Surveillance of intestinal schistosomiasis during control: a comparison of four diagnostic tests across five Ugandan primary schools in the Lake Albert region

Home-Made Lateral Flow Test Strip Versus POC-CCA Assay for Detection of Active Schistosomiasis in Egypt

BACKGROUND

For years, the Kato-Katz (KK) technique has been considered the gold standard for diagnosing schistosomiasis. The aim of this study was to compare the effectiveness of our previously developed gold nanoparticle-based lateral flow test strip (AuNPs-LFTS) for diagnosing active Schistosoma mansoni with that of the commercially available point-of-care Circulating Cathodic Antigen detection (POC-CCA) kit.

METHODS

In this study, we collected sixty positive and twenty negative urine samples from patients in endemic hot spots in the Nile Delta, as well as from patients visiting the internal medicine clinic at Theodor Bilharz Research Institute (TBRI). We produced monoclonal antibodies (MAbs) against S. mansoni soluble egg antigen (SEA) from cloned hybridoma cells (4D/1D). These MAbs were conjugated with gold and mesoporous silica nanoparticles, and used to develop the LFTS.

RESULTS

The LFTS demonstrated a limit of detection (LoD) of 3 ng/ml. The sensitivity and specificity of the developed LFTS were found to be 96.7% and 95%, respectively, compared to 85% and 90% for the POC-CCA detection kit. The cases were divided into groups based on egg count in the stool, categorized as light, moderate, and heavy infections. The sensitivity of the LFTS in the group with light infection was higher than that of the POC-CCA. When using the KK technique (eggs per gram of stool sample [EPG]) as the reference test, the kappa value for the nano-based strips was 0.902, compared to 0.672 for the CCA strips, indicating an almost perfect agreement between KK and our developed LFTS.

CONCLUSION

These results confirm the reliability and effectiveness of the LFTS compared to commercially available kits for rapid, sensitive, and early diagnosis of schistosomiasis. However, it is recommended to conduct further assessments of the developed strip on a larger scale with a broader range of cases before considering its introduction to local or international markets.

Molecular epidemiology and population genetics of Schistosoma mansoni infecting school-aged children situated along the southern shoreline of Lake Malawi, Malawi

BACKGROUND

In areas of low disease endemicity, highly sensitive diagnostic tools to identify, diagnose, and monitor intestinal schistosomiasis transmission are needed to reliably measure the burden and risk of infection. Here, we used highly sensitive molecular diagnostic methods to investigate Schistosoma mansoni prevalence and transmission along the southern shoreline of Lake Malawi, five years post-disease outbreak.

METHODOLOGY AND PRINCIPAL FINDINGS

Faecal and urine samples were provided by school-aged children situated along the southern shoreline of Lake Malawi. Kato-Katz faecal-egg microscopy and point-of-care circulating cathodic antigen (POC-CCA) rapid diagnostic tests were then performed to diagnose infection with S. mansoni. Urine-egg microscopy was also used to diagnose infection with Schistosoma haematobium. In addition, Schistosoma miracidia were isolated from faecal material using a standard miracidium hatching technique. A two-step real-time PCR approach was then used to diagnose infection with S. mansoni using DNA isolated from faecal samples. Furthermore, isolated miracidia were genotyped to species level through PCR and Sanger sequencing. Phylogenetic analyses were then carried out to identify which previously defined S. mansoni cox1 lineage group S. mansoni miracidia were most closely related to. The measured prevalence of S. mansoni infection varied considerably depending on which diagnostic assay was used. When compared to real-time PCR, faecal-egg microscopy had a sensitivity of 9% and a specificity of 100%. When POC-CCA 'trace' results were considered positive, POC-CCA had a sensitivity of 73% and a specificity of 81% when compared to real-time PCR. However, when considered negative, POC-CCA sensitivity was reduced to 56%, whereas specificity was increased to 90%. In addition, a high degree of S. haematobium DNA was detected in DNA isolated from faecal samples and motile S. haematobium miracidia were recovered from faecal samples. Schistosoma mansoni miracidia were closely related to two independent cox1 lineage groups, suggesting multiple recent introduction and colonisation events originating from surrounding east African countries.

CONCLUSIONS AND SIGNIFICANCE

Intestinal schistosomiasis is now highly prevalent along the southern shoreline of Lake Malawi just five years post-disease outbreak. In addition, a high prevalence of urogenital schistosomiasis persists. The revision of ongoing schistosomiasis control programmes in this area is therefore recommended. Our study also highlights the need for reliable diagnostic assays capable of distinguishing between Schistosoma species in multispecies co-endemic areas.

Evaluation of a modified quantitative polymerase chain reaction assay for genus Schistosoma detection using stool and urine samples from schistosomiasis endemic areas in Kenya

INTRODUCTION

The microscopy-based Kato-Katz and urine filtration techniques have traditionally faced challenges in the detection of schistosomiasis in areas with low infection levels. A modified singleplex Schistosoma genus-specific quantitative real-time polymerase chain reaction (qPCR) assay was therefore evaluated as a sensitive and confirmatory schistosomiasis diagnostic test.

METHODOLOGY

The qPCR assay utilized primers and probe targeting internal transcribed spacer- 2 (ITS2) sequence of S. mansoni, S. haematobium and S. intercalatum. A plasmid (pDMD801, 100pg/ul) was used as an internal amplification control and its qPCR assays were run in parallel to the Schistosoma assays. This assay utilized samples collected from 774 participants and microscopically examined for three consecutive days. A total of 699 day-one samples (urine and stools) from two schistosomiasis endemic sites were analyzed. Similarly, 75 persons from a non-endemic control site provided both urine and stool samples that were also analyzed.

RESULTS

Using microscopy, the proportion of positives in the two endemic regions altogether was 289/699 (41.3%). Using qPCR, 50.4% of the samples (352/699) were found to be positive for schistosome infection. The percentage of positive samples was slightly higher at 57.8% (203/351) in the S. mansoni endemic site compared with the S. haematobium site at 42.8% (149/348). Majority of the microscopy results were light infections at 26.8% (n = 94) and 26.1% (n = 91) while qPCR majority of the infections were high at 41.6% (n = 146) and 31.3% (n = 109) for the S. mansoni and S. haematobium sites, respectively. There were no positives detected by either microscopy or qPCR in the non-endemic site. Using Bayesian Latent Class Model, which does not use any technique as a gold standard, qPCR showed higher sensitivity (86.4% (PCI: 82.1-90.3)) compared to microscopy (75.6% (PCI: 71.1-80.0)).

CONCLUSIONS

This study documents a single day-one sample modified Schistosoma qPCR assay as a powerful improved molecular assay for the detection of schistosomiasis infection that utilize either stool or urine samples. The assay is therefore recommended for monitoring in areas with low infection levels to enable accurate determination of the disease's control endpoint.

Evaluation of sensitivity and specificity of Kato-Katz and circulating cathodic antigen in terms of Schistosoma japonicum using latent class analysis

Schistosoma japonicum is endemic in the Philippines. The Kato-Katz (KK) method was used to diagnose S. japonicum. This is impractical, particularly when the sample size is limited. Knowledge on point-of-care circulating cathodic antigen (CCA) test performance for S. japonicum is limited. Determining the sensitivity and specificity of new diagnostics is difficult when the gold standard test is less effective or absent. Latent class analysis (LCA) can address some limitations. A total of 484 children and 572 adults from the Philippines were screened for S. japonicum. We performed Bayesian LCA to estimate the infection prevalence, sensitivity and specificity of each test by stratifying them into two age groups. Observed prevalence assessed by KK was 50.2% and 31.8%, and by CCA was 89.9% and 66.8%, respectively. Using Bayesian LCA, among children, the sensitivity and specificity of CCA were 94.8% (88.7-99.4) and 21.5% (10.5-36.1) while those of KK were 66.0% (54.2-83.3) and 78.1% (61.1-91.3). Among adults, the sensitivity and specificity of CCA were 86.4% (76.6-96.9) and 62.8% (49.1-81.1) while those of KK were 43.6% (35.1-53.9) and 85.5% (75.8-94.6). Overall, CCA was more sensitive than KK, regardless of the age group at diagnosis, as KK was more specific. KK and CCA have different diagnostic performance, which should inform their use in the planning and implementation of S. japonicum control programs.

Diagnostic tests for human Schistosoma mansoni and Schistosoma haematobium infection: a systematic review and meta-analysis

BACKGROUND

Accurate diagnosis is pivotal for implementing strategies for surveillance, control, and elimination of schistosomiasis. Despite their low sensitivity in low-endemicity areas, microscopy-based urine filtration and the Kato-Katz technique are considered as reference diagnostic tests for Schistosoma haematobium and Schistosoma mansoni infections, respectively. We aimed to collate all available evidence on the accuracy of other proposed diagnostic techniques.

METHODS

In this systematic review and meta-analysis, we searched PubMed, Embase, the Cochrane Library, and LILACS for studies published from database inception to Dec 31, 2022, investigating the sensitivity and specificity of diagnostic tests for S haematobium and S mansoni infections against Kato-Katz thick smears or urine microscopy (reference tests) involving adults (aged ≥18 years), school-aged children (aged 7 to 18 years), or preschool-aged children (aged 1 month to 7 years). We extracted raw data on true positives, true negatives, false positives, and false negatives for the diagnostic tests and data on the number of participants, study authors, publication year, journal, study design, participants' age and sex, prevalence of Schistosoma infection, and treatment status. To account for imperfect reference tests, we used a hierarchical Bayesian latent class meta-analysis to model test accuracy.

FINDINGS

Overall, we included 121 studies, assessing 28 different diagnostic techniques. Most studies (103 [85%] of 121) were done in Africa, 14 (12%) in South America, one (1%) in Asia, and one (1%) in an unknown country. Compared with the reference test, Kato-Katz thick smears, circulating cathodic antigen urine cassette assay version 1 (CCA1, 36 test comparisons) had excellent sensitivity (95% [95% credible interval 88-99]) and reasonable specificity (74% [63-83]) for S mansoni. ELISA-based tests had a performance comparable to circulating cathodic antigen, but there were few available test comparisons. For S haematobium, proteinuria (42 test comparisons, sensitivity 73% [62-82]; specificity 94% [89-98]) and haematuria (75 test comparisons, sensitivity 85% [80-90]; specificity 96% [92-99]) reagent strips showed high specificity, with haematuria reagent strips having better sensitivity. Despite limited data, nucleic acid amplification tests (NAATs; eg, PCR or loop-mediated isothermal amplification [LAMP]) showed promising results with sensitivity estimates above 90%. We found an unclear risk of bias of about 70% in the use of the reference or index tests and of 50% in patient selection. All analyses showed substantial heterogeneity (I2>80%).

INTERPRETATION

Although NAATs and immunological diagnostics show promise, the limited information available precludes drawing definitive conclusions. Additional research on diagnostic accuracy and cost-effectiveness is needed before the replacement of conventional tests can be considered.

FUNDING

WHO and Luxembourg Institute of Health.

Current and upcoming point-of-care diagnostics for schistosomiasis

Point-of-care (POC) diagnostics are simple and effective portable tools that can be used for fast mapping of helminthic diseases and monitoring control programs. Most POC tests (POCTs) available for schistosomiasis diagnosis are lateral flow immunoassays (LFIAs). The emergence of simple and rapid DNA isolation methods, along with isothermal nucleic acid amplification strategies - for example, loop-mediated isothermal amplification (LAMP) and recombinase polymerase amplification (RPA) - and recent clustered regularly interspaced short palindromic repeats (CRISPR)-based diagnostic methods facilitate the development of molecular-based POC diagnostics for schistosomiasis. Furthermore, smartphone-based techniques increase real-time connectivity and readout accuracy of POCTs. This review discusses the recent advances in immunological-, molecular-based POCTs and mobile phone microscopes for the diagnosis/screening of schistosomiasis.

Accuracy of Diagnostic Tests for Detecting Schistosoma mansoni and S. haematobium in Sub-Saharan Africa: A Systematic Review and Meta-Analysis

Introduction

Schistosomiasis is causing high morbidity and significant mortality in endemic areas. Kato-Katz stool examination and urine filtration techniques are the conventional methods for the detection of intestinal and urinary schistosomiasis. The most appropriate diagnostic tools for the detection of schistosomiasis especially in low-prevalence settings should be used. Therefore, this study is aimed at investigating the diagnostic accuracy of S. mansoni and S. haematobium diagnostic tools in sub-Saharan Africa.

Methods

Electronic databases such as PubMed, PubMed Central/Medline, HINARI, Scopus, EMBASE, Science Direct, Google Scholar, and Cochrane Library were reviewed. The pooled estimates and heterogeneity were determined using Midas in Stata 14.0. The diagnostic accuracy of index tests was compared using the hierarchical summary of the receiver operating characteristic (HSROC) curve in Stata 14.0.

Results

Twenty-four studies consisting of 12,370 individuals were tested to evaluate the accuracy of antigen, antibody, and molecular test methods for the detection of S. mansoni and S. haematobium. The pooled estimate of sensitivity and specificity of CCA was 88% (95% CI: 83-92) and 72 (95% CI: 62-80), respectively, when it is compared with parasitological stool examination for S. mansoni detection. On the other hand, ELISA showed a pooled estimate of sensitivity and specificity of 95% (95% CI: 93-96) and 35% (95% CI: 21-52), respectively, for the examination of S. mansoni using stool examination as a reference test. With regard to S. haematobium, the pooled estimate of sensitivity and specificity of polymerase chain reaction was 97% (95% CI: 78-100) and 94% (95% CI: 74-99), respectively. Moreover, the sensitivity and specificity of urine CCA vary between 41-80% and 55-91%, respectively, compared to urine microscopy.

Conclusion

The effort of schistosomiasis elimination requires accurate case identification especially in low-intensity infections. This study showed that CCA had the highest sensitivity and moderate specificity for the diagnosis of S. mansoni. Similarly, the sensitivity of ELISA was excellent, but its specificity was low. The diagnostic accuracy of PCR for the detection of S. haematobium was excellent compared to urine microscopic examination.

Accuracy Study of Kato-Katz and Helmintex Methods for Diagnosis of Schistosomiasis Mansoni in a Moderate Endemicity Area in Sergipe, Northeastern Brazil

Schistosomiasis is a neglected tropical disease (NTD) caused by blood flukes from the genus Schistosoma. Brazil hosts the main endemic area in the Americas, where Schistosoma mansoni is the only species causing the disease. Kato-Katz (KK) thick smear is the WHO recommended screening test for populational studies, but there is growing evidence for the sensitivity limitations associated with KK, especially in areas with low parasite loads. Helmintex (HTX) is another highly sensitive egg-detection method, based on the magnetic properties of S. mansoni eggs and their isolation in a magnetic field. The objective of this study is to evaluate both KK and HTX in a moderate endemic locality, Areia Branca, located in the municipality of Pacatuba, in the state of Sergipe in northeastern Brazil. From 234 individual fecal samples, two KK thick smears were prepared and evaluated for each sample. Similarly, 30 g of each fecal sample was processed by HTX protocol. Eggs were detected in 80 (34.18%) residents. Twenty-three (9.83%) samples were positive for eggs (only by KK), and 77 (32.91%) samples showed positive for eggs (only by HTX). Sensitivity, specificity, and accuracy estimates gave values of 28.75%, 100% and 75.64%, respectively, for KK, and 96.25%, 100% and 98.72% respectively, for HTX. The positive predictive value was 100% for both methods, while the negative predictive value was 72.99% for KK and 98.09% for HTX. Overall, HTX presented a superior performance compared to the one sample, two slides KK examination. The study confirms the role of HTX as a reference method for the definition of true-positive samples in comparative accuracy studies and its potential role in the late stages when the certification of schistosomiasis transmission interruption is required. Diagnostic tests are important tools for the elimination of this NTD, besides the effective implementation of safe water, basic sanitation, snail control, and the treatment of infected populations.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Point-of-Care Sample Preparation and Automated Quantitative Detection of Schistosoma haematobium Using Mobile Phone Microscopy

Schistosoma haematobium continues to pose a significant public health burden despite ongoing global control efforts. One of several barriers to sustained control (and ultimately elimination) is the lack of access to highly sensitive diagnostic or screening tools that are inexpensive, rapid, and can be used at the point of sample collection. Here, we report an automated point-of-care diagnostic based on mobile phone microscopy that rapidly images and identifies S. haematobium eggs in urine samples. Parasite eggs are filtered from urine within a specialized, inexpensive cartridge that is then automatically imaged by the mobile phone microscope (the "SchistoScope"). Parasite eggs are captured at a constriction point in the tapered cartridge for easy imaging, and the automated quantification of eggs is obtained upon analysis of the images by an algorithm. We demonstrate S. haematobium egg detection with greater than 90% sensitivity and specificity using this device compared with the field gold standard of conventional filtration and microscopy. With simple sample preparation and image analysis on a mobile phone, the SchistoScope combines the diagnostic performance of conventional microscopy with the analytic performance of an expert technician. This portable device has the potential to provide rapid and quantitative diagnosis of S. haematobium to advance ongoing control efforts.

Comparison of quantitative polymerase chain reaction, Kato-Katz and circulating cathodic antigen rapid test for the diagnosis of Schistosoma mansoni infection: A cross-sectional study in Kirinyaga County, Kenya

The current standard diagnostic tests for Schistosoma mansoni are the Kato-Katz and circulating cathodic antigen (CCA) techniques. However, these techniques have been documented to have several limitations that have a direct impact on schistosomiasis control programmes. Therefore, there is a need for more sensitive and specific tests for diagnosing schistosomiasis. This study compared the performance of quantitative polymerase chain reaction (qPCR), Kato-Katz, and point-of-care circulating cathodic antigen (POC-CCA) techniques in the diagnosis of S. mansoni infection in the Mwea irrigation scheme, Kirinyaga County in Central Kenya. We carried out a cross-sectional study on 357 individuals residing in four villages in the Mwea irrigation scheme. The participants provided urine and stool samples which were screened for S. mansoni infections using the three techniques. The prevalence of S. mansoni by each technique was calculated and 95% confidence intervals estimated using binomial regression model. Sensitivity and specificity were determined using 2 × 2 contingency tables and compared using the McNemar’s chi-square test. Positive and negative predictive values were also determined using the weighted generalized score chi-square test for paired data. The study showed that the prevalence of S. mansoni was 32.8%, 62.5% and 72.8% using Kato-Katz, POC-CCA and qPCR techniques, respectively. Further, when using Kato-Katz as a gold standard, POC-CCA sensitivity was 78.6% and specificity was 45.4%, while qPCR sensitivity was 97.4% and specificity was 39.2%. When using qPCR as the gold standard, Kato-Katz sensitivity was 43.8% and specificity was 96.9%, while POC-CCA sensitivity was 78.1% and specificity was 79.4%. Finally, when using the averaged results from the three techniques as the gold standard, the sensitivity was 41.6%, 79.4% and 92.5% for Kato-Katz, POC-CCA and qPCR, respectively, with a specificity of 100% for all techniques. Kato-Katz technique showed low sensitivity compared to the POC-CCA and qPCR despite it being the most commonly preferred method of choice to diagnose S. mansoni infections. qPCR showed superior sensitivity followed by POC-CCA, hence it can be used as an alternative or to confirm the results obtained by the Kato-Katz technique.

•

Comparison of the performance of Kato-Katz, POC-CCA and qPCR for diagnosis of S. mansoni in Kirinyaga County, Kenya.

•

A total of 357 urine and stool samples were tested for S. mansoni infection.

•

qPCR estimated the highest prevalence followed by POC-CCA and Kato-Katz.

•

qPCR showed a generally high sensitivity and specificity.

Schistosomiasis with a Focus on Africa

Schistosomiasis is a common neglected tropical disease of impoverished people and livestock in many developing countries in tropical Africa, the Middle East, Asia, and Latin America. Substantial progress has been made in controlling schistosomiasis in some African countries, but the disease still prevails in most parts of sub-Saharan Africa with an estimated 800 million people at risk of infection. Current control strategies rely primarily on treatment with praziquantel, as no vaccine is available; however, treatment alone does not prevent reinfection. There has been emphasis on the use of integrated approaches in the control and elimination of the disease in recent years with the development of health infrastructure and health education. However, there is a need to evaluate the present status of African schistosomiasis, primarily caused by Schistosoma mansoni and S. haematobium, and the factors affecting the disease as the basis for developing more effective control and elimination strategies in the future. This review provides an historical perspective of schistosomiasis in Africa and discusses the current status of control efforts in those countries where the disease is endemic.

Use of Schistosoma mansoni soluble egg antigen (SEA) for antibody detection and diagnosis of schistosomiasis: The need for improved accuracy evaluations of diagnostic tools

Many antigens for use in antibody-detection systems for schistosomiasis have been investigated over the past 40 years. In particular, soluble egg antigens (SEA) are still widely used in enzyme-linked immunosorbent assays (ELISAs) for detection of immunoglobulin classes and subclasses. Here, we conducted a literature review to examine accuracy evaluations of SEA-Immunoglobulin G (IgG)-ELISAs performed to detect Schistosoma mansoni infections and published between 1979 and 2019. S. mansoni is the main causative agent for intestinal schistosomiasis in many countries in Africa and Central and South America. After retrieving 214 relevant abstracts from the PubMed database, we selected 15 publications to undergo a full review. Sensitivity and specificity values varied from 71 to 99%, and from 6 to 100%, respectively. In addition, 11/15 studies did not state confidence intervals. Therefore, the findings from this review indicate that after four decades, we still do not have consistent evaluation estimates of SEA-IgG-ELISAs. Antigen mass per well and dilution of test sera in these articles varied from 0.018 µg to 1.5 µg, and from 1:50 to 1:500, respectively. Most of the reported accuracy evaluations used control sera which were selected based on parasitological examinations for egg detection, although ill-defined criteria were also noted. The number and composition of control serum panels was considered not adequate in approximately half of the studies. It is also noteworthy that among more than 30 diagnostic antigen preparations under development since the 1970s, most were not validated in the field and they failed to reach populations in need. Thus, attention to guidelines for standardization, estimations of accuracy, and reporting of results is needed to facilitate coordinated efforts aimed at schistosomiasis control and elimination.

Latent Class Analysis: Insights about design and analysis of schistosomiasis diagnostic studies

Various global health initiatives are currently advocating the elimination of schistosomiasis within the next decade. Schistosomiasis is a highly debilitating tropical infectious disease with severe burden of morbidity and thus operational research accurately evaluating diagnostics that quantify the epidemic status for guiding effective strategies is essential. Latent class models (LCMs) have been generally considered in epidemiology and in particular in recent schistosomiasis diagnostic studies as a flexible tool for evaluating diagnostics because assessing the true infection status (via a gold standard) is not possible. However, within the biostatistics literature, classical LCM have already been criticised for real-life problems under violation of the conditional independence (CI) assumption and when applied to a small number of diagnostics (i.e. most often 3-5 diagnostic tests). Solutions of relaxing the CI assumption and accounting for zero-inflation, as well as collecting partial gold standard information, have been proposed, offering the potential for more robust model estimates. In the current article, we examined such approaches in the context of schistosomiasis via analysis of two real datasets and extensive simulation studies. Our main conclusions highlighted poor model fit in low prevalence settings and the necessity of collecting partial gold standard information in such settings in order to improve the accuracy and reduce bias of sensitivity and specificity estimates.

Accurate schistosomiasis diagnosis is essential to assess the impact of large scale and repeated mass drug administration to control or even eliminate this disease. However, in schistosomiasis diagnostic studies, several inherent study design issues pose a real challenge for the currently available statistical tools used for diagnostic modelling and associated data analysis and conclusions. More specifically, those study design issues are: 1) the inclusion of small number of diagnostic tests (i.e. most often five), 2) non formal consensus about a schistosomiasis gold standard, 3) the contemporary use of relatively small sample sizes in relevant studies due to lack of research funding, 4) the differing levels of prevalence of the studied disease even within the same area of one endemic country and 5) other real world factors such as: the lack of appropriate equipment, the variability of certain methods due to biological phenomena and training of technicians across the endemic countries because of scarce financial resources contributing to the existing lack of a schistosomiasis gold standard. The current study aims to caution practitioners from blindly applying statistical models with small number of diagnostic tests and sample sizes, proposing design guidelines of future schistosomiasis diagnostic accuracy studies with recommendations for further research. While our study is centred around the diagnosis of schistosomiasis, we feel that the recommendations can be adapted to other major tropical infectious diseases as well.

Piloting an integrated approach for estimation of environmental risk of Schistosoma haematobium infections in pre-school-aged children and their mothers at Barombi Kotto, Cameroon

Within schistosomiasis control, assessing environmental risk of currently non-treated demographic groups e.g. pre-school-aged children (PSAC) and their mothers is important. We conducted a pilot micro-epidemiological assessment at the crater lake of Barombi Kotto, Cameroon with GPS tracking and infection data from 12 PSAC-mother pairs (n = 24) overlaid against environmental sampling inclusive of snail, parasite and water-use information. Several high-risk locations or 'hotspots' with elevated water contact, increased intermediate snail host densities and detectable schistosome environmental DNA (eDNA) were identified. Exposure between PSAC and mother pairs was temporally and spatially associated, suggesting interventions which can benefit both groups simultaneously might be feasible. When attempting to interrupt parasite transmission in future, overlaid maps of snail, parasite and water contact data can guide fine-scale spatial targeting of environmental interventions.

Intestinal schistosomiasis: Can a urine sample decide the infection?

Intestinal schistosomiasis, one of the neglected tropical diseases whose control depends on accurate diagnosis of the disease prevalence. The use of low sensitive Kato Katz (KK) fecal egg detection method as a reference gold standard is not an accurate indication especially in low transmission areas. Latent class analysis frameworks especially the Bayesian could be used instead to compare between different diagnostic tests without the use of a gold standard method as a reference. Thus, this study compared two urine-based tests for the detection of circulating antigen and cell free DNA of Schistosoma mansoni versus KK method using the Bayesian latent class analytical framework and in two models where the trace results of point of contact - assay of circulating cathodic antigen (POC-CCA) were once estimated as positive, and as negative in the other model. The Bayesian framework in the trace CCA positive model showed an estimate of disease prevalence of 26% (95% BCI:0 to 60%). POC-CCA showed the highest sensitivity (74% with BCI: 9 to 91%) and lowest specificity for (20% with BCI: 0% to 37%) and the reverse for KK. For POC-CCA with traces considered negative, it was found that results between the three tests were moderated where the positivity for infection by Schistosoma antigen detection and PCR for cell free DNA approached that estimated by the Bayesian framework (44%), and the specificity for point of contact assay(81%; 95%BCI: 59% to 100%) rose in hand with its sensitivity(77%, 95% BCI:53% to 100%) and with results for PCR test (sensitivity = 80%; 95% BCI: 61% to 100%, specificity = 69%; 95% BIC: 47% to 100%). KK remains with the highest specificity while its sensitivity in the two models never exceeded 22%. Thus, we conclude that the use of a single urine sample could be very sensitive and highly specific in the diagnosis of intestinal schistosomiasis using either the trace negative model of point of contact assay, or conventional PCR, when compared to the fecal egg detection using duplicate KK. However, the use of a single tool restricts the management of the disease in areas of low endemicity.

Detecting Schistosoma mansoni infections among pre-school-aged children in southern Ghana: a diagnostic comparison of urine-CCA, real-time PCR and Kato-Katz assays

Background

In Ghana, pre-school-aged children (PSAC) are at risk of intestinal schistosomiasis and are living in need of praziquantel treatment. To better assess the infection burden within this vulnerable demographic group, we have provided a comparative assessment of the prevalence of Schistosoma mansoni in pre-school-aged children by urine circulating cathodic antigen (CCA) dipsticks, real-time PCR Taqman® faecal assays and Kato-Katz coproscopy.

Methods

In all, 190 pre-school-aged children were sampled from three endemic communities (viz. Tomefa, Torgahkope/Adakope, and Manheam) around Weija dam, Southern Ghana. Fresh stool and urine samples were collected from all participants for diagnosis.

Results

Among all the three communities, the urine-CCA assay recorded the highest prevalence values of 90.5% (95% CI 80.4–96.4), 87.9% (95% CI 76.7–95), and 81.2% (95% CI 69.9–89.6) in Tomefa, Torgahkope/Adakope, and Manheam respectively. Prevalence by real-time PCR was 50% (95% CI 35.5–64.5), 8% (95% CI 2.2–19.2) and 16.7% (95% CI 8.3–28.5), while by Kato-Katz was 55.6% (95% CI 42.5–68.1), 8.6% (95% CI 2.9–19) and 11.6% (95% CI 5.1–21.6) respectively. Children aged 1 year and over were found to be positive with the urine-CCA assay; by the ages of 3–4, over 50% were urine-CCA patent. The sensitivity and specificity of the POC-CCA dipsticks, when compared against the combined results of Kato-Katz/TaqMan results was found to be 84.1% (95% CI = 72.7–92.1) and 12.9% (95% CI = 6.6–22) respectively.

Conclusions

We propose that the urine-CCA dipstick may be a useful rapid diagnostic tool to estimate the prevalence of intestinal schistosomiasis in PSAC, particularly in rapid identification of at-risk areas. However, our assessment has shown that it possible to record false positives when compared to combined Kato-Katz and qPCR results. To guide PSAC praziquantel treatment needs, we propose the urine CCA assay should be included in routine surveillance of intestinal schistosomiasis alongside other diagnostics such as Kato-Katz and urine filtration.

Sensitivity of the Point-of-Care Circulating Cathodic Antigen Urine Cassette Test for Diagnosis of Schistosoma mansoni in Low-Endemicity Settings in Côte d'Ivoire

The sensitivity of a point-of-care circulating cathodic antigen (POC-CCA) urine cassette test for diagnosis of Schistosoma mansoni in low-endemicity settings is poorly understood. We conducted a cross-sectional survey in 14 villages in western Côte d'Ivoire and diagnosed children aged 9-12 years for schistosomiasis. Two stool samples were subjected to triplicate Kato-Katz thick smears each for diagnosis of S. mansoni, whereas a single urine sample was examined by POC-CCA for S. mansoni, filtration for Schistosoma haematobium, and reagent strip for microhematuria. According to the Kato-Katz technique, we found 45 out of 681 children positive for S. mansoni (6.6%) with a mean intensity among infected children of 72.2 eggs per gram of stool. Point-of-care circulating cathodic antigen revealed a prevalence of S. mansoni of 33.0% when trace results were considered positive and 12.5% when trace results were considered negative. Eggs of S. haematobium were found in eight participants (1.2%), whereas the prevalence of microhematuria was 13.5%. A single POC-CCA urine cassette test revealed a several-fold higher prevalence of S. mansoni than multiple Kato-Katz thick smears in this low-endemicity area. Our findings have important ramifications for choosing an appropriate diagnostic tool in low-endemic areas that might be targeted for elimination.

Schistosoma mansoni Infection as a Predictor of Low Aerobic Capacity in Ugandan Children

Using the 20-meter shuttle run test (20mSRT) as a morbidity metric, we assessed whether Schistosoma mansoni infection was associated with decreased aerobic capacity in Ugandan children across a range of altitudes, either at low (∼600 m) or high (∼1,000 m) altitudes. A total of 305 children were recruited from six schools within the Buliisa District, Lake Albert, Uganda. A subset (n = 96) of these had been previously assessed and treated for schistosomiasis ± malaria 2 weeks prior. Fitness scores on the 20mSRT were translated into VO2max using a standardized equation. Unadjusted and multivariable-adjusted analyses were performed using VO2max as the primary outcome. Analysis of fitness scores from 304 children, inclusive of the subset follow-up cohort, revealed a median VO2max of 45.4 mL kg-1 min-1 (interquartile range: 42.9-48.0 mL kg-1 min-1). Children residing at high altitudes demonstrated increased aerobic capacities (46.3 versus 44.8 mL kg-1 min-1, P = 0.031). The prevalence of stunting, wasting, S. mansoni egg patent infection, malaria, giardiasis, anemia, and fecal occult blood were 36.7%, 16.1%, 44.3%, 65.2%, 21.4%, 50.6%, and 41.2%, respectively. Median VO2max was elevated in those previously treated, compared with those newly recruited (46.3 versus 44 mL kg-1 min-1, P < 0.001). Multivariable-adjusted analysis revealed a strong negative association between S. mansoni egg patent infection and VO2max at low altitude (beta coefficient: -3.96, 95% CI: -6.56 to -137, P = 0.004). This is the first study to document a negative association between S. mansoni infection and aerobic capacity at low altitudes using the 20mSRT.

The Advances in Molecular and New Point-of-Care (POC) Diagnosis of Schistosomiasis Pre- and Post-praziquantel Use: In the Pursuit of More Reliable Approaches for Low Endemic and Non-endemic Areas

Like soil-transmitted helminth infections, schistosomiasis is an important neglected tropical disease (NTD) related to poverty with a major impact on public health in developing countries. Diagnosis of active infection is crucial for surveillance of controlled or post-elimination schistosomiasis areas. In addition, the use of conventional diagnostic tools in non-exposed populations (such as travelers) results in misdiagnoses in the prepatent period of infection. Also, the accuracy of standard tests applied in low-endemicity areas (LEAs) decreases after several rounds of treatment. We aimed to determine whether it would be necessary to replace schistosomiasis conventional diagnostic tests such as parasitological methods in LEAs. Also, we evaluate the use of new tools in non-endemic areas. Reliable, cheap and easy-to-use diagnostic tools are needed to respond to the demands of a new era of elimination and eradication of schistosomiasis. To this end, molecular diagnosis-including nucleic acid-based assays (loop-mediated isothermal amplification, polymerase chain reaction) and circulating cathodic and anodic antigen detection tests have become promising strategies. In this review, we attempt to address the use of alternative diagnostic tests for active infection detection and drug-monitoring after specific schistosomiasis treatment.

Non-invasive surveillance of Plasmodium infection by real-time PCR analysis of ethanol preserved faeces from Ugandan school children with intestinal schistosomiasis

Background

As part of ongoing co-surveillance of intestinal schistosomiasis and malaria in Ugandan school children, a non-invasive detection method for amplification of Plasmodium DNA using real-time (rt)PCR analysis of ethanol preserved faeces (EPF) was assessed. For diagnostic tabulations, results were compared to rtPCR analysis of dried blood spots (DBS) and field-based point-of-care (POC) rapid diagnostic tests (RDTs).

Methods

A total of 247 school children from 5 primary schools along the shoreline of Lake Albert were examined with matched EPF and DBS obtained. Mean prevalence and prevalence by school was calculated by detection of Plasmodium DNA by rtPCR using a 18S rDNA Taqman^® probe. Diagnostic sensitivity, specificity, positive and negative predictive values were tabulated and compared against RDTs.

Results

By rtPCR of EPF and DBS, 158 (63.9%; 95% CI 57.8–69.7) and 198 (80.1%, 95% CI 74.7–84.6) children were positive for Plasmodium spp. By RDT, 138 (55.8%; 95% CI 49.6–61.9) and 45 (18.2%; 95% CI 13.9–23.5) children were positive for Plasmodium falciparum, and with non-P. falciparum co-infections, respectively. Using RDT results as a convenient field-based reference, the sensitivity of rtPCR of EPF and DBS was 73.1% (95% CI 65.2–79.8) and 94.2% (95% CI 88.9–97.0) while specificity was 47.7% (95% CI 38.5–57.0) and 37.6% (95% CI 29.0–46.9), respectively. With one exception, school prevalence estimated by analysis of EPF was higher than that by RDT. Positive and negative predictive values were compared and discussed.

Conclusions

In this high transmission setting, EPF sampling with rtPCR analysis has satisfactory diagnostic performance in estimation of mean prevalence and prevalence by school upon direct comparison with POC-RDTs. Although analysis of EPF was judged inferior to that of DBS, it permits an alternative non-invasive sampling regime that could be implemented alongside general monitoring and surveillance for other faecal parasites. EPF analysis may also have future value in passive surveillance of low transmission settings.

Advancing the multi-disciplinarity of parasitology within the British Society for Parasitology: studies of host-parasite evolution in an ever-changing world

The study of parasites typically crosses into other research disciplines and spans across diverse scales, from molecular- to populational-levels, notwithstanding promoting an understanding of parasites set within evolutionary time. Today, the 2030 Sustainable Development Goals (SDGs) help frame much of contemporary parasitological research, since parasites can be found in all ecosystems, blighting human, animal and plant health. In recognition of the multi-disciplinary nature of parasitological research, the 2017 Autumn Symposium of the British Society for Parasitology was held in London to provide a forum for novel exchange across medical, veterinary and wildlife fields of study. Whilst the meeting was devoted to the topic of parasitism, it sought to foster mutualism, the antithesis perhaps of parasitism, by forging new academic connections and social networks to exchange novel ideas. The meeting also celebrated the longstanding career of Professor David Rollinson, FLS in the award of the International Federation for Tropical Medicine Medal for his efforts spanning 40 years of parasitological research. Indeed, David has done so much to explore and promote the fascinating biology of parasitism, as exemplified by the 15 manuscripts contained within this Special Issue.

Developing a real-time PCR assay based on multiplex high-resolution melt-curve analysis: a pilot study in detection and discrimination of soil-transmitted helminth and schistosome species

With the push towards control and elimination of soil-transmitted helminthiasis and schistosomiasis in low- and middle-income countries, there is a need to develop alternative diagnostic assays that complement the current in-country resources, preferably at a lower cost. Here, we describe a novel high-resolution melt (HRM) curve assay with six PCR primer pairs, designed to sub-regions of the nuclear ribosomal locus. Used within a single reaction and dye detection channel, they are able to discriminate Ancylostoma duodenale, Necator americanus, Strongyloides stercoralis, Ascaris lumbricoides, Trichuris trichiuria and Schistosoma spp. by HRM curve analysis. Here we describe the primers and the results of a pilot assessment whereby the HRM assay was tested against a selection of archived fecal samples from Ghanaian children as characterized by Kato-Katz and real-time PCR analysis with species-specific TaqMan hydrolysis probes. The resulting sensitivity and specificity of the HRM was 80 and 98.6% respectively. We judge the assay to be appropriate in modestly equipped and resourced laboratories. This method provides a potentially cheaper alternative to the TaqMan method for laboratories in lower resource settings. However, the assay requires a more extensive assessment as the samples used were not representative of all target organisms.

Comparison of sensitivity and specificity of three diagnostic tests to detect Schistosoma mansoni infections in school children in Mwanza region, Tanzania

Background

Schistosomiasis remains one of the most prevalent parasitic infections in the world and has significant economic and public health consequences, particularly in poor communities. Reliable and accurate diagnosis plays a key role in surveillance, prevention and control of schistosomiasis. Currently, the microscopic Kato Katz (KK) stool thick smear technique is the most commonly used method to diagnose Schistosoma mansoni infections in epidemiological surveys. It is well-known that the sensitivity of this parasitological method decreases when infection intensities are moderate to low, however. The urine-based Point-of Care Circulating Cathodic Antigen (POC-CCA) test has been extensively evaluated as a further diagnostic tool. Several studies have shown that the POC-CCA test is more sensitive but less specific than the KK method. However, to clarify the meaning of inconsistent results between KK and POC-CCA tests in clinical routine, this study compares the accuracy of microscopy and POC-CCA versus real-time polymerase chain reaction (real-time PCR) results of urine and faecal samples from African school children participants.

Methodology

This was a school-based cross-sectional study conducted in 2015 among 305 school children aged 7–16 years from two primary schools located in Ilemela and Magu Districts, north-western Tanzania. Single stool and urine samples were collected from each participant and examined for the presence of Schistosoma mansoni eggs, parasite antigen, and parasite DNA using KK thick smears, POC-CCA tests, and real-time PCR, respectively.

Principal findings

The prevalence of S. mansoni infection, calculated by KK was 85.2%, by real-time PCR 92.9% and by POC-CCA 94.9%. In comparison to KK, the POC-CCA and real-time PCR tests had sensitivities of 89.7% and 99.5% and specificities of 22.73% and 29.55%, respectively. However, due to the known limitations of the KK assay, we also used latent class analysis (LCA) that included POC-CCA, KK, and schistosome-specific real-time PCR results to determine their sensitivities and specificities. The POC-CCA test had the highest sensitivity (99.5%) and a specificity of 63.4% by LCA and the real-time PCR test had a sensitivity of 98.7% and the highest specificity (81.2%).

Conclusion

In moderate and high prevalence areas, the POC-CCA cassette test is more sensitive than the KK method and can be used for screening and geographical mapping of S. mansoni infections. Real-time PCR is highly sensitive and also shows the highest specificity among the 3 investigated diagnostic procedures. It can offer added value in diagnosing schistosomiasis.