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Seminars in Immunopathology Jun 2020Schistosomiasis (bilharzia) is a neglected tropical disease caused by trematode worms of the genus Schistosoma. The transmission cycle involves human (or other... (Review)
Review
Schistosomiasis (bilharzia) is a neglected tropical disease caused by trematode worms of the genus Schistosoma. The transmission cycle involves human (or other mammalian) water contact with surface water contaminated by faeces or urine, as well as specific freshwater snails acting as intermediate hosts. The main disease-causing species are S. haematobium, S. mansoni and S. japonicum. According to the World Health Organisation, over 250 million people are infected worldwide, leading to considerable morbidity and the estimated loss of 1.9 million disability-adjusted life years (DALYs), a likely underestimated figure. Schistosomiasis is characterised by focal epidemiology and an over-dispersed population distribution, with higher infection rates in children. Complex immune mechanisms lead to the slow acquisition of immune resistance, but innate factors also play a part. Acute schistosomiasis, a feverish syndrome, is most evident in travellers following a primary infection. Chronic schistosomiasis affects mainly individuals with long-standing infections residing in poor rural areas. Immunopathological reactions against schistosome eggs trapped in host tissues lead to inflammatory and obstructive disease in the urinary system (S. haematobium) or intestinal disease, hepatosplenic inflammation and liver fibrosis (S. mansoni and S. japonicum). An effective drug-praziquantel-is available for treatment but, despite intensive efforts, no schistosomiasis vaccines have yet been accepted for public use. In this review, we briefly introduce the schistosome parasites and the immunopathogenic manifestations resulting from schistosomiasis. We then explore aspects of the immunology and host-parasite interplay in schistosome infections paying special attention to the current status of schistosomiasis vaccine development highlighting the advancement of a new controlled human challenge infection model for testing schistosomiasis vaccines.
Topics: Animals; Anthelmintics; Child; Humans; Schistosoma haematobium; Schistosoma mansoni; Schistosomiasis; Vaccines
PubMed: 32076812
DOI: 10.1007/s00281-020-00789-x -
Frontiers in Immunology 2023Schistosomiasis is a neglected tropical disease caused by dioecious blood flukes of the genus and second to malaria as a parasitic disease with significant... (Review)
Review
Schistosomiasis is a neglected tropical disease caused by dioecious blood flukes of the genus and second to malaria as a parasitic disease with significant socio-economic impacts. Mating is essential for maturation of male and female schistosomes and for females to lay of eggs, which are responsible for the pathogenesis and propagation of the life cycle beyond the mammalian host. Single-sex schistosomes, which do not produce viable eggs without mating, have been overlooked given the symptomatic paucity of the single-sex schistosomiasis and limited diagnostic toolkit. Besides, single-sex schistosomes are less sensitive to praziquantel. Therefore, these issues should be considered to achieve the elimination of this infection disease. The aim of this review is to summarize current progress in research of single-sex schistosomes and host-parasite interactions.
Topics: Animals; Male; Female; Schistosomiasis; Schistosoma; Praziquantel; Host-Parasite Interactions; Life Cycle Stages; Mammals
PubMed: 37153566
DOI: 10.3389/fimmu.2023.1158805 -
PLoS Neglected Tropical Diseases Feb 2018Schistosomiasis affects over 200 million people worldwide, most of whom are children. Research and control strategies directed at preschool-aged children (PSAC), i.e.,... (Review)
Review
Schistosomiasis affects over 200 million people worldwide, most of whom are children. Research and control strategies directed at preschool-aged children (PSAC), i.e., ≤5 years old, have lagged behind those in older children and adults. With the recent WHO revision of the schistosomiasis treatment guidelines to include PSAC, and the recognition of gaps in our current knowledge on the disease and its treatment in this age group, there is now a concerted effort to address these shortcomings. Global and national schistosome control strategies are yet to include PSAC in treatment schedules. Maximum impact of schistosome treatment programmes will be realised through effective treatment of PSAC. In this review, we (i) discuss the current knowledge on the dynamics and consequences of paediatric schistosomiasis and (ii) identify knowledge and policy gaps relevant to these areas and to the successful control of schistosome infection and disease in this age group. Herein, we highlight risk factors, immune mechanisms, pathology, and optimal timing for screening, diagnosis, and treatment of paediatric schistosomiasis. We also discuss the tools required for treating schistosomiasis in PSAC and strategies for accessing them for treatment.
Topics: Animals; Child; Child, Preschool; Humans; Immunity; Infection Control; Morbidity; Risk Factors; Schistosoma; Schistosomiasis
PubMed: 29420537
DOI: 10.1371/journal.pntd.0006144 -
Parasites & Vectors Sep 2016Schistosomiasis, caused mainly by S. mansoni, S. haematobium and S. japonicum, continues to be a serious tropical disease and public health problem resulting in an... (Review)
Review
Schistosomiasis, caused mainly by S. mansoni, S. haematobium and S. japonicum, continues to be a serious tropical disease and public health problem resulting in an unacceptably high level of morbidity in countries where it is endemic. Praziquantel, the only drug currently available for treatment, is unable to kill developing schistosomes, it does not prevent re-infection and its continued extensive use may result in the future emergence of drug-resistant parasites. This scenario provides impetus for the development and deployment of anti-schistosome vaccines to be used as part of an integrated approach for the prevention, control and eventual elimination of schistosomiasis. This review considers the present status of candidate vaccines for schistosomiasis, and provides some insight on future vaccine discovery and design.
Topics: Drug Discovery; Humans; Schistosomiasis; Vaccines
PubMed: 27716365
DOI: 10.1186/s13071-016-1799-4 -
PLoS Pathogens Dec 2016The interaction between schistosomiasis and Salmonella is a particularly important issue in Africa, where dual infection by the parasite and the bacterium are likely... (Review)
Review
The interaction between schistosomiasis and Salmonella is a particularly important issue in Africa, where dual infection by the parasite and the bacterium are likely common. In this review, the ways in which schistosomiasis affects human biology as it relates to Salmonella are described. Those who are infected by both organisms experience reduced immunological functioning, exhibit irreversible organ damage due to prolonged schistosomiasis infection, and become latent carriers of Salmonella enterica serotypes Typhi and Paratyphi and S. Typhimurium. The sequestration of the bacteria in the parasite leads to ineffective antibiotic treatment because the bacteria cannot be completely killed, and lingering infection may then lead to antimicrobial resistance. These manifestations are likely not just for those dually infected but also for those first infected with schistosomes and, later, Salmonella. More data are needed to better understand dual infection, particularly as it may impact treatment and prevention of schistosomiasis and Salmonella in sub-Saharan Africa.
Topics: Coinfection; Humans; Salmonella; Salmonella Infections; Schistosomiasis
PubMed: 27907208
DOI: 10.1371/journal.ppat.1005928 -
ELife Aug 2022The global community has adopted ambitious goals to eliminate schistosomiasis as a public health problem, and new tools are needed to achieve them. Mass drug... (Review)
Review
The global community has adopted ambitious goals to eliminate schistosomiasis as a public health problem, and new tools are needed to achieve them. Mass drug administration programs, for example, have reduced the burden of schistosomiasis, but the identification of hotspots of persistent and reemergent transmission threaten progress toward elimination and underscore the need to couple treatment with interventions that reduce transmission. Recent advances in DNA sequencing technologies make whole-genome sequencing a valuable and increasingly feasible option for population-based studies of complex parasites such as schistosomes. Here, we focus on leveraging genomic data to tailor interventions to distinct social and ecological circumstances. We consider two priority questions that can be addressed by integrating epidemiological, ecological, and genomic information: (1) how often do non-human host species contribute to human schistosome infection? and (2) what is the importance of locally acquired versus imported infections in driving transmission at different stages of elimination? These questions address processes that can undermine control programs, especially those that rely heavily on treatment with praziquantel. Until recently, these questions were difficult to answer with sufficient precision to inform public health decision-making. We review the literature related to these questions and discuss how whole-genome approaches can identify the geographic and taxonomic sources of infection, and how such information can inform context-specific efforts that advance schistosomiasis control efforts and minimize the risk of reemergence.
Topics: Animals; Genomics; Mass Drug Administration; Parasites; Schistosoma; Schistosomiasis
PubMed: 36040013
DOI: 10.7554/eLife.79320 -
Frontiers in Cellular and Infection... 2014Schistosomes, a class of parasitic trematode worms, cause schistosomiasis. Accumulating evidence suggests that microRNAs (miRNAs)-small, non-coding RNAs that are known... (Review)
Review
Schistosomes, a class of parasitic trematode worms, cause schistosomiasis. Accumulating evidence suggests that microRNAs (miRNAs)-small, non-coding RNAs that are known to play critical regulatory roles in many organisms-may be involved in schistosome development and sexual maturation, as well as the pathogenesis of schistosomiasis. Schistosoma miRNAs, such as Bantam and miR-10, may be involved in the pathological processes of schistosomiasis, and recent studies suggest that schistosome-specific miRNAs (e.g., Bantam, miR-3479-3p) in the bloodstream of a final host could be used as biomarkers for schistosomiasis diagnosis. Furthermore, aberrant miRNAs, such as miR-223 and miR-454, can be produced by a host in response to schistosome infection, and these miRNAs may contribute to the pathogenesis of schistosomiasis-associated liver injury. Here, we summarize recent progress evaluating the relationship between schistosome miRNAs and schistosomiasis and discuss how these miRNAs can mediate the pathogenesis of schistosomiasis and be used as biomarkers for schistosomiasis diagnosis.
Topics: Animals; Gene Expression Regulation; Host-Pathogen Interactions; Humans; MicroRNAs; RNA, Helminth; Schistosoma; Schistosomiasis
PubMed: 25426450
DOI: 10.3389/fcimb.2014.00165 -
Acta Tropica Apr 2022Schistosomiasis is a public health issue of concern in Gabon, with the disease being reported from all regions of the country. The topic has been of interest for the... (Review)
Review
INTRODUCTION
Schistosomiasis is a public health issue of concern in Gabon, with the disease being reported from all regions of the country. The topic has been of interest for the local researchers and physicians for over two decades. The objective of this narrative review was to provide an overview of the research activities in the area from 2000 to early 2021.
METHODS
We performed a narrative literature review. The search strategy was designed to get a broad overview of the different research topics on schistosomiasis and the national control programme, and included grey literature.
RESULTS
A total of 159 articles was screened, and 42 were included into the review in addition to the grey literature. During the past two decades, the work on schistosomiasis originated from five out of the nine provinces of the country, with diverse aspects of the disease investigated; including immunology, epidemiology, diagnosis and treatment. Several studies investigated various aspects of schistosomiasis-related morbidity in the respective study populations. The body of work demonstrates that much effort was made to understand the details of the host immune response to schistosomiasis, and the immune profile changes induced in patients treated with praziquantel. Although some MDA campaigns were conducted in the country; little, however, is known on the epidemiological situation of the disease, particularly of its distribution within the population, as well as co-infections with other parasitic diseases also endemic in the area.
CONCLUSION
Progress has been made over the past two decades in the understanding of schistosomiasis in the country, including disease-related morbidity and its interaction with other parasitic infections, and the immunology and epidemiology of the disease. However, for optimising control of the disease, there is a need to fine-tune these findings with detailed local epidemiological and malacological data. We call for such studies to accomplish the knowledge of schistosomiasis in the country, particularly in areas of moderate or high endemicity, and recommend this approach to comparable schistosomiasis-endemic areas elsewhere.
Topics: Coinfection; Gabon; Humans; Morbidity; Praziquantel; Schistosomiasis
PubMed: 35051384
DOI: 10.1016/j.actatropica.2022.106317 -
Human Vaccines Nov 2011Schistosomiasis is a major neglected tropical disease of public health importance to a billion people. An estimated 200 million people are currently infected; an... (Review)
Review
Schistosomiasis is a major neglected tropical disease of public health importance to a billion people. An estimated 200 million people are currently infected; an additional 779 million individuals are at risk to acquire the infection in 74 countries. Despite many years of implementation of mass anti-parasitic drug therapy programs and other control measures, this disease has not been contained and continues to spread to new geographic areas. The discovery of a protective vaccine still remains the most potentially effective means for the control of this disease, especially if the vaccine provides long-term immunity against the infection. A vaccine would contribute to the reduction of schistosomiasis morbidity through induced immune responses leading to decrease in parasite load and reduced egg production. This vaccine could be administered to children between the ages of 3 and 12 years to prevent severe infection in a particularly high risk population. This review summarizes the current status of schistosomiasis vaccine development.
Topics: Animals; Antigens, Helminth; Child; Child, Preschool; Humans; Neglected Diseases; Parasite Load; Schistosomiasis; Tropical Medicine; Vaccines
PubMed: 22048120
DOI: 10.4161/hv.7.11.17017 -
The American Journal of Tropical... Jul 2020The Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) was established in late 2008 to conduct operational research that would inform practices... (Review)
Review
The Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) was established in late 2008 to conduct operational research that would inform practices related to the control and elimination of schistosomiasis. This article traces SCORE's beginnings and underpinnings. These include an emphasis on openness and contributing to the development of a cohesive schistosomiasis control community, building linkages between researchers and national programs, and focusing on answering questions that will help Neglected Tropical Disease program managers to better control and eliminate schistosomiasis. It describes the development and implementation of SCORE's multiple projects. SCORE began by drawing on advice from a broad range of experts by holding wide-ranging meetings that informed the priorities and protocols for SCORE research. SCORE's major efforts included large, multicountry field studies comparing multiple strategies for mass drug administration with praziquantel, assessment of approaches to elimination, evaluation of a point-of-care assay for field mapping , and increasing the sensitivity of a laboratory-based diagnostic. SCORE also supported studies on morbidity due to schistosomiasis, quantification of vector snails and the detection of schistosome infections in snails, and changes in schistosome population genetics under praziquantel drug pressure. SCORE data and specimens are archived and will remain available for future research. Although much remains to be carried out, our hope is that through the already published articles and SCORE results described in this supplement, we will have provided a body of evidence to assist policy makers in the development of judicious guidelines for the control and elimination of schistosomiasis.
Topics: Animals; Disease Reservoirs; Disease Vectors; History, 21st Century; Humans; Mass Drug Administration; Morbidity; Neglected Diseases; Parasitology; Praziquantel; Prevalence; Schistosoma haematobium; Schistosoma mansoni; Schistosomiasis; Schistosomiasis mansoni; Snails
PubMed: 32400343
DOI: 10.4269/ajtmh.19-0785