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

Acute schistosomiasis in paediatric travellers and comparison with their companion adults

BACKGROUND

Schistosomiasis in non-immune travellers can cause acute schistosomiasis, a multi-systemic hypersensitivity reaction. Little is known regarding acute schistosomiasis in children. We describe acute schistosomiasis in paediatric travellers and compare them with adult travellers.

METHODS

A retrospective study of paediatric travellers (0-18 years old) diagnosed with schistosomiasis at Sheba Medical Center. Patients' findings are compared with those of adult travellers from the same travel groups.

RESULTS

in total, 18 children and 24 adults from five different trips to Tanzania, Uganda, Nigeria and Laos were infected (90% of the exposed travellers). The median bathing time of the infected children was 30 min (interquartile range (IQR) 15-30 min). The most common presentations were respiratory symptoms in 13 (72%), eosinophilia in 13 (72%) and fever in 11 (61%). Acute illness included a median of 2.5 symptoms. Three children required hospitalization and three were asymptomatic. Fatigue was significantly less common in children compared with similarly exposed adults (33% vs 71%, P = 0.03). Rates of hospitalization and steroid treatment were similar. The median eosinophil count in children was 1045 cells/μl (IQR 625-2575), lower than adults [2900 cells/μl (IQR 1170-4584)], P = 0.02.

CONCLUSIONS

Children may develop acute schistosomiasis following short exposure to contaminated freshwater, demonstrating a high infection rate. Severity seems to be similar to adults, although children report fatigue less commonly and show lower eosinophil counts. The disease should be suspected in children with multi-systemic illness and in asymptomatic children with relevant travel history.

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

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

Case Report: Diagnosis and Assessment of Cure Approaches for Acute Schistosomiasis in Pre-School Children

Acute schistosomiasis (AS) manifests with a broad spectrum of clinical features in pediatric populations. Diagnosis may be difficult in the absence of detectable numbers of eggs. As a result, new approaches may be required to achieve an accurate diagnosis. Optimal praziquantel (PZQ) treatment regimen for young children is debatable. Also, the post-treatment response is still poorly evaluated due to the lack of reliable markers. A group of 6 children (a toddler and 5 pre-school children) and one pre-adolescent were investigated for AS clinical manifestations and followed-up for two years after treatment. Ova detection was performed by Kato-Katz (KK) and presence of Schistosoma mansoni DNA was assessed by real-time PCR (rt-PCR) in stool samples. IgG and IgE anti-Schistosoma levels and urinary antigen were detected by ELISA and point-of-care circulating cathodic antigen (POC-CCA) testing in serum and urine, respectively. AS clinical symptoms were present in 5/7 (71.4%) of the infected children, and hypereosinophilia was detected in all of them. Ova detection and serology were positive in only 3/7 (44.9%) and 4/7 (57.1%), respectively. However, real-time PCR (rt-PCR) showed the presence of Schistosoma DNA in 6/7 (85.7%) of the cases, and urinary antigen was detected in all infected children. The long-term follow-up after treatment with three doses of PZQ (80mg/kg/dose), showed high cure rates (CR) as demonstrated by the DNA-based assay as well as reduced levels of side effects. CR based on urinary antigen detection ranged from 28.6 to 100%, being the highest CR due to double testing the 2-year post-treatment samples. The results suggest that high dose and repeated treatment with PZQ might be effective for AS in young children. Also, new laboratory markers should be considered to diagnosis and monitor the drug response.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Detection of Schistosoma mansoni DNA using polymerase chain reaction from serum and dried blood spot card samples of an adult population in North-western Tanzania

BACKGROUND

Real-time polymerase chain reaction (PCR) is a sensitive and specific method for diagnosing schistosomiasis. However, this method should be performed in a laboratory, usually located distant from the sample collection site. Therefore, it is important to have fast sampling preservation methods, which allow simple transport prior to DNA extraction and amplification. The aim of this study was to verify if blood samples applied to filter paper are suitable for analysis of Schistosoma mansoni DNA by real-time PCR.

METHODS

A cross-sectional study was conducted among 100 study participants aged 17 to 70 years in a fishing village on the southern shore of Lake Victoria, Tanzania. Serum samples and ethylenediaminetetraacetic acid (EDTA)-anticoagulated whole blood for preparation of dried blood spots (DBS) were collected to test for Schistosoma mansoni infection by real-time PCR. A combined diagnostic reference of positive results of serum-based real-time PCR and the Kato-Katz (KK) method was used for analysis. Sensitivity and negative predictive value (NPV) were calculated. The Wilcoxon signed-rank test was chosen to compare the mean cycle threshold (Ct) values from serum and DBS.

RESULTS

According to the reference, 92.5% S. mansoni positive samples were determined. The serum-based real-time PCR performed excellently with 95.4% sensitivity, whereas the DBS-based real-time PCR showed a low sensitivity (45.4%). The Ct-values were significantly higher in DBS (median: 37.3) than in serum samples (median: 27.5, P < 0.001), reflecting a lower parasite-specific DNA load on the filter cards. With increasing egg counts, an increase in sensitivity was observed for all methods. The POC-CCA test and the serum-based real-time PCR showed a sensitivity of 100% for medium and severe infections. The DBS real-time PCR showed a sensitivity of only 85.7% even for severe infections.

CONCLUSIONS

DBS-based real-time PCR did not provide good results in our study and therefore should not be recommended or must be tested concerning temperature of storage, storage duration, use of different filter papers and extraction methods before it is used in future studies. In contrast, our results showed that the POC-CCA test is a sensitive and precise test for detecting S. mansoni infections .

Acute Schistosomiasis With a Schistosoma mattheei × Schistosoma haematobium Hybrid Species in a Cluster of 34 Travelers Infected in South Africa

Background

Diagnosis of schistosomiasis remains elusive soon after infection. We evaluated several diagnostic methods in a cluster of travelers with simultaneous freshwater exposure in South Africa.

Methods

Eosinophil count, schistosome antibody tests, stool and urine microscopy, and serum Dra1 PCR assays were performed at weeks 4–5 (early symptomatic phase), 7–8 (praziquantel treatment), and 13–14 (after treatment). Sequencing was done on serum samples from 3 patients to identify the species.

Results

Of the 34 travelers (16 adults and 18 children), 32 developed symptoms 2–6 weeks after exposure. A raised eosinophil count (&gt;750/µL) was seen in 12 of 33 at weeks 4–5, and in 22 of 34 at weeks 7–8. Schistosoma antibodies were detected in 3 of 33 at weeks 4–5 and in 12 of 34 at weeks 7–8 and weeks 13–14. The Dra1 PCR result was positive in 24 of 33 travelers at weeks 4–5, in 31 of 34 at weeks 7–8, in 25 of 34 at weeks 13–14, and at least once in all. Ova were absent in all urine and stool samples obtained. Sequencing identified Schistosoma mattheei nuclear and Schistosoma haematobium mitochondrial DNA, indicative of a hybrid species.

Conclusions

The Dra1 PCR confirmed the diagnosis in all exposed travelers at a much earlier stage than conventional tests. The causative species is probably an S. mattheei × S. haematobium hybrid.

Mapping Schistosoma mansoni endemicity in Rwanda: a critical assessment of geographical disparities arising from circulating cathodic antigen versus Kato-Katz diagnostics

BACKGROUND

Schistosomiasis is a neglected tropical disease caused by Schistosoma parasites. Intervention relies on identifying high-risk regions, yet rapid Schistosoma diagnostics (Kato-Katz stool assays (KK) and circulating cathodic antigen urine assays (CCA)) yield different prevalence estimates. We mapped S. mansoni prevalence and delineated at-risk regions using a survey of schoolchildren in Rwanda, where S. mansoni is an endemic parasite. We asked if different diagnostics resulted in disparities in projected infection risk.

METHODS

Infection data was obtained from a 2014 Rwandan school-based survey that used KK and CCA diagnostics. Across 386 schools screened by CCA (N = 19,217). To allow for uncertainty when interpreting ambiguous CCA trace readings, which accounted for 28.8% of total test results, we generated two presence-absence datasets: CCA trace as positive and CCA trace as negative. Samples (N = 9,175) from 185 schools were also screened by KK. We included land surface temperature (LST) and the Normalized Difference Vegetation and Normalized Difference Water Indices (NDVI, NDWI) as predictors in geostatistical regressions.

FINDINGS

Across 8,647 children tested by both methods, prevalence was 35.93% for CCA trace as positive, 7.21% for CCA trace as negative and 1.95% for KK. LST was identified as a risk factor using KK, whereas NDVI was a risk factor for CCA models. Models predicted high endemicity in Northern and Western regions of Rwanda, though the CCA trace as positive model identified additional high-risk areas that were overlooked by the other methods. Estimates of current burden for children at highest risk (boys aged 5-9 years) varied by an order of magnitude, with 671,856 boys projected to be infected by CCA trace as positive and only 60,453 projected by CCA trace as negative results.

CONCLUSIONS

Our findings show that people in Rwanda's Northern, Western and capital regions are at high risk of S. mansoni infection. However, variation in identification of environmental risk factors and delineation of at-risk regions using different diagnostics likely provides confusing messages to disease intervention managers. Further research and statistical analyses, such as latent class analysis, can be used to improve CCA result classification and assess its use in guiding treatment regimes.

Intestinal parasites including Cryptosporidium, Cyclospora, Giardia, and Microsporidia, Entamoeba histolytica, Strongyloides, Schistosomiasis, and Echinococcus: Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention, and management of intestinal parasites in the pre- and post-transplant period. Intestinal parasites are prevalent in the developing regions of the world. With increasing travel to and from endemic regions, changing immigration patterns, and the expansion of transplant medicine in developing countries, they are increasingly recognized as a source of morbidity and mortality in solid-organ transplant recipients. Parasitic infections may be acquired from the donor allograft, from reactivation, or from de novo acquisition post-transplantation. Gastrointestinal multiplex assays have been developed; some of the panels include testing for Cryptosporidium, Cyclospora, Entamoeba histolytica, and Giardia, and the performance is comparable to conventional methods. A polymerase chain reaction test, not yet widely available, has also been developed to detect Strongyloides in stool samples. New recommendations have been developed to minimize the risk of Strongyloides donor-derived events. Deceased donors with epidemiological risk factors should be screened for Strongyloides and recipients treated if positive as soon as the results are available. New therapeutic agents and studies addressing the optimal treatment regimen for solid-organ transplant recipients are unmet needs.

[Urogenital tuberculosis and schistosomiasis (bilharzia) : Urological challenges in displaced persons]

We are observing the largest worldwide wave of migration ever. Displaced persons usually do not have access to general health care and are faced with a lack of hygienic conditions and infection control while fleeing, which leads to an accumulation of "exotic" infectious diseases. The number of patients with tuberculosis (TB) had declined for many years in Germany; however, increasing numbers of cases have recently been observed. For urologists, of course, the manifestations of urogenital TB (UGTB) are of particular interest. Therefore, the basics regarding diagnosis and therapy of UGTB are discussed in this article and explained using case studies. The second important "exotic" infectious disease that urologists are increasingly facing is schistosomiasis. The larvae (found mostly in stagnant water) penetrate through intact human skin, mature and migrate into the liver, from where they immigrate into the venous capillaries of the intestine, the small pelvis, the bladder wall and the distal ureter, and there cause chronic inflammation. All urologists should be familiar with the diagnosis, therapy and prophylaxis of urogenital schistosomiasis and the oncogenesis of schistosomiasis-associated bladder carcinoma.

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

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

Exotic Tourist Destinations and Transmission of Infections by Swimming Pools and Hot Springs-A Literature Review

A growing number of people undertake international travel, and yet faster growth of such travel is expected in the tropics. Information on the hazards presented by pool and hot spring waters in tropical countries is very limited. This review aims to collate available information on pool water quality, alongside data on cases and outbreaks associated with swimming in pools in tropical regions affecting both local populations and travellers. Bacteria species commonly causing cases and outbreaks in the tropics as well as elsewhere in the world were excluded, and the review focuses on studies related to pathogens that, with the exception of Cryptosporidium, are unusual in more temperate climates. Studies concerning subtropical countries were included in the light of climate change. Diseases transmitted by vectors breeding in poorly maintained, neglected or abandoned pools were also included. 83 studies dealing with Microsporidia, Leptospira spp., Schistosomas spp., Cryptosporidium spp., Acanthamoeba spp., Naegleria spp., Clostridium trachomatis, viruses, and vectors breeding in swimming pool and hot tub waters, and fulfilling predefined criteria, have been included in our survey of the literature. In conclusion, prevention strategies for pool safety in the tropics are imperative. Public health authorities need to provide guidance to westerners travelling to exotic destinations on how to protect their health in swimming pools.

Improved diagnosis of active Schistosoma infection in travellers and migrants using the ultra-sensitive in-house lateral flow test for detection of circulating anodic antigen (CAA) in serum

Schistosomiasis is a parasitic disease affecting over 250 million people in the tropics. In non-endemic regions, imported Schistosoma infections are commonly diagnosed by serology, but based on antibody detection an active infection cannot be distinguished from a cured infection and it may take more than 8 weeks after exposure before seroconversion occurs. In endemic populations, excellent results have been described in diagnosing low-grade active Schistosoma infections by the detection of the adult worm-derived circulating anodic antigen (CAA) utilising robust lateral flow (LF) assays combined with up-converting phosphor (UCP) reporter technology. The purpose of this study is to explore the diagnostic value of the UCP-LF CAA assay in a non-endemic setting. CAA concentrations were determined in 111 serum samples originating from 81 serology-positive individuals. In nine individuals, serum could be collected before travel and an additional five provided samples before and after seroconversion occurred. Based on detectable CAA levels, an active infection was seen in 56/81 (69%) of the exposed individuals, while the 10 controls and the 9 sera collected before travel were tested negative for CAA. Positive CAA levels were observed starting 4 weeks after exposure and in four cases CAA was detected even before Schistosoma-specific antibodies became positive. Higher serum CAA levels were seen in migrants than in travellers and CAA concentrations dropped sharply when testing follow-up samples after treatment. This explorative study indicates the UCP-LF CAA serum assay to be a highly accurate test for detecting active low-grade Schistosoma infections in a non-endemic routine diagnostic setting.

Lake tourism fatalities: a 46-year history of death at Lake Powell

BACKGROUND

This study investigates tourist mortality at Lake Powell over a 46-year period. To date no comprehensive long-term investigation examining the relationship between the lake environment and tourist mortality exists.

METHODS

A retrospective study was conducted of all tourist fatalities between 1959 and 2005.

RESULTS

There were 351 fatal incidents resulting in 386 deaths between 1959 and 2005. Over the 46-year period, the average number of fatalities was 8.4 (±5.26) per year. Out of all fatalities, 282 were classified as accidental, 80 were classified as natural deaths, 13 were suicides and 5 were classified as homicides. Males accounted for 80% of fatalities and tourists aged 20-29 years and 10-19 years accounted for 36% of all fatalities. The highest number of fatalities was recorded in July (74), May (64), August (63) and June (59). Out of all accidental deaths, boating (29%) and swimming (22%) were the most common pre-death activities. High winds capsizing boats and carbon monoxide poisoning from boat engines were common factors contributing to 31 boating fatalities. Fatigue and exhaustion contributed to 22 swimming deaths.

CONCLUSIONS

Recreational boating and swimming account for over half of all accidental deaths. Tourists visiting Lake Powell for recreational purposes should be informed of the risks associated with the lake environment.

Serological approaches for the diagnosis of schistosomiasis - A review

Schistosomiasis is a common disease in endemic areas of Sub-Saharan Africa, South America and Asia. It is rare in Europe, mainly imported from endemic countries due to travelling or human migration. Available methods for the diagnosis of schistosomiasis comprise microscopic, molecular and serological approaches, with the latter detecting antigens or antibodies associated with Schistosoma spp. infection. The serological approach is a valuable screening tool in low-endemicity settings and for travel medicine, though the interpretation of any diagnostic results requires knowledge of test characteristics and a patient's history. Specific antibody detection by most currently used assays is only possible in a relatively late stage of infection and does not allow for the differentiation of acute from previous infections for therapeutic control or the discrimination between persisting infection and re-infection. Throughout the last decades, new target antigens have been identified, and assays with improved performance and suitability for use in the field have been developed. For numerous assays, large-scale studies are still required to reliably characterise assay characteristics alone and in association with other available methods for the diagnosis of schistosomiasis. Apart from S. mansoni, S. haematobium and S. japonicum, for which most available tests were developed, other species of Schistosoma that occur less frequently need to be taken into account. This narrative review describes and critically discusses the results of published studies on the evaluation of serological assays that detect antibodies against different Schistosoma species of humans. It provides insights into the diagnostic performance and an overview of available assays and their suitability for large-scale use or individual diagnosis, and thus sets the scene for serological diagnosis of schistosomiasis and the interpretation of results.

Diagnosis and Clinical Management of Schistosoma haematobium-Schistosoma bovis Hybrid Infection in a Cluster of Travelers Returning From Mali

Ten Belgian travelers returned from Mali with a Schistosoma haematobium-Schistosoma bovis hybrid infection, confirmed by DNA sequencing from eggs. Clinical symptoms and laboratory findings resembled those of classic acute schistosomiasis, but the detected eggs were morphologically unusual.

Molecular testing for clinical diagnosis and epidemiological investigations of intestinal parasitic infections

Over the past few decades, nucleic acid-based methods have been developed for the diagnosis of intestinal parasitic infections. Advantages of nucleic acid-based methods are numerous; typically, these include increased sensitivity and specificity and simpler standardization of diagnostic procedures. DNA samples can also be stored and used for genetic characterization and molecular typing, providing a valuable tool for surveys and surveillance studies. A variety of technologies have been applied, and some specific and general pitfalls and limitations have been identified. This review provides an overview of the multitude of methods that have been reported for the detection of intestinal parasites and offers some guidance in applying these methods in the clinical laboratory and in epidemiological studies.

Advances in the Diagnosis of Human Schistosomiasis

Schistosomiasis is a major neglected tropical disease that afflicts more than 240 million people, including many children and young adults, in the tropics and subtropics. The disease is characterized by chronic infections with significant residual morbidity and is of considerable public health importance, with substantial socioeconomic impacts on impoverished communities. Morbidity reduction and eventual elimination through integrated intervention measures are the focuses of current schistosomiasis control programs. Precise diagnosis of schistosome infections, in both mammalian and snail intermediate hosts, will play a pivotal role in achieving these goals. Nevertheless, despite extensive efforts over several decades, the search for sensitive and specific diagnostics for schistosomiasis is ongoing. Here we review the area, paying attention to earlier approaches but emphasizing recent developments in the search for new diagnostics for schistosomiasis with practical applications in the research laboratory, the clinic, and the field. Careful and rigorous validation of these assays and their cost-effectiveness will be needed, however, prior to their adoption in support of policy decisions for national public health programs aimed at the control and elimination of schistosomiasis.

Clinical consequences of new diagnostic tools for intestinal parasites

Following the success of nucleic acid-based detection in virology and bacteriology, multiplex real-time PCRs are increasingly used as first-line diagnostics in clinical parasitology, replacing microscopy. The detection and quantification of parasite-specific DNA in faeces is highly sensitive and specific and allows for cost-effective high-throughput screening. In this paper we discuss the clinical consequences of this radical change in diagnostic approach, as well as its potential drawbacks. In the Netherlands, routine diagnostic laboratories have been pioneering the implementation of multiplex real-time PCR for the detection of pathogenic intestinal protozoa and this has resulted in increased detection rates of Giardia lamblia and Cryptosporidium spp. As a consequence of this new diagnostic approach, expertise in the field of parasite morphology by conventional light microscopy seems to be disappearing in most of the high-throughput microbiological laboratories. As a result, to maintain a high standard of care, a formalized exchange of critical information between clinicians and laboratory staff is necessary to determine the most appropriate testing either in local laboratories or in reference centres, based on clinical signs and symptoms, exposure and immune status. If such a diagnostic algorithm is lacking, important infections in travellers, immigrants and immunocompromised patients may be missed.

Laboratory diagnosis of schistosomiasis and Katayama syndrome in returning travellers

The gold standard for laboratory diagnosis of schistosomiasis is the presence of typical eggs in stool or urine. The laboratory diagnosis of schistosomiasis and Katayama syndrome in returning travellers is difficult because the number of excreted eggs is often very limited. In early infections and in patients with only a few contacts with contaminated water, the total number of parasites, migrating larvae or schistosomulae, and adult worms, is very low. Eggs can only be found in faeces or urine when there is at least one pair of adult worms at the final location. The number of parasites increases as a function of the number of contacts with infected water. The exact latency between contamination and egg production is unknown. It is estimated that excretion of eggs starts after 40-50 days. The specific diagnosis of early schistosomiasis and Katayama fever relies essentially on serologic tests or preferably on PCR (if available). These assays are much more sensitive (up to four times) in the early phase of schistosomiasis than microscopic examination for typical eggs. Eosinophilia (sometimes exceeding 50%) is often present in patients with acute schistosomiasis (Katayama fever), but may be limited or absent in late fibrotic manifestations of the disease.

Application of PCR-based methods for diagnosis of intestinal parasitic infections in the clinical laboratory

For many years PCR- and other DNA-based methods of pathogen detection have been available in most clinical microbiology laboratories; however, until recently these tools were not routinely exploited for the diagnosis of parasitic infections. Laboratories were initially reluctant to implement PCR as incorporation of such assays within the algorithm of tools available for the most accurate diagnosis of a large variety of parasites was unclear. With regard to diagnosis of intestinal parasitic infections, the diversity of parasites that one can expect in most settings is far less than the parasitological textbooks would have you believe, hence developing a simplified diagnostic triage is feasible. Therefore the classical algorithm based on population, patient groups, use of immuno-suppressive drugs, travel history etc. is also applicable to decide when to perform and which additional techniques are to be used, if a multiplex PCR panel is used as a first-line screening diagnostic.

Failure of repeated treatment with praziquantel and arthemeter in four patients with acute schistosomiasis

Schistosomiasis is on the rise but still difficult to treat in international travelers; it should be suspected in patients returning from endemic areas. Praziquantel (PZQ) is not effective and may aggravate symptoms. More recently, combination treatment with artemisinin derivatives have shown promising results. We report four cases of acute schistosomiasis (AS) in which several courses of combined therapy had been necessary to obtain negative serology.

Diagnostic issues of acute schistosomiasis with Schistosoma mekongi in a traveler: a case report

A Belgian traveler returning from Laos developed acute schistosomiasis. Feces microscopy and polymerase chain reaction (PCR) followed by sequence analysis revealed Schistosoma mekongi. Schistosome antibody test results and real-time PCR in serum were initially negative or not interpretable. A HRP-2 antigen test for Plasmodium falciparum and an enzyme-linked immunosorbent assay (ELISA) antibody test for Trichinella yielded false-positive results.

A Schistosoma haematobium-specific real-time PCR for diagnosis of urogenital schistosomiasis in serum samples of international travelers and migrants

BACKGROUND

Diagnosis of urogenital schistosomiasis by microscopy and serological tests may be elusive in travelers due to low egg load and the absence of seroconversion upon arrival. There is need for a more sensitive diagnostic test. Therefore, we developed a real-time PCR targeting the Schistosoma haematobium-specific Dra1 sequence.

METHODOLOGY/PRINCIPAL FINDINGS

The PCR was evaluated on urine (n = 111), stool (n = 84) and serum samples (n = 135), and one biopsy from travelers and migrants with confirmed or suspected schistosomiasis. PCR revealed a positive result in 7/7 urine samples, 11/11 stool samples and 1/1 biopsy containing S. haematobium eggs as demonstrated by microscopy and in 22/23 serum samples from patients with a parasitological confirmed S. haematobium infection. S. haematobium DNA was additionally detected by PCR in 7 urine, 3 stool and 5 serum samples of patients suspected of having schistosomiasis without egg excretion in urine and feces. None of these suspected patients demonstrated other parasitic infections except one with Blastocystis hominis and Entamoeba cyst in a fecal sample. The PCR was negative in all stool samples containing S. mansoni eggs (n = 21) and in all serum samples of patients with a microscopically confirmed S. mansoni (n = 22), Ascaris lumbricoides (n = 1), Ancylostomidae (n = 1), Strongyloides stercoralis (n = 1) or Trichuris trichuria infection (n = 1). The PCR demonstrated a high specificity, reproducibility and analytical sensitivity (0.5 eggs per gram of feces).

CONCLUSION/SIGNIFICANCE

The real-time PCR targeting the Dra1 sequence for S. haematobium-specific detection in urine, feces, and particularly serum, is a promising tool to confirm the diagnosis, also during the acute phase of urogenital schistosomiasis.

Schistosomiasis: current epidemiology and management in travelers

Schistosomiasis is increasingly encountered among travelers returning from the tropics, mainly from Africa. Schistosoma-infected travelers have served as sentinels for the existence of unknown foci of transmission even outside Africa. Acute schistosomiasis (also termed Katayama syndrome) is the common manifestation among travelers and may follow exposure to any of the Schistosoma species. Neuroschistosomiasis is a rare complication but may result in severe disability. Diagnosis in travelers is hampered by the poor sensitivity of microscopy in urine and stool, especially during acute infections, while seroconversion may be delayed for a period of weeks. During acute schistosomiasis, symptomatic treatment is the only available therapy, while for chronic schistosomiasis, praziquantel is the only drug available, despite reports of emerging resistance to it. Since the potential for exposure to Schistosoma through travel will probably continue to increase, it is clear that new, sensitive diagnostic methods and drugs affecting the parasite in all its stages are needed.

Acute schistosomiasis in travelers: 14 years' experience at the Hospital for Tropical Diseases, London

We report 79 cases of acute schistosomiasis. Most of these cases were young, male travelers who acquired their infection in Lake Malawi. Twelve had a normal eosinophil count at presentation and 11 had negative serology, although two had neither eosinophilia nor positive serology when first seen. Acute schistosomiasis should be considered in any febrile traveler with a history of fresh water exposure in an endemic area once malaria has been excluded.

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.

Acute pulmonary schistosomiasis in travelers: case report and review of the literature

We report the case of an American traveler who developed acute pulmonary schistosomiasis after swimming in a lake in Madagascar, and we review the literature on acute pulmonary schistosomiasis. Schistosomiasis is one of the world's most prevalent parasitic diseases, with three species (Schistosoma mansoni, Schistosoma haematobium and Schistosoma japonicum) causing the greatest burden of disease. Pulmonary manifestations may develop in infected travelers from non-endemic areas after their first exposure. The pathophysiology of acute pulmonary disease is not well-understood, but is related to immune response, particularly via inflammatory cytokines. Diagnosis of schistosomiasis may be either through identification of characteristic ova in urine or stool or through serology. Anti-inflammatory drugs can provide symptomatic relief; praziquantel, the mainstay of chronic schistosomiasis treatment, is likely not effective against acute disease; the only reliable prevention remains avoidance of contaminated freshwater in endemic areas, as there is no vaccine. Travelers who have been exposed to potentially contaminated freshwater in endemic areas should seek testing and, if infected, treatment, in order to avoid severe manifestations of acute schistosomiasis and prevent complications of chronic disease. Clinicians are reminded to elicit a detailed travel and exposure history from their patients.

Human schistosome infection and allergic sensitisation

Several field studies have reported an inverse relationship between the prevalence of helminth infections and that of allergic sensitisation/atopy. Recent studies show that immune responses induced by helminth parasites are, to an extent, comparable to allergic sensitisation. However, helminth products induce regulatory responses capable of inhibiting not only antiparasite immune responses, but also allergic sensitisation. The relative effects of this immunomodulation on the development of protective schistosome-specific responses in humans has yet to be demonstrated at population level, and the clinical significance of immunomodulation of allergic disease is still controversial. Nonetheless, similarities in immune responses against helminths and allergens pose interesting mechanistic and evolutionary questions. This paper examines the epidemiology, biology and immunology of allergic sensitisation/atopy, and schistosome infection in human populations.

Schistosoma real-time PCR as diagnostic tool for international travellers and migrants

OBJECTIVE

To evaluate the use of a genus-specific PCR that combines high sensitivity with the detection of different Schistosoma species for diagnosis in international travellers and migrants in comparison to standard microscopy.

METHODS AND RESULTS

The genus-specific real-time PCR was developed to target the 28S ribosomal RNA gene of the major human Schistosoma species. It was validated for analytical specificity and reproducibility and demonstrated an analytical sensitivity of 0.2 eggs per gram of faeces. Its diagnostic performance was further evaluated on 152 faecal, 32 urine and 38 serum samples from patients presenting at the outpatient clinic of the Institute of Tropical Medicine in Antwerp (Belgium). We detected Schistosoma DNA in 76 faecal (50.0%) and five urine (15.6%) samples of which, respectively, nine and one were not detected by standard microscopy. Only two of the 38 serum samples of patients with confirmed schistosomiasis were positive with the presently developed PCR. Sequence analysis on positive faecal samples allowed identification of the Schistosoma species complex.

CONCLUSION

The real-time PCR is highly sensitive and may offer added value in diagnosing imported schistosomiasis. The genus-specific PCR can detect all schistosome species that are infectious to humans and performs very well with faeces and urine, but not in serum.