Katayama syndrome

Research progress in the treatment of schistosomiasis with traditional Chinese medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Schistosomiasis, caused by infection with organisms of the Schistoma genus, is a parasitic and infectious disease that poses a significant risk to human health. Schistosomiasis has been a widespread issue in China for at least 2000 years. Traditional Chinese medicine (TCM) has a rich history of treating this disease, and the significant theoretical and practical knowledge attained therein may be useful in modern practice.

AIM OF THE STUDY

To comprehensively review TCM for the treatment of schistosomiasis, summarize the molecular basis, mechanism of action, active ingredients and formulas of TCM, and clarify the value of TCM for expanding drug options for the clinical treatment of schistosomiasis.

MATERIALS AND METHODS

In PubMed, Web of Science, ScienceDirect, Google Scholar and CNKI databases, "Schistosomiasis", "Schistosoma mansoni", "Schistosoma japonicum", "Liver fibrosis" and "Granuloma" were used as the key words. Information related to in vivo animal studies and clinical studies of TCM for the treatment of schistosomiasis in the past 25 years was retrieved, and the inclusion criteria focused on medicinal plants that had a history of use in China.

RESULTS

In this study, we collected and organized a large amount of literature on the treatment of schistosomiasis by TCM. TCM exerts therapeutic effects through antischistosomal and immunomodulatory effects, suppresses HSC activation and proliferation, reduces ECM deposition, and inhibits oxidative stress and other activities. The treatment of schistosomiasis by TCM has a unique advantage, especially for the treatment of schistosomal liver fibrosis, and the treatment of schistosomiasis with TCM in combination with praziquantel is superior to monotherapy.

CONCLUSION

Schistosomiasis remains a global public health problem, and TCM has made significant progress in the prevention and treatment of schistosomiasis and is a potential source of drugs for the treatment of schistosomiasis. However, research on drug screening and the mechanism of action of TCM for the treatment of schistosomiasis is lacking, and further studies and research are needed.

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

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

Schistosomiasis in the Military-A Narrative Review

Schistosomiasis is a parasitosis caused by trematodes of the genus Schistosoma. Humans are infected when coming into contact with freshwater containing the parasites' infective stages, which are amplified through freshwater-dwelling snails acting as intermediate hosts. Schistosomiasis has posed significant problems for troops exposed to freshwater in endemic regions ever since the Napoleonic wars. Schistosomiasis has substantial differences in clinical presentation, depending on the type of parasite, intensity of infection and reinfection, clinical form, and disease stage. It can remain undiagnosed for long periods of time, with well-known long-term morbidity and mortality risks. The diagnosis of schistosomiasis depends on its stage and relays on several tests, all with limitations in sensitivity and specificity. The diagnostic gold standard is the detection of eggs in urine, feces, or tissue biopsies, but this can raise problems in patients such as military personnel, in which the worm burden is usually low. Praziquantel is the drug of choice for schistosomiasis. Currently, there is no available commercial vaccine against any Schistosoma parasite. Avoiding freshwater exposure is the best prevention. Herein, we review the clinical presentation, diagnosis, treatment, and prevention of schistosomiasis in the military. This information may decrease the impact of schistosomiasis on this particular professional group.

Early symptom-associated inflammatory responses shift to type 2 responses in controlled human schistosome infection

Schistosomiasis is an infection caused by contact with Schistosoma-contaminated water and affects more than 230 million people worldwide with varying morbidity. The roles of T helper 2 (TH2) cells and regulatory immune responses in chronic infection are well documented, but less is known about human immune responses during acute infection. Here, we comprehensively map immune responses during controlled human Schistosoma mansoni infection using male or female cercariae. Immune responses to male or female parasite single-sex infection were comparable. An early TH1-biased inflammatory response was observed at week 4 after infection, which was particularly apparent in individuals experiencing symptoms of acute schistosomiasis. By week 8 after infection, inflammatory responses were followed by an expansion of TH2 and regulatory cell subsets. This study demonstrates the shift from TH1 to both TH2 and regulatory responses, typical of chronic schistosomiasis, in the absence of egg production and provides immunological insight into the clinical manifestations of acute schistosomiasis.

Imported schistosomiasis in travelers: Experience from a referral tropical medicine unit in Barcelona, Spain

BACKGROUND

Acute schistosomiasis occurs most often in travelers to endemic regions. The aim of the study is to describe the epidemiological, clinical and parasitological characteristics of patients with schistosomiasis acquired during an international travel.

METHODS

Observational retrospective study including all travel-related schistosomiasis cases seen at the International Health Unit Vall d'Hebron-Drassanes (Barcelona, Spain) from 2009 to 2022. Diagnosis of schistosomiasis was defined by the presence of Schistosoma eggs in stools or urine or the positivity of a serological test. We collected demographic, epidemiological, clinical, parasitological, and therapeutic information.

RESULTS

917 cases of schistosomiasis were diagnosed, from whom 96 (10.5 %) were travel-related. Mean age of the patients was 34.9 years, and 53.1 % were women. Median duration of the travel was 72 days, and geographical areas where travelers had contact with fresh water were Africa (82.3 %), Asia (12.5 %), and South America (5.2 %). Twenty (20.8 %) patients reported having had some clinical symptom, being gastrointestinal symptoms the most frequent. Two patients developed the classical Katayama syndrome. In eleven (11.5 %) cases eggs were observed in urine or feces samples, and 85 (88.5 %) cases were diagnosed by a positive serology. Ninety-one (94.8 %) patients received treatment with praziquantel with different therapeutic schemes. The two patients with Katayama syndrome received concomitant treatment with corticosteroids.

CONCLUSIONS

Schistosomiasis in travelers represented 10 % of the overall schistosomiasis cases in our center. Increasing the awareness in the pre-travel advice and implementing specific screening in those travelers at risk (long travelers, contact with fresh water) could reduce the incidence and associated morbidity in this group.

Assessment of the selected hematological profiles among malaria and Schistosoma mansoni co-infected patients, Northwest Ethiopia

Malaria and schistosomiasis are infectious diseases that cause hematological profiles abnormalities. Malaria and Schistosoma mansoni co-infection causes exacerbation of health consequences and co-morbidities. The aim of this study was to assess the selected hematological profiles among malaria and S. mansoni co-infected patients at Dembiya Selected Health Institutions. An institutional-based comparative cross-sectional study was conducted from March 30 to August 10, 2022. A total of 140 individuals were enrolled in the study using a convenient sampling technique. Wet mount and Kato Katz technique were conducted to detect S. mansoni in Stool sample. Blood films were prepared for the detection of plasmodium. The data was coded and entered into EpiData version 3.1 before being analyzed with SPSS version 25. A P-value of less than 0.05 was considered statistically significant. Mean of WBC, neutrophil, lymphocyte, eosinophil, RBC, hemoglobin, and hematocrit [4.IU/L,2.2 IU/L, 1.4 IU/L, 0.1 IU/L, 3.13 IU/L, 9.5 g/dL, and 28.7%, resepectively] in co-infected were significantly lower than [7.5 IU/L, 4.6 IU/L, 2.1 IU/L, 0.38 IU/L, 4.8 IU/L, 14.6 g/dL, and 43.7%, resepectively] in the healthy control participants. Mean of RBC, hemoglobin, and hematocrit [3.13 IU/L, 9.5 g/dL, 28.7%, resepectively] in co-infected were significantly lower compared to [3.8 IU/L, 11.5 g/dL, 33.9%, resepectively] in the malaria monoinfected participants and [3.7 IU/L,11.5 g/dL, 33.6%, resepectively] in the S. mansoni monoinfected participants. The result of hematological profiles in healthy participants had no significant difference compared to light,moderate and heavy S. mansoni infection intensity in coinfection. The number of S. mansoni eggs per gram of stool had been negatively correlated with hematological profiles of co-infected participants except lymphocyte and monocyte which correlated positively. Hematological profiles status in coinfection were significantly altered compared to malaria monoinfection, S. mansoni monoinfection, and healthy participants.Therefore, hematological tests should be used to monitor and manage coinfection related complications, and to reduce coinfection associated morbidity and mortality.

Katayama syndrome disguised as eosinophilic asthma with acute systemic symptoms and pulmonary nodules

Background

Katayama syndrome is an acute manifestation of schistosomiasis, a parasitic infection that manifests itself through a hypersensitivity reaction to migrating larvae and early egg deposition. Left undiagnosed and untreated, acute schistosomiasis can develop into chronic schistosomiasis which can lead to debilitating morbidity such as pulmonary hypertension. This case highlights that Katayama syndrome can also been seen in regions where the parasite is not endemic, as it occurs in travelers returning from endemic regions or in immigrants.

Case presentation

We describe the case of a 26-year-old asthmatic male, who presented with systemic symptoms including fever, myalgia, night sweats as well as gastro-intestinal and pulmonary complaints since five days. At presentation, there was a raised blood eosinophil count and nodular lesions were seen on computed tomography. After considering diagnoses such as tuberculosis, vasculitis and hypereosinophilic syndrome, it was repeated history taking that revealed that the patient had suffered from swimmer's itch during a stay in Guinea. A stool sample showed microscopic presence of Schistosoma mansoni eggs, confirming the diagnosis of Katayama syndrome. The patient was treated with tapered corticosteroids to suppress the hypersensitivity reaction and praziquantel was added to cure the parasitic infection. This led to a complete resolution of the patients' symptoms and radiological abnormalities. Negative stool samples confirmed the eradication of the schistosomes.

Conclusions

Swimmer's itch and Katayama syndrome are manifestations of acute schistosomiasis. It is important to recognize the syndrome, because early diagnosis and adequate treatment can prevent chronic disease and significant morbidity.

Pseudotumoral Encephalic Schistosomiasis: A Literature Review

Pseudotumoral encephalic schistosomiasis (PES) is the chronic form of cerebral neuroschistosomiasis, and is rarely encountered in clinical practice. Clinically, PES closely resembles other intracranial space-occupying lesions including brain tumors. Laboratory investigations are usually inconclusive, and neuroradiologic findings are frequently reported as non-specific. Such diagnostic difficulties may result in delayed diagnosis and treatment. Across the literature, there is a paucity of information about and controversy over many aspects of the disease. Particularly, inconsistent magnetic resonance imaging (MRI) findings, a wide variation of medical treatment protocols, lacking consensus regarding the indications of surgery, and undetermined information regarding the impact of the extent of resection on prognosis. We herein review the pertinent literature with the aim of providing focused information regarding the pathogenesis of PES, its currently identified more distinctive neuroimaging features, and the indications and extent of surgery in light of the state-of-the-art operative neurosurgical practice. A distinctive multinodular arborizing pattern of PES lesions can often be observed on MRI in patients with PES. Praziquantel is considered by many authors to be the drug of choice in all cases, and seems to be effective at variable dose regimens. Although lesion excision utilizing current technology is generally safe, the indications and extent of surgery are still undetermined and should be decided on a case-by-case basis. Multicenter collaborative research is further needed to fill the existing gaps in the current knowledge on PES.

Beyond schistosomiasis: unraveling co-infections and altered immunity

Schistosomiasis is a neglected tropical disease caused by the helminth Schistosoma spp. and has the second highest global impact of all parasites. Schistosoma are transmitted through contact with contaminated fresh water predominantly in Africa, Asia, the Middle East, and South America. Due to the widespread prevalence of Schistosoma, co-infection with other infectious agents is common but often poorly described. Herein, we review recent literature describing the impact of Schistosoma co-infection between species and Schistosoma co-infection with blood-borne protozoa, soil-transmitted helminths, various intestinal protozoa, Mycobacterium, Salmonella, various urinary tract infection-causing agents, and viral pathogens. In each case, disease severity and, of particular interest, the immune landscape, are altered as a consequence of co-infection. Understanding the impact of schistosomiasis co-infections will be important when considering treatment strategies and vaccine development moving forward.

Chronic intestinal schistosomiasis caused by co-infection with Schistosoma intercalatum and Schistosoma mansoni

The Grand Round concerns a 24-year-old man from Zimbabwe who was studying and living in Poland. The patient had been complaining of abdominal pain, fatigue, alternating diarrhoea and constipation, and presence of blood in his stool for 3 years. The patient had the following diagnostic tests: colonoscopy, CT scan, histopathology, and parasitological and molecular tests. Results of the examinations showed that the cause of the patient's complaints was chronic intestinal schistosomiasis due to the co-infection with Schistosoma intercalatum and Schistosoma mansoni. The patient had two cycles of praziquantel therapy (Biltricide) and responded well to the treatment. In the Grand Round, we describe full diagnostics as well as clinical and therapeutic management in the patient with S intercalatum and S mansoni co-infection. This case allows us to draw attention to cases of forgotten chronic tropical diseases (including rare ones) in patients from regions with a high endemic index staying in non-endemic regions of the world for a long time. Co-infection with S intercalatum and S mansoni should be considered as a very rare clinical case.

Single-cell RNA sequencing reveals a peripheral landscape of immune cells in Schistosomiasis japonica

BACKGROUND

Schistosomiasis, also known as bilharzia, is a devastating parasitic disease. This progressive and debilitating helminth disease is often associated with poverty and can lead to chronic poor health. Despite ongoing research, there is currently no effective vaccine for schistosomiasis, and praziquantel remains the only available treatment option. According to the progression of schistosomiasis, infections caused by schistosomes are classified into three distinct clinical phases: acute, chronic and advanced schistosomiasis. However, the underlying immune mechanism involved in the progression of schistosomiasis remains poorly understood.

METHODS

We employed single-cell RNA sequencing (scRNA-seq) to profile the immune landscape of Schistosomiasis japonica infection based on peripheral blood mononuclear cells (PBMCs) from a healthy control group (n = 4), chronic schistosomiasis group (n = 4) and advanced schistosomiasis group (n = 2).

RESULTS

Of 89,896 cells, 24 major cell clusters were ultimately included in our analysis. Neutrophils and NK/T cells accounted for the major proportion in the chronic group and the healthy group, and monocytes dominated in the advanced group. A preliminary study showed that NKT cells were increased in patients with schistosomiasis and that CXCR2 + NKT cells were proinflammatory cells. Plasma cells also accounted for a large proportion of B cells in the advanced group. MHC molecules in monocytes were notably lower in the advanced group than in the chronic group or the healthy control group. However, monocytes in the advanced group exhibited high expression of FOLR3 and CCR2.

CONCLUSIONS

Overall, this study enhances our understanding of the immune mechanisms involved in schistosomiasis. It provides a transcriptional atlas of peripheral immune cells that may contribute to elimination of the disease. This preliminary study suggests that the increased presence of CCR2 + monocyte and CXCR2 + NKT cells might participate in the progression of schistosomiasis.

Modelling morbidity for neglected tropical diseases: the long and winding road from cumulative exposure to long-term pathology

Reducing the morbidities caused by neglected tropical diseases (NTDs) is a central aim of ongoing disease control programmes. The broad spectrum of pathogens under the umbrella of NTDs lead to a range of negative health outcomes, from malnutrition and anaemia to organ failure, blindness and carcinogenesis. For some NTDs, the most severe clinical manifestations develop over many years of chronic or repeated infection. For these diseases, the association between infection and risk of long-term pathology is generally complex, and the impact of multiple interacting factors, such as age, co-morbidities and host immune response, is often poorly quantified. Mathematical modelling has been used for many years to gain insights into the complex processes underlying the transmission dynamics of infectious diseases; however, long-term morbidities associated with chronic or cumulative exposure are generally not incorporated into dynamic models for NTDs. Here we consider the complexities and challenges for determining the relationship between cumulative pathogen exposure and morbidity at the individual and population levels, drawing on case studies for trachoma, schistosomiasis and foodborne trematodiasis. We explore potential frameworks for explicitly incorporating long-term morbidity into NTD transmission models, and consider the insights such frameworks may bring in terms of policy-relevant projections for the elimination era. This article is part of the theme issue 'Challenges and opportunities in the fight against neglected tropical diseases: a decade from the London Declaration on NTDs'.

A case of pericardial schistosomiasis and non-Hodgkin high grade B-cell lymphoma

Chronic schistosomiasis affects either the genitourinary or gastrointestinal tract. Rarely, schistosomes cause ectopic disease, such as in the case of a South African woman from a non-endemic province, who presented with suspected pericardial tamponade because of tuberculosis. However, histology and polymerase chain reaction from pericardial biopsy confirmed Schistosoma haematobium. A finding of mediastinal non-Hodgkin lymphoma came to light when our patient's clinical condition unexpectedly deteriorated.

Contribution

This case highlights an unusual manifestation of schistosomiasis.

Open-source environmental data as an alternative to snail surveys to assess schistosomiasis risk in areas approaching elimination

BACKGROUND

Although the presence of intermediate snails is a necessary condition for local schistosomiasis transmission to occur, using them as surveillance targets in areas approaching elimination is challenging because the patchy and dynamic quality of snail host habitats makes collecting and testing snails labor-intensive. Meanwhile, geospatial analyses that rely on remotely sensed data are becoming popular tools for identifying environmental conditions that contribute to pathogen emergence and persistence.

METHODS

In this study, we assessed whether open-source environmental data can be used to predict the presence of human Schistosoma japonicum infections among households with a similar or improved degree of accuracy compared to prediction models developed using data from comprehensive snail surveys. To do this, we used infection data collected from rural communities in Southwestern China in 2016 to develop and compare the predictive performance of two Random Forest machine learning models: one built using snail survey data, and one using open-source environmental data.

RESULTS

The environmental data models outperformed the snail data models in predicting household S. japonicum infection with an estimated accuracy and Cohen's kappa value of 0.89 and 0.49, respectively, in the environmental model, compared to an accuracy and kappa of 0.86 and 0.37 for the snail model. The Normalized Difference in Water Index (an indicator of surface water presence) within half to one kilometer of the home and the distance from the home to the nearest road were among the top performing predictors in our final model. Homes were more likely to have infected residents if they were further from roads, or nearer to waterways.

CONCLUSION

Our results suggest that in low-transmission environments, leveraging open-source environmental data can yield more accurate identification of pockets of human infection than using snail surveys. Furthermore, the variable importance measures from our models point to aspects of the local environment that may indicate increased risk of schistosomiasis. For example, households were more likely to have infected residents if they were further from roads or were surrounded by more surface water, highlighting areas to target in future surveillance and control efforts.

Endemic or regionally limited parasitic and fungal infections in haematopoietic stem-cell transplantation recipients: a Worldwide Network for Blood and Marrow Transplantation (WBMT) Review

There is a scarcity of data on endemic and regionally limited fungal and parasitic infections in recipients of haematopoietic stem-cell transplantation (HSCT) outside western Europe and North America. This Worldwide Network for Blood and Marrow Transplantation (WBMT) Review is one of two papers aiming to provide guidance to transplantation centres worldwide regarding prevention, diagnosis, and treatment based on the currently available evidence and expert opinion. These recommendations were created and reviewed by physicians with expertise in HSCT or infectious disease, representing several infectious disease and HSCT groups and societies. In this paper, we review the literature on several endemic and regionally limited parasitic and fungal infections, some of which are listed as neglected tropical diseases by WHO, including visceral leishmaniasis, Chagas disease, strongyloidiasis, malaria, schistosomiasis, histoplasmosis, blastomycosis, and coccidioidomycosis.

Immunological mechanisms involved in macrophage activation and polarization in schistosomiasis

Human schistosomiasis is caused by helminths of the genus Schistosoma. Macrophages play a crucial role in the immune regulation of this disease. These cells acquire different phenotypes depending on the type of stimulus they receive. M1 macrophages can be ‘classically activated’ and can display a proinflammatory phenotype. M2 or ‘alternatively activated’ macrophages are considered anti-inflammatory cells. Despite the relevance of macrophages in controlling infections, the role of the functional types of these cells in schistosomiasis is unclear. This review highlights different molecules and/or macrophage activation and polarization pathways during Schistosoma mansoni and Schistosoma japonicum infection. This review is based on original and review articles obtained through searches in major databases, including Scopus, Google Scholar, ACS, PubMed, Wiley, Scielo, Web of Science, LILACS and ScienceDirect. Our findings emphasize the importance of S. mansoni and S. japonicum antigens in macrophage polarization, as they exert immunomodulatory effects in different stages of the disease and are therefore important as therapeutic targets for schistosomiasis and in vaccine development. A combination of different antigens can provide greater protection, as it possibly stimulates an adequate immune response for an M1 or M2 profile and leads to host resistance; however, this warrants in vitro and in vivo studies.

Schistosoma mansoni Infections and Morbidities Among School Children in Hotspot Areas of Jimma Town, Southwest Ethiopia: A Cross-Sectional Study

BACKGROUND

Schistosoma mansoni is endemic in all regions of Ethiopia. School-age children are highly vulnerable to schistosomiasis-related morbidities. This study aimed to determine the prevalence of S. mansoni and morbidities among schoolchildren in schistosomiasis hotspot areas of Jimma Town.

METHODS

Cross-sectional study was conducted among schoolchildren in Jimma Town. Stool sample was examined using Kato-Katz for the detection of S. mansoni.

RESULTS

A total of 332 schoolchildren were included in the study. The prevalence of S. mansoni and STHs was 20.2% and 19.9%, respectively. Males (adjusted odds ratio (AOR) = 4.9; 95% CI: 2.4-10.1; p = .001), swimming habits (AOR = 3.0; 95% CI: 1.1-8.3; p = .033) and schools attended (AOR = 4.3; 95% CI: 1.4-13.6; p = .012, AOR = 3.8; 95% CI: 1.3-10.9; p = .014) were associated factors for S. mansoni infections. Blood in stool (AOR = 2.0; CI: 1.0-4.1; p = .045) and feeling general malaise (AOR = 4.0; CI: 1.4-11.3; p = .007) were significantly associated with S. mansoni infection-related morbidities. Moreover, prevalence of stunting among schoolchildren 6 to 11 years of age was 29.7% (71/239).

CONCLUSION

The transmission of S. mansoni among schoolchildren is moderate. Sex, swimming habits and schools attended were associated with S. mansoni infections. Blood in stool and general malaise were clinical characteristics associated with S. mansoni infections. Integration of health promotion is needed to achieve control and elimination goals. Attention should also be given to stunted growth of the children.

Status Quo and Future Perspectives of Molecular and Genomic Studies on the Genus Biomphalaria-The Intermediate Snail Host of Schistosoma mansoni

Schistosomiasis, or also generally known as bilharzia or snail fever, is a parasitic disease that is caused by trematode flatworms of the genus Schistosoma. It is considered by the World Health Organisation as the second most prevalent parasitic disease after malaria and affects more than 230 million people in over 70 countries. People are infected via a variety of activities ranging from agricultural, domestic, occupational to recreational activities, where the freshwater snails Biomphalaria release Schistosoma cercariae larvae that penetrate the skin of humans when exposed in water. Understanding the biology of the intermediate host snail Biomphalaria is thus important to reveal the potential spread of schistosomiasis. In this article, we present an overview of the latest molecular studies focused on the snail Biomphalaria, including its ecology, evolution, and immune response; and propose using genomics as a foundation to further understand and control this disease vector and thus the transmission of schistosomiasis.

Spinal Schistosomiasis Masquerading as an Intramedullary Tumor

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Open-source environmental data as an alternative to snail surveys to assess schistosomiasis risk in areas approaching elimination

Background: Although the presence of intermediate snails is a necessary condition for local schistosomiasis transmission to occur, using them as surveillance targets in areas approaching elimination is challenging because the patchy and dynamic quality of snail host habitats makes collecting and testing snails labor-intensive. Meanwhile, geospatial analyses that rely on remotely sensed data are becoming popular tools for identifying environmental conditions that contribute to pathogen emergence and persistence. Methods: In this study, we assessed whether open-source environmental data can be used to predict the presence of human Schistosoma japonicum infections among households with a similar or improved degree of accuracy compared to prediction models developed using data from comprehensive snail surveys. To do this, we used infection data collected from rural communities in Southwestern China in 2016 to develop and compare the predictive performance of two Random Forest machine learning models: one built using snail survey data, and one using open-source environmental data. Results: The environmental data models outperformed the snail data models in predicting household S. japonicum infection with an estimated accuracy and Cohen’s kappa value of 0.89 and 0.49, respectively, in the environmental model, compared to an accuracy and kappa of 0.86 and 0.37 for the snail model. The Normalized Difference in Water Index (NDWI) within half to one kilometer of the home and the distance from the home to the nearest road were among the top performing predictors in our final model. Homes were more likely to have infected residents if they were further from roads, or nearer to waterways. Conclusion: Our results suggest that in low-transmission environments, investing in training geographic information systems professionals to leverage open-source environmental data could yield more accurate identification of pockets of human infection than using snail surveys. Furthermore, the variable importance measures from our models point to aspects of the local environment that may indicate increased risk of schistosomiasis. For example, households were more likely to have infected residents if they were further from roads or were surrounded by more surface water, highlighting areas to target in future surveillance and control efforts.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for differential identification of adult Schistosoma worms

BACKGROUND

Schistosomiasis is a major neglected tropical disease that affects up to 250 million individuals worldwide. The diagnosis of human schistosomiasis is mainly based on the microscopic detection of the parasite's eggs in the feces (i.e., for Schistosoma mansoni or Schistosoma japonicum) or urine (i.e., for Schistosoma haematobium) samples. However, these techniques have limited sensitivity, and microscopic expertise is waning outside endemic areas. Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) has become the gold standard diagnostic method for the identification of bacteria and fungi in many microbiological laboratories. Preliminary studies have recently shown promising results for parasite identification using this method. The aims of this study were to develop and validate a species-specific database for adult Schistosoma identification, and to evaluate the effects of different storage solutions (ethanol and RNAlater) on spectra profiles.

METHODS

Adult worms (males and females) of S. mansoni and S. japonicum were obtained from experimentally infected mice. Species identification was carried out morphologically and by cytochrome oxidase 1 gene sequencing. Reference protein spectra for the creation of an in-house MALDI-TOF MS database were generated, and the database evaluated using new samples. We employed unsupervised (principal component analysis) and supervised (support vector machine, k-nearest neighbor, Random Forest, and partial least squares discriminant analysis) machine learning algorithms for the identification and differentiation of the Schistosoma species.

RESULTS

All the spectra were correctly identified by internal validation. For external validation, 58 new Schistosoma samples were analyzed, of which 100% (58/58) were correctly identified to genus level (log score values ≥ 1.7) and 81% (47/58) were reliably identified to species level (log score values ≥ 2). The spectra profiles showed some differences depending on the storage solution used. All the machine learning algorithms classified the samples correctly.

CONCLUSIONS

MALDI-TOF MS can reliably distinguish adult S. mansoni from S. japonicum.

One Health Concept against Schistosomiasis: An Overview

Schistosomiasis (bilharziasis) is a parasitic disease caused by Schistosoma spp. that belongs to trematode worms. These worms are known as “blood parasites”. This disease is included in “neglected tropical diseases” and “water-borne diseases”. The main species are Schistosoma (S.) haematobium, S. japonicum, S. mansoni, S. intercalatum, S. mekongi, S. guineensis and S. intercalatum, though there are more than 20 different species. The parasite in the definitive host may affect many organs and systems. The disease may become chronic and lasts 3–8 years and even up to 20–30 years. The definitive host is primarily human; however, in endemic areas animals such as monkeys, cattle, horses, rodents, cats, dogs are reservoirs. According to World Health Organization (WHO), schistosomiasis affects 250 million people, and causes 1.9 million deaths yearly in endemic areas. Moreover, due to global warming, the spread of the disease may increase. The effective way to fight against schistosomiasis is following the “one-health system”. Indeed, to overcome or “eradicate” this disease, we have to strive against different forms at different evolutionary stages of the worm such as, forms in humans, domestic or wild animals, and freshwater snails. If we combine the knowledge of professionals, we may achieve this goal.

Urinary Bladder Schistosomiasis Mimicking Neoplasm: A Case Report

Schistosomiasis is a neglected disease that is prevalent in tropical and subtropical areas. A 20-year-old woman presented to the emergency room with a history of right flank pain and lower abdominal discomfort for one day, which coincided with the onset of menses. The patient did not provide any history of premenstrual hematuria. The physical examination revealed right costovertebral angle tenderness and was otherwise unremarkable. The urinalysis demonstrated a mild increase in red and white blood cells and no ova or parasite. The blood test was normal, except for eosinophilia. A right pedunculated intraluminal urinary bladder mass was detected by the computerized axial tomographic scan and ultrasonography, and after the transurethral resection of the mass, the patient was diagnosed with urinary schistosomiasis. The patient received two doses of oral praziquantel of 1200 mg every 12 h for one day. The cure was confirmed with a one-month post-treatment follow-up that revealed a normal urine microscope and eosinophil count. The S. haematobium infection should be evaluated as a possible cause of urinary bladder lesion in those who have travelled or lived in endemic areas.

Tropical parasitic itch in returned travellers and immigrants from endemic areas

Itch is the most common skin symptom among tropical parasitic diseases (TPD), but there are limited data about its characteristics in these conditions. In dermatology practices and travellers' health clinics in the developed world, itch is a common complaint among travellers returning from endemic areas, as well among migrants arriving from endemic areas, where they may have been exposed to TPD. Studying aspects of pruritus among TPD may lead to improvements in prompt, accurate diagnosis and management of these conditions. This review examines the major itch-inducing TPDs, including schistosomiasis, echinococcosis, onchocerciasis, scabies, cutaneous larva migrans, larva currens, African trypanosomiasis, dracunculiasis and other causes of travel associated pruritus. We focus on the link between pruritus and other symptoms, aetiology, clinical staging and therapeutic options for these parasitic illnesses. Because some tropical parasitic diseases can present with significant pruritus, we attempt to identify aspects of the pruritus that are characteristic of-or unique to-specific conditions. These diagnostic insights may help clinicians create a rational and focused differential diagnosis and help determine optimal disease management pathways. In this sense, management involves treating the individual, seeking epidemiologically linked cases, preventing recurrences or relapses, and reducing spread of the disease.

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

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

Schistosomiasis at the Crossroad to Elimination: Review of Eclipsed Research with Emphasis on the Post-Transmission Agenda

While chronic schistosomiasis is pathologically well defined, the acute form of the disease is less well understood. It is generally agreed that early lesions, such as lung nodules and bladder polyps, are reversible, which impedes identification of the time elapsed since exposure. The intermediate stage between the acute and the chronic forms of schistosomiasis requires further investigation, as does the clinical stage due to lesions remaining after treatment. With current schistosomiasis control efforts gradually progressing to elimination, there is a need to focus on post-transmission schistosomiasis, which not only refers to remaining lesions from previous infections, but also accounts for the potential presence of surviving worms after treatment. This issue is particularly salient for migrants from endemic to non-endemic countries and should be kept in mind for returning expatriates from schistosomiasis-endemic countries. Negative stool examination or urine filtration are generally taken as indicative of cure since rectoscopy for Schistosoma mansoni infection, or cystoscopy for S. haematobium infection, are rarely performed. However, pathology of affected organs may persist indefinitely, while potentially remaining live worms could produce additional pathology. Hence, post-transmission schistosomiasis can prevail for years after elimination of the disease, and thus, warrant further attention.

An update on female and male genital schistosomiasis and a call to integrate efforts to escalate diagnosis, treatment and awareness in endemic and non-endemic settings: The time is now

The last decades have brought important insight and updates in the diagnosis, management and immunopathology of female genital schistosomiasis (FGS) and male genital schistosomiasis (MGS). Despite sharing a common parasitic aetiological agent, FGS and MGS have typically been studied separately. Infection with Schistosoma haematobium manifests with gender-specific clinical manifestations and consequences of infection, albeit having a similar pathogenesis within the human genital tract. Schistosoma haematobium is a known urinary bladder carcinogen, but its potential causative role in other types of neoplasia, such as cervical cancer, is not fully understood. Furthermore, the impact of praziquantel treatment on clinical outcomes remains largely underexplored, as is the interplay of FGS/MGS with relevant reproductive tract infections such as HIV and Human Papillomavirus. In non-endemic settings, travel and immigrant health clinics need better guidance to correctly identify and treat FGS and MGS. Our review outlines the latest advances and remaining knowledge gaps in FGS and MGS research. We aim to pave a way forward to formulate more effective control measures and discuss elimination targets. With a growing community awareness in health practitioners, scientists and epidemiologists, alongside the sufferers from these diseases, we aspire to witness a new generation of young women and men free from the downstream disabling manifestations of disease.

Clinical Spectrum of Schistosomiasis: An Update

Schistosomiasis is a helminthic infection and one of the neglected tropical diseases (NTDs). It is caused by blood flukes of the genus Schistosoma. It is an important public health problem, particularly in poverty-stricken areas, especially those within the tropics and subtropics. It is estimated that at least 236 million people worldwide are infected, 90% of them in sub-Saharan Africa, and that this disease causes approximately 300,000 deaths annually. The clinical manifestations are varied and affect practically all organs. There are substantial differences in the clinical presentation, depending on the phase and clinical form of schistosomiasis in which it occurs. Schistosomiasis can remain undiagnosed for a long period of time, with secondary clinical lesion. Here, we review the clinical profile of schistosomiasis. This information may aid in the development of more efficacious treatments and improved disease prognosis.

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

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

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.

Helminth infections in the US military: from strongyloidiasis to schistosomiasis

BACKGROUND

Helminth infections caused by parasitic worms, including nematodes (roundworms), cestodes (tapeworms) and trematodes (flukes), can cause chronic symptoms and serious clinical outcomes if left untreated. The US military frequently conducts activities in helminth-endemic regions, particularly Africa, the Middle East and Southeast Asia. However, the military does not currently screen for these infections, and to date, no comprehensive surveillance studies have been completed to assess the frequency of helminth diagnoses in the military personnel and their families.

METHODS

To determine the burden of helminth infections in the US Military Health System (MHS), we conducted a retrospective analysis of International Classification of Diseases (ICD)-9/10 diagnosis codes from all medical encounters in the MHS Data Repository (MDR) from fiscal years (FY) 2012 to 2018. Chart reviews were conducted to assign ICD diagnoses as incorrect, suspected, probable or confirmed based on the laboratory results and symptoms.

RESULTS

Abstraction of MHS data revealed over 50 000 helminth diagnoses between FY 2012 and FY 2018. Of these, 38 445 of diagnoses were amongst unique subjects. After chart review, we found there were 34 425 validated helminth infections diagnosed amongst the unique subjects of US military personnel, retirees and dependents. Nearly 4000 of these cases represented infections other than enterobiasis. There were 351 validated strongyloidiasis diagnoses, 317 schistosomiasis diagnoses and 191 diagnoses of cysticercosis during the study period. Incidence of intestinal nematode infection diagnoses showed an upward trend, whilst the incidence of cestode infection diagnoses decreased.

CONCLUSIONS

The results of this study demonstrate that helminth infections capable of causing severe morbidity are often diagnosed in the US military. As helminth infections are often asymptomatic or go undiagnosed, the true burden of helminth infections in US military personnel and dependents may be higher than observed here. Prospective studies of US military personnel deployed to helminth-endemic areas may be indicated to determine if post-deployment screening and/or empirical treatment are warranted.

Medical Imaging in the Diagnosis of Schistosomiasis: A Review

Schistosomiasis is one of the most important parasitic diseases and it is endemic in tropical and subtropical areas. Clinical and laboratory data are fundamental for the diagnosis of schistosomiasis, but diagnostic imaging techniques such as x-rays, ultrasound (US), computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography/computed tomography (PET/CT) may be helpful in the evaluation of disease severity and complications. In this context, the aim of this review is to explore the actual role of diagnostic imaging in the diagnosis of schistosomiasis, underlining advantages and drawbacks providing information about the utilization of diagnostic imaging techniques in this context. Furthermore, we aim to provide a useful guide regarding imaging features of schistosomiasis for radiology and nuclear medicine physicians of non-endemic countries: in fact, in the last years non-endemic countries have experienced important flows of migrants from endemic areas, therefore it is not uncommon to face cases of this disease in daily practice.

Fever in the Returned Pediatric Traveler

Global mobility has been steadily increasing in recent years. The assessment of the febrile child returning from international travel is a diagnostic challenge. The COVID-19 pandemic has profoundly affected international travel and made evaluation and management of the sick returned traveler more challenging. Children visiting friends and relatives abroad remain at higher risk of infection compared to tourists. This review presents a guidance on the initial assessment of a traveling febrile child including interpretation of medical history, physical examination, and laboratory findings. Important clues to etiology include exposure to different infectious agents, incubation periods of pathogens, and prophylaxis regimens and vaccines received. Early identification of potentially life-threatening and highly contagious infections is essential. In this article, we discuss the epidemiology, evaluation, and management of specific travel related infections such as malaria, typhoid fever, dengue fever, viral hemorrhagic fever, rickettsiosis, leptospirosis, schistosomiasis, gastrointestinal, and respiratory infections.

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.

Algorithm for diagnosis of early Schistosoma haematobium using prodromal signs and symptoms in pre-school age children in an endemic district in Zimbabwe

Introduction

Prompt diagnosis of acute schistosomiasis benefits the individual and provides opportunities for early public health intervention. In endemic areas schistosomiasis is usually contracted during the first 5 years of life, thus it is critical to look at how the infection manifests in this age group. The aim of this study was to describe the prodromal signs and symptoms of early schistosomiasis infection, correlate these with early disease progression and risk score to develop an easy to use clinical algorithm to identify early Schistosoma haematobium infection cases in resource limited settings.

Methodology

Two hundred and four, preschool age children who were lifelong residence of a schistosomiasis endemic district and at high risk of acquiring schistosomiasis were followed up from July 2019 to December 2019, during high transmission season. The children received interval and standard full clinical evaluations and laboratory investigations for schistosomiasis by clinicians blinded from their schistosomiasis infection status. Diagnosis of S. haematobium was by urine filtration collected over three consecutive days. Signs and symptoms of schistosomiasis at first examination visit were compared to follow-up visits. Signs and symptoms common on the last schistosomiasis negative visit (before a subsequent positive) were assigned as early schistosomiasis infection (ESI), after possible alternative causes were ruled out. Logistic regression identified clinical predictors. A model based score was assigned to each predictor to create a risk for every child. An algorithm was created based on the predictor risk scores and validated on a separate cohort of 537 preschool age children.

Results

Twenty-one percent (42) of the participants were negative for S. haematobium infection at baseline but turned positive at follow-up. The ESI participants at the preceding S. haematobium negative visit had the following prodromal signs and symptoms in comparison to non-ESI participants; pruritic rash adjusted odds ratio (AOR) = 21.52 (95% CI 6.38–72.66), fever AOR = 82 (95% CI 10.98–612), abdominal pain AOR = 2.6 (95% CI 1.25–5.43), pallor AOR = 4 (95% CI 1.44–11.12) and a history of facial/body swelling within the previous month AOR = 7.31 (95% CI 3.49–15.33). Furthermore 16% of the ESI group had mild normocytic anaemia, whilst 2% had moderate normocytic anaemia. A risk score model was created using a rounded integer from the relative risks ratios. The diagnostic algorithm created had a sensitivity of 81% and a specificity of 96.9%, Positive predictive value = 87.2% and NPV was 95.2%. The area under the curve for the algorithm was 0.93 (0.90–0.97) in comparison with the urine dipstick AUC = 0.58 (0.48–0.69). There was a similar appearance in the validation cohort as in the derivative cohort.

Conclusion

This study demonstrates for the first time prodromal signs and symptoms associated with early S. haematobium infection in pre-school age children. These prodromal signs and symptoms pave way for early intervention and management, thus decreasing the harm of late diagnosis. Our algorithm has the potential to assist in risk-stratifying pre-school age children for early S. haematobium infection. Independent validation of the algorithm on another cohort is needed to assess the utility further.

Schistosoma haematobium causes urogenital infection and in endemic areas schistosomiasis is usually contracted during the first 5 years of life, thus it is critical to look at how the infection manifests in this age group. Prompt diagnosis of acute schistosomiasis is required to benefit the individuals and provide opportunities for early treatment and public health intervention. The study examined symptoms that correlated with early disease progression and risk scored to develop an easy to use clinical algorithm to identify early S. haematobium infection cases. The children received standard full clinical evaluations by clinicians who were blinded from schistosomiasis diagnosis by parasitological examination. An algorithm was created based on the predictor risk scores and participants had the following prodromal signs and symptoms; pruritic rash, abdominal pain, pallor, abdominal pain, inguinal lymphadenopathy and a history of facial/body swelling within the previous month. A risk score model, diagnostic algorithm, was created that compared to urine dipstick and parasitology. This study demonstrates the clinical signs and symptoms associated with early S. haematobium infection in pre-school age children. These prodromal signs and symptoms pave way for early intervention and management, thus decreasing the harm of late diagnosis common in populations from endemic areas.

Ultraviolet disinfection of Schistosoma mansoni cercariae in water

BACKGROUND

Schistosomiasis is a parasitic disease that is transmitted by skin contact with waterborne schistosome cercariae. Mass drug administration with praziquantel is an effective control method, but it cannot prevent reinfection if contact with cercariae infested water continues. Providing safe water for contact activities such as laundry and bathing can help to reduce transmission. In this study we examine the direct effect of UV light on Schistosoma mansoni cercariae using ultraviolet light-emitting diodes (UV LEDs) and a low-pressure (LP) mercury arc discharge lamp.

METHODOLOGY

S. mansoni cercariae were exposed to UV light at four peak wavelengths: 255 nm, 265 nm, 285 nm (UV LEDs), and 253.7 nm (LP lamp) using bench scale collimated beam apparatus. The UV fluence ranged from 0-300 mJ/cm2 at each wavelength. Cercariae were studied under a stereo-microscope at 0, 60, and 180 minutes post-exposure and the viability of cercariae was determined by assessing their motility and morphology.

CONCLUSION

Very high UV fluences were required to kill S. mansoni cercariae, when compared to most other waterborne pathogens. At 265 nm a fluence of 247 mJ/cm2 (95% confidence interval (CI): 234-261 mJ/cm2) was required to achieve a 1-log10 reduction at 0 minutes post-exposure. Cercariae were visibly damaged at lower fluences, and the log reduction increased with time post-exposure at all wavelengths. Fluences of 127 mJ/cm2 (95% CI: 111-146 mJ/cm2) and 99 mJ/cm2 (95% CI: 85-113 mJ/cm2) were required to achieve a 1-log10 reduction at 60 and 180 minutes post-exposure at 265 nm. At 0 minutes post-exposure 285 nm was slightly less effective, but there was no statistical difference between 265 nm and 285 nm after 60 minutes. The least effective wavelengths were 255 nm and 253.7 nm. Due to the high fluences required, UV disinfection is unlikely to be an energy- or cost-efficient water treatment method against schistosome cercariae when compared to other methods such as chlorination, unless it can be demonstrated that UV-damaged cercariae are non-infective using alternative assay methods or there are improvements in UV LED technology.

Schistosomiasis with a Focus on Africa

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

Schistosomes in the Lung: Immunobiology and Opportunity

Schistosome infection is a major cause of global morbidity, particularly in sub-Saharan Africa. However, there is no effective vaccine for this major neglected tropical disease, and re-infection routinely occurs after chemotherapeutic treatment. Following invasion through the skin, larval schistosomula enter the circulatory system and migrate through the lung before maturing to adulthood in the mesenteric or urogenital vasculature. Eggs released from adult worms can become trapped in various tissues, with resultant inflammatory responses leading to hepato-splenic, intestinal, or urogenital disease – processes that have been extensively studied in recent years. In contrast, although lung pathology can occur in both the acute and chronic phases of schistosomiasis, the mechanisms underlying pulmonary disease are particularly poorly understood. In chronic infection, egg-mediated fibrosis and vascular destruction can lead to the formation of portosystemic shunts through which eggs can embolise to the lungs, where they can trigger granulomatous disease. Acute schistosomiasis, or Katayama syndrome, which is primarily evident in non-endemic individuals, occurs during pulmonary larval migration, maturation, and initial egg-production, often involving fever and a cough with an accompanying immune cell infiltrate into the lung. Importantly, lung migrating larvae are not just a cause of inflammation and pathology but are a key target for future vaccine design. However, vaccine efforts are hindered by a limited understanding of what constitutes a protective immune response to larvae. In this review, we explore the current understanding of pulmonary immune responses and inflammatory pathology in schistosomiasis, highlighting important unanswered questions and areas for future research.

Structure, Immunoreactivity, and In Silico Epitope Determination of SmSPI S. mansoni Serpin for Immunodiagnostic Application

The human parasitic disease Schistosomiasis is caused by the Schistosoma trematode flatworm that infects freshwaters in tropical regions of the world, particularly in Sub-Saharan Africa, South America, and the Far-East. It has also been observed as an emerging disease in Europe, due to increased immigration. In addition to improved therapeutic strategies, it is imperative to develop novel, rapid, and sensitive diagnostic tests that can detect the Schistosoma parasite, allowing timely treatment. Present diagnosis is difficult and involves microscopy-based detection of Schistosoma eggs in the feces. In this context, we present the 3.22 Å resolution crystal structure of the circulating antigen Serine protease inhibitor from S. mansoni (SmSPI), and we describe it as a potential serodiagnostic marker. Moreover, we identify three potential immunoreactive epitopes using in silico-based epitope mapping methods. Here, we confirm effective immune sera reactivity of the recombinant antigen, suggesting the further investigation of the protein and/or its predicted epitopes as serodiagnostic Schistosomiasis biomarkers.

Loop-Mediated Isothermal Amplification in Schistosomiasis

Human schistosomiasis is one of the most important parasitic diseases, causing around 250 million cases (mostly in Africa) and 280,000–500,000 deaths every year. Due to the limited resources and the far-removed nature of many endemic areas, the implementation of new, sensitive and specific diagnostic tools has had little success. This is particularly true for PCR-based molecular methods that require expensive equipment and trained personnel to be executed. Loop-mediated isothermal amplification (LAMP) along with other isothermal techniques appeared in the early 21st century as an alternative to those methods, overcoming some of the aforementioned limitations and achieving a more inexpensive diagnostic. However, to this date, neither LAMP nor any other isothermal technique have signified a meaningful change in the way schistosomiasis diagnosis is routinely performed. Here, we present the recent developments in LAMP-based schistosomiasis diagnosis. We expose the main advantages and disadvantages of LAMP technology over PCR and other classical diagnostic methods focusing in various research approaches on intermediate hosts, animal models and patients. We also examine its potential clinical application in post-therapy monitoring, as well as its usefulness as a point-of-care test.

Tropical Infections in Returning Travelers

In the modern era, the relative ease and faster speed of travel have made the world a global village. An increasing number of people are traveling to distant and sometimes exotic locations for vacation/leisure or at times for business purposes. Along with the experiences of far-fetched lands, sometimes they bring bugs/organisms that are not native to their motherland. This makes the diagnosis and management of illnesses in a traveler challenging. In this review, we have tried to outline a management protocol for travelers returning with fever, with specific emphasis on trypanosomiasis and schistosomiasis.

How to cite this article: Suri V, Bhalla A. Tropical Infections in Returning Travelers. Indian J Crit Care Med 2021;25(Suppl 2):S175–S183.

Imported Schistosomiasis: A New Public Health Challenge for China

Significantly increased imported schistosomiasis cases have been reported in China as the economy grows. The aim of this study is to review and summarize the current status, clinical features, and transmission risk of imported infections of Schistosoma mansoni and Schistosoma haematobium in China. A retrospective study was performed to review all information regarding the imported cases of schistosomiasis collected from published literature and the database of the National Notifiable Disease Report System from 1979 to 2019. The characterization of epidemiological and clinical features was analyzed. A total of 355 cases of imported schistosomiasis have been reported in 15 provinces (autonomous regions, municipalities) in China since 1979, including 78 cases of infection with S. mansoni (21.97%), 262 cases with S. haematobium (73.80%), and 15 cases with unidentified Schistosoma species. Eosinophilia was the most common sign of the infection with S. mansoni (91.03%). The parasitological findings were confirmed in 89.74% (70/78) of cases infected with S. mansoni and 32.06% (84/262) of cases infected with S. haematobium. There was no imported case of infection of Schistosoma japonicum, Schistosoma intercalatum, or Schistosoma mekongi reported in China during this period. Praziquantel is the best therapeutic drug for curing imported schistosomiasis. In addition, Biomphalaria straminea, the intermediate host of S. mansoni, has already been found in Guangdong province in south China. There is a rising risk that the existence of the intermediate host B. straminea and the imported cases of S. mansoni infection could cause the spread of the infections and make these endemic. Thus, better understanding of the clinical features and the transmission pattern of these Schistosoma infections would assist Chinese physicians in the diagnosis and treatment of these imported schistosomiasis cases.

Host Immunity and Inflammation to Pulmonary Helminth Infections

Helminths, including nematodes, cestodes and trematodes, are complex parasitic organisms that infect at least one billion people globally living in extreme poverty. Helminthic infections are associated with severe morbidity particularly in young children who often harbor the highest burden of disease. While each helminth species completes a distinct life cycle within the host, several helminths incite significant lung disease. This impact on the lungs occurs either directly from larval migration and host immune activation or indirectly from a systemic inflammatory immune response. The impact of helminths on the pulmonary immune response involves a sophisticated orchestration and activation of the host innate and adaptive immune cells. The consequences of activating pulmonary host immune responses are variable with several helminthic infections leading to severe, pulmonary compromise while others providing immune tolerance and protection against the development of pulmonary diseases. Further delineation of the convoluted interface between helminth infection and the pulmonary host immune responses is critical to the development of novel therapeutics that are critically needed to prevent the significant global morbidity caused by these parasites.

Recent Progress in the Development of Liver Fluke and Blood Fluke Vaccines

Liver flukes (Fasciola spp., Opisthorchis spp., Clonorchis sinensis) and blood flukes (Schistosoma spp.) are parasitic helminths causing neglected tropical diseases that result in substantial morbidity afflicting millions globally. Affecting the world’s poorest people, fasciolosis, opisthorchiasis, clonorchiasis and schistosomiasis cause severe disability; hinder growth, productivity and cognitive development; and can end in death. Children are often disproportionately affected. F. hepatica and F. gigantica are also the most important trematode flukes parasitising ruminants and cause substantial economic losses annually. Mass drug administration (MDA) programs for the control of these liver and blood fluke infections are in place in a number of countries but treatment coverage is often low, re-infection rates are high and drug compliance and effectiveness can vary. Furthermore, the spectre of drug resistance is ever-present, so MDA is not effective or sustainable long term. Vaccination would provide an invaluable tool to achieve lasting control leading to elimination. This review summarises the status currently of vaccine development, identifies some of the major scientific targets for progression and briefly discusses future innovations that may provide effective protective immunity against these helminth parasites and the diseases they cause.

Current status and future prospects of protein vaccine candidates against Schistosoma mansoni infection

Schistosomiasis is an acute and chronic tropical parasitic disease caused by blood dwelling worm of the genus Schistosoma. It is the most destructive disease globally and is a major cause of morbidity and mortality for developing countries. Three main species of schistosomes infect human beings from which S. mansoni is the most common and widespread. Over the last several decades, chemotherapy using praziquantel has been a commonly used strategy for the treatment and control of schistosomiasis. However, control programs focused exclusively on chemotherapy have been challenging because of the frequency and rapidity of reinfection and these programs were expensive. Thus, new schistosomiasis control strategies will be needed. Vaccination strategy would be an ideal tool for a significant and sustainable reduction in the transmission and disease burden of schistosomiasis. An effective anti schistosome vaccine would greatly contribute to decreasing schistosomiasis-associated morbidity via protective immune responses leading to reduced worm burdens and decreased egg production. Vaccine development is a long process that can take decades. There have been three candidate vaccines that have been produced by Good Manufacturing Procedure and entered human clinical trials for S. mansoni are Sm14, SmTSP-2, and Sm-p80. Other candidates that are in pre-clinical trials at various stages include paramyosin, Sm29, SmKI-1, and Sm23. Since the growth of several new technologies, including genomics, transcriptomics, microarrays, immunomic profiling, and proteomics, have helped in the identification of promising new target schistosome antigens. Therefore, this review considers the present status of protein vaccine candidates against Schistosoma mansoni and provides some insight on prospects vaccine design and discovery.

Clinical Use of Schistosoma mansoni Antigens as Novel Immunotherapies for Autoimmune Disorders

The hygiene hypothesis states that improved hygiene and the resulting disappearance of once endemic diseases is at the origin of the enormous increase in immune related disorders such as autoimmune diseases seen in the industrialized world. Helminths, such as Schistosoma mansoni, are thought to provide protection against the development of autoimmune diseases by regulating the host's immune response. This modulation primarily involves induction of regulatory immune responses, such as generation of tolerogenic dendritic cells and alternatively activated macrophages. This points toward the potential of employing helminths or their products/metabolites as therapeutics for autoimmune diseases that are characterized by an excessive inflammatory state, such as multiple sclerosis (MS), type I diabetes (T1D) and inflammatory bowel disease (IBD). In this review, we examine the known mechanisms of immune modulation by S. mansoni, explore preclinical and clinical studies that investigated the use of an array helminthic products in these diseases, and propose that helminthic therapy opens opportunities in the treatment of chronic inflammatory disorders.

New Insights on Acute and Chronic Schistosomiasis: Do We Need a Redefinition?

A precise timeframe to differentiate acute schistosomiasis (AS) and chronic schistosomiasis (CS) is not well defined. Based on recent published literature, lung nodular lesions in AS and CS seem to have the same pathophysiology, that is, eggs laid in situ by adult worms, during an ectopic migration. Moreover, the occurrence of lung nodules due to clusters of eggs and the systemic immunoallergic reaction of AS (Katayama syndrome) may be two separate clinical entities, which may overlap during the early phase of infection. Consequently, the classical distinction between AS and CS loses much of its conceptual validity. If adult worms play a more important role in the early phase of the disease the clinical management of AS should probably be revised.