10 ml urine. Sensitivity of the reagent strips increased significantly for each unit log10 egg count per 10 ml urine in children (odds ratio, OR: 4.7; 95% confidence interval, CI: 4.0–5.7; P < 0.0001) and adults (OR: 2.6; 95% CI: 1.9–3.7, P < 0.0001). Sensitivity for diagnosing ultra-light intensity infections was very low in children (50.1%; 95% CI: 46.5–53.8%) and adults (58.7%; 95% CI: 51.9–65.2%). Among the 4477 and 1566 urine filtration slides read twice from children and adults, most were correctly identified as negative or positive (kappa = 0.84 for children and kappa = 0.81 for adults). However, 294 and 75 slides had discrepant results and were positive in only one of the two readings. The majority of these discrepant slides (76.9% of children and 84.0% of adults) had counts of 1–5 eggs per 10 ml urine.

Conclusions

We found that many individuals infected with S. haematobium in Zanzibar excrete > 5 eggs per 10 ml urine. These ultra-light infections impose a major challenge for accurate diagnosis. Next-generation diagnostic tools to be used in settings where interruption of transmission is the goal should reliably detect infections with ≤ 5 eggs per 10 ml urine.

Trial Registration

ISRCTN, ISRCTN48837681. Registered 05 September 2012 - Retrospectively registered.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3136-6) contains supplementary material, which is available to authorized users.

Experimental infection of human volunteers

Controlled human infection (CHI) trials, in which healthy volunteers are experimentally infected, can accelerate the development of novel drugs and vaccines for infectious diseases of global importance. The use of CHI models is expanding from around 60 studies in the 1970s to more than 120 publications in this decade, primarily for influenza, rhinovirus, and malaria. CHI trials have provided landmark data for several registered drugs and vaccines, and have generated unprecedented scientific insights. Because of their invasive nature, CHI studies demand critical ethical review according to established frameworks. CHI-associated serious adverse events are rarely reported. Novel CHI models need standardised safety data from comparable CHI models to facilitate evidence-based risk assessments, as well as funds to produce challenge inoculum according to regulatory requirements. Advances such as the principle of controlled colonisation, the expansion of models to endemic areas, and the use of genetically attenuated strains will further broaden the scope of CHI trials.

Sm-p80-based vaccine trial in baboons: efficacy when mimicking natural conditions of chronic disease, praziquantel therapy, immunization, and Schistosoma mansoni re-encounter

Sm-p80-based vaccine efficacy for Schistosoma mansoni was evaluated in a baboon model of infection and disease. The study was designed to replicate a human vaccine implementation scenario for endemic regions in which vaccine would be administered following drug treatment of infected individuals. In our study, the Sm-p80-based vaccine reduced principal pathology producing hepatic egg burdens by 38.0% and egg load in small and large intestines by 72.2% and 49.4%, respectively, in baboons. Notably, hatching rates of eggs recovered from liver and small and large intestine of vaccinated animals were significantly reduced, by 60.4%, 48.6%, and 82.3%, respectively. Observed reduction in egg maturation/hatching rates was supported by immunofluorescence and confocal microscopy showing unique differences in Sm-p80 expression in worms of both sexes and matured eggs. Vaccinated baboons had a 64.5% reduction in urine schistosome circulating anodic antigen, a parameter that reflects worm numbers/health status in infected hosts. Preliminary analyses of RNA sequencing revealed unique genes and canonical pathways associated with establishment of chronic disease, praziquantel-mediated parasite killing, and Sm-p80-mediated protection in vaccinated baboons. Overall, our study demonstrated efficacy of the Sm-p80 vaccine and provides insight into some of the epistatic interactions associated with protection.