Humoral immune responses in patients with acute Schistosoma mansoni infection who were followed up for two years after treatment

Circulating cell-free DNA as a biomarker for diagnosis of Schistosomiasis japonica

BACKGROUND

Schistosomiasis, a neglected tropical disease, remains an important public health problem. Although there are various methods for diagnosing schistosomiasis, many limitations still exist. Early diagnosis and treatment of schistosomiasis can significantly improve survival and prognosis of patients.

METHODOLOGY

Circulating cell-free (cf)DNA has been widely used in the diagnosis of various diseases. In our study, we evaluated the diagnostic value of circulating cfDNA for schistosomiasis caused by Schistosoma japonicum. We focused on the tandem sequences and mitochondrial genes of S. japonicum to identify highly sensitive and specific targets for diagnosis of Schistosomiasis japonica.

RESULTS

Through data screening and analysis, we ultimately identified four specific tandem sequences (TD-1, TD-2, TD-3. and TD-4) and six mitochondrial genes (COX1(1), COX1(2), CYTB, ATP6, COX3, and ND5). We designed specific primers to detect the amount of circulating cfDNA in S. japonicum-infected mouse and chronic schistosomiasis patients. Our results showed that the number of tandem sequences was significantly higher than that of the mitochondrial genes. A S. japonicum infection model in mice suggested that infection of S. japonicum can be diagnosed by detecting circulating cfDNA as early as the first week. We measured the expression levels of circulating cfDNA (TD-1, TD-2, and TD-3) at different time points and found that TD-3 expression was significantly higher than that of TD-1 or TD-2. We also infected mice with different quantities of cercariae (20 s and 80 s). The level of cfDNA (TD-3) in the 80 s infection group was significantly higher than in the 20 s infection group. Additionally, cfDNA (TD-3) levels increased after egg deposition. Meanwhile, we tested 42 patients with chronic Schistosomiasis japonica and circulating cfDNA (TD-3) was detected in nine patients.

CONCLUSIONS

We have screened highly sensitive targets for the diagnosis of Schistosomiasis japonica, and the detection of circulating cfDNA is a rapid and effective method for the diagnosis of Schistosomiasis japonica. The levels of cfDNA is correlated with cercariae infection severity. Early detection and diagnosis of schistosomiasis is crucial for patient treatment and improving prognosis.

Evaluation of antibody serology to determine current helminth and Plasmodium falciparum infections in a co-endemic area in Southern Mozambique

Background

Soil-transmitted helminths (STH), Schistosoma spp. and Plasmodium falciparum are parasites of major public health importance and co-endemic in many sub-Saharan African countries. Management of these infections requires detection and treatment of infected people and evaluation of large-scale measures implemented. Diagnostic tools are available but their low sensitivity, especially for low intensity helminth infections, leaves room for improvement. Antibody serology could be a useful approach thanks to its potential to detect both current infection and past exposure.

Methodology

We evaluated total IgE responses and specific-IgG levels to 9 antigens from STH, 2 from Schistosoma spp., and 16 from P. falciparum, as potential markers of current infection in a population of children and adults from Southern Mozambique (N = 715). Antibody responses were measured by quantitative suspension array Luminex technology and their performance was evaluated by ROC curve analysis using microscopic and molecular detection of infections as reference.

Principal findings

IgG against the combination of EXP1, AMA1 and MSP2 (P. falciparum) in children and NIE (Strongyloides stercoralis) in adults and children had the highest accuracies (AUC = 0.942 and AUC = 0.872, respectively) as markers of current infection. IgG against the combination of MEA and Sm25 (Schistosoma spp.) were also reliable markers of current infection (AUC = 0.779). In addition, IgG seropositivity against 20 out of the 27 antigens in the panel differentiated the seropositive endemic population from the non-endemic population, suggesting a possible role as markers of exposure although sensitivity could not be assessed.

Conclusions

We provided evidence for the utility of antibody serology to detect current infection with parasites causing tropical diseases in endemic populations. In addition, most of the markers have potential good specificity as markers of exposure. We also showed the feasibility of measuring antibody serology with a platform that allows the integration of control and elimination programs for different pathogens.

Parasitic worms and Plasmodium falciparum, the causal agent of malaria, are among the most relevant parasitic diseases of our time and efforts are under way for their control and, ultimately, elimination. An accurate diagnosis is relevant for case management, but also allows calculating the prevalence and evaluating the effectiveness of treatment and control measures. Unfortunately, current diagnostic methods for parasitic worms are not optimal and many infections remain undetected. As for P. falciparum, current diagnostic techniques are satisfactory but do not allow for ascertaining exposure, which is relevant for evaluating control measures. Here we investigated the utility of measuring antibodies to these parasites as a diagnostic method. Our results indicate that it is possible to detect current infection with parasitic worms and P. falciparum using antibody detection with a moderate to high accuracy. We also show that antibodies against the antigens in this study have potential as markers of exposure. Importantly, we used a platform that allows for the simultaneous detection of immunoglobulins to different parasites, which would be extremely useful as a tool to integrate control and elimination programs for several pathogens.

Concealed urogenital schistosomiasis causing chronic pelvic pain: A case report

Urogenital schistosomiasis may mimic or co-exist with other disease. Clinicians should maintain a high index of suspicion for schistosomiasis in women from endemic areas and travelers to avoid significant morbidity and unnecessary interventions.

Validity of urine-CCA cassette test and indirect haem-agglutination assay (IHA) in the detection of schistosomiasis-mansoni infection relative to microscopic examination

Several immunodiagnostic assays have been commercially presented over the last years as easy diagnostic methods for schistosomiasis using serum or urine samples. The performance of immunochromatographic test (ICT) and indirect hemagglutination assay (IHA) was validated in the identification of active schistosomiasis infection. Detection of circulating cathodic antigen (CCA) of the parasite in urine samples and anti-Schistosoma antibodies in serum using ICT (Urine-CCA Cassette test) and IHA respectively. Proved diagnosis of Schistosoma mansoni infection was defined by the sum of positive results from microscopic examination (Gold standard) and Kato-Katz method. Out of 173 (mean age, 45 ± 10 years; 70 from Giza, 103 from different Egyptian governorates), 9 4 adult patients were infected. Urine-CCA cassette test despite showing high specificity (91.14%) it was of low sensitivity (23.40%). PPVs was 75.86% and NPV was 50.00% and diagnostic accuracy of 54.34%. The IHA showed a sensitivity of 57.45% and specificity of 48.10%. PPVs was 56.84% whereas NPVs was 48.72%. As for diagnostic accuracy, it was 53.18%. Urine-CCA Cassette test had lower sensitivity than expected for detection of circulating antigen and the IHA kit is generally more expensive than microscopic examination and Urine-CCA cassette test with low sensitivity and specificity. On the basis of this diagnostic performance none of the two tested immune-assays can be a sole tool in the principal diagnosis of active schistosomiasis infections.

Case Report of Urinary Schistosomiasis in a Returned Traveler in Korea

A 23-year-old Korean woman with a residence history in Kenya and Malawi for about 2 years presented with gross hematuria for 1 month. Blood tests were within normal range except eosinophilia. Asymmetrically diffuse wall thickening and calcification were observed at the urinary bladder on CT. Multiple erythematous nodular lesions were observed in the cystoscopy and transurethral resection was done. Numerous eggs of Schistosoma haematobium with granulomatous inflammation were observed in the submucosal layer of the bladder. The patient was diagnosed with schistosomiasis-related cystitis and treated with praziquantel (40 mg/kg/day) twice before and after transurethral resection. This case suggests that S. haematobium infection should be considered as a cause of hematuria in Korea when the patient had a history of traveling endemic areas of schistosomiasis.

Spirorchiidiasis in marine turtles: the current state of knowledge

Blood flukes of the family Spirorchiidae are important disease agents in marine turtles. The family is near cosmopolitan in distribution. Twenty-nine marine species across 10 genera are currently recognized, but taxonomic problems remain and it is likely that more species will be discovered. Spirorchiids infect the circulatory system, where they and their eggs cause a range of inflammatory lesions. Infection is sometimes implicated in the death of the turtle. In some regions, prevalence in stranded turtles is close to 100%. Knowledge of life cycles, important for control and epidemiological studies, has proven elusive until recently, when the first intermediate host identifications were made. Recent molecular studies of eggs and adult worms indicate that a considerable level of intrageneric and intraspecific diversity exists. The characterization of this diversity is likely to be of importance in exploring parasite taxonomy and ecology, unravelling life cycles, identifying the differential pathogenicity of genotypes and species, and developing antemortem diagnostic tools, all of which are major priorities for future spirorchiid research. Diagnosis to date has been reliant on copromicroscopy or necropsy, which both have significant limitations. The current lack of reliable antemortem diagnostic options is a roadblock to determining the true prevalence and epidemiology of spirorchiidiasis and the development of effective treatment regimes.

Towards elimination of schistosomiasis after 5000 years of endemicity in Egypt

Schistosomiasis is a snail-transmitted infectious disease caused by a long lasting infection with a blood fluke of the genus Schistosoma. S. haematobium and S. mansoni are the species endemic in Egypt. The country has been plagued and seriously suffered from schistosomiasis over the past 5000 years. Great strides had been done in controlling the disease since 1922. The history, epidemiology and the different control approaches were reviewed. Currently, Egypt is preparing towards schistosomiasis elimination by 2020. The new strategy depends on four main axes; large scale treatment in all areas of residual transmission by targeting entire populations with PZQ, intensified snail control, heath education and behavioral changes and expansion of the complementary public health interventions. While on the road towards elimination, we addressed here the important challenges, lessons and the key issues from the different control strategies to help the achievement of our goal. Notably, frangibility of the drug based control, emergence of resistance against PZQ, persistence of some hot spots areas, the need of further control efforts to the high risk individuals and community involvement in the control programs, reconsideration of diagnostic tests used in surveillance, and continous monitoring of the field to detect changes in the snail intermediate host. Importantly, the adaptation between the parasite and its intermediate snail host throughout water bodies in Egypt merits attention as Schistosoma infection can be introduced to the new reclaimed areas. This review may help supplying information for the policy makers to tailor control measures suitable to the local context that could help in the transfer from control to elimination.

Diagnosis of schistosomiasis mansoni: an evaluation of existing methods and research towards single worm pair detection

The inadequacy of current diagnostics for the detection of low worm burdens in humans means that schistosomiasis mansoni is more widespread than previously acknowledged. With the inception of mass drug treatment programmes aimed at disease elimination and the advent of human vaccine trials, the need for more sensitive diagnostics is evident. In this review, we evaluate the merits and limitations of the principal diagnostic methods, namely detection of eggs in faeces; anti-schistosome antibodies in serum; parasite-derived proteins and glycans in serum or urine; parasite DNA in blood, faeces or urine. Only in the baboon model, where actual worm burden is determined by portal perfusion, have faecal smear and circulating antigen methods been calibrated, and shown to have thresholds of detection of 10-19 worm pairs. There is scope for improvement in all the four methods of detection, e.g. the identification of single targets for host antibodies to improve the specificity of enzyme linked immunosorbent assay. Despite recent advances in the definition of the schistosome secretome, there have been no comprehensive biomarker investigations of parasite products in the urine of infected patients. Certainly, the admirable goal of eliminating schistosomiasis will not be achieved unless individuals with low worm burdens can be diagnosed.

Real-time PCR diagnosis of Schistosoma japonicum in low transmission areas of China

Background

Schistosomiasis in the People’s Republic of China (PRC) can be traced back to antiquity. In the past 60 years, the Chinese government has made great efforts to control this persistent disease with elimination slated by 2020 through the implementation of a comprehensive control strategy. This strategy aims to reduce the role of bovines and humans as sources of infection as a pre-requisite for elimination through transmission interruption. The goal of elimination will be achievable only by the implementation of a sustainable surveillance and control system, with sensitive diagnosis a key feature so that the true disease burden is not underestimated. Currently used diagnostics lack the necessary sensitivity to accurately determine the prevalence of Schistosoma japonicum infection in areas with low infection intensities. It is of critical importance to find and treat people and to identify animals with low-level infections if the National Control Programme for China is to achieve schistosomiasis elimination.

Methods

We evaluated a real-time polymerase chain reaction (qPCR) assay using 633 human stool samples collected from five villages in Hunan, Anhui, Hubei, and Jiangxi provinces, and 182 bovine (70 cattle and 112 buffalo) stool samples obtained from four villages in Hunan, Anhui, and Jiangxi provinces in the PRC. All stool samples were subjected to the miracidium hatching test (MHT, a diagnostic procedure used in the National Schistosomiasis Control Programme) and the qPCR assay. Samples positive by MHT were subjected to either the Kato-Katz technique for humans, or the formalin-ethyl acetate sedimentation-digestion (FEA-SD) procedure for bovines, to determine infection intensities.

Results

The qPCR assay exhibited a high level of sensitivity in the detection of S. japonicum infections. With both the human and bovine samples, a significantly higher prevalence was determined using the qPCR assay (11.06% humans, 24.73% bovines) than with the MHT (0.93% humans, 7.69% bovines). The animal contamination index (calculated using data obtained with the qPCR technique) for all positive bovines was 27 618 000 eggs per day, indicating a considerable amount of environmental egg contamination that would be underestimated using less sensitive diagnostic procedures.

Conclusions

The qPCR assay we have evaluated will be applicable as a future field diagnostic and surveillance tool in low-transmission zones where schistosomiasis elimination is targeted and for monitoring post-intervention areas to verify that elimination has been maintained.

Electronic supplementary material

The online version of this article (10.1186/s40249-018-0390-y) contains supplementary material, which is available to authorized users.

Hepatosplenic schistosomiasis: playing hide-and-seek with an elusive parasite

A 27-year-old man of Eritrean origin presented with persistent left-sided abdominal pain. Initial investigation showed signs of liver fibrosis, portal hypertension and splenomegaly. A diagnosis of hepatosplenic schistosomiasis was suspected on grounds of elevated total IgE, grey area antischistosomiasis antibodies and the high endemic status of his native country. However, repeated microscopy of faecal and urine samples, as well as rectal biopsies, failed to demonstrate schistosomal eggs. Finally, the diagnosis of hepatosplenic schistosomiasis was established through demonstration of a Schistosoma mansoni egg in a liver biopsy taken in an attempt to clarify the cause of the above findings. The patient had recently been treated for uncomplicated malaria. Lowered schistosomiasis worm/egg burden and hence reduced sensitivity of classic microscopy-based schistosomiasis testing was attributed to the antischistosomal activity of the antimalarial chemotherapy.

Diagnosing Urogenital Schistosomiasis: Dealing with Diminishing Returns

Urogenital schistosomiasis, caused by Schistosoma haematobium, is the most prevalent form of schistosomiasis affecting humans, and can result in severe bladder, kidney, ureteral, and genital pathologies. Chronic infection with S. haematobium has been linked with bladder cancer and increased risk for HIV infection. As mass drug administration with praziquantel increases in an attempt to transition from control to elimination of schistosomiasis, the need for updated, more sensitive diagnostic tools becomes more apparent, especially for use in areas of low infection intensity and for individuals with light infections. Here, we review established and investigational diagnostic tests utilized for urogenital schistosomiasis, highlighting new insights and recent advances.

Towards improved diagnosis of neglected zoonotic trematodes using a One Health approach

Reaching the goal of control, elimination and eradication of the Neglected Tropical Disease in a foreseeable future provides significant challenges at the ground level especially regarding helminthiasis. Helminths are still mainly diagnoses by egg identification in stool, methods with low sensitivity and for most species low specificity. Cross-sectoral collaboration with regard to zoonoses is almost non-existing and cross-validation by inter-laboratory evaluation of diagnostic tests is not a common practice. The aim of this review was to elucidate the dilemma of helminth diagnosis using zoonotic trematodes as examples. Much progress has been made improving the diagnostic sensitivity of Opisthorchis and Clonorchis using DNA-based techniques but the specificity of these tests is still a challenge due to the many most common but neglected intestinal trematodes. The burden of these diseases and ways to control them remains to be elucidated. Although efficacious drugs are available, the effectiveness of mass drug administration remains to be assessed. The importance of animal reservoirs and ways to control the diseases in animals are yet unknown. Diagnostic challenges regarding Schistosoma japonicum and Schistosoma mekongi include the many light infections and the persisting influx from the animal reservoirs. The sensitivity of the faecal based techniques suited morbidity control but will be insufficient for elimination of the helminths. More accurate diagnostic tools are required and new algorithms for detection and progression of helminth elimination will be needed. Standardized inter-laboratory test validation, inter-sectoral collaboration and establishment of an international One Health diagnostic platform, sharing best practices on diagnosis of helminth zoonoses, could all significantly contribute to control and elimination of these diseases.

Long-term outcome after liver transplantation for hepatic schistosomiasis: a single-center experience over 15 years

Our objective was to study the long-term outcomes of patients who had undergone liver transplantation because of schistosomiasis at our institute over the last 15 years. Four hundred forty-one patients underwent liver transplantation at our institute, and 14 did so for schistosomiasis. The survival of patients who underwent transplantation for schistosomiasis was compared with that of patients who underwent transplantation for other liver diseases. Survival curves were drawn via the Kaplan-Meier method and were compared with the log-rank test. P < 0.05 was considered significant. All 14 patients were male, and the average age was 56.8 ± 8.4 years. The average Model for End-Stage Liver Disease score was 18.2 ± 5.6, and the average Child-Pugh score was 10.6 ± 1.2. All patients had splenomegaly; pretransplant variceal bleeding occurred in 7 patients (50%), and portal vein thrombosis was diagnosed in 5 patients (36%). Patient survival was 75% 1 year after transplantation and 75% at the end of follow-up because no patients were lost after the first year. Patients who underwent transplantation for other causes achieved survival rates of 86% and 76% 1 and 10 years after transplantation, respectively. There was no significant survival difference between the 2 groups (P = 0.66). All patients who survived the early posttransplant period had functioning liver grafts with no reported diagnoses of schistosomiasis in the new grafts. In conclusion, liver transplantation for patients with schistosomiasis has a favorable outcome with no risk of reactivation.

Diagnostic and prognostic value of cell free circulating Schistosoma mansoni DNA: an experimental study

Searching for a more sensitive and accurate marker for schistosomiasis diagnosis and treatment follow up is a potential necessity. Hereby, we evaluated usefulness of circulating free DNA as a marker for schistosomiasis diagnosis, assessing drug efficacy and monitoring the control interventions impact using SYBR green real-time PCR. A batch of mice were infected by 90 ± 10 Schistosoma mansoni cercariae. Starting from the 2nd day post infection (p.i.), groups of 2 or 3 mice were sacrificed every 3 days until 30 days p.i. The remaining animals were treated by a single dose of 400 mg/kg mefloquine and sacrificed in group at 5, 10, 21 days post treatment (35, 40, 51 days p.i.). Using SYBR green real time qPCR, pooled sera DNA were extracted and amplified. The results showed that, circulating free S. mansoni DNA was detected from the 2nd day post infection (p.i.) onwards with gradual decrease in the cycle threshold value Ct which indicates the gradual elevation of the DNA level (Log quantity was 2.6-3.1 IU/ml), As the infection progressed, DNA quantity was increased(Log quantity was 6.29 IU/ml). Initial increase of circulating free DNA was observed 10 days post treatment (40 days p.i.) (Log quantity was 7.38 IU/ml). That was followed by a progressive decrease in DNA level by the end of 21st day, post treatment (51 p.i.) (Log quantity 4.35 IU/ml). In conclusion, circulating free S. mansoni DNA is a reliable marker in the diagnosis of schistosomiasis and for assessing drug efficacy and monitoring the impact of control interventions.

Detection of Schistosoma mansoni infection by TaqMan® Real-Time PCR in a hamster model

An experimental study in hamsters was performed to evaluate the capability for detecting Schistosoma mansoni DNA in serum and fecal samples during the pre and post-egg-laying periods of infection using TaqMan® Real-Time PCR system (qPCR), was compared with the circumoval precipitin test (COPT) and the Kato-Katz technique, especially among individuals with low parasitic burden. Twenty-four hamsters were infected with cercariae. Three hamsters were sacrificed per week under anesthesia, from 7 days post infection (DPI) up to 56 DPI. A serum sample and a pool of feces were collected from each hamster. The presence of S. mansoni eggs in fecal samples was evaluated by Kato-Katz method and in the hamsters gutby histopathology. Detection of S. mansoni DNA was performed using qPCR and S. mansoni antibody using COPT. The first detection of eggs in feces by Kato-Katz method and S. mansoni DNA in feces by qPCR occurred 49 DPI. Nevertheless, S. mansoni DNA was detected in serum samples from 14 up to 56 DPI. COPT was positive at 35 DPI. The results not only confirm the reliability of S. mansoni DNA detection by qPCR, but also demonstrate that serum is a trustworthy source of DNA in the pre patent infection period.

The detection of antibodies againstSchistosoma mansonisoluble egg antigens (SEA) and CEF6 in ELISA, before and after chemotherapy

Circulating IgG antibody reactivity and excreted egg counts were investigated in 489 Kenyans given chemotherapy for schistosomiasis mansoni. Antibody reactivity was measured in ELISA, using either unfractionated aqueous soluble constituents of Schistosoma mansoni eggs (SEA) or CEF6 (a soluble fraction of S. mansoni eggs containing two cationic antigens) as the antigen source. Antibody reactivity for each antigen source was strongly associated with egg counts, both pre- and post-treatment. Approximately 6 months after chemotherapy, egg counts were zero in 84% of the subjects. The mean optical densities (OD) measured in the post-treatment ELISA were 60% (CEF6) or 45% (SEA) lower than the pre-treatment values, the reduction in the OD with CEF6 as antigen source being significantly greater than that observed with SEA (P <0.001). The usefulness of an assay for antibody reactivity in monitoring the effects of the treatment of schistosomiasis is discussed.

Long-term frozen storage of urine samples: a trouble to get PCR results in Schistosoma spp. DNA detection?

Background

Human schistosomiasis remains a serious worldwide public health problem. At present, a sensitive and specific assay for routine diagnosis of schistosome infection is not yet available. The potential for detecting schistosome-derived DNA by PCR-based methods in human clinical samples is currently being investigated as a diagnostic tool with potential application in routine schistosomiasis diagnosis. Collection of diagnostic samples such as stool or blood is usually difficult in some populations. However, urine is a biological sample that can be collected in a non-invasive method, easy to get from people of all ages and easy in management, but as a sample for PCR diagnosis is still not widely used. This could be due to the high variability in the reported efficiency of detection as a result of the high variation in urine samples’ storage or conditions for handling and DNA preservation and extraction methods.

Methodology/Principal Findings

We evaluate different commercial DNA extraction methods from a series of long-term frozen storage human urine samples from patients with parasitological confirmed schistosomiasis in order to assess the PCR effectiveness for Schistosoma spp. detection. Patientś urine samples were frozen for 18 months up to 7 years until use. Results were compared with those obtained in PCR assays using fresh healthy human urine artificially contaminated with Schistosoma mansoni DNA and urine samples from mice experimentally infected with S. mansoni cercariae stored frozen for at least 12 months before use. PCR results in fresh human artificial urine samples using different DNA based extraction methods were much more effective than those obtained when long-term frozen human urine samples were used as the source of DNA template.

Conclusions/Significance

Long-term frozen human urine samples are probably not a good source for DNA extraction for use as a template in PCR detection of Schistosoma spp., regardless of the DNA method of extraction used.

Prospective European-wide multicentre study on a blood based real-time PCR for the diagnosis of acute schistosomiasis

Background

Acute schistosomiasis constitutes a rare but serious condition in individuals experiencing their first prepatent Schistosoma infection. To circumvent costly and time-consuming diagnostics, an early and rapid diagnosis is required. So far, classic diagnostic tools such as parasite microscopy or serology lack considerable sensitivity at this early stage of Schistosoma infection. To validate the use of a blood based real-time polymerase chain reaction (PCR) test for the detection of Schistosoma DNA in patients with acute schistosomiasis who acquired their infection in various endemic regions we conducted a European-wide prospective study in 11 centres specialized in travel medicine and tropical medicine.

Methods

Patients with a history of recent travelling to schistosomiasis endemic regions and freshwater contacts, an episode of fever (body temperature ≥38.5°C) and an absolute or relative eosinophil count of ≥700/μl or 10%, were eligible for participation. PCR testing with DNA extracted from serum was compared with results from serology and microscopy.

Results

Of the 38 patients with acute schistosomiasis included into the study, PCR detected Schistosoma DNA in 35 patients at initial presentation (sensitivity 92%). In contrast, sensitivity of serology (enzyme immunoassay and/or immunofluorescence assay) or parasite microscopy was only 70% and 24%, respectively.

Conclusion

For the early diagnosis of acute schistosomiasis, real-time PCR for the detection of schistosoma DNA in serum is more sensitive than classic diagnostic tools such as serology or microscopy, irrespective of the region of infection. Generalization of the results to all Schistosoma species may be difficult as in the study presented here only eggs of S. mansoni were detected by microscopy. A minimum amount of two millilitre of serum is required for sufficient diagnostic accuracy.

The urine circulating cathodic antigen (CCA) dipstick: a valid substitute for microscopy for mapping and point-of-care diagnosis of intestinal schistosomiasis

BACKGROUND

The World Health Organization now recommends the provision of praziquantel treatment to preschool-aged children infected with schistosomiasis. For intestinal schistosomiasis the current operational field diagnostic standard is examination of a thick Kato-Katz smear by microscopy prepared from a single stool specimen, and although pragmatic, this methodology has well-known shortcomings. Here, as a potential alternative, the performance of the urine circulating cathodic antigen (CCA) dipstick test was assessed in terms of disease-mapping and point-of-care diagnosis for intestinal schistosomiasis in preschool-aged children. Our manuscript reports on findings at baseline and at the end of a one-year longitudinal treatment study.

METHODOLOGY/PRINCIPAL FINDINGS

A total of 925 children (mean age 2.8 years) were initially recruited from six lakeshore villages representative of high, moderate and low levels of disease transmission. At baseline, all children were tested for intestinal schistosomiasis by microscopic examination of duplicate Kato-Katz smears prepared from a single stool faecal, by antigen detection with the urine CCA dipstick test and by serology with a commercially available ELISA test (as 'gold-standard') that measures host antibody titres to soluble egg antigens. As a point-of-care diagnosis, the urine CCA dipstick test achieved sensitivity and specificity values ranging from 52.5-63.2% and 57.7-75.6%, respectively, with faecal microscopy achieving very high specificities (>87%) but sensitivities as low as 16.7% in the low transmission setting.

CONCLUSION/SIGNIFICANCE

The urine CCA test was shown to be more effective than faecal microscopy especially in lower transmission settings. The diagnostic performance of this test was not significantly impacted by treatment history or co-infections with other intestinal helminths.

Evaluation of an IgY-based immunomagnetic enzyme-linked immunosorbent assay system for detection of circulating Schistosoma japonicum antigen in serum samples from patients in China

We have developed a novel egg yolk antibody (IgY)-coated magnetic beads antigen-capture immunoassay for detection of a circulating antigen of Schistosoma japonicum in serum samples of patients in schistosomiasis-endemic areas of China. This IgY-based immunomagnetic bead enzyme-linked immunosorbent assay (IgY-IMB-ELISA) uses polyclonal IgY-coated magnetic beads as a capture antibody, and a monoclonal IgG as a detection antibody. The sensitivity of the magnetic immunoassay was 100% (40 of 40) in cases of acute infection and 91.5% (107 of 117) in chronic cases of schistosomiasis, and no positive reaction was found in 0 of 49 healthy persons. Cross-reactivity was 3.3% (1 of 33) with clonorchiasis and 0% (0 of 20) with paragonimiasis. There was a significant correlation between ELISA absorbance value and egg count (eggs per gram feces) and a correlation coefficient of 0.88 in a small sample of 14 patients. The results demonstrated that the IgY-IMB-ELISA is a sensitive and specific assay for detection of human schistosomiasis japonica.

Acute schistosomiasis in a cluster of travelers from Rwanda: diagnostic contribution of schistosome DNA detection in serum compared to parasitology and serology

BACKGROUND

Diagnosis of acute schistosomiasis is often elusive in travelers. Serum schistosome DNA detection is a promising new diagnostic tool. Its performance is compared with current diagnostic procedures in a cluster of travelers recently infected in Rwanda.

METHODS

Recent infection with schistosomiasis was suspected in 13 Belgian children and adults, within 2 months after swimming in the Muhazi Lake, Rwanda. All were subjected to clinical examination, eosinophil count, feces parasite detection, schistosome antibody tests [enzyme-linked immunosorbent assay (ELISA) and hemagglutination inhibition assay (HAI)], and schistosome DNA detection in serum by real-time polymerase chain reaction.

RESULTS

All 13 patients, between 6 and 29 years old, had a high eosinophil count (median 2,120 µL(-1) ; range 1,150-14,270). Seven of nine persons exposed for the first time developed symptoms compatible with acute schistosomiasis. Eggs of Schistosoma mansoni were found in a concentrated feces sample of 9/13 (69%), with low egg counts (median 20 eggs per gram; range 10-120). Antischistosome antibodies (ELISA and/or HAI) were present in serum of 10/13 (77%) patients. Combining schistosome antibody tests and fecal microscopy demonstrated schistosomiasis in 11/13 (85%) patients. Schistosome-specific DNA was isolated in all 13 (100%) serum samples.

CONCLUSION

In this cluster of travelers with acute schistosomiasis, schistosome DNA detection in serum was able to confirm infection in all exposed persons. It clearly outperformed antibody tests and microscopic parasite detection methods as a qualitative diagnostic test.

Multiplex bead assay for serum samples from children in Haiti enrolled in a drug study for the treatment of lymphatic filariasis

A multiplex bead assay (MBA) was used to analyze serum samples collected longitudinally from children enrolled in a drug trial for treatment of filariasis in Leogane, Haiti. Recombinant antigens Bm14 and Bm33 from Brugia malayi, third polar tube protein (PTP3) from Encephalitozoon cuniculi, and merozoite surface protein-1(19) (MSP-1(19)) from Plasmodium falciparum were coupled to carboxylated polystyrene microspheres. IgG responses to PTP3 and MSP-1(19) were not affected by albendazole (ALB), diethylcarbamazine (DEC), or combination of diethylcarbamazine and albendazole (DEC/ALB). However, IgG and IgG4 responses to Bm14 and Bm33 were significantly decreased (P < 0.001) by DEC and DEC/ALB treatment. Antibody responses to Bm14 and Bm33 decreased after DEC treatment (but not placebo) among children who were negative for microfilaremia and antigenemia at baseline, suggesting that these children harbored early stages of infection. The MBA is an excellent serologic technique for multiple antigens that offers substantial advantages over single-antigen based enzyme-linked immunosorbent assay in mass drug administration studies for monitoring changes in antibody levels.

Hepatic schistosomiasis

Praziquantel is the treatment of choice for schistosomiasis because of its efficacy, ease of administration, limited side effects, and low cost. Praziquantel has been so effective that alternative therapies are increasingly difficult to obtain, and the development of novel medications has been limited. The possibility of praziquantel resistance is a grave concern. Low cure rates for praziquantel have been reported in several countries, but despite widespread use, no significant loss of efficacy has occurred to date. The primary goal of antischistosomal therapy is parasite eradication, which reduces the likelihood of chronic complications, including advanced hepatic fibrosis. Mild to moderate hepatic fibrosis results from the immune response to schistosome eggs deposited in the portal venules and reverses with successful treatment. Most individuals clear schistosomiasis with a single course of therapy. Repeat doses cure the majority of patients in whom eradication does not occur after the initial dose. A secondary goal of therapy for patients with persistent or recurrent infection is egg burden reduction, which also reduces the risk of hepatic fibrosis and lowers community spread. Community eradication programs in highly endemic regions use periodic retreatment to limit chronic schistosomiasis' morbidity. Advanced liver fibrosis and portal hypertension due to chronic schistosomiasis are irreversible. Variceal bleeding is the primary cause of death in hepatic schistosomiasis. The bleeding risk is best reduced through use of beta-blocker prophylaxis or endoscopic banding or sclerotherapy. Surgical management of varices, including splenectomy with esophagogastric devascularization or selective shunts such as the distal splenorenal, is effective in patients with recalcitrant bleeding. Because hepatic synthetic function is normal in patients with schistosomiasis, procedures that reduce portal pressures may lower hepatic perfusion and cause hepatic impairment. The risk of encephalopathy after shunt surgery is higher in patients with schistosomiasis than in those with cirrhosis. For these reasons, nonselective shunt surgery such as the proximal splenorenal or the transjugular intrahepatic portosystemic shunt should not be performed in patients with advanced hepatic schistosomiasis.

The immune response to schistosome antigens in formerly infected travelers

We investigated the type and strength of the immune response to schistosome antigens in a group of 20 Dutch travelers who had been infected with Schistosoma spp. during a group visit to Mali in 1991 and 8 non-infected controls. At the time, 9 had Katayama syndrome (KS), and 11 remained asymptomatic. All had been treated with praziquantel. Eight years later, serology remained positive in all 20 formerly infected travelers. The lymphocyte proliferative responses and cytokine responses (interleukin 13 [IL-13], IL-10, and interferon [IFN-γ] responses to soluble egg antigens and the IL-13, IL-10, and IL-5 response to adult worm antigen) were stronger in the travelers than in the controls and tended to be stronger in those with KS compared with those who had remained asymptomatic. In conclusion, Schistosoma infection induced a memory immune response, and people who experienced KS tended to have a stronger immune response to schistosome antigens than their asymptomatic counterparts.

High rate of failure in treatment of imported schistosomiasis

BACKGROUND

There is an increasing number of imported cases of schistosomiasis in Europe, but there are only few studies on the efficacy of praziquantel for the treatment of schistosomiasis in non-endemic settings.

METHODS

Patients treated for schistosomiasis in 2003 to 2008 were offered reexamination with serology, eosinophil count, IgE, microscopy of 24 h urine samples and/or rectal biopsies >3 months after treatment. All patients had been treated with at least one dose of praziquantel 40 to 60 mg/kg >12 weeks after exposure and had not been reexposed to schistosomiasis after treatment.

RESULTS

Twenty-eight traveler (15 tourists and 13 expatriates) and two immigrants were reexamined after treatment. Viable ova were detected in six traveler (20%). Ova were found in 5/23 (22%) rectal biopsies and in 2/12 (17%) urine samples. Treatment failure was suspected in a symptomatic patient who 2 years after treatment had eightfold rise in antibody titer and elevated IgE but no detectable ova in urine or rectal biopsies. Additional 13 patients had one or more parameters, which could indicate persistent infection. There were no significant differences in eosinophil count, IgE or, change in antibody titer between patients with versus without detectable ova after treatment.

CONCLUSIONS

In traveler with a low parasite burden, assessment of treatment results can be difficult because of the low sensitivity of microscopy and persistence of antibodies for several years after treatment. We found a high rate of treatment failure among traveler, indicating that nonimmune patients may need more than the recommended single day of treatment for eradication of parasites. Until more sensitive and specific methods for detection of persistent, active infection are available, repeated treatment should be considered in patients with continuous symptoms or other indications of treatment failure even when viable ova cannot be detected by microscopy.

Diagnosing schistosomiasis by detection of cell-free parasite DNA in human plasma

Introduction

Schistosomiasis (bilharzia), one of the most relevant parasitoses of humans, is confirmed by microscopic detection of eggs in stool, urine, or organ biopsies. The sensitivity of these procedures is variable due to fluctuation of egg shedding. Serological tests on the other hand do not distinguish between active and past disease. In patients with acute disease (Katayama syndrome), both serology and direct detection may produce false negative results. To overcome these obstacles, we developed a novel diagnostic strategy, following the rationale that Schistosoma DNA may be liberated as a result of parasite turnover and reach the blood. Cell-free parasite DNA (CFPD) was detected in plasma by PCR.

Methodology/Principal Findings

Real-time PCR with internal control was developed and optimized for detection of CFPD in human plasma. Distribution was studied in a mouse model for Schistosoma replication and elimination, as well as in human patients seen before and after treatment. CFPD was detectable in mouse plasma, and its concentration correlated with the course of anti-Schistosoma treatment. Humans with chronic disease and eggs in stool or urine (n = 14) showed a 100% rate of CFPD detection. CFPD was also detected in all (n = 8) patients with Katayama syndrome. Patients in whom no viable eggs could be detected and who had been treated for schistomiasis in the past (n = 30) showed lower detection rates (33.3%) and significantly lower CFPD concentrations. The duration from treatment to total elimination of CFPD from plasma was projected to exceed one year.

Conclusions/Significance

PCR for detection of CFPD in human plasma may provide a new laboratory tool for diagnosing schistosomiasis in all phases of clinical disease, including the capacity to rule out Katayama syndrome and active disease. Further studies are needed to confirm the clinical usefulness of CFPD quantification in therapy monitoring.

Bilharzia (schistosomiasis) occurs in the tropics and subtropics and is one of the most important parasite diseases of humans. It is caused by flukes residing in the vessels of the gut or bladder, causing fever, pain, and bleeding. Bladder cancer or esophageal varices may follow. Diagnosis is difficult, requiring detection of parasite eggs in stool, urine, or gut/bladder biopsies. In this paper, we introduce a fundamentally new way of diagnosing bilharzia from the blood. It has been known for almost 20 years that patients with cancer have tumor-derived DNA circulating in their blood, which can be used for diagnostic purposes. During pregnancy, free DNA from the fetus can be detected in motherly blood, which can be used for diagnosing a range of fetal diseases and pregnancy-associated complications. We found that parasite DNA can be detected in the same way in the blood of patients with bilharzia. In patients with early disease, diagnosis was possible earlier than with any other test. DNA could be detected in all patients with active disease in our study. Patients after treatment had significantly lower parasite DNA concentrations and turned negative 1–2 years after treatment. Future studies should implement the method in large cohorts of patients and should define criteria for the confirmation of the success of treatment by comparing the concentration of fluke DNA before and after therapy.

Clinical therapy of schistosomiasis mansoni: the Brazilian contribution

The review gives a detailed account of the history of drug development, treatment and drug resistance for clinical therapy of schistosomiasis mansoni, specially emphasizing the importance of Brazilian contribution on antischistosomal chemotherapy, as well as on the control of this parasitic disease.

Real-time PCR for detection of low intensity Schistosoma japonicum infections in a pig model

Decades of successful Schistosoma japonicum control have increased the interest in how to diagnose low intensity infections. A real-time PCR assay targeting the mitochondrial NADH dehydrogenase I gene in S. japonicum was evaluated in infected pigs with very low egg output. Six out of 12 S. japonicum infected pigs were treated with praziquantel 8 weeks after infection and all pigs were followed for 16 weeks post-infection. One commercial and one non-commercial extraction method were evaluated in combination with PCR on faecal samples. PCR with either extraction method were equally sensitive as the DBL-filtration/sedimentation technique in the acute, productive stage. PCR recovered slightly more positive samples in the chronic stage, but most faecal samples were negative for both PCR and microscopy from week 9 post-infection irrespective of treatment. IgG antibody titers against soluble egg antigen IgG remained high throughout the study in both the treated and non-treated group. PCR was consistently negative in serum and urine samples and negative in most of the caecal biopsies. We conclude that the S. japonicum faecal PCR is a highly sensitive test. However, in clinical samples when faecal egg output almost reaches nil in the chronic stage despite persistent worm burdens, both the faecal PCR and microscopy results were negative. Real-time PCR is less labour intensive than most microscopy methods, but has a higher material cost per sample.

Human schistosomiasis

Schistosomiasis or bilharzia is a tropical disease caused by worms of the genus Schistosoma. The transmission cycle requires contamination of surface water by excreta, specific freshwater snails as intermediate hosts, and human water contact. The main disease-causing species are S haematobium, S mansoni, and S japonicum. According to WHO, 200 million people are infected worldwide, leading to the loss of 1.53 million disability-adjusted life years, although these figures need revision. Schistosomiasis is characterised by focal epidemiology and overdispersed population distribution, with higher infection rates in children than in adults. Complex immune mechanisms lead to the slow acquisition of immune resistance, though innate factors also play a part. Acute schistosomiasis, a feverish syndrome, is mostly seen in travellers after primary infection. Chronic schistosomal disease affects mainly individuals with long-standing infections in poor rural areas. Immunopathological reactions against schistosome eggs trapped in the tissues lead to inflammatory and obstructive disease in the urinary system (S haematobium) or intestinal disease, hepatosplenic inflammation, and liver fibrosis (S mansoni, S japonicum). The diagnostic standard is microscopic demonstration of eggs in the excreta. Praziquantel is the drug treatment of choice. Vaccines are not yet available. Great advances have been made in the control of the disease through population-based chemotherapy but these required political commitment and strong health systems.

Detailed clinical and ultrasound examination of children and adolescents in a Schistosoma mansoni endemic area in Kenya: hepatosplenic disease in the absence of portal fibrosis

Hepatosplenic schistosomiasis involving organomegaly, portal fibrosis and portal hypertension has been observed in autopsy studies. Here, we have tested the hypothesis that hepatosplenic disease including organomegaly and markers of increased portal pressure can occur in school aged children in the absence of fibrosis. A case-only study of 96 children aged 7-20 years defined by ultrasound detectable hepatomegaly was undertaken in Makueni district, Kenya. A novel method of clinical examination that involved a consensus scoring by three or four examiners was used to classify children as presenting with severe or moderate hepatosplenic disease after palpation of livers and spleens. Ultrasound examination of livers and spleens was based on the Niamey protocol. Clinical measurements included spleen enlargement along the mid-clavicular and mid-axillary lines, liver enlargement along the mid-sternal (MSL) and mid-clavicular lines, as well as organ consistency. The clinical examination indicated that 9% and 60% of the children had severe or moderate hepatosplenomegaly, respectively. Amongst egg-positive children, all clinical measurements, except MSL liver enlargement, correlated with egg count, as did portal vein diameter, spleen length and liver length measured by ultrasound. Peri-portal fibrosis was not observed in any child, whereas 28% of the children were classified as having increased portal pressure according to World Health Organization criteria. There was no effect of malaria parasitaemia or hepatitis seropositvity on any of the observed parameters. These results indicate that hepatosplenic disease in school-aged children attributable to S. mansoni infection, involving hepatosplenomegaly and increased portal vein diameter, can occur in the absence of peri-portal fibrosis.

Antibody subclass profile and avidity during acute and chronic human Schistosoma mansoni infection

The avidity of IgA, IgM, IgG and IgG subclass antibodies against Schistosoma mansoni soluble egg antigen (SEA) was determined by ELISA in serum samples collected in 1995 from individuals in Brazil with acute (n = 36) and chronic (n = 40) schistosomiasis. Fifteen individuals at the acute phase were also evaluated 6 months after clinical diagnosis. Predominance of low-avidity IgG, IgG1, IgG2, IgG3 and IgA characterized the acute phase. IgG4 was detected in only 2 individuals with acute disease (5.6%). Levels of anti-SEA IgM were similar between the study groups. IgG1 avidity showed the strongest association with the chronological evolution of the infection, presenting 100% of low avidity during the acute infection and reaching 100% of high avidity 6 months after. It is suggested that distinct anti-Schistosoma egg antigens subclass profile and antibody avidity characterize the clinical phases of S. mansoni infection. In particular, determination of anti-SEA IgG1 offers a new tool for the laboratory analysis of the disease.

Immunodiagnosis of schistosomiasis by determination of the circulating antigens CAA and CCA, in particular in individuals with recent or light infections

In the present paper, we evaluate determination of circulating anodic (CAA) and cathodic (CCA) antigen for the diagnosis of an active Schistosoma infection in humans, in comparison to the diagnostic performance of parasitological examination and the demonstration of specific antibodies. Illustrated by three different studies, which all deal with the diagnosis of either recent or low intensity infections, we further discuss our experiences with these diagnostic methods. For the diagnosis of recent infections, specific antibody determination showed to be very sensitive, particularly in individuals originating from non-endemic areas. For the assessment of cure and for the diagnosis of active infections in endemic areas, the methods of choice are parasitological examination and CAA or CCA determination. Depending on infection levels of the target population and on logistic conditions, CAA and CCA determination may either replace parasitological examination or, in the case of light infections, may be used as a complementary diagnostic tool.

Presentation and outcome of 1107 cases of schistosomiasis from Africa diagnosed in a non-endemic country

Schistosomiasis is found in a significant proportion of returning travellers and immigrants to Britain. This study is a retrospective review of 1107 consecutive cases of schistosomiasis from Africa diagnosed by microscopy or serology presenting to the Hospital for Tropical Diseases, London, UK. 50.4% of cases were asymptomatic. The most common symptom which resolved on treatment was tiredness. Serology was positive in 951 (86%), and ova seen in 45%. Urine dipstick testing was positive for blood in 21% and protein in 15%, with eosinophilia in 44%. In this population urine dipstick, full blood count and serology were all insufficient screening tools used alone. Among patients with full follow-up data 3 months or more after treatment with praziquantel, definite treatment failure occured in 4 of 271 (1.5%), restricting the analysis to those with ova seen at diagnosis. There was no significant difference in treatment failure between 1 and 3 days of treatment. Antibody level was the same or higher than at treatment in 55% of cases seen after about 3 months and 38% after 1 year, confirming it is probably of limited clinical use in detecting treatment failure.

Persisting antibody reaction in paragonimiasis after praziquantel treatment is elicited mainly by egg antigens

Antibody responses in serum and cerebrospinal fluid (CSF) samples from patients with active and chronic paragonimiasis and in sera from patients on whom follow-up studies were done after praziquantel treatment were analyzed using antigens of Paragonimus westermani prepared from eggs, metacercariae, juveniles of 4- and 7-week old, adult worms and recombinant protein of 28 kDa cruzipain-like cysteine protease (rPw28CCP). The patient sera/CSFs of active and chronic paragonimiasis revealed strong antibody reactions against the crude extracts of 4- and 7-week old juveniles as well as against those from egg and adult. rPw28CCP also showed specific reaction to the sera with active paragonimiasis. After the treatment, levels of specific antibodies in the sera gradually decreased to negative range in most patients. In some cases with persisting high antibody levels, however, the reactions at 27 kDa egg protein were sustained throughout the observation period of 34 months. The reactions at 35 and 32 kDa in adult extract and rPw28CCP disappeared rapidly after the treatment. Persistent antibody reactions even after successful treatment are provoked by continuous antigenic challenge from eggs which were not resolved by treatment.

Cross reacting antibodies against keyhole limpet haemocyanin may interfere with the diagnostics of acute schistosomiasis

The number of individuals catching schistosomiasis has increased with the popularity of 'primitive tourism' in Africa. Highly immunogenic material originating from the intestine of intravascular adult schistosomes gives rise to an antibody response making possible early identification of infected individuals using serology. Antibodies against gut associated antigens (anti-GAA), detected by indirect immunofluorescence microscopy employing sections of adult worms as antigen may occur before the onset of egg production. In the present study we show that this well known schistosomiasis-specific anti-GAA staining reaction can be confused with a similar staining reaction with ducts of both male and female worms. Antibodies with duct reactivity were seen in sera both from schistosomiasis-patients and patients with some other invasive worm infections. Cross reactive anti-duct antibodies appear to have different specificity. One cross reactive antibody reacted with antigenic epitopes present in keyhole limpet haemocyanin (KLH). Anti-duct reactivity could be inhibited by absorption with KLH. This was most obvious in the trichinellosis patient sera.