The relative contribution of immigration or local increase for persistence of urban schistosomiasis in Salvador, Bahia, Brazil

Burden of schistosomiasis in global, regional, and national 1990-2019: A systematic analysis for the Global Burden of Disease Study 2019

BACKGROUND

Despite the gradual decline of schistosomiasis due to the efforts of the WHO and various countries, with the WHO setting a goal to eliminate schistosomiasis by 2030, a comprehensive global assessment of the current status of schistosomiasis has not been conducted.

OBJECTIVES

To provide a detailed description of the changes in schistosomiasis from 1990 to 2019 by using the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 database.

METHODS

We obtained all relevant data on schistosomiasis worldwide from the Global Burden of Diseases (GBD) database from 1990 to 2019. The mortality, prevalence, disability-adjusted life-years (DALYs), Years of Life Lost (YLLs), Years Lived with Disability (YLDs) of schistosomiasis were examined by Socio-demographic Index (SDI), age, sex, and year at the global, region and national level.

RESULTS

From 1990 to 2019, the age-standardized rate(ASR)-prevalence of schistosomiasis has decreased from 2600.9 per 100,000(95% uncertainty interval (UI) 2191.2 to 3059.3) to 1805.0 per 100,000(95% UI 1503.4 to 2146.9). The estimated annual percentage change (EAPC) from 1990 to 2019 was 1.28 (95% UI 1.22 to 1.33) in high SDI regions and -2.45 (95% UI -3.03 to -1.86) in low SDI regions. In North Africa and the Middle East, the most substantial reduction in DALYs occurred, with an observed EAPC of -5.36.

CONCLUSION

The burden of schistosomiasis has decreased over the past three decades worldwide. However, the high SDI regions have shown the increasing burden of schistosomiasis. Besides, Multiple countries in Africa still bear a significant burden of schistosomiasis, necessitating robust prevention and control efforts.

Malacological, socio-environmental evaluation, and evidence of local transmission and maintenance of schistosomiasis in an urban area of Northeast Brazil

To present the current epidemiological scenario of schistosomiasis related to urban transmission through an epidemiological risk assessment in Porto de Galinhas, a coastal area of Pernambuco, Brazil. Malacological and parasitological surveys were performed between the years 2018 and 2020. Snails were identified taxonomically and examined to confirm infection by Schistosoma mansoni, and so to identify Schistosomiasis Transmission Foci (STF) by the artificial light exposure technique. Stool samples were examined using the Kato-Katz method to identify schistosomiasis cases. Socioeconomic, environmental, behavioural and health data were collected by a questionnaire applied to participates in the survey and used to predict the schistosomiasis risk occurrence by multivariate logistic regression. In all, a total of 6466 snails of Biomphalaria glabrata were collected and 36 breeding sites were identified, of which 25 % were STF. A total of 2236 individuals took part of the survey which identified 187 cases of schistosomiasis, registering a positivity percentage of 8.36 %. The surveys identified the neighbourhoods with the highest risk for transmission while the socioenvironmental analysis identifies other risk factors for disease occurrence, such as gender, age range, level of education and absence of water drainage. We found that areas with poor sanitation, flooding during winter periods and dwellings located near mangroves should be treated by health authorities as priority areas for health interventions to minimize disease transmission. In addition, efforts to improve the population's educational level could certainly contribute to the adoption of measures to prevent and control this neglected tropical disease.

Evidence for local transmission and maintenance of schistosomiasis in an urban neighbourhood in Northeast Brazil

Schistosomiasis is a tropical neglected disease commonly associated with rural areas; however, urban schistosomiasis has been reported worldwide, and increasing urbanization is one of the most important demographic shifts of the 20th and now 21st centuries. The pattern of urbanization is not uniform so that within the same city the rates and sources of population increase vary. Here, we report on the parasite composition in one neighbourhood in the metropolitan area of Salvador, Bahia, Brazil. Using epidemiological data and population genetics, we find evidence for local transmission and maintenance of Schistosoma mansoni infection within an urban population and little contribution from rural-urban migration. Our findings provide direction for local mitigation strategies and to assist the public living in this neighbourhood to interrupt the local transmission cycle.

Cryptic population structure and transmission dynamics uncovered for Schistosoma mansoni populations by genetic analyses

Patterns of diversity in pathogen genomes provide a window into the spatiotemporal spread of disease. In this study, we tested the hypothesis that Schistosoma mansoni parasites form genetic clusters that coincide with the communities of their human hosts. We also looked for genetic clustering of parasites at the sub-community level. Our data consists of 14 microsatellite DNA markers, typed from pooled DNA samples from [Formula: see text] infected individuals living in three Brazilian communities. We found a one-to-one correspondence between genetic clusters found by K-means cluster analysis and communities when [Formula: see text]. These clusters are also easily identified in a neighbor-joining tree and principal coordinates plots. K-means analysis with [Formula: see text] also reveals genetic clusters of parasites at the sub-community level. These sub-clusters also appear on the neighbor-joining tree and principal coordinates plots. A surprising finding is a genetic relationship between subgroups in widely separated human communities. This connection suggests the existence of common transmission sites that have wide influence. In summary, the genetic structure of S. mansoni in Brazil juxtaposes local isolation that is occasionally broken by long-range migration. Permanent eradication of schistosomes will require both local efforts and the identification of regional infection reservoirs.

Integrating genomic and epidemiologic data to accelerate progress toward schistosomiasis elimination

The global community has adopted ambitious goals to eliminate schistosomiasis as a public health problem, and new tools are needed to achieve them. Mass drug administration programs, for example, have reduced the burden of schistosomiasis, but the identification of hotspots of persistent and reemergent transmission threaten progress toward elimination and underscore the need to couple treatment with interventions that reduce transmission. Recent advances in DNA sequencing technologies make whole-genome sequencing a valuable and increasingly feasible option for population-based studies of complex parasites such as schistosomes. Here, we focus on leveraging genomic data to tailor interventions to distinct social and ecological circumstances. We consider two priority questions that can be addressed by integrating epidemiological, ecological, and genomic information: (1) how often do non-human host species contribute to human schistosome infection? and (2) what is the importance of locally acquired versus imported infections in driving transmission at different stages of elimination? These questions address processes that can undermine control programs, especially those that rely heavily on treatment with praziquantel. Until recently, these questions were difficult to answer with sufficient precision to inform public health decision-making. We review the literature related to these questions and discuss how whole-genome approaches can identify the geographic and taxonomic sources of infection, and how such information can inform context-specific efforts that advance schistosomiasis control efforts and minimize the risk of reemergence.

A systematic literature review of schistosomiasis in urban and peri-urban settings

BACKGROUND

Schistosomiasis is a parasitic disease caused by trematode worms of the genus Schistosoma and belongs to the neglected tropical diseases. The disease has been reported in 78 countries, with around 290.8 million people in need of treatment in 2018. Schistosomiasis is predominantly considered a rural disease with a subsequent focus of research and control activities in rural settings. Over the past decades, occurrence and even expansion of schistosomiasis foci in peri-urban and urban settings have increasingly been observed. Rural-urban migration in low- and middle-income countries and subsequent rapid and unplanned urbanization are thought to explain these observations. Fifty-five percent (55%) of the world population is already estimated to live in urban areas, with a projected increase to 68% by 2050. In light of rapid urbanization and the efforts to control morbidity and ultimately achieve elimination of schistosomiasis, it is important to deepen our understanding of the occurrence, prevalence, and transmission of schistosomiasis in urban and peri-urban settings. A systematic literature review looking at urban and peri-urban schistosomiasis was therefore carried out as a first step to address the research and mapping gap.

METHODOLOGY

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a systematic computer-aided literature review was carried out using PubMed, ScienceDirect, and the World Health Organization Database in November 2019, which was updated in March 2020. Only papers for which at least the abstract was available in English were used. Relevant publications were screened, duplicates were removed, guidelines for eligibility were applied, and eligible studies were reviewed. Studies looking at human Schistosoma infections, prevalence, and intensity of infection in urban and peri-urban settings were included as well as those focusing on the intermediate host snails.

PRINCIPAL FINDINGS

A total of 248 publications met the inclusion criteria. The selected studies confirm that schistosomiasis is prevalent in peri-urban and urban areas in the countries assessed. Earlier studies report higher prevalence levels in urban settings compared to data extracted from more recent publications, yet the challenge of migration, rapid uncontrolled urbanization, and resulting poor living conditions highlight the potential for continuous or even newly established transmission to take place.

CONCLUSIONS

The review indicates that schistosomiasis has long existed in urban and peri-urban areas and remains a public health problem. There is, however, a challenge of comparability of settings due to the lack of a clear definition of what constitutes urban and peri-urban. There is a pressing need for improved monitoring of schistosomiasis in urban communities and consideration of treatment strategies.

The changing profile of schistosomiasis in a changing urban landscape

Since 2007, most of humanity resides in urban areas, a trend which continues worldwide. Diseases usually associated with rural contexts are now emerging or newly recognised in cities. In the neighbourhood of São Bartolomeu in Salvador, Brazil, the prevalence of Schistosoma mansoni infection in 2011 was >20%. Following enrollment and treatment of a portion of the community, ~25% of the area underwent urban renewal. In 2015, we returned to enrol individuals who had previously participated and a cohort that had not taken part in 2011. Thus, infected individuals in one group experienced specific drug treatment plus improved living conditions and the second group only improved living conditions. Between 2011 and 2015 there were no organised treatment programs, but adequate sanitation increased from 69% to 92% coverage, household flooding decreased, and the presence of indoor toilets increased to 99% of households. Ownership of household appliances also increased significantly. The overall prevalence of schistosome infections was 6.2%. In 2015, the cohort first seen in 2011 had a higher prevalence (8.7%) than those first seen in 2015 (4.8%) and showed a few demographic differences. The 2011 cohort was older, more likely born in Salvador, less likely to have lived outside of Salvador, spent a greater percentage of their lifetime in Salvador, but more likely to have travelled. The population structure of the parasites from both cohorts underwent a marked change with similar increased component and infrapopulation differentiation and >10 fold decrease in effective population size. There was a 4-5 year shift in age-specific prevalence in 2015 for all compared with 2011. While praziquantel may have helped reduce prevalence, our evidence suggests that the structural changes and improvements in living conditions had the biggest impact on schistosomiasis in this community.

Population Structure and Dynamics of Helminthic Infection: Schistosomiasis

While disease and outbreaks are mainly clonal for bacteria and other asexually reproducing organisms, sexual reproduction in schistosomes and other helminths usually results in unique individuals. For sexually reproducing organisms, the traits conserved in clones will instead be conserved in the group of organisms that tends to breed together, the population. While the same tools are applied to characterize DNA, how results are interpreted can be quite different at times (see another article in this collection, http://www.asmscience.org/content/journal/microbiolspec/10.1128/microbiolspec.AME-0002-2018). It is difficult to know what the real effect any control program has on the parasite population without assessing the health of this population, how they respond to the control measure, and how they recover, if they do. This review, part of the Microbiology Spectrum Curated Collection: Advances in Molecular Epidemiology of Infectious Diseases, concentrates on one approach using pooled samples to study schistosome populations and shows how this and other approaches have contributed to our understanding of this parasite family's biology and epidemiology. *This article is part of a curated collection.

Antibiotic Resistance in Enterobacteriaceae from Surface Waters in Urban Brazil Highlights the Risks of Poor Sanitation

Surface waters are an unappreciated reservoir of antimicrobial resistance (AMR). Poor sanitation brings different species of environmental bacteria into contact, facilitating horizontal gene transfer. To investigate the role of surface waters as potential reservoirs of AMR, we studied the point prevalence of fecal contamination, AMR genes, and Enterobacteriaceae in an urban lake and rural river system in Northeast Brazil in comparison with a lake and sewer system in Northeast Ohio in the United States. Surface water samples were examined for evidence of human fecal contamination using microbial source tracking and screened for plasmid-mediated fluoroquinolone resistance and carbapenemase genes. Enterobacteriaceae were detected using selective agar followed by antimicrobial susceptibility testing and detection of AMR genes by microarray, and classified by repetitive sequence-based polymerase chain reaction and multilocus sequence typing. Concentrations of human fecal bacteria in the Brazilian urban lake and sewage in Northeast Ohio were similarly high. Filtered water samples from the Brazilian urban lake, however, showed the presence of bla OXA-48, bla KPC, bla VIM-2, qnrS, and aac(6')-lb-cr, whereas only bla VIM-2 was identified in raw sewage from Northeast Ohio. From the Brazilian urban lake, 85% of the Enterobacteriaceae (n = 40) cultured were resistant to at least one clinically important antibiotic, including ST131 Escherichia coli harboring the extended-spectrum beta-lactamase CTX-M. Although two isolates demonstrated polymyxin resistance, mcr-1/2 was not detected. Our findings indicate that surface waters in an urban Brazilian site can serve as an environmental reservoir of AMR and that improving wastewater treatment and sanitation generally may ameliorate AMR dissemination.

Diagnosis of Schistosoma mansoni infections: what are the choices in Brazilian low-endemic areas?

The population of Brazil is currently characterised by many individuals harbouring low-intensity Schistosoma mansoni infections. The Kato-Katz technique is the diagnostic method recommended by the World Health Organization (WHO) to assess these infections, but this method is not sensitive enough in the context of low egg excretion. In this regard, potential alternatives are being employed to overcome the limits of the Kato-Katz technique. In the present review, we evaluated the performance of parasitological and immunological approaches adopted in Brazilian areas. Currently, the diagnostic choices involve a combination of strategies, including the utilisation of antibody methods to screen individuals and then subsequent confirmation of positive cases by intensive parasitological investigations.

Serological proteomic screening and evaluation of a recombinant egg antigen for the diagnosis of low-intensity Schistosoma mansoni infections in endemic area in Brazil

Background

Despite decades of use of control programs, schistosomiasis remains a global public health problem. To further reduce prevalence and intensity of infection, or to achieve the goal of elimination in low-endemic areas, there needs to be better diagnostic tools to detect low-intensity infections in low-endemic areas in Brazil. The rationale for development of new diagnostic tools is that the current standard test Kato-Katz (KK) is not sensitive enough to detect low-intensity infections in low-endemic areas. In order to develop new diagnostic tools, we employed a proteomics approach to identify biomarkers associated with schistosome-specific immune responses in hopes of developing sensitive and specific new methods for immunodiagnosis.

Methods and findings

Immunoproteomic analyses were performed on egg extracts of Schistosoma mansoni using pooled sera from infected or non-infected individuals from a low-endemic area of Brazil. Cross reactivity with other soil-transmitted helminths (STH) was determined using pooled sera from individuals uniquely infected with different helminths. Using this approach, we identified 23 targets recognized by schistosome acute and chronic sera samples. To identify immunoreactive targets that were likely glycan epitopes, we compared these targets to the immunoreactivity of spots treated with sodium metaperiodate oxidation of egg extract. This treatment yielded 12/23 spots maintaining immunoreactivity, suggesting that they were protein epitopes. From these 12 spots, 11 spots cross-reacted with sera from individuals infected with other STH and 10 spots cross-reacted with the negative control group. Spot number 5 was exclusively immunoreactive with sera from S. mansoni-infected groups in native and deglycosylated conditions and corresponds to Major Egg Antigen (MEA). We expressed MEA as a recombinant protein and showed a similar recognition pattern to that of the native protein via western blot. IgG-ELISA gave a sensitivity of 87.10% and specificity of 89.09% represented by area under the ROC curve of 0.95. IgG-ELISA performed better than the conventional KK (2 slides), identifying 56/64 cases harboring 1–10 eggs per gram of feces that were undiagnosed by KK parasitological technique.

Conclusions

The serological proteome approach was able to identify a new diagnostic candidate. The recombinant egg antigen provided good performance in IgG-ELISA to detect individuals with extreme low-intensity infections (1 egg per gram of feces). Therefore, the IgG-ELISA using this newly identified recombinant MEA can be a useful tool combined with other techniques in low-endemic areas to determine the true prevalence of schistosome infection that is underestimated by the KK method. Further, to overcome the complexity of ELISA in the field, a second generation of antibody-based rapid diagnostic tests (RDT) can be developed.

Schistosomiasis remains a serious global public health problem. Detecting parasite eggs in patient stool samples using the KK method is the standard diagnostic recommended by the World Health Organization (WHO) for infection by S. mansoni. As a result of intensive control strategies, many previously high-endemic areas are now considered low-endemic areas and the KK method does not function well in low-endemic areas and therefore cannot be considered the gold standard. Thus, a new emphasis on strategies to accurately diagnose low-intensity infections was outlined in a plan from the WHO focusing on elimination of disease as a public health problem. Successful diagnoses and treatment of infected individuals may result in eradication of low-burden transmitters and consequently contribute to interruption of disease transmission. In this regard, immunological techniques have proven to be more sensitive and promising for identifying low-intensity infections where KK may be negative. The identification of antigens is the initial step for developing new immunodiagnostic assays. In this study, we used sets of pooled human sera samples from controls with acute and chronic infections to identify new target antigens via proteomic screening. Using these approaches, we initially identified 12 different egg proteins in S. mansoni-infected individuals (acute and chronic phase). A single antigen, identified as MEA, was shown to be highly specific as this antigen was not recognized by sera from negative patients or patients infected with other STH. The recombinant MEA protein functioned in an ELISA as a highly sensitive and specific antigen to detect patient IgG-antibodies. Recombinant MEA performed significantly better to detect low-intensity infections (1 egg per gram of feces) than the KK method using 2 slides. Therefore, we were able to use a proteomic screening approach to identify a potential new candidate antigen for development of far more sensitive diagnostic assays. Further diagnostic assays employing the MEA could be useful tools on their own or in combination with other methods for diagnosis of schistosome infection in populations living in extreme low-intensity endemic areas of Brazil.

Systematic review and meta-analysis on Schistosoma mansoni infection prevalence, and associated risk factors in Brazil

We performed a systematic review and meta-analysis on the prevalence and factors associated with Schistosoma mansoni infection in Brazil. We searched the PubMed, Web of Science and Latin-American and Caribbean System on Health Sciences Information (LILACS) databases, scientific publications articles, according to The PRISMA Statement, from 2000 to 2016. A total of 27 studies were included according to the established criteria. The prevalence of S. mansoni infection varied widely, from 0·1 to 73·1%, based on Kato-Katz technique. Of the identified studies, 42·9% were performed in the state of Minas Gerais, and 33·3% were performed in the northeast region of Brazil. We identified sex, age, education level, family income, contact with water and the presence of the intermediate host snail as major risk factors associated with infection. The meta-analysis summarized a high prevalence rate pooled for Schistosoma mansoni. On the other hand, the analysis of the subgroup showed a highly significant reduction of the prevalence rate after control measures. The epidemiological factors evidenced in the studies show the influence of environmental and social conditions on the occurrence of schistosomiasis.

Rapid Risk Assessment Report for Schistosomiasis Epidemic in Jianli County Caused by the Sunk "Oriental Star" Cruise Ship

BACKGROUND

At 9:28 pm on June 1, 2015, the cruise ship "Oriental Star" sank into Yangtze River in Jianli County, with 422 people killed. When the accident occurred, the Chinese government took immediate action and dispatched more than 9000 rescuers. The risk for outbreak of schistosomiasis was increased because of the shipwreck. Obviously it is critical to carry out risk assessment as soon as possible.

METHODS

By means of the Delphi method, the situation was analyzed so that the government could fathom the severity of the accident. Then, through matrix and sigma-plotting (3-dimensional graphics) methods, related authorities performed risk assessment after site investigation.

RESULTS

The latest news reported that more than 9000 people were involved in the rescue. The affected river was analyzed and mapped using SigmaPlot software, according to which the possibility, harmfulness, and controllability of the accident were determined to be medium (6), medium (6), and poor (7), respectively.

CONCLUSION

The site of the accident where the cruise ship sank and rescue operations were carried out is a schistosomiasis epidemic area with high mortality and morbidity. The chance of an outbreak of the schistosomiasis epidemic in Jianli County is quite high. To protect people in this county from the epidemic, relevant logistic services should be arranged and all remains should be cleared up carefully. (Disaster Med Public Health Preparedness. 2018;12:147-153).

Establishment of first engineering specifications for environmental modification to eliminate schistosomiasis epidemic foci in urban areas

Snail control is a key link in schistosomiasis control, but no unified methods for eliminating snails have been produced to date. This study was conducted to explore an engineering method for eliminating Oncomelania hupensis applicable to urban areas. The engineering specifications were established using the Delphi method. An engineering project based on these specifications was conducted in Hankou marshland to eliminate snails, including the transformation of the beach surface and ditches. Molluscicide was used as a supplement. The snail control effect was evaluated by field investigation. The engineering results fulfilled the requirements of the design. The snail density decreased to 0/0.11m², and the snail area dropped to 0m² after the project. There was a statistically significant difference in the number of frames with snails before and after the project (P<0.05). Snails were completely eliminated through one year of continuous monitoring, and no new snails were found after a flood disaster. This study demonstrates that engineering specifications for environmental modification were successfully established. Environmental modification, mainly through beach and ditch remediation, can completely change the environment of Oncomelania breeding. This method of environmental modification combined with mollusciciding was highly effective at eliminating snails.

China-Africa and China-Asia Collaboration on Schistosomiasis Control: A SWOT Analysis

Schistosomiasis, a disease caused by a trematode, parasitic worm, is a worldwide public health problem. In spite of great progress with regard to morbidity control, even elimination of this infection in recent decades, there are still challenges to overcome in sub-Saharan Africa and endemic areas in Southeast Asia. Regarded as one of the most successful countries with respect to schistosomiasis control, The People's Republic of China has accumulated considerable experience and learnt important lessons in various local settings that could benefit schistosomiasis control in other endemic countries. Based on an analysis of conceived strengths, weaknesses, opportunities and threats (SWOT) of potential collaborative activities with regard to schistosomiasis in Africa and Asia, this article addresses the importance of collaborative efforts and explores the priorities that would be expected to facilitate the transfer of Chinese experience to low- and middle-income countries in Africa and Asia.

Repeated praziquantel treatments remodel the genetic and spatial landscape of schistosomiasis risk and transmission

Repeated treatments with praziquantel reduce schistosomiasis prevalence and morbidity, but transmission persists and populations often recover within a few years. To identify factors associated with persistence, we surveyed and treated all identified Schistosoma mansoni infections in two rural Brazilian communities (Jenipapo and Volta do Rio) in 2009, 2012 and 2013. Eggs were collected from all infected individuals and genotyped with 11 microsatellite markers to evaluate parasite differentiation and diversity. After successive rounds of community-wide treatment, prevalence decreased from 45% to 24% then 16%. Intensity of infection decreased by 57% over this period, and the number of eggs transmitted to the environment decreased by 92%. During all time periods the majority of eggs were excreted by those >15years of age. The incidence was 23% in 2012 and 15% in 2013, consistent with a decrease in transmission. There was little immigration or gene flow over a distance of 6km. On reinfection, infrapopulations were moderately differentiated indicating that pretreatment multilocus genotypes were not fully reacquired. The effective population size responded to census population decline more rapidly than differentiation. Reinfection was concentrated in the downstream portion of Jenipapo, consistent with the observed increased human fecal contamination. At this scale and in this area S. mansoni infections exist on a fragmented landscape with a highly focal pattern of transmission that may facilitate future elimination.

Ecotourism as a source of infection with Schistosoma mansoni in Minas Gerais, Brazil

BACKGROUND

In recent years, a new pattern of schistosomiasis transmission has been described which is related to recreational activities associated with rural or ecological tourism and migratory flows and accompanying changes in social dynamics in Brazil. The objective of this report is to describe two schistosomiasis outbreaks that occurred during the practice of rural tourism in Minas Gerais, Brazil, and review this pattern of transmission within the wider context of schistosomiasis control.

FINDINGS

The first outbreak was characterized by its high infection rate, showing that 59 % of the exposed eco-tourists became positive for infection with Schistosoma mansoni. In addition, all three disease transmitting species of intermediate host snails were found in the area. In the second outbreak, all members of one tourist family were infected and reported contact with water in a well-known tourist area. The malacological survey in the region revealed an infection rate with S. mansoni of 8.3 % among the collected snails.

CONCLUSIONS

Infection of urban dwellers that report contact with contaminated water associated with ecotourism represents a new pattern of disease transmission and dissemination. The infection with the disease at these occasions finds its expression in outbreaks of acute schistosomiasis among internal tourists to rural areas. Therefore, epidemiological surveillance in endemic areas should be aware of this schistosomiasis transmission pattern, and a multidisciplinary approach, most of all sanitation and health education measures, is required in order increase the efficiency of control strategies.