Special Issue "Prospects for Schistosomiasis Elimination"

A special issue of Tropical Medicine and Infectious Disease (ISSN 2414-6366).

Deadline for manuscript submissions: closed (30 November 2018)

Special Issue Editors

Guest Editor
Prof. Robert Bergquist

WHO/TDR (retired); affiliated to Swiss TPH, Basel, Switzerland
Website | E-Mail
Interests: epidemiology; medical parasitology; neglected tropical diseases (NTDs) with special reference to schistosomiasis, diagnostics, chemotherapy, vaccinology, remote sensing and other geospatial techniques
Guest Editor
Prof. Dr. Darren Gray

Department of Global Health, Research School of Population Health, ANU College of Health and Medicine, 62 Mills Rd, The Australian National University, Australia
Website | E-Mail
Phone: +61 2 6125 8595
Interests: global health; tropical health; international health; infectious disease epidemiology; Schistosomiasis; soil-transmitted helminths; clinical trials; medical parasitology

Special Issue Information

Dear Colleagues,

This Special Issue focuses on current efforts to limit the ravages of schistosomiasis with a view to eliminate this helminth, parasitic infection as a public health issue on a world-wide scale. Excellent progress has moved China and several countries in North Africa and the Middle East close to the elimination of schistosomiasis and this provides hope that the reign of the 'God of Plague' is near. The disease has, however, still a strong  presence in sub-Saharan Africa with endemic areas stretching from Latin America to Southeast Asia putting more than 800 million people at risk, while the number of those actually infected remains as high as somewhere between 200 and 250 million people, the majority living in low- and middle income countries. Schistosomiasis is one of the neglected tropical diseases (NTDs) targeted by the World Health Organization for increased control and eventual elimination in the next 10–20 years. Morbidity control has in principle been achieved thanks to large-scale, repeated chemotherapy with praziquantel, but there are still areas with many cases of advanced disease. The next steps involve interruption of transmission through effective control of the intermediate snail host and preventive measures and, for areas endemic for Schistosoma japonicum and S. mekongi, also control of the infection in domestic animals. However, due to the chronic nature of schistosomiasis lasting sequelae (post-transmission schistosomiasis) needing lifelong management, the impact of schistosomiasis may well continue to be felt for a long time after transmission has been curbed. Control methods used include chemotherapy, snail control through mollusciciding and environmental management, health education and water, sanitation and hygiene (WASH) interventions. The current arsenal includes an excellent drug and highly sensitive and specific diagnostic techniques but there is still need for new complementary drugs and vaccine development.

Prof. Robert Bergquist
Assoc. Prof. Darren Gray
Guest Editors

Manuscript Submission Information

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Keywords

  • Schistosomiasis
  • Neglected tropical diseases
  • North Africa
  • Sub-Saharan Africa
  • South East Asia
  • Latin America
  • Middle East
  • Elimination
  • Eradication
  • Control
  • Integrated intervention
  • Mathematical modelling
  • Diagnostics
  • Praziquantel
  • Chemotherapy
  • Snail control
  • Transmission
  • Vaccine development
  • Zoonoses
  • One Health

Published Papers (23 papers)

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Editorial

Jump to: Research, Review, Other

Open AccessEditorial
Schistosomiasis Elimination: Beginning of the End or a Continued March on a Trodden Path
Trop. Med. Infect. Dis. 2019, 4(2), 76; https://doi.org/10.3390/tropicalmed4020076
Received: 12 April 2019 / Accepted: 15 April 2019 / Published: 5 May 2019
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Abstract
In spite of spectacular progress towards the goal of elimination of schistosomiasis, particularly in China but also in other areas, research gaps and outstanding issues remain. Although expectations of achieving elimination of this disease have never been greater, all constraints have not been [...] Read more.
In spite of spectacular progress towards the goal of elimination of schistosomiasis, particularly in China but also in other areas, research gaps and outstanding issues remain. Although expectations of achieving elimination of this disease have never been greater, all constraints have not been swept aside. Indeed, there are some formidable obstacles, such as insufficient amounts of drugs to treat everybody and still limited use of high-sensitive diagnostic techniques, both for the definitive and the intermediate hosts, which indicate that prevalence is considerably underrated in well-controlled areas. Elimination will be difficult to achieve without a broad approach, including a stronger focus on transmission, better diagnostics and the establishment of a reliable survey system activating a rapid response when called for. Importantly, awareness of the crucial importance of transmission has been revived resulting in renewed interest in snail control together with more emphasis on health education and sanitation. The papers collected in this special issue entitled ‘Prospects for Schistosomiasis Elimination’ reflect these issues and we are particularly pleased to note that some also discuss the crucial question when to declare a country free of schistosomiasis and present techniques that together create an approach that can show unequivocally when interruption of transmission has been achieved. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
Open AccessEditorial
“Farewell to the God of Plague”: The Importance of Political Commitment Towards the Elimination of Schistosomiasis
Trop. Med. Infect. Dis. 2018, 3(4), 108; https://doi.org/10.3390/tropicalmed3040108
Received: 25 September 2018 / Accepted: 27 September 2018 / Published: 3 October 2018
Cited by 3 | PDF Full-text (629 KB) | HTML Full-text | XML Full-text
Abstract
Schistosomiasis control in China has always been conducted with strong political leadership and support at the highest level of government [1] [...] Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
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Research

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Open AccessArticle
Phylogeography of Bulinus truncatus (Audouin, 1827) (Gastropoda: Planorbidae) in Selected African Countries
Trop. Med. Infect. Dis. 2018, 3(4), 127; https://doi.org/10.3390/tropicalmed3040127
Received: 27 September 2018 / Revised: 8 December 2018 / Accepted: 13 December 2018 / Published: 19 December 2018
Cited by 1 | PDF Full-text (2258 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The transmission of some schistosome parasites is dependent on the planorbid snail hosts. Bulinus truncatus is important in urinary schistosomiasis epidemiology in Africa. Hence, there is a need to define the snails’ phylogeography. This study assessed the population genetic structure of B. truncatus [...] Read more.
The transmission of some schistosome parasites is dependent on the planorbid snail hosts. Bulinus truncatus is important in urinary schistosomiasis epidemiology in Africa. Hence, there is a need to define the snails’ phylogeography. This study assessed the population genetic structure of B. truncatus from Giza and Sharkia (Egypt), Barakat (Sudan) and Madziwa, Shamva District (Zimbabwe) using mitochondrial cytochrome oxidase subunit 1 gene (COI) and internal transcribed spacer 1 (ITS 1) markers. COI was sequenced from 94 B. truncatus samples including 38 (Egypt), 36 (Sudan) and 20 (Zimbabwe). However, only 51 ITS 1 sequences were identified from Egypt (28) and Sudan (23) (because of failure in either amplification or sequencing). The unique COI haplotypes of B. truncatus sequences observed were 6, 11, and 6 for Egypt, Sudan, and Zimbabwe, respectively. Also, 3 and 2 unique ITS 1 haplotypes were observed in sequences from Egypt and Sudan respectively. Mitochondrial DNA sequences from Sudan and Zimbabwe indicated high haplotype diversity with 0.768 and 0.784, respectively, while relatively low haplotype diversity was also observed for sequences from Egypt (0.334). The location of populations from Egypt and Sudan on the B. truncatus clade agrees with the location of both countries geographically. The clustering of the Zimbabwe sequences on different locations on the clade can be attributed to individuals with different genotypes within the population. No significant variation was observed within B. truncatus populations from Egypt and Sudan as indicated by the ITS 1 tree. This study investigated the genetic diversity of B. truncatus from Giza and Sharkia (Egypt), Barakat area (Sudan), and Madziwa (Zimbabwe), which is necessary for snail host surveillance in the study areas and also provided genomic data of this important snail species from the sampled countries. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
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Open AccessArticle
Field Evaluation of a Loop-Mediated Isothermal Amplification (LAMP) Platform for the Detection of Schistosoma japonicum Infection in Oncomelania hupensis Snails
Trop. Med. Infect. Dis. 2018, 3(4), 124; https://doi.org/10.3390/tropicalmed3040124
Received: 20 October 2018 / Revised: 10 December 2018 / Accepted: 11 December 2018 / Published: 15 December 2018
Cited by 4 | PDF Full-text (1503 KB) | HTML Full-text | XML Full-text
Abstract
Schistosoma infection in snails can be monitored by microscopy or indirectly by sentinel mice. As both these approaches can miss infections, more sensitive tests are needed, particularly in low-level transmission settings. In this study, loop-mediated isothermal amplification (LAMP) technique, designed to detect a [...] Read more.
Schistosoma infection in snails can be monitored by microscopy or indirectly by sentinel mice. As both these approaches can miss infections, more sensitive tests are needed, particularly in low-level transmission settings. In this study, loop-mediated isothermal amplification (LAMP) technique, designed to detect a specific 28S ribosomal Schistosoma japonicum (Sj28S) gene with high sensitivity, was compared to microscopy using snail samples from 51 areas endemic for schistosomiasis in five Chinese provinces. In addition, the results were compared with those from polymerase chain reaction (PCR) by adding DNA sequencing as a reference. The testing of pooled snail samples with the LAMP assay showed that a dilution factor of 1/50, i.e., one infected snail plus 49 non-infected ones, would still result in a positive reaction after the recommended number of amplification cycles. Testing a total of 232 pooled samples, emanating from 4006 snail specimens, showed a rate of infection of 6.5%, while traditional microscopy found only 0.4% positive samples in the same materials. Parallel PCR analysis confirmed the diagnostic accuracy of the LAMP assay, with DNA sequencing even giving LAMP a slight lead. Microscopy and the LAMP test were carried out at local schistosomiasis-control stations, demonstrating that the potential of the latter assay to serve as a point-of-care (POC) test with results available within 60–90 min, while the more complicated PCR test had to be carried out at the National Institute of Parasitic Diseases (NIPD) in Shanghai, China. In conclusion, LAMP was found to be clearly superior to microscopy and as good as, or better than, PCR. As it can be used under field conditions and requires less time than other techniques, LAMP testing would improve and accelerate schistosomiasis control. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
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Open AccessArticle
Baseline Mapping of Schistosomiasis and Soil Transmitted Helminthiasis in the Northern and Eastern Health Regions of Gabon, Central Africa: Recommendations for Preventive Chemotherapy
Trop. Med. Infect. Dis. 2018, 3(4), 119; https://doi.org/10.3390/tropicalmed3040119
Received: 24 August 2018 / Revised: 6 November 2018 / Accepted: 7 November 2018 / Published: 11 November 2018
Cited by 1 | PDF Full-text (7172 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In order to follow the Preventive Chemotherapy (PC) for the transmission control as recommended by WHO, Gabon initiated in 2014 the mapping of Schistosomiasis and Soil Transmitted Helminthiasis (STH). Here, we report the results of the Northern and Eastern health regions, representing a [...] Read more.
In order to follow the Preventive Chemotherapy (PC) for the transmission control as recommended by WHO, Gabon initiated in 2014 the mapping of Schistosomiasis and Soil Transmitted Helminthiasis (STH). Here, we report the results of the Northern and Eastern health regions, representing a third of the land area and 12% of its total population. All nine departments of the two regions were surveyed and from each, five schools were examined with 50 schoolchildren per school. The parasitological examinations were realized using the filtration method for urine and the Kato-Katz technique for stool samples. Overall 2245 schoolchildren (1116 girls and 1129 boys), mean aged 11.28 ± 0.04 years, were examined. Combined schistosomiasis and STH affected 1270 (56.6%) with variation between regions, departments, and schools. For schistosomiasis, prevalence were 1.7% across the two regions, with no significant difference (p > 0.05) between the Northern (1.5%) and the Eastern (1.9%). Schistosomiasis is mainly caused by Schistosoma haematobium with the exception of one respective case of S. mansoni and S. guineensis. STH are more common than schistosomiasis, with an overall prevalence of 56.1% significantly different between the Northern (58.1%) and Eastern (53.6%) regions (p = 0.034). Trichuris trichiura is the most abundant infection with a prevalence of 43.7% followed by Ascaris lumbricoides 35.6% and hookworms 1.4%. According to these results, an appropriate PC strategy is given. In particular, because of the low efficacy of a single recommended drug on T. trichiura and hookworms, it is important to include two drugs for the treatment of STH in Gabon, due to the high prevalence and intensities of Trichuris infections. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
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Open AccessArticle
Potential Impact of Climate Change on Schistosomiasis: A Global Assessment Attempt
Trop. Med. Infect. Dis. 2018, 3(4), 117; https://doi.org/10.3390/tropicalmed3040117
Received: 18 October 2018 / Revised: 26 October 2018 / Accepted: 27 October 2018 / Published: 3 November 2018
Cited by 3 | PDF Full-text (1834 KB) | HTML Full-text | XML Full-text
Abstract
Based on an ensemble of global circulation models (GCMs), four representative concentration pathways (RCPs) and several ongoing and planned Coupled Model Intercomparison Projects (CMIPs), the Intergovernmental Panel on Climate Change (IPCC) predicts that global, average temperatures will increase by at least 1.5 °C [...] Read more.
Based on an ensemble of global circulation models (GCMs), four representative concentration pathways (RCPs) and several ongoing and planned Coupled Model Intercomparison Projects (CMIPs), the Intergovernmental Panel on Climate Change (IPCC) predicts that global, average temperatures will increase by at least 1.5 °C in the near future and more by the end of the century if greenhouse gases (GHGs) emissions are not genuinely tempered. While the RCPs are indicative of various amounts of GHGs in the atmosphere the CMIPs are designed to improve the workings of the GCMs. We chose RCP4.5 which represented a medium GHG emission increase and CMIP5, the most recently completed CMIP phase. Combining this meteorological model with a biological counterpart model accounted for replication and survival of the snail intermediate host as well as maturation of the parasite stage inside the snail at different ambient temperatures. The potential geographical distribution of the three main schistosome species: Schistosoma japonicum, S. mansoni and S. haematobium was investigated with reference to their different transmission capabilities at the monthly mean temperature, the maximum temperature of the warmest month(s) and the minimum temperature of the coldest month(s). The set of six maps representing the predicted situations in 2021–2050 and 2071–2100 for each species mainly showed increased transmission areas for all three species but they also left room for potential shrinkages in certain areas. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
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Open AccessArticle
Low Praziquantel Treatment Coverage for Schistosoma mansoni in Mayuge District, Uganda, Due to the Absence of Treatment Opportunities, Rather Than Systematic Non-Compliance
Trop. Med. Infect. Dis. 2018, 3(4), 111; https://doi.org/10.3390/tropicalmed3040111
Received: 5 September 2018 / Revised: 25 September 2018 / Accepted: 26 September 2018 / Published: 8 October 2018
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Abstract
The World Health Organization (WHO) recommends praziquantel mass drug administration (MDA) to control schistosomiasis in endemic regions. We aimed to quantify recent and lifetime praziquantel coverage, and reasons for non-treatment, at an individual level to guide policy recommendations to help Uganda reach WHO [...] Read more.
The World Health Organization (WHO) recommends praziquantel mass drug administration (MDA) to control schistosomiasis in endemic regions. We aimed to quantify recent and lifetime praziquantel coverage, and reasons for non-treatment, at an individual level to guide policy recommendations to help Uganda reach WHO goals. Cross-sectional household surveys (n = 681) encompassing 3208 individuals (adults and children) were conducted in 2017 in Bugoto A and B, Mayuge District, Uganda. Participants were asked if they had received praziquantel during the recent MDA (October 2016) and whether they had ever received praziquantel in their lifetime. A multivariate logistic regression analysis with socio-economic and individual characteristics as covariates was used to determine factors associated with praziquantel uptake. In the MDA eligible population (≥5 years of age), the most recent MDA coverage was 48.8%. Across individuals’ lifetimes, 31.8% of eligible and 49.5% of the entire population reported having never taken praziquantel. Factors that improved individuals’ odds of taking praziquantel included school enrolment, residence in Bugoto B and increasing years of village-residency. Not being offered (49.2%) and being away during treatment (21.4%) were the most frequent reasons for not taking the 2016 praziquantel MDA. Contrary to expectations, chronically-untreated individuals were rarely systematic non-compliers, but more commonly not offered treatment. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
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Open AccessArticle
Young Adults in Endemic Areas: An Untreated Group in Need of School-Based Preventive Chemotherapy for Schistosomiasis Control and Elimination
Trop. Med. Infect. Dis. 2018, 3(3), 100; https://doi.org/10.3390/tropicalmed3030100
Received: 24 July 2018 / Revised: 16 August 2018 / Accepted: 31 August 2018 / Published: 5 September 2018
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Abstract
Parasitologic surveys of young adults in college and university settings are not commonly done, even in areas known to be endemic for schistosomiasis and soil-transmitted helminths. We have done a survey of 291 students and staff at the Kisumu National Polytechnic in Kisumu, [...] Read more.
Parasitologic surveys of young adults in college and university settings are not commonly done, even in areas known to be endemic for schistosomiasis and soil-transmitted helminths. We have done a survey of 291 students and staff at the Kisumu National Polytechnic in Kisumu, Kenya, using the stool microscopy Kato-Katz (KK) method and the urine point-of-care circulating cathodic antigen (POC-CCA) test. Based on three stools/two KK slides each, in the 208 participants for whom three consecutive stools were obtained, Schistosoma mansoni prevalence was 17.8%. When all 291 individuals were analyzed based on the first stool, as done by the national neglected tropical disease (NTD) program, and one urine POC-CCA assay (n = 276), the prevalence was 13.7% by KK and 23.2% by POC-CCA. Based on three stools, 2.5% of 208 participants had heavy S. mansoni infections (≥400 eggs/gram feces), with heavy S. mansoni infections making up 13.5% of the S. mansoni cases. The prevalence of the soil-transmitted helminths (STH: Ascaris lumbricoides, Trichuris trichiura and hookworm) by three stools was 1.4%, 3.1%, and 4.1%, respectively, and by the first stool was 1.4%, 2.4% and 1.4%, respectively. This prevalence and intensity of infection with S. mansoni in a college setting warrants mass drug administration with praziquantel. This population of young adults is ‘in school’ and is both approachable and worthy of inclusion in national schistosomiasis control and elimination programs. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
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Open AccessArticle
A Rapid Appraisal of Factors Influencing Praziquantel Treatment Compliance in Two Communities Endemic for Schistosomiasis in Côte d’Ivoire
Trop. Med. Infect. Dis. 2018, 3(2), 69; https://doi.org/10.3390/tropicalmed3020069
Received: 13 April 2018 / Revised: 9 May 2018 / Accepted: 14 June 2018 / Published: 19 June 2018
Cited by 3 | PDF Full-text (589 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Over the past decade, a significant reduction in the prevalence of schistosomiasis has been achieved, partially explained by the large-scale administration of praziquantel. Yet, the burden of schistosomiasis remains considerable, and factors influencing intervention coverage are important. This study aimed to deepen the [...] Read more.
Over the past decade, a significant reduction in the prevalence of schistosomiasis has been achieved, partially explained by the large-scale administration of praziquantel. Yet, the burden of schistosomiasis remains considerable, and factors influencing intervention coverage are important. This study aimed to deepen the understanding of low treatment coverage rates observed in two schistosomiasis-endemic villages in Côte d’Ivoire. The research was conducted in August 2015, in Moronou and Bigouin, two villages of Côte d’Ivoire that are endemic for Schistosoma haematobium and S. mansoni, respectively. After completion of a clinical trial, standard praziquantel treatment (single 40 mg/kg oral dose) was offered to all village inhabitants by community health workers using a house-to-house approach. Factors influencing treatment coverage were determined by a questionnaire survey, randomly selecting 405 individuals. The overall treatment coverage rate was only 47.6% (2730/5733) with considerable intervillage heterogeneity (27.7% in Bigouin (302/1091) versus 52.3% in Moronou (2428/4642)). Among the 200 individuals interviewed in Moronou, 50.0% were administered praziquantel, while only 19.5% of the 205 individuals interviewed in Bigouin received praziquantel. The main reasons for low treatment coverage were work-related (agricultural activities), the bitter taste of praziquantel and previous experiences with adverse events. The most suitable period for treatment campaigns was reported to be the dry season. More than three-quarter of the interviewees who had taken praziquantel (overall, 116/140; Moronou, 84/100; Bigouin, 32/40) declared that they would not participate in future treatments (p < 0.001). In order to enhance praziquantel treatment coverage, careful consideration should be given to attitudes and practices, such as prior or perceived adverse events and taste of praziquantel, and appropriate timing, harmonized with agricultural activities. Without such understanding, breaking the transmission of schistosomiasis remains a distant goal. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
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Review

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Open AccessReview
Asian Schistosomiasis: Current Status and Prospects for Control Leading to Elimination
Trop. Med. Infect. Dis. 2019, 4(1), 40; https://doi.org/10.3390/tropicalmed4010040
Received: 14 January 2019 / Revised: 12 February 2019 / Accepted: 12 February 2019 / Published: 26 February 2019
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Abstract
Schistosomiasis is an infectious disease caused by helminth parasites of the genus Schistosoma. Worldwide, an estimated 250 million people are infected with these parasites with the majority of cases occurring in sub-Saharan Africa. Within Asia, three species of Schistosoma cause disease. Schistosoma japonicum [...] Read more.
Schistosomiasis is an infectious disease caused by helminth parasites of the genus Schistosoma. Worldwide, an estimated 250 million people are infected with these parasites with the majority of cases occurring in sub-Saharan Africa. Within Asia, three species of Schistosoma cause disease. Schistosoma japonicum is the most prevalent, followed by S. mekongi and S. malayensis. All three species are zoonotic, which causes concern for their control, as successful elimination not only requires management of the human definitive host, but also the animal reservoir hosts. With regard to Asian schistosomiasis, most of the published research has focused on S. japonicum with comparatively little attention paid to S. mekongi and even less focus on S. malayensis. In this review, we examine the three Asian schistosomes and their current status in their endemic countries: Cambodia, Lao People’s Democratic Republic, Myanmar, and Thailand (S. mekongi); Malaysia (S. malayensis); and Indonesia, People’s Republic of China, and the Philippines (S. japonicum). Prospects for control that could potentially lead to elimination are highlighted as these can inform researchers and disease control managers in other schistosomiasis-endemic areas, particularly in Africa and the Americas. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
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Open AccessReview
Elimination of Schistosomiasis Mekongi from Endemic Areas in Cambodia and the Lao People’s Democratic Republic: Current Status and Plans
Trop. Med. Infect. Dis. 2019, 4(1), 30; https://doi.org/10.3390/tropicalmed4010030
Received: 23 December 2018 / Revised: 21 January 2019 / Accepted: 30 January 2019 / Published: 7 February 2019
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Abstract
The areas endemic for schistosomiasis in the Lao People’s Democratic Republic and in Cambodia were first reported 50 and 60 years ago, respectively. However, the causative parasite Schistosoma mekongi was not recognized as a separate species until 1978. The infection is distributed along [...] Read more.
The areas endemic for schistosomiasis in the Lao People’s Democratic Republic and in Cambodia were first reported 50 and 60 years ago, respectively. However, the causative parasite Schistosoma mekongi was not recognized as a separate species until 1978. The infection is distributed along a limited part of the Mekong River, regulated by the focal distribution of the intermediate snail host Neotricula aperta. Although more sensitive diagnostics imply a higher figure, the current use of stool examinations suggests that only about 1500 people are presently infected. This well-characterized setting should offer an exemplary potential for the elimination of the disease from its endemic areas; yet, the local topography, reservoir animals, and a dearth of safe water sources make transmission control a challenge. Control activities based on mass drug administration resulted in strong advances, and prevalence was reduced to less than 5% according to stool microscopy. Even so, transmission continues unabated, and the true number of infected people could be as much as 10 times higher than reported. On-going control activities are discussed together with plans for the future. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
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Open AccessReview
Status of Schistosomiasis Elimination in the Caribbean Region
Trop. Med. Infect. Dis. 2019, 4(1), 24; https://doi.org/10.3390/tropicalmed4010024
Received: 21 December 2018 / Revised: 23 January 2019 / Accepted: 26 January 2019 / Published: 31 January 2019
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Abstract
Schistosomiasis elimination status in the Caribbean is reviewed with information on historical disease background, attempts to control it and current situation for each locality in the region where transmission has been eliminated (Sint Maarten, Saint Kitts, Vieques), eliminated but not yet verified (Puerto [...] Read more.
Schistosomiasis elimination status in the Caribbean is reviewed with information on historical disease background, attempts to control it and current situation for each locality in the region where transmission has been eliminated (Sint Maarten, Saint Kitts, Vieques), eliminated but not yet verified (Puerto Rico, Dominican Republic, Antigua, Montserrat, Guadeloupe, Martinique) and still ongoing (Saint Lucia, Suriname). Integrated control initiatives based on selective and mass treatment and snail control using environmental, chemical and biological methods along with public service improvements (housing, safe water, sanitation) and changes in demography (urbanization) and economy (change from sugarcane and banana production to tourism) have resulted in reduction in the burden of schistosomiasis over the past century. Introduction of Biomphalaria-competitor snails into the region as a cost-effective, low maintenance control method appears to have had the most sustainable impact on transmission reduction. A regional inventory of B. glabrata, other Biomphalaria species and Biomphalaria-competitor snails as well as investigation of possible animal reservoir hosts in persisting endemic areas would be helpful for control. Elimination of schistosomiasis appears achievable in the Caribbean. However, a regional surveillance and monitoring program is needed to verify elimination in the various localities and identify and monitor areas still endemic or at risk. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
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Open AccessReview
Use of Geospatial Surveillance and Response Systems for Vector-Borne Diseases in the Elimination Phase
Trop. Med. Infect. Dis. 2019, 4(1), 15; https://doi.org/10.3390/tropicalmed4010015
Received: 28 December 2018 / Revised: 14 January 2019 / Accepted: 15 January 2019 / Published: 18 January 2019
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Abstract
The distribution of diseases caused by vector-borne viruses and parasites are restricted by the environmental requirements of their vectors, but also by the ambient temperature inside the host as it influences the speed of maturation of the infectious agent transferred. The launch of [...] Read more.
The distribution of diseases caused by vector-borne viruses and parasites are restricted by the environmental requirements of their vectors, but also by the ambient temperature inside the host as it influences the speed of maturation of the infectious agent transferred. The launch of the Soil Moisture Active Passive (SMAP) satellite in 2015, and the new ECOSTRESS instrument onboard the International Space Station (ISS) in 2018, established the leadership of the National Aeronautics Space Administration (NASA) in ecology and climate research by allowing the structural and functional classification of ecosystems that govern vector sustainability. These advances, and the availability of sub-meter resolution data from commercial satellites, contribute to seamless mapping and modelling of diseases, not only at continental scales (1 km2) and local community or agricultural field scales (15–30 m2), but for the first time, also at the habitat–household scale (<1 m2). This communication presents current capabilities that are related to data collection by Earth-observing satellites, and draws attention to the usefulness of geographical information systems (GIS) and modelling for the study of important parasitic diseases. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
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Open AccessReview
Artemether and Praziquantel: Origin, Mode of Action, Impact, and Suggested Application for Effective Control of Human Schistosomiasis
Trop. Med. Infect. Dis. 2018, 3(4), 125; https://doi.org/10.3390/tropicalmed3040125
Received: 19 November 2018 / Revised: 5 December 2018 / Accepted: 11 December 2018 / Published: 19 December 2018
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Abstract
The stumbling block for the continued, single-drug use of praziquantel (PZQ) against schistosomiasis is less justified by the risk of drug resistance than by the fact that this drug is inactive against juvenile parasites, which will mature and start egg production after chemotherapy. [...] Read more.
The stumbling block for the continued, single-drug use of praziquantel (PZQ) against schistosomiasis is less justified by the risk of drug resistance than by the fact that this drug is inactive against juvenile parasites, which will mature and start egg production after chemotherapy. Artemisinin derivatives, currently used against malaria in the form of artemisinin-based combination therapy (ACT), provide an opportunity as these drugs are not only active against malaria plasmodia, but surprisingly also against juvenile schistosomes. An artemisinin/PZQ combination would be complementary, and potentially additive, as it would kill two schistosome life cycle stages and thus confer a transmission-blocking modality to current chemotherapy. We focus here on single versus combined regimens in endemic settings. Although the risk of artemisinin resistance, already emerging with respect to malaria therapy in Southeast Asia, prevents use in countries where ACT is needed for malaria care, an artemisinin-enforced praziquantel treatment (APT) should be acceptable in regions of North Africa (including Egypt), the Middle East, China, and Brazil that are not endemic for malaria. Thanks to recent progress with respect to high-resolution diagnostics, based on circulating schistosome antigens in humans and molecular approaches for snail surveys, it should be possible to keep areas scheduled for schistosomiasis elimination under surveillance, bringing rapid response to bear on problems arising. The next steps would be to investigate where and for how long APT should be applied to make a lasting impact. A large-scale field trial in an area with modest transmission should tell how apt this approach is. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
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Open AccessReview
Current Status of the Sm14/GLA-SE Schistosomiasis Vaccine: Overcoming Barriers and Paradigms towards the First Anti-Parasitic Human(itarian) Vaccine
Trop. Med. Infect. Dis. 2018, 3(4), 121; https://doi.org/10.3390/tropicalmed3040121
Received: 15 October 2018 / Revised: 12 November 2018 / Accepted: 12 November 2018 / Published: 21 November 2018
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Abstract
Schistosomiasis, a disease historically associated with poverty, lack of sanitation and social inequality, is a chronic, debilitating parasitic infection, affecting hundreds of millions of people in endemic countries. Although chemotherapy is capable of reducing morbidity in humans, rapid re-infection demonstrates that the impact [...] Read more.
Schistosomiasis, a disease historically associated with poverty, lack of sanitation and social inequality, is a chronic, debilitating parasitic infection, affecting hundreds of millions of people in endemic countries. Although chemotherapy is capable of reducing morbidity in humans, rapid re-infection demonstrates that the impact of drug treatment on transmission control or disease elimination is marginal. In addition, despite more than two decades of well-executed control activities based on large-scale chemotherapy, the disease is expanding in many areas including Brazil. The development of the Sm14/GLA-SE schistosomiasis vaccine is an emblematic, open knowledge innovation that has successfully completed phase I and phase IIa clinical trials, with Phase II/III trials underway in the African continent, to be followed by further trials in Brazil. The discovery and experimental phases of the development of this vaccine gathered a robust collection of data that strongly supports the ongoing clinical phase. This paper reviews the development of the Sm14 vaccine, formulated with glucopyranosyl lipid A (GLA-SE), from the initial experimental developments to clinical trials including the current status of phase II studies. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
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Open AccessReview
Treading the Path towards Genetic Control of Snail Resistance to Schistosome Infection
Trop. Med. Infect. Dis. 2018, 3(3), 86; https://doi.org/10.3390/tropicalmed3030086
Received: 18 July 2018 / Revised: 8 August 2018 / Accepted: 13 August 2018 / Published: 15 August 2018
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Abstract
Schistosomiasis remains the most important tropical snail-borne trematodiasis that threatens many millions of human lives. In achieving schistosomiasis elimination targets, sustainable control of the snail vectors represents a logical approach. Nonetheless, the ineffectiveness of the present snail control interventions emphasizes the need to [...] Read more.
Schistosomiasis remains the most important tropical snail-borne trematodiasis that threatens many millions of human lives. In achieving schistosomiasis elimination targets, sustainable control of the snail vectors represents a logical approach. Nonetheless, the ineffectiveness of the present snail control interventions emphasizes the need to develop new complementary strategies to ensure more effective control outcomes. Accordingly, the use of genetic techniques aimed at driving resistance traits into natural vector populations has been put forward as a promising tool for integrated snail control. Leveraging the Biomphalaria-Schistosoma model system, studies unraveling the complexities of the vector biology and those exploring the molecular basis of snail resistance to schistosome infection have been expanding in various breadths, generating many significant discoveries, and raising the hope for future breakthroughs. This review provides a compendium of relevant findings, and without neglecting the current existing gaps and potential future challenges, discusses how a transgenic snail approach may be adapted and harnessed to control human schistosomiasis. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
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Open AccessReview
When Should the Emphasis on Schistosomiasis Control Move to Elimination?
Trop. Med. Infect. Dis. 2018, 3(3), 85; https://doi.org/10.3390/tropicalmed3030085
Received: 29 June 2018 / Revised: 4 August 2018 / Accepted: 10 August 2018 / Published: 15 August 2018
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Abstract
The stated goal of the World Health Organization’s program on schistosomiasis is paraphrased as follows: to control morbidity and eliminate transmission where feasible. Switching from a goal of controlling morbidity to interrupting transmission may well be currently feasible in some countries in the [...] Read more.
The stated goal of the World Health Organization’s program on schistosomiasis is paraphrased as follows: to control morbidity and eliminate transmission where feasible. Switching from a goal of controlling morbidity to interrupting transmission may well be currently feasible in some countries in the Caribbean, some areas in South America, northern Africa, and selected endemic areas in sub-Saharan Africa where there have been improvements in sanitation and access to clean water. However, in most of sub-Saharan Africa, where programmatic interventions still consist solely of annual mass drug administration, such a switch in strategies remains premature. There is a continued need for operational research on how best to reduce transmission to a point where interruption of transmission may be achievable. The level of infection at which it is feasible to transition from control to elimination must also be defined. In parallel, there is also a need to develop and evaluate approaches for achieving and validating elimination. There are currently neither evidence-based methods nor tools for breaking transmission or verifying that it has been accomplished. The basis for these statements stems from numerous studies that will be reviewed and summarized in this article; many, but not all of which were undertaken as part of SCORE, the Schistosomiasis Consortium for Operational Research and Evaluation. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
Open AccessReview
DNA Diagnostics for Schistosomiasis Control
Trop. Med. Infect. Dis. 2018, 3(3), 81; https://doi.org/10.3390/tropicalmed3030081
Received: 24 June 2018 / Revised: 25 July 2018 / Accepted: 30 July 2018 / Published: 1 August 2018
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Abstract
Despite extensive efforts over the last few decades, the global disease burden of schistosomiasis still remains unacceptably high. This could partly be attributed to the lack of accurate diagnostic tools for detecting human and animal schistosome infections in endemic areas. In low transmission [...] Read more.
Despite extensive efforts over the last few decades, the global disease burden of schistosomiasis still remains unacceptably high. This could partly be attributed to the lack of accurate diagnostic tools for detecting human and animal schistosome infections in endemic areas. In low transmission and low prevalence areas where schistosomiasis elimination is targeted, case detection requires a test that is highly sensitive. Diagnostic tests with low sensitivity will miss individuals with low infection intensity and these will continue to contribute to transmission, thereby interfering with the efficacy of the control measures operating. Of the many diagnostic approaches undertaken to date, the detection of schistosome DNA using DNA amplification techniques including polymerase chain reaction (PCR) provide valuable adjuncts to more conventional microscopic and serological methods, due their accuracy, high sensitivity, and the capacity to detect early pre-patent infections. Furthermore, DNA-based methods represent important screening tools, particularly in those endemic areas with ongoing control where infection prevalence and intensity have been reduced to very low levels. Here we review the role of DNA diagnostics in the path towards the control and elimination of schistosomiasis. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
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Open AccessReview
Schistosome Vaccines for Domestic Animals
Trop. Med. Infect. Dis. 2018, 3(2), 68; https://doi.org/10.3390/tropicalmed3020068
Received: 18 May 2018 / Revised: 5 June 2018 / Accepted: 14 June 2018 / Published: 19 June 2018
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Abstract
Schistosomiasis is recognized as a tropical disease of considerable public health importance, but domestic livestock infections due to Schistosoma japonicum, S. bovis, S. mattheei and S. curassoni are often overlooked causes of significant animal morbidity and mortality in Asia and Africa. [...] Read more.
Schistosomiasis is recognized as a tropical disease of considerable public health importance, but domestic livestock infections due to Schistosoma japonicum, S. bovis, S. mattheei and S. curassoni are often overlooked causes of significant animal morbidity and mortality in Asia and Africa. In addition, whereas schistosomiasis japonica is recognized as an important zoonosis in China and the Philippines, reports of viable schistosome hybrids between animal livestock species and S. haematobium point to an underappreciated zoonotic component of transmission in Africa as well. Anti-schistosome vaccines for animal use have long been advocated as part of the solution to schistosomiasis control, benefitting humans and animals and improving the local economy, features aligning with the One Health concept synergizing human and animal health. We review the history of animal vaccines for schistosomiasis from the early days of irradiated larvae and then consider the recombinant DNA technology revolution and its impact in developing schistosome vaccines that followed. We evaluate the major candidates tested in livestock, including the glutathione S-transferases, paramyosin and triose-phosphate isomerase, and summarize some of the future challenges that need to be overcome to design and deliver effective anti-schistosome vaccines that will complement current control options to achieve and sustain future elimination goals. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)

Other

Open AccessOpinion
Schistosomiasis in the Philippines: Innovative Control Approach is Needed if Elimination is the Goal
Trop. Med. Infect. Dis. 2019, 4(2), 66; https://doi.org/10.3390/tropicalmed4020066
Received: 8 January 2019 / Revised: 20 March 2019 / Accepted: 4 April 2019 / Published: 13 April 2019
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Abstract
In 1996, schistosomiasis due to Schistosoma japonicum was declared eradicated in Japan. In the People’s Republic of China, S. japonicum transmission has been interrupted in the major endemic areas in the coastal plains but the disease persists in the lake and marshland regions [...] Read more.
In 1996, schistosomiasis due to Schistosoma japonicum was declared eradicated in Japan. In the People’s Republic of China, S. japonicum transmission has been interrupted in the major endemic areas in the coastal plains but the disease persists in the lake and marshland regions south of the Yangtze River. The disease remains a public health problem in endemic areas in the Philippines and in isolated areas in Indonesia. Comprehensive multidisciplinary campaigns had led to eradication of schistosomiasis in Japan and have been successful in the interruption of disease transmission in the major endemic regions of the People’s Republic of China. Unfortunately, the integrated measures cannot be duplicated in schistosomiasis endemic areas in the Philippines because of limited resources. The problem is also more complicated due to the topography in the Philippines and transmission is not seasonal as in China. An innovative approach is needed in the Philippines if schistosomiasis elimination is the goal. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
Open AccessConcept Paper
A Call for Systems Epidemiology to Tackle the Complexity of Schistosomiasis, Its Control, and Its Elimination
Trop. Med. Infect. Dis. 2019, 4(1), 21; https://doi.org/10.3390/tropicalmed4010021
Received: 18 October 2018 / Revised: 22 January 2019 / Accepted: 24 January 2019 / Published: 29 January 2019
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Abstract
Ever since the first known written report of schistosomiasis in the mid-19th century, researchers have aimed to increase knowledge of the parasites, their hosts, and the mechanisms contributing to infection and disease. This knowledge generation has been paramount for the development of improved [...] Read more.
Ever since the first known written report of schistosomiasis in the mid-19th century, researchers have aimed to increase knowledge of the parasites, their hosts, and the mechanisms contributing to infection and disease. This knowledge generation has been paramount for the development of improved intervention strategies. Yet, despite a broad knowledge base of direct risk factors for schistosomiasis, there remains a paucity of information related to more complex, interconnected, and often hidden drivers of transmission that hamper intervention successes and sustainability. Such complex, multidirectional, non-linear, and synergistic interdependencies are best understood by looking at the integrated system as a whole. A research approach able to address this complexity and find previously neglected causal mechanisms for transmission, which include a wide variety of influencing factors, is needed. Systems epidemiology, as a holistic research approach, can integrate knowledge from classical epidemiology, with that of biology, ecology, social sciences, and other disciplines, and link this with informal, tacit knowledge from experts and affected populations. It can help to uncover wider-reaching but difficult-to-identify processes that directly or indirectly influence exposure, infection, transmission, and disease development, as well as how these interrelate and impact one another. Drawing on systems epidemiology to address persisting disease hotspots, failed intervention programmes, and systematically neglected population groups in mass drug administration programmes and research studies, can help overcome barriers in the progress towards schistosomiasis elimination. Generating a comprehensive view of the schistosomiasis system as a whole should thus be a priority research agenda towards the strategic goal of morbidity control and transmission elimination. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
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Open AccessCorrection
Correction: Tendler, M., et al. Current Status of the Sm14/GLA-SE Schistosomiasis Vaccine: Overcoming Barriers and Paradigms towards the First Anti-Parasitic Human(itarian) Vaccine. Trop. Med. Infect. Dis. 2018, 3, 121
Trop. Med. Infect. Dis. 2019, 4(1), 16; https://doi.org/10.3390/tropicalmed4010016
Received: 16 January 2019 / Accepted: 18 January 2019 / Published: 19 January 2019
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Abstract
The authors wish to make the following correction to this paper [...] Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
Open AccessOpinion
WIPO Re:Search—A Platform for Product-Centered Cross-Sector Partnerships for the Elimination of Schistosomiasis
Trop. Med. Infect. Dis. 2019, 4(1), 11; https://doi.org/10.3390/tropicalmed4010011
Received: 30 November 2018 / Revised: 26 December 2018 / Accepted: 2 January 2019 / Published: 9 January 2019
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Abstract
Schistosomiasis is an acute and chronic disease that affects over 200 million people worldwide, and with over 700 million people estimated to be at risk of contracting this disease, it is a pressing issue in global health. However, research and development (R&D) to [...] Read more.
Schistosomiasis is an acute and chronic disease that affects over 200 million people worldwide, and with over 700 million people estimated to be at risk of contracting this disease, it is a pressing issue in global health. However, research and development (R&D) to develop new approaches to preventing, diagnosing, and treating schistosomiasis has been relatively limited. Praziquantel, a drug developed in the 1970s, is the only agent used in schistosomiasis mass drug administration (MDA) campaigns, indicating a critical need for a diversified therapeutic pipeline. Further, gaps in the vaccine and diagnostic pipelines demonstrate a need for early-stage innovation in all areas of schistosomiasis product R&D. As a platform for public-private partnerships (PPPs), the WIPO Re:Search consortium engages the private sector in early-stage R&D for neglected diseases by forging mutually beneficial collaborations and facilitating the sharing of intellectual property (IP) assets between the for-profit and academic/non-profit sectors. The Consortium connects people, resources, and ideas to fill gaps in neglected disease product development pipelines by leveraging the strengths of these two sectors. Using WIPO Re:Search as an example, this article highlights the opportunities for the PPP model to play a key role in the elimination of schistosomiasis. Full article
(This article belongs to the Special Issue Prospects for Schistosomiasis Elimination)
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