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BACKGROUND: In areas of low disease endemicity, highly sensitive diagnostic tools to identify, diagnose, and monitor intestinal schistosomiasis transmission are needed to reliably measure the burden and risk of infection. Here, we used highly sensitive molecular diagnostic methods to investigate Schistosoma mansoni prevalence and transmission along the southern shoreline of Lake Malawi, five years post-disease outbreak. METHODOLOGY AND PRINCIPAL FINDINGS: Faecal and urine samples were provided by school-aged children situated along the southern shoreline of Lake Malawi. Kato-Katz faecal-egg microscopy and point-of-care circulating cathodic antigen (POC-CCA) rapid diagnostic tests were then performed to diagnose infection with S. mansoni. Urine-egg microscopy was also used to diagnose infection with Schistosoma haematobium. In addition, Schistosoma miracidia were isolated from faecal material using a standard miracidium hatching technique. A two-step real-time PCR approach was then used to diagnose infection with S. mansoni using DNA isolated from faecal samples. Furthermore, isolated miracidia were genotyped to species level through PCR and Sanger sequencing. Phylogenetic analyses were then carried out to identify which previously defined S. mansoni cox1 lineage group S. mansoni miracidia were most closely related to. The measured prevalence of S. mansoni infection varied considerably depending on which diagnostic assay was used. When compared to real-time PCR, faecal-egg microscopy had a sensitivity of 9% and a specificity of 100%. When POC-CCA 'trace' results were considered positive, POC-CCA had a sensitivity of 73% and a specificity of 81% when compared to real-time PCR. However, when considered negative, POC-CCA sensitivity was reduced to 56%, whereas specificity was increased to 90%. In addition, a high degree of S. haematobium DNA was detected in DNA isolated from faecal samples and motile S. haematobium miracidia were recovered from faecal samples. Schistosoma mansoni miracidia were closely related to two independent cox1 lineage groups, suggesting multiple recent introduction and colonisation events originating from surrounding east African countries. CONCLUSIONS AND SIGNIFICANCE: Intestinal schistosomiasis is now highly prevalent along the southern shoreline of Lake Malawi just five years post-disease outbreak. In addition, a high prevalence of urogenital schistosomiasis persists. The revision of ongoing schistosomiasis control programmes in this area is therefore recommended. Our study also highlights the need for reliable diagnostic assays capable of distinguishing between Schistosoma species in multispecies co-endemic areas.
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Fezes , Lagos , Epidemiologia Molecular , Schistosoma mansoni , Esquistossomose mansoni , Animais , Malaui/epidemiologia , Schistosoma mansoni/genética , Schistosoma mansoni/isolamento & purificação , Schistosoma mansoni/classificação , Esquistossomose mansoni/epidemiologia , Esquistossomose mansoni/parasitologia , Esquistossomose mansoni/diagnóstico , Humanos , Criança , Fezes/parasitologia , Lagos/parasitologia , Feminino , Masculino , Prevalência , Filogenia , Adolescente , Genética Populacional , Genótipo , DNA de Helmintos/genéticaRESUMO
Mass-drug administration (MDA) of human populations using praziquantel monotherapy has become the primary strategy for controlling and potentially eliminating the major neglected tropical disease schistosomiasis. To understand how long-term MDA impacts schistosome populations, we analysed whole-genome sequence data of 570 Schistosoma mansoni samples (and the closely related outgroup species, S. rodhaini) from eight countries incorporating both publicly-available sequence data and new parasite material. This revealed broad-scale genetic structure across countries but with extensive transmission over hundreds of kilometres. We characterised variation across the transient receptor potential melastatin ion channel, TRPMPZQ, a target of praziquantel, which has recently been found to influence praziquantel susceptibility. Functional profiling of TRPMPZQ variants found in endemic populations identified four mutations that reduced channel sensitivity to praziquantel, indicating standing variation for resistance. Analysis of parasite infrapopulations sampled from individuals pre- and post-treatment identified instances of treatment failure, further indicative of potential praziquantel resistance. As schistosomiasis is targeted for elimination as a public health problem by 2030 in all currently endemic countries, and even interruption of transmission in selected African regions, we provide an in-depth genomic characterisation of endemic populations and an approach to identify emerging praziquantel resistance alleles.
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The human parasitic fluke, Schistosoma haematobium hybridizes with the livestock parasite S. bovis in the laboratory, but the extent of hybridization in nature is unclear. We analyzed 34.6 million single nucleotide variants in 162 samples from 18 African countries, revealing a sharp genetic discontinuity between northern and southern S. haematobium. We found no evidence for recent hybridization. Instead the data reveal admixture events that occurred 257-879 generations ago in northern S. haematobium populations. Fifteen introgressed S. bovis genes are approaching fixation in northern S. haematobium with four genes potentially driving adaptation. We identified 19 regions that were resistant to introgression; these were enriched on the sex chromosomes. These results (i) demonstrate strong barriers to gene flow between these species, (ii) indicate that hybridization may be less common than currently envisaged, but (iii) reveal profound genomic consequences of interspecific hybridization between schistosomes of medical and veterinary importance.
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BACKGROUND: Lymnaeid snails of the genus Austropeplea are an important vector of the liver fluke (Fasciola hepatica), contributing to livestock production losses in Australia and New Zealand. However, the species status within Austropeplea is ambiguous due to heavy reliance on morphological analysis and a relative lack of genetic data. This study aimed to characterise the mitochondrial genome of A. cf. brazieri, an intermediate host of liver fluke in eastern Victoria. METHODS: The mitochondrial genome was assembled and annotated from a combination of second- and third-generation sequencing data. For comparative purposes, we performed phylogenetic analyses of the concatenated nucleotide sequences of the mitochondrial protein-coding genes, cytochrome c oxidase subunit 1 and 16S genes. RESULTS: The assembled mt genome was 13,757 base pairs and comprised 37 genes, including 13 protein-coding genes, 22 transfer RNA genes and 2 ribosomal RNA genes. The mt genome length, gene order and nucleotide compositions were similar to related species of lymnaeids. Phylogenetic analyses of the mt nucleotide sequences placed A. cf. brazieri within the same clade as Orientogalba ollula with strong statistical supports. Phylogenies of the cox1 and 16S mt sequences were constructed due to the wide availability of these sequences representing the lymnaeid taxa. As expected in both these phylogenies, A. cf. brazieri clustered with other Austropeplea sequences, but the nodal supports were low. CONCLUSIONS: The representative mt genome of A. cf. brazieri should provide a useful resource for future molecular, epidemiology and parasitological studies of this socio-economically important lymnaeid species.
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Genoma Mitocondrial , Filogenia , Caramujos , Animais , Genoma Mitocondrial/genética , Caramujos/parasitologia , Austrália , Fasciola hepatica/genética , Fasciola hepatica/classificação , Complexo IV da Cadeia de Transporte de Elétrons/genética , Vetores de Doenças , Análise de Sequência de DNARESUMO
BACKGROUND: Urogenital schistosomiasis is caused by the parasitic trematode Schistosoma haematobium. Sensitive and specific point-of-care diagnostics are needed for elimination of this disease. Recombinase polymerase amplification (RPA) assays meet these criteria, and an assay to diagnose S. haematobium has been developed (Sh-RPA). However, false-positive results can occur, and optimisation of reaction conditions to mitigate these is needed. Ease of use and compatibility of DNA extraction methods must also be considered. METHODS: Using synthetic DNA, S. haematobium genomic DNA (gDNA), and urine samples from clinical cases, Sh-RPA reactions incorporating different betaine concentrations (0 M, 1 M, 2.5 M, 12.5 M) and the sample-to-water ratios were tested to determine effects on assay specificity and sensitivity. In addition, five commercial DNA extraction kits suitable for use in resource-limited settings were used to obtain gDNA from single S. haematobium eggs and evaluated in terms of DNA quality, quantity, and compatibility with the Sh-RPA assay. All samples were also evaluated by quantitative polymerase chain reaction (qPCR) to confirm DNA acquisition. RESULTS: The analytical sensitivity of the Sh-RPA with all betaine concentrations was ≥ 10 copies of the synthetic Dra1 standard and 0.1 pg of S. haematobium gDNA. The addition of betaine improved Sh-RPA assay specificity in all reaction conditions, and the addition of 2.5 M of betaine together with the maximal possible sample volume of 12.7 µl proved to be the optimum reaction conditions. DNA was successfully isolated from a single S. haematobium egg using all five commercial DNA extraction kits, but the Sh-RPA performance of these kits varied, with one proving to be incompatible with RPA reactions. CONCLUSIONS: The addition of 2.5 M of betaine to Sh-RPA reactions improved reaction specificity whilst having no detrimental effect on sensitivity. This increases the robustness of the assay, advancing the feasibility of using the Sh-RPA assay in resource-limited settings. The testing of commercial extraction kits proved that crude, rapid, and simple methods are sufficient for obtaining DNA from single S. haematobium eggs, and that these extracts can be used with Sh-RPA in most cases. However, the observed incompatibility of specific kits with Sh-RPA highlights the need for each stage of a molecular diagnostic platform to be robustly tested prior to implementation.
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Técnicas de Amplificação de Ácido Nucleico , Sistemas Automatizados de Assistência Junto ao Leito , Schistosoma haematobium , Esquistossomose Urinária , Sensibilidade e Especificidade , Animais , Schistosoma haematobium/genética , Schistosoma haematobium/isolamento & purificação , Esquistossomose Urinária/diagnóstico , Esquistossomose Urinária/urina , Esquistossomose Urinária/parasitologia , Técnicas de Amplificação de Ácido Nucleico/métodos , Humanos , DNA de Helmintos/genética , DNA de Helmintos/isolamento & purificação , Recombinases/metabolismo , Recombinases/genética , Técnicas de Diagnóstico Molecular/métodosRESUMO
INTRODUCTION: Multiplathogen home-based self-sampling offers an opportunity to increase access to screening and treatment in endemic settings with high coinfection prevalence of sexually transmitted (HIV, Trichomonas vaginalis (Tv), human papillomavirus (HPV)) and non-sexually transmitted pathogens (Schistosoma haematobium (Sh)). Chronic coinfections may lead to disability (female genital schistosomiasis) and death (cervical cancer). The Zipime-Weka-Schista (Do self-testing sister!) study aims to evaluate the validity, acceptability, uptake, impact and cost-effectiveness of multipathogen self-sampling for genital infections among women in Zambia. METHODS AND ANALYSIS: This is a longitudinal cohort study aiming to enrol 2500 non-pregnant, sexually active and non-menstruating women aged 15-50 years from two districts in Zambia with 2-year follow-up. During home visits, community health workers offer HIV and Tv self-testing and cervicovaginal self-swabs for (1) HPV by GeneXpert and, (2) Sh DNA detection by conventional (PCR)and isothermal (recombinase polymerase assay) molecular methods. Schistosoma ova and circulating anodic antigen are detected in urine. At a clinic follow-up, midwives perform the same procedures and obtain hand-held colposcopic images. High-risk HPV positive women are referred for a two-quadrant cervical biopsy according to age and HIV status. A cost-effectiveness analysis is conducted in parallel. ETHICS AND DISSEMINATION: The University of Zambia Biomedical Research Ethics Committee (UNZABREC) (reference: 1858-2021), the London School of Hygiene and Tropical Medicine (reference: 25258), Ministry of Health and local superintendents approved the study in September 2021.Written informed consent was obtained from all participants prior to enrolment. Identifiable data collected are stored securely and their confidentiality is protected in accordance with the Data Protection Act 1998.
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Análise Custo-Benefício , Infecções por HIV , Programas de Rastreamento , Infecções por Papillomavirus , Humanos , Feminino , Zâmbia/epidemiologia , Estudos Longitudinais , Adulto , Adolescente , Adulto Jovem , Pessoa de Meia-Idade , Infecções por Papillomavirus/diagnóstico , Infecções por Papillomavirus/epidemiologia , Infecções por HIV/diagnóstico , Infecções por HIV/epidemiologia , Programas de Rastreamento/métodos , Programas de Rastreamento/economia , Coinfecção/diagnóstico , Autoteste , Animais , Esquistossomose Urinária/diagnóstico , Esquistossomose Urinária/epidemiologia , Vaginite por Trichomonas/diagnóstico , Vaginite por Trichomonas/epidemiologia , Trichomonas vaginalis/isolamento & purificação , Neoplasias do Colo do Útero/diagnóstico , Neoplasias do Colo do Útero/virologia , Papillomavirus HumanoRESUMO
Schistosomiasis is a neglected tropical disease (NTD) caused by infection with parasitic trematodes of the genus Schistosoma that can lead to debilitating morbidity and mortality. The World Health Organization recommend molecular xenomonitoring of Biomphalaria spp. freshwater snail intermediate hosts of Schistosoma mansoni to identify highly focal intestinal schistosomiasis transmission sites and monitor disease transmission, particularly in low-endemicity areas. A standardised protocol to do this, however, is needed. Here, two previously published primer sets were selected to develop and validate a multiplex molecular xenomonitoring end-point PCR assay capable of detecting S. mansoni infections within individual Biomphalaria spp. missed by cercarial shedding. The assay proved highly sensitive and highly specific in detecting and amplifying S. mansoni DNA and also proved highly sensitive in detecting and amplifying non-S. mansoni trematode DNA. The optimised assay was then used to screen Biomphalaria spp. collected from a S. mansoni-endemic area for infection and successfully detected S. mansoni infections missed by cercarial shedding as well as infections with non-S. mansoni trematodes. The continued development and use of molecular xenomonitoring assays such as this will aid in improving disease control efforts, significantly reducing disease-related morbidities experienced by those in schistosomiasis-endemic areas.
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Improvements in diagnostics for schistosomiasis in both humans and snail hosts are priorities to be able to reach the World Health Organization (WHO) goal of eliminating the disease as a public health problem by 2030. In this context, molecular isothermal amplification tests, such as Recombinase Polymerase Amplification (RPA), are promising for use in endemic areas at the point-of-need for their accuracy, robustness, simplicity, and time-effectiveness. The developed recombinase polymerase amplification assay targeting the Schistosoma mansoni mitochondrial minisatellite region (SmMIT-RPA) was used to detect S. mansoni DNA from both laboratory and field Biomphalaria snails. Laboratory snails were experimentally infected and used at one, seven, and 28 days post-exposure (dpe) to 10 S. mansoni miracidia to provide samples in the early pre-patent infection stage. Field samples of Biomphalaria spp. were collected from the Mucuri Valley and Jequitinhonha Valley regions in the state of Minas Gerais, Brazil, which are endemic for S. mansoni. The sensitivity and specificity of the SmMIT-RPA assay were analysed and compared with existing loop-mediated isothermal amplification (LAMP), PCR-based methods, parasitological examination of the snails, and nucleotide sequencing. The SmMIT-RPA assay was able to detect S. mansoni DNA in the experimentally infected Biomphalaria glabrata as early as one dpe to 10 miracidia. It also detected S. mansoni infections (55.5% prevalence) in the field samples with the highest accuracy (100% sensitivity and specificity) compared with the other molecular tests used as the reference. Results from this study indicate that the SmMIT-RPA assay is a good alternative test to be used for snail xenomonitoring of S. mansoni due to its high sensitivity, accuracy, and the possibility of detecting early pre-patent infection. Its simplicity and portability also make it a suitable methodology in low-resource settings.
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Biomphalaria , Esquistossomose mansoni , Esquistossomose , Animais , Humanos , Schistosoma mansoni/genética , Recombinases/genética , Repetições Minissatélites , Biomphalaria/genética , Esquistossomose mansoni/diagnóstico , Esquistossomose mansoni/epidemiologia , Nucleotidiltransferases/genética , DNA de Helmintos/genéticaRESUMO
Zanzibar is among the few places in sub-Saharan Africa where interruption of Schistosoma transmission seems an achievable goal. Our systematic review identifies and discusses milestones in schistosomiasis research, control and elimination efforts in Zanzibar over the past 100 years. The search in online databases, libraries, and the World Health Organization Archives revealed 153 records published between May 1928 and August 2022. The content of records was summarised to highlight the pivotal work leading towards urogenital schistosomiasis elimination and remaining research gaps. The greatest achievement following 100 years of schistosomiasis interventions and research is undoubtedly the improved health of Zanzibaris, exemplified by the reduction in Schistosoma haematobium prevalence from>50% historically down to<5% in 2020, and the absence of severe morbidities. Experiences from Zanzibar have contributed to global schistosomiasis guidelines, whilst also revealing challenges that impede progression towards elimination. Challenges include: transmission heterogeneity requiring micro-targeting of interventions, post-treatment recrudescence of infections in transmission hotspots, biological complexity of intermediate host snails, emergence of livestock Schistosoma species complicating surveillance whilst creating the risk for interspecies hybridisation, insufficient diagnostics performance for light intensity infections and female genital schistosomiasis, and a lack of acceptable sanitary alternatives to freshwater bodies. Our analysis of the past revealed that much can be achieved in the future with practical implementation of integrated interventions, alongside operational research. With continuing national and international commitments, interruption of S. haematobium transmission across both islands is within reach by 2030, signposting the future demise of urogenital schistosomiasis across other parts of sub-Saharan Africa.
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Esquistossomose Urinária , Feminino , Animais , Esquistossomose Urinária/epidemiologia , Esquistossomose Urinária/prevenção & controle , Tanzânia , Lacunas de Evidências , GadoRESUMO
BACKGROUND: The use of applications involving single nucleotide polymorphisms (SNPs) has greatly increased since the beginning of the 2000s, with the number of associated techniques expanding rapidly in the field of molecular research. Tetra-primer amplification refractory mutation system-PCR (T-ARMS-PCR) is one such technique involving SNP genotyping. It has the advantage of amplifying multiple alleles in a single reaction with the inclusion of an internal molecular control. We report here the development of a rapid, reliable and cost-effective duplex T-ARMS-PCR assay to distinguish between three Schistosoma species, namely Schistosoma haematobium (human parasite), Schistosoma bovis and Schistosoma curassoni (animal parasites), and their hybrids. This technique will facilitate studies of population genetics and the evolution of introgression events. METHODS: During the development of the technique we focused on one of the five inter-species internal transcribed spacer (ITS) SNPs and one of the inter-species 18S SNPs which, when combined, discriminate between all three Schistosoma species and their hybrid forms. We designed T-ARMS-PCR primers to amplify amplicons of specific lengths for each species, which in turn can then be visualized on an electrophoresis gel. This was further tested using laboratory and field-collected adult worms and field-collected larval stages (miracidia) from Spain, Egypt, Mali, Senegal and Ivory Coast. The combined duplex T-ARMS-PCR and ITS + 18S primer set was then used to differentiate the three species in a single reaction. RESULTS: The T-ARMS-PCR assay was able to detect DNA from both species being analysed at the maximum and minimum levels in the DNA ratios (95/5) tested. The duplex T-ARMS-PCR assay was also able to detect all hybrids tested and was validated by sequencing the ITS and the 18S amplicons of 148 of the field samples included in the study. CONCLUSIONS: The duplex tetra-primer ARMS-PCR assay described here can be applied to differentiate between Schistosoma species and their hybrid forms that infect humans and animals, thereby providing a method to investigate the epidemiology of these species in endemic areas. The addition of several markers in a single reaction saves considerable time and is of long-standing interest for investigating genetic populations.
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Schistosoma haematobium , Schistosoma , Animais , Adulto , Humanos , Schistosoma haematobium/genética , Schistosoma/genética , Reação em Cadeia da Polimerase/métodos , DNA , Mutação , Senegal/epidemiologiaRESUMO
Schistosomiasis is a major neglected tropical disease targeted for elimination as a public health issue by 2030, however there is an urgent need for more sensitive and specific diagnostic tests suitable to resource-limited settings. Here we developed CATSH, a CRISPR-assisted diagnostic test for Schistosoma haematobium, utilising recombinase polymerase amplification, Cas12a-targeted cleavage and portable real-time fluorescence detection. CATSH showed high analytical sensitivity, consistent detection of a single parasitic egg and specificity for urogenital Schistosoma species. Thanks to a novel CRISPR-compatible sample preparation developed using simulated urine samples containing parasitic eggs, CATSH had a sample-to-result within 2 h. The components of CATSH can be lyophilised, reducing cold chain dependence and widening access to lower and middle-income countries. This work presents a new application of CRISPR diagnostics for highly sensitive and specific detection of parasitic pathogens in remote areas and could have a significant impact on the elimination of neglected tropical diseases.
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Schistosoma haematobium , Esquistossomose Urinária , Animais , Schistosoma haematobium/genética , Esquistossomose Urinária/diagnóstico , Sensibilidade e Especificidade , Doenças Negligenciadas , OvosRESUMO
Bulinus senegalensis and Bulinus umbilicatus, two sympatric freshwater snails found in temporal ponds in Senegal, were thought to be involved in the transmission of Schistosoma haematobium and/or Schistosoma curassoni. To better understand the role of these Bulinus species in the transmission of human and animal Schistosoma species, B. senegalensis and B. umbilicatus were collected in 2015, during a malacological survey, from a temporal pond in Niakhar, central Senegal. Snails were induced to shed cercariae on two consecutive days. Individual cercariae from each snail were collected and preserved for molecular identification. Infected snails were identified by analysis of a partial region of the cytochrome c oxidase subunit 1 (cox1) gene. Six individual cercariae shed from each infected snail were identified by analyses of the cox1, nuclear ITS and partial 18S rDNA regions. Of the 98 snails collected, one B. senegalensis had a mixed infection shedding S. haematobium, S. bovis and S. haematobium-S. bovis hybrid cercariae and one B. umbilicatus was found to be shedding only S. haematobium. These data provide molecular confirmation for B. senegalensis transmitting S. bovis and S. haematobium-S. bovis hybrids in Senegal. The multiple Bulinus species involved in the human urogenital schistosomiasis in Senegal provides a high force of transmission warranting detailed mapping, surveillance and regular treatment of at-risk populations.
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Background: Accurate diagnosis followed by timely treatment is an effective strategy for the prevention of complications together with reducing schistosomiasis transmission. Recombinase Polymerase Amplification (RPA) is a simple, rapid, sensitive, and specific isothermal method with low resource needs. This research aimed at the development and optimisation of a real-time (RT) and a lateral flow (LF) RPA assay for the detection of Schistosoma mansoni. Methodology: Recombinase Polymerase Amplification reactions were performed at full- (as recommended) and half-volumes (to reduce costs), with RT or LF detection systems targeting the S. mansoni mitochondrial minisatellite region. The specificity was assessed using gDNA from other Schistosoma species, helminths co-endemic with S. mansoni, human stool, and urine, and Biomphalaria snail hosts. The analytical sensitivity was evaluated using serial dilutions of gDNA, synthetic copies of the target, and single eggs. The ability of both assays to detect the S. mansoni DNA in human urine and stool samples was also tested. The long-term stability of the RT-RPA reagents was evaluated by storing the reaction components in different temperature conditions for up to 3 weeks. Results: The RT- and the LF-RPA (SmMIT- and SmMIT-LF-RPA, respectively) presented similar results when used full- and half-volumes, thus the latter was followed in all experiments. The SmMIT-RPA was 100% specific to S. mansoni, able to detect a single egg, with a limit of detection (LOD) of down to 1 fg of gDNA and one synthetic copy of the target. The assay was able to detect S. mansoni DNA from stool containing 1 egg/g and in spiked urine at a concentration of 10 fg/µl. SmMIT-RPA reagents were stable for up to 3 weeks when kept at 19°C, and 2 weeks when stored at 27°C. The SmMIT-LF-RPA cross-reacted with Clinostomidae, presented the LOD of 10 fg and one synthetic copy of the target, being able to detect a single egg and 1 egg/g in a stool sample. The LOD in spiked urine samples was 10 pg/µl. Conclusion: The half-volume SmMIT-RPA is a promising method to be used in the field. It is specific, sensitive, robust, and tolerant to inhibitors, with a long-term stability of the reaction components and the real-time visualisation of results.
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The World Health Organization's revised NTD Roadmap and the newly launched Guidelines target elimination of schistosomiasis as a public health problem in all endemic areas by 2030. Key to meeting this goal is elucidating how selective pressures imposed by interventions shape parasite populations. Our aim was to identify any differential impact of a unique cluster-randomized tri-armed elimination intervention (biannual mass drug administration (MDA) applied alone or in association with either mollusciciding (snail control) or behavioural change interventions) across two Zanzibarian islands (Pemba and Unguja) on the population genetic composition of Schistosoma haematobium over space and time. Fifteen microsatellite loci were used to analyse individual miracidia collected from infected individuals across islands and intervention arms at the start (2012 baseline: 1,522 miracidia from 176 children; 303 from 43 adults; age-range 6-75, mean 12.7 years) and at year 5 (2016: 1,486 miracidia from 146 children; 214 from 25 adults; age-range 9-46, mean 12.4 years). Measures of genetic diversity included allelic richness (Ar), Expected (He) and Observed heterozygosity (Ho), inbreeding coefficient (FST), parentage analysis, estimated worm burden, worm fecundity, and genetic sub-structuring. There was little evidence of differential selective pressures on population genetic diversity, inbreeding or estimated worm burdens by treatment arm, with only the MDA+snail control arm within Unguja showing trends towards reduced diversity and altered inbreeding over time. The greatest differences overall, both in terms of parasite fecundity and genetic sub-structuring, were observed between the islands, consistent with Pemba's persistently higher mean infection intensities compared to neighbouring Unguja, and within islands in terms of infection hotspots (across three definitions). These findings highlight the important contribution of population genetic analyses to elucidate extensive genetic diversity and biological drivers, including potential gene-environmental factors, that may override short term selective pressures imposed by differential disease control strategies. Trial Registration: ClinicalTrials.gov ISRCTN48837681.
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Anti-Helmínticos , Esquistossomose Urinária , Animais , Anti-Helmínticos/uso terapêutico , Genética Populacional , Ilhas , Praziquantel/uso terapêutico , Schistosoma haematobium/genética , Esquistossomose Urinária/tratamento farmacológico , Esquistossomose Urinária/epidemiologia , Esquistossomose Urinária/prevenção & controle , Caramujos/genética , Caramujos/parasitologia , Tanzânia/epidemiologiaRESUMO
BACKGROUND: The Zanzibar Archipelago (Pemba and Unguja islands) is targeted for the elimination of human urogenital schistosomiasis caused by infection with Schistosoma haematobium where the intermediate snail host is Bulinus globosus. Following multiple studies, it has remained unclear if B. nasutus (a snail species that occupies geographically distinct regions on the Archipelago) is involved in S. haematobium transmission on Zanzibar. Additionally, S. haematobium was thought to be the only Schistosoma species present on the Zanzibar Archipelago until the sympatric transmission of S. bovis, a parasite of ruminants, was recently identified. Here we re-assess the epidemiology of schistosomiasis on Pemba and Unguja together with the role and genetic diversity of the Bulinus spp. involved in transmission. METHODOLOGY/PRINCIPAL FINDINGS: Malacological and parasitological surveys were conducted between 2016 and 2019. In total, 11,116 Bulinus spp. snails were collected from 65 of 112 freshwater bodies surveyed. Bulinus species identification were determined using mitochondrial cox1 sequences for a representative subset of collected Bulinus (n = 504) and together with archived museum specimens (n = 6), 433 B. globosus and 77 B. nasutus were identified. Phylogenetic analysis of cox1 haplotypes revealed three distinct populations of B. globosus, two with an overlapping distribution on Pemba and one on Unguja. For B. nasutus, only a single clade with matching haplotypes was observed across the islands and included reference sequences from Kenya. Schistosoma haematobium cercariae (n = 158) were identified from 12 infected B. globosus and one B. nasutus collected between 2016 and 2019 in Pemba, and cercariae originating from 69 Bulinus spp. archived in museum collections. Schistosoma bovis cercariae (n = 21) were identified from seven additional B. globosus collected between 2016 and 2019 in Pemba. By analysing a partial mitochondrial cox1 region and the nuclear ITS (1-5.8S-2) rDNA region of Schistosoma cercariae, we identified 18 S. haematobium and three S. bovis haplotypes representing populations associated with mainland Africa and the Indian Ocean Islands (Zanzibar, Madagascar, Mauritius and Mafia). CONCLUSIONS/SIGNIFICANCE: The individual B. nasutus on Pemba infected with S. haematobium demonstrates that B. nasutus could also play a role in the local transmission of S. haematobium. We provide preliminary evidence that intraspecific variability of S. haematobium on Pemba may increase the transmission potential of S. haematobium locally due to the expanded intermediate host range, and that the presence of S. bovis complicates the environmental surveillance of schistosome infections.
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Bulinus , Esquistossomose Urinária , Animais , Bulinus/genética , Bulinus/parasitologia , Cercárias/genética , Água Doce/parasitologia , Humanos , Filogenia , Schistosoma haematobium/genética , Esquistossomose Urinária/parasitologia , Caramujos , Tanzânia/epidemiologiaRESUMO
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.
Assuntos
Esquistossomose Urinária , Animais , Feminino , Genitália Feminina/parasitologia , Genitália Masculina , Humanos , Masculino , Praziquantel/uso terapêutico , Schistosoma haematobium , Esquistossomose Urinária/diagnóstico , Esquistossomose Urinária/tratamento farmacológico , Esquistossomose Urinária/epidemiologiaRESUMO
BACKGROUND: Female genital schistosomiasis (FGS) is a neglected and disabling gynecological disease that can result from infection with the parasitic trematode Schistosoma haematobium. Accurate diagnosis of FGS is crucial for effective case management, surveillance and control. However, current methods for diagnosis and morbidity assessment can be inaccessible to those at need, labour intensive, costly and unreliable. Molecular techniques such as PCR can be used to reliably diagnose FGS via the detection of Schistosoma DNA using cervicovaginal lavage (CVL) samples as well as lesser-invasive vaginal self-swab (VSS) and cervical self-swab samples. PCR is, however, currently unsuited for use in most endemic settings. As such, in this study, we assessed the use of a rapid and portable S. haematobium recombinase polymerase amplification (Sh-RPA) isothermal molecular diagnostic assay, coupled with simplified sample preparation methodologies, to detect S. haematobium DNA using CVL and VSS samples provided by patients in Zambia. METHODOLOGY/PRINCIPAL FINDINGS: VSS and CVL samples were screened for FGS using a previously developed Sh-RPA assay. DNA was isolated from VSS and CVL samples using the QIAamp Mini kit (n = 603 and 527, respectively). DNA was also isolated from CVL samples using two rapid and portable DNA extraction methods: 1) the SpeedXtract Nucleic Acid Kit (n = 223) and 2) the Extracta DNA Tissue Prep Kit (n = 136). Diagnostic performance of the Sh-RPA using VSS DNA extacts (QIAamp Mini kit) as well as CVL DNA extracts (QIAamp Mini kit, SpeedXtract Nucleic Acid Kit and Extracta DNA Tissue Prep Kit) was then compared to a real-time PCR reference test. Results suggest that optimal performance may be achieved when the Sh-RPA is used with PuVSS samples (sensitivity 93.3%; specificity 96.6%), however no comparisons between different DNA extraction methods using VSS samples could be carried out within this study. When using CVL samples, sensitivity of the Sh-RPA ranged between 71.4 and 85.7 across all three DNA extraction methods when compared to real-time PCR using CVL samples prepared using the QIAamp Mini kit. Interestingly, of these three DNA extraction methods, the rapid and portable SpeedXtract method had the greatest sensitivity and specificity (85.7% and 98.1%, respectively). Specificity of the Sh-RPA was >91% across all comparisons. CONCLUSIONS/SIGNIFICANCE: These results supplement previous findings, highlighting that the use of genital self-swab sampling for diagnosing FGS should be explored further whilst also demonstrating that rapid and portable DNA isolation methods can be used to detect S. haematobium DNA within clinical samples using RPA. Although further development and assessment is needed, it was concluded that the Sh-RPA, coupled with simplified sample preparation, shows excellent promise as a rapid and sensitive diagnostic tool capable of diagnosing FGS at the point-of-care in resource-poor schistosomiasis-endemic settings.
Assuntos
Schistosoma haematobium , Esquistossomose , Animais , DNA , Feminino , Genitália Feminina , Humanos , Técnicas de Amplificação de Ácido Nucleico/métodos , Reação em Cadeia da Polimerase em Tempo Real , Recombinases , Schistosoma haematobium/genética , Sensibilidade e Especificidade , Irrigação TerapêuticaRESUMO
Urogenital schistosomiasis is caused by the blood fluke Schistosoma haematobium and is one of the most neglected tropical diseases worldwide, afflicting > 100 million people. It is characterised by granulomata, fibrosis and calcification in urogenital tissues, and can lead to increased susceptibility to HIV/AIDS and squamous cell carcinoma of the bladder. To complement available treatment programs and break the transmission of disease, sound knowledge and understanding of the biology and ecology of S. haematobium is required. Hybridisation/introgression events and molecular variation among members of the S. haematobium-group might effect important biological and/or disease traits as well as the morbidity of disease and the effectiveness of control programs including mass drug administration. Here we report the first chromosome-contiguous genome for a well-defined laboratory line of this blood fluke. An exploration of this genome using transcriptomic data for all key developmental stages allowed us to refine gene models (including non-coding elements) and annotations, discover 'new' genes and transcription profiles for these stages, likely linked to development and/or pathogenesis. Molecular variation within S. haematobium among some geographical locations in Africa revealed unique genomic 'signatures' that matched species other than S. haematobium, indicating the occurrence of introgression events. The present reference genome (designated Shae.V3) and the findings from this study solidly underpin future functional genomic and molecular investigations of S. haematobium and accelerate systematic, large-scale population genomics investigations, with a focus on improved and sustained control of urogenital schistosomiasis.
Assuntos
Variação Genética , Genoma de Protozoário , Schistosoma haematobium/genética , Esquistossomose Urinária/parasitologia , Transcriptoma , Animais , Cromossomos/parasitologia , Genes de Protozoários , Genoma , Estudo de Associação Genômica Ampla , Análise de Sequência de DNARESUMO
Schistosoma mansoni, a snail-borne, blood fluke that infects humans, was introduced into the Americas from Africa during the Trans-Atlantic slave trade. As this parasite shows strong specificity to the snail intermediate host, we expected that adaptation to South American Biomphalaria spp. snails would result in population bottlenecks and strong signatures of selection. We scored 475,081 single nucleotide variants in 143 S. mansoni from the Americas (Brazil, Guadeloupe and Puerto Rico) and Africa (Cameroon, Niger, Senegal, Tanzania, and Uganda), and used these data to ask: (i) Was there a population bottleneck during colonization? (ii) Can we identify signatures of selection associated with colonization? (iii) What were the source populations for colonizing parasites? We found a 2.4- to 2.9-fold reduction in diversity and much slower decay in linkage disequilibrium (LD) in parasites from East to West Africa. However, we observed similar nuclear diversity and LD in West Africa and Brazil, suggesting no strong bottlenecks and limited barriers to colonization. We identified five genome regions showing selection in the Americas, compared with three in West Africa and none in East Africa, which we speculate may reflect adaptation during colonization. Finally, we infer that unsampled populations from central African regions between Benin and Angola, with contributions from Niger, are probably the major source(s) for Brazilian S. mansoni. The absence of a bottleneck suggests that this is a rare case of a serendipitous invasion, where S. mansoni parasites were pre-adapted to the Americas and able to establish with relative ease.
Assuntos
Biomphalaria , Parasitos , América , Animais , Biomphalaria/genética , Biomphalaria/parasitologia , Humanos , Schistosoma mansoni/genética , Senegal/epidemiologia , Caramujos/genética , TanzâniaRESUMO
Schistosomiasis remains a public health concern across sub-Saharan Africa; current control programmes rely on accurate mapping and high mass drug administration (MDA) coverage to attempt disease elimination. Inter-species hybridisation can occur between certain species, changing epidemiological dynamics within endemic regions, which has the potential to confound control interventions. The impact of hybridisation on disease dynamics is well illustrated in areas of Cameroon where urogenital schistosomiasis, primarily due to Schistosoma haematobium and hybrid infections, now predominate over intestinal schistosomiasis caused by Schistosoma guineensis. Genetic markers have shown the ability to identify hybrids, however the underlying genomic architecture of divergence and introgression between these species has yet to be established. In this study, restriction site associated DNA sequencing (RADseq) was used on archived adult worms initially identified as; Schistosoma bovis (n = 4), S. haematobium (n = 9), S. guineensis (n = 3) and S. guineensis x S. haematobium hybrids (n = 4) from Mali, Senegal, Niger, São Tomé and Cameroon. Genome-wide evidence supports the existence of S. guineensis and S. haematobium hybrid populations across Cameroon. The hybridisation of S. guineensis x S. haematobium has not been demonstrated on the island of São Tomé, where all samples showed no introgression with S. haematobium. Additionally, all S. haematobium isolates from Nigeria, Mali and Cameroon indicated signatures of genomic introgression from S. bovis. Adaptive loci across the S. haematobium group showed that voltage-gated calcium ion channels (Cav) could play a key role in the ability to increase the survivability of species, particularly in host systems. Where admixture has occurred between S. guineensis and S. haematobium, the excess introgressive influx of tegumental (outer helminth body) and antigenic genes from S. haematobium has increased the adaptive response in hybrids, leading to increased hybrid population fitness and viability.