Schistosomiasis in America

Temporal trends and spatial and spatiotemporal distribution of schistosomiasis mansoni in northeast Brazil between 2005 and 2016

BACKGROUND

Schistosoma mansoni is a parasitic disease of great magnitude for Brazilian public health. We aimed to analyse the temporal trend and spatial and spatiotemporal distribution of positivity rates for schistosomiasis mansoni in northeast Brazil.

METHODS

This is a descriptive study with an ecological approach, carried out between 2005 and 2016. We calculated the positivity rate for the disease and then performed a segmented trend analysis (Joinpoint). For spatial analysis, we smoothed the positivity rates using the local empirical Bayesian method. We checked for spatial autocorrelation using Moran's global and local. Subsequently, we performed Kulldorff's space time sweep analysis.

RESULTS

In the period under review, 7 745 650 tests were performed in the northeast, of which 577 793 were positive for Schistosoma mansoni. In the historical series of positivities, it is noted that the highest rates were in Sergipe, Alagoas and Pernambuco. The states of Alagoas and Sergipe showed higher positivity in relation to the average positivity of the northeast and of Brazil. The spatial analysis maps identify clusters of high risk of schistosomiasis cases, mainly in coastal municipalities. There was also stability in positivity rates in some states and the maintenance of endemic areas.

CONCLUSIONS

Thus effective public health policies are needed in health education in order to reduce schistosomiasis positivity and improve the health conditions of the northeastern population.

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.

[Schistosomiasis, soil-transmitted helminthiases and sanitation in Latin America and the Caribbean: a systematic reviewRelación entre la prevalencia de esquistosomiasis y geohelmintiasis y las condiciones sanitarias en América Latina y el Caribe: una revisión sistemática]

Objective

To investigate the relationship between the prevalence of schistosomiasis and soil-transmitted helminthiasis with variables related to access to water, sanitation and solid waste in Latin American and Caribbean (LAC) countries.

Method

A systematic review was performed in the LILACS, PubMed, Web of Science, and SciELO databases. Studies published between 1950 and August 2021, with an ecological design and a focus on population groups (states, municipalities and/or districts), having the prevalence of infection by Schistosoma mansoni, Ancylostoma sp., Necator americanus, Ascaris lumbricoides or Trichuris trichiura as primary variable and access to water, sewage and/or solid waste as explanatory variables were included. Open access articles with full text available in English, Spanish, or Portuguese were considered. The risk of bias and the quality of the studies were assessed according to the Joanna Briggs Institute manual.

Results

Of 2 714 articles, nine were eligible, published between 1994 and 2021 and covering 22 LAC countries and 14 350 municipalities. All articles had moderate methodological quality. Environmental variables indicated an association between water supply and solid waste collection with schistosomiasis; water supply with ascariasis, trichuriasis and hookworm; and sewage with ascariasis and hookworm. Except for one article, which had regional coverage for LAC, all the others were developed in Brazil.

Conclusion

There is a clear need to expand research on the association between household and collective health conditions and parasitic diseases for all endemic countries in LAC to support environmental strategies to control these diseases.

An 11-year epidemiological analysis of schistosomiasis in Ecuador: Investigating a non-endemic, neglected, and challenging-to-identify parasitic disease

Schistosomiasis is a neglected disease caused by parasites of the genus Schistosoma and transmitted by snails of the genus Biomphalaria. At least five species have the potential to infect humans living in or visiting tropical areas worldwide. In Latin America, Schistosoma mansoni is particularly common; however, it has not been reported in Ecuador. In this study, we assess the available official data on schistosomiasis in Ecuador to describe the prevalence of this neglected disease. We conducted a nationwide study to determine the demographic and spatial distribution patterns of schistosomiasis infection in Ecuador, using hospital discharge official data as a proxy for infection incidence from 2011 to 2021. We calculated crude and age-sex-adjusted morbidity and hospital admission rates by region, province, canton, and elevation. In the last decade of available data, schistosomiasis accounted for at least 551 hospital admissions in Ecuador. Women represented 53.7% (n = 296) of cases, equivalent to 3.2 cases per 1,000,000 inhabits. The highest number of cases (61.2%, n = 337) was found in the Coastal region. However, the highest incidence rates were observed in the Amazon region's provinces of Pastaza (173.44 cases/1,000,000).

Toxic, cytotoxic and genotoxic effect of plumbagin in the developmental stages of Biomphalaria glabrata (Say, 1818-intermediate host) and cercaricidal activity against the infectious agent of schistosomiasis mansoni

BACKGROUND

Snails of the genus Biomphalaria are intermediate hosts of Schistosoma mansoni, the main etiological agent of schistosomiasis mansoni, which affects about 236.6 million people in tropical and subtropical regions of the world. The World Health Organization recommends the population control of vector snails as one of the strategies to reduce the prevalence and incidence of schistosomiasis. In this study, molluscicidal and antiparasitic activities of plumbagin, a naturally sourced naphthoquinone with a range of biological effects, were evaluated against B. glabrata and cercariae of S. mansoni.

RESULTS

After 24 h of exposure, plumbagin demonstrated molluscicidal activity at low concentrations against embryos (LC₅₀ of 0.56, 0.93, 0.68, 0.51 and 0.74 μg mL^-1 for the blastula, gastrula, trochophore, veliger and hippo stage, respectively) and adult snails (LC₅₀ of 3.56 μg mL^-1 ). There were no changes in exposed snails' fecundity or fertility; however, plumbagin was able to increase the frequency of DNA damage and the number of hemocytes, with apoptosis and binucleation being the main hemocyte alterations. In addition, plumbagin showed death of S. mansoni cercariae in the concentration of 1.5 μg mL^-1 in 60 min, while showing moderate toxicity to Artemia salina.

CONCLUSION

Plumbagin proved to be a promising substance for the control of B. glabrata population, intermediate host of S. mansoni, as well as the cercariae, infective stage for humans (definitive host), while being moderately toxic to A. salina, a crustacean widely used in ecotoxicity tests. © 2022 Society of Chemical Industry.

Teachers as multipliers of knowledge about schistosomiasis: a possible approach for health education programmes

Background

In the past decade, Brazil has significantly reduced the prevalence of schistosomiasis through a combined effort of early treatment of infected people, expansion of basic sanitation infrastructure and educational measures. Despite these efforts, in some areas, prevalence of schistosomiasis exceeds 20% of the school population, who lack knowledge of the risks of the disease. Action can be taken in schools to empower this population about their health condition. This paper describes the role of the teacher as a multiplier of knowledge about schistosomiasis and proposes two different approaches to training these teachers.

Methods

This study used mixed methods to evaluate training of teachers and educational intervention with those teachers’ pupils. Two training courses, each with 40 h of face-to-face activity, were offered to 19 teachers, using two different but complementary approaches, based on theoretical references and specific educational strategies: Critical Pedagogical Approach (Training Course I, held in 2013) and Creative Play Approach (Training Course II, held in 2014).The courses included classroom activities, laboratory and field work. After the training, the teachers conducted activities on schistosomiasis with their pupils. These activities involved constructing educational materials and cultural productions. The pupils’ knowledge about the disease was evaluated before the activities and 12 months later. The teachers’ acceptance and perceptions were assessed through structured interviews and subsequent thematic analysis. The Shistosoma mansoni infection status of teachers and their students was also assessed using the Kato Katz stool test.

Results

The parasitological study showed 31.6% of the teachers and 21.4% of the pupils to be positive for S. mansoni. The teachers’ knowledge of important aspects of schistosomiasis transmission and prevention was fragmented and incorrect prior to the training. The teachers’ knowledge changed significantly after the training and they were strongly accepting of the pedagogical methods used during the training. The level of their pupils’ knowledge about the disease had increased significantly (p < 0.05). However, pupils responded that, even after the educational activities, they still had contact with the city’s contaminated waters (p > 0.05).

Conclusions

The results of this study underline the importance of schools and teachers as partners in controlling and eliminating schistosomiasis. Teacher training on the disease significantly increases their pupils’ knowledge, reflecting empowerment with regard to local health conditions.

Schistosoma mansoni infection decreases IL-33-mRNA expression and increases CXCL9 and CXCL10 production by peripheral blood cells

Schistosoma mansoni infections, particularly egg antigens, induce Th2-dominant granulomatous responses accompanied by remarkable immunoregulatory mechanisms that avoid intense fibrosis. Interleukin (IL)-33 is a cytokine that stimulates the early activation of Th2 responses, and its soluble ST2 receptor (sST2) avoids granulomatous response, as well as CXCL9 and CXCL10 chemokines that have antifibrotic activity. However, in schistosomiasis, these molecules have not been suitably studied. Therefore, this study aimed to measure IL-33 and sST2 RNA, cytokines, and chemokines in peripheral blood cultures from individuals living in schistosomiasis-endemic areas. Peripheral blood cells from individuals with S. mansoni (n = 34) and non-infected individuals (n = 31) were cultured under mitogen stimulation. Supernatant chemokines and cytokines were evaluated using a cytometric bead array, and IL-33 and sST2 mRNA expression was measured using qPCR. Infected individuals showed higher levels of CXCL8, CXCL9, CXCL10, IFN-γ, TNF-α, IL-6, IL-2, IL-4, and IL-10; there was a lower expression of IL-33 mRNA and similar expression of sST2mRNA in infected than non-infected individuals. In conclusion, for the first time, we demonstrated lower IL-33mRNA expression and high levels of the antifibrotic chemokines CXCL9 and CXCL10 in schistosomiasis mansoni, which could control exacerbations of the disease in individuals from endemic areas.

The Effect of Different Formulations of Praziquantel in Reducing Worms in the Prepatent Period of Schistosomiasis in Murine Models

Schistosomiasis is a widely distributed parasitic disease and one of the most important neglected tropical diseases globally, for which Praziquantel® (PZQ) is the only available treatment. In this context, tests with new PZQ formulations become relevant for disease control. This study evaluated the effects of PZQ treatment in the prepatent phase of schistosomiasis using two formulations: nanoencapsulated (PZQ-NANO) and active pharmaceutical ingredient (PZQ-API). Five experimental groups were established, for which the following serological parameters were evaluated: ALT, AST, ALP, and TP. Animals treated with PZQ-API at 15 and 30 days post-infection showed decreased eggs per gram of feces (EPG) compared to untreated infected animals. The same animals showed reductions of 63.6 and 65.1%, respectively, at 60 days post-infection. Animals treated with PZQ-NANO experienced no significant changes in EPG at any time of observation. Animals treated with either PZQ-API or PZQ-NANO had higher ALT and AST levels in the patent period (60 and 90 days post-infection). Treatment with PZQ, either API or NANO, at 15 days post-infection reduced AST, ALT, and TP levels. It is concluded that prepatent treatment with PZQ-API can reduce the parasite load of infected animals and that treatment at 15 days post-infection can prevent increased serum levels of ALT, AST, and TP.

Urban schistosomiasis: An ecological study describing a new challenge to the control of this neglected tropical disease

Background

Social and environmental vulnerabilities contribute to the persistence and increase of Schistosomiasis, which has been a public health problem in Brazil and worldwide. In this study, we aimed to monitor the entry, installation, and maintenance of schistosomiasis transmission in an urban area on the Brazilian coast over two decades (2000-2010/2010-2020).

Methods

This population-based cross-sectional study was conducted in Porto de Galinhas, state of Pernambuco, Brazil, to investigate the dynamics of schistosomiasis transmission in the urban area. Through 3 malacological and parasitological surveys and using geoprocessing technologies, schistosomiasis transmission foci (STF), as well as cases of the disease were identified and quantified. Statistical and geoprocessing tools were used to analyse the data.

Findings

Overall, the number of STF decreased from 15 (2000) to 11 (2010) and then to 9 (2020). Although the infection ratio of snails in 2000 has decreased from 16·1% to 5·8% in 2010, we observed an increase to 7·2% in 2020. Additionally, 6,499 individuals were analysed (2012 in 2000; 2459 in 2010, and 2028 in 2020) and the prevalence of human infection has decreased over years, from 32·5% (2000), 16·6% (2010) to 8·8% (2020). The disorderly urbanization process was directly related to the spatial distribution of STF and schistosomiasis cases, causing a new scenario where people became infected by walking on unpaved and flooded streets.

Interpretation

Although we observed a decreasing in schistosomiasis cases and STF, this NTD became a health problem related to urbanization in the study area. The challenge to overcome this new sort of transmission will require a greater understanding of the disorderly migration, spatial occupation, and degradation of the environment.

Funding

National Council for Scientific and Technological Development (CNPq), Ministry of Science, Technology, Innovations and Communications, Brazil.

Basic and associated causes of schistosomiasis-related mortality in Brazil: A population-based study and a 20-year time series of a disease still neglected

Background

Schistosomiasis is a persistent public health problem in Brazil. Regardless advances in diagnosis and mass treatment, schistosomiasis has a severe impact on morbimortality in the country and remains a neglected tropical disease. Herein, we assessed the basic and associated causes of schistosomiasis-related deaths and the temporal and spatial patterns of mortality from the disease in Brazil between 1999 and 2018.

Methods

We conducted an ecological and time series study. The segmented log-linear regression model was applied to assess time trends, considering all deaths recorded in the category B65/ICD-10. Additionally, we elaborated maps of mortality rates from schistosomiasis in Brazil.

Results

A total of 4168 schistosomiasis-related deaths were recorded in Brazil in this period, as an associated cause. Time trend analysis revealed an increase in the average age of deaths from schistosomiasis (annual percentage change (APC) = 0.84), and stable trend in Brazil (APC = 0.31). Concerning schistosomiasis-related deaths, we observed disorders related to the digestive system, liver diseases, septicemias, and chronic diseases. Surprisingly, there were deaths caused by non-endemic Schistosoma species in Brazil. Also, municipalities from non-endemic areas in Brazil presented schistosomiasis-related deaths.

Conclusion

Altogether, our analyses demonstrated that schistosomiasis remains a significant cause of death in Brazil, and it is increasing in some areas, especially in the Northeast region. Additionally, women and the elderly showed a stable time trend of deaths. Thereby, it urgently requires improvements in the control programs strategies, in the sense of an effective reduction in cases and deaths from the disease in Brazil.

Identification of Risk Areas for Intestinal Schistosomiasis, Based on Malacological and Environmental Data and on Reported Human Cases

The aim of the present study was to use an integrated approach for the identification of risk areas for Schistosoma mansoni transmission in an area of low endemicity in Minas Gerais, Brazil. For that, areas of distribution of Biomphalaria glabrata were identified and were related to environmental variables and communities with reported schistosomiasis cases, in order to determine the risk of infection by spatial analyses with predictive models. The research was carried out in the municipality of Alvorada de Minas, with data obtained between the years 2017 and 2019 inclusive. The Google Earth Engine was used to obtain geo-climatic variables (temperature, precipitation, vegetation index and digital elevation model), R software to determine Pearson's correlation and MaxEnt software to obtain an ecological model. ArcGis Software was used to create maps with data spatialization and risk maps, using buffer models (diameters: 500, 1,000 and 1,500 m) and CoKriging. Throughout the municipality, 46 collection points were evaluated. Of these, 14 presented snails of the genus Biomphalaria. Molecular analyses identified the presence of different species of Biomphalaria, including B. glabrata. None of the snails eliminated S. mansoni cercariae. The distribution of B. glabrata was more abundant in areas of natural vegetation (forest and cerrado) and, for spatial analysis (Buffer), the main risk areas were identified especially in the main urban area and toward the northern and eastern extensions of the municipality. The distribution of snails correlated with temperature and precipitation, with the latter being the main variable for the ecological model. In addition, the integration of data from malacological surveys, environmental characterization, fecal contamination, and data from communities with confirmed human cases, revealed areas of potential risk for infection in the northern and eastern regions of the municipality. In the present study, information was integrated on epidemiological aspects, transmission and risk areas for schistosomiasis in a small, rural municipality with low endemicity. Such integrated methods have been proposed as important tools for the creation of schistosomiasis transmission risk maps, serve as an example for other communities and can be used for control actions by local health authorities, e.g., indicate priority sectors for sanitation measures.

Population-based, spatiotemporal modeling of social risk factors and mortality from schistosomiasis in Brazil between 1999 and 2018

Schistosomiasis remains a significant public health concern in Brazil. To identify areas at, and social determinants of health (SDH) associated with, high-risk for schistosomiasis-related mortality from Brazil, we conducted a spatial and spatiotemporal modeling assessing all deaths confirmed in Brazil between 1999 and 2018. We used the segmented log-linear regression model to assess temporal trends, and the local empirical Bayesian estimator, the Global and Local Moran Index for spatial analysis. A total of 12,251 schistosomiasis-related deaths were reported in this period. Within the Mortality Information System (SIM) of the Brazilian Ministry of Health, the states of Alagoas (AL), Pernambuco (PE) and Sergipe (SE) recording the highest mortality rates: 2.21, 1.92 and 0.80 deaths/100,000 inhabitants, respectively. Analyses revealed an increase in the mean age of schistosomiasis-related deaths over the time assessed (APC = 0.9; p-value<0.05). Spatial analysis identified a concentration of municipalities presenting high risk of schistosomiasis-related mortality along the coastline of PE and AL. Similarly, we identified the formation of high space-time clusters in municipalities in the states of PE, AL, SE, Bahia, and Minas Gerais. Finally, mortality rates showed a significant correlation with 96.96% of SDH indices. The data reveal additional important changes in schistosomiasis-related deaths in Brazil between 1999 and 2018, such as a slow reduction among males (unlike females that displayed no change). Regardless, our analyses indicates that schistosomiasis continues to have the greatest detrimental impact in poor regions of Brazil and suggest the need for enhancement of current control measures to accelerate progress.

Quality of life and quality-adjusted life years of chronic schistosomiasis mansoni patients in Brazil in 2015

Background

Measures of health-related quality of life (HRQoL) have been used to express the impact of neglected diseases and to generate indicators for health economic assessments. Schistosomiasis mansoni is a neglected disease with various clinical manifestations, including severe repercussions, caused by parasitic worms. Here we describe the quality of life of chronic schistosomiasis mansoni patients and estimate the quality-adjusted life years (QALYs) associated with chronic schistosomiasis mansoni in Brazil in 2015.

Methods

A HRQoL study was carried out using the three-level European Quality of Life 5-Dimensions (EQ-5D-3L) questionnaire in 147 chronic schistosomiasis mansoni patients at an outpatient monitoring facility of an endemic state for schistosomiasis.

Results

Losses in HRQoL were observed in all five dimensions of the EQ-5D-3L. Patients >60 y and 40-49 y of age reported the highest frequencies of problems. The average utility index was 0.71, and the median index was significantly lower among female patients and patients with comorbidities (0.68; p<0.05) compared with the entire sample. Approximately 26.7 QALYs were estimated for the study population and 31.2 QALYs for the chronic schistosomiasis mansoni patients in Brazil.

Conclusions

The advanced forms of schistosomiasis mansoni, even during treatment, contribute to important health losses in the population dealing with the disease.

Usnic acid potassium salt from Cladonia substellata (Lichen): Synthesis, cytotoxicity and in vitro anthelmintic activity and ultrastructural analysis against adult worms of Schistosoma mansoni

We report for the first time the in vitro effect of Potassium Salt, derived from Usnic Acid (PS-UA), isolated from the lichen Cladonia substellata Vanio, on couples of Schistosoma mansoni. As schistosomicide parameters, we evaluated mortality, motility, cell viability of the worms and tegument changes by scanning electron microscopy (SEM). Exposure to a concentration of 100 μM caused 75% mortality after 3 h. After 6 h, changes in motility in concentrations of 50 and 25 μM are evidenced. After 12 h and 24h, the concentrations of 50 and 100 μM caused 6.25% and 87.5% and 50% and 100% mortality, respectively. PS-UA reduced the cell viability of the worms by 27.36% and 52.82% at concentrations 50 and 100 μM, respectively. Through SEM we observed progressive dose-and time-dependent, alterations such as swelling, blisters, dorsoventral contraction, erosion until disintegration of the tubercles in the tegument of male and female. PS-UA did not alter the viability of human peripheral blood mononuclear cells and showed high selectivity indices (IC₅₀ > 200 μM). Our results indicate that PS-UA represents a possible candidate for a new anthelmintic drug in the control of schistosomiasis.

Modulation of Allergic Reactivity in Humans Is Dependent on Schistosoma mansoni Parasite Burden, Low Levels of IL-33 or TNF-α and High Levels of IL-10 in Serum

Helminth infections and allergies are characterized by a predominant type-2 immune response. In schistosomiasis, the Th-2 response is usually accompanied by induction of immunoregulatory mechanisms that contribute to worm survival and less severe schistosomiasis. Although helminth-induced immunomodulatory mechanisms seem to affect atopy, epidemiological studies on the relationship between helminths and allergy have been inconsistent, and data suggest that the modulatory effects may be influenced by helminth species, chronicity of infection, and parasite burden. Here we performed a cross-sectional study to investigate the effects of Schistosoma mansoni parasite burden and immune response on allergic reactivity of individuals living in a schistosomiasis endemic area in Brazil. Fecal samples from the participants were collected for extensive parasitological examinations by spontaneous sedimentation, Kato-Katz, Helmintex and Saline Gradient tests and molecular detection of S. mansoni by qPCR. Additionally, the concentrations of cytokines and chemokines, total IgE and IgE-reactivity to common house dust allergens were quantified from serum samples. IgE reactivity to dust allergens was detected in 47 individuals (23.8%), and 140 individuals (54.4%) were diagnosed with S. mansoni infection. Most of the infected population (108 individuals) presented very low parasite burden (≤12 eggs/g of feces). The frequency and intensity (p ≤ 0.03) of allergic reactivity were lower in S. mansoni-infected compared with non-infected individuals. Multivariable logistic regression models adjusted by age revealed that allergic reactivity was positively associated with low IL-10 response (OR, 4.55, 95% CI, 0.56–7.36) and high concentration of the inflammatory mediators IL-33 (OR, 2.70, 95% CI, 1.02–7.15) or TNF-α (OR, 6.88, 95% CI, 0.32–143.39) in serum, and inversely associated with S. mansoni infection (OR, 0.38, 95% CI, 0.16–0.87). Most importantly, the logistic regression demonstrated that the modulatory effects of Schistosoma infection depend on parasite burden, with individuals infected with ≤12 eggs/g of feces showing allergic IgE-reactivity similar to non-infected individuals Altogether, our data show that immunomodulation of allergic reactivity depends on S. mansoni burden, low type-2 inflammatory response, and high level of IL-10.

Systemic Cytokine and Chemokine Profiles in Individuals With Schistosoma mansoni Infection and Low Parasite Burden

Intestinal schistosomiasis, caused by the parasitic trematode Schistosoma mansoni, is a chronic disease and the prolonged and continuous exposure to S. mansoni antigens results in a deviation of the host's immune response. For diagnosis, the Kato-Katz (KK) method is recommended, however, this method showed low accuracy in areas of low endemicity. This study aimed to characterize the cytokine and chemokine profile of individuals with an extremely low parasite load (<4 eggs per gram of feces), e.g., individuals who were detected by alternative parasitological methods, such as the saline gradient and/or Helmintex®. In order to search for immunological markers for infection, the immunological profile in serum samples of these individuals was then compared with patients detected with the KK method and with a higher parasite load and with individuals repetitively negative by extensive stool exams. The study was conducted in Northern Minas Gerais in a rural area of the Municipality of Januária. Serum samples of a total of 139 parasitologically well-characterized individuals were assessed for the following immunological markers by commercially available immunoassays: TNF-α, IL-1β, IL-6, IL-17A, IL-5, IL-10, IL-13, IL-33, IL-27, CCL3, CCL5, CXCL10, CCL11, and CCL17. As a result, there were no significant differences in concentrations or frequencies for immunological markers between egg-negative individuals or individuals with ultra-low (<4 epg) or low (4-99 epg) parasite loads. However, we found significant correlations between egg counts and eosinophil counts and between egg counts and IL-1β or TNF-α concentrations. The most striking alterations were found in individuals with the highest parasite load (≥100 epg). They had significantly higher TNF-α concentrations in serum when compared with individuals with a low parasite load (4-99 epg) and CCL17 concentrations were significantly elevated when compared with egg-negative individuals. Radar diagrams of frequencies for cytokine and chemokine responders in each infection group confirmed a distinct profile only in the infection group with highest parasite loads (≥100 epg).

The South-American distribution and southernmost record of Biomphalaria peregrina-a potential intermediate host of schistosomiasis

Schistosomiasis remains a major parasitic disease, endemic in large parts of South America. Five neotropical species of Biomphalaria have been found to act as intermediate hosts of Schistosoma mansoni in natural populations, while others have been shown to be susceptible in experimental infections, although not found infected in the field. Among these potential intermediate hosts, Biomphalaria peregrina represents the most widespread species in South America, with confirmed occurrence records from Venezuela to northern Patagonia. In this study, we report the southernmost record for the species at the Pinturas River, in southern Patagonia, which finding implies a southward reassessment of the limit for the known species of this genus. The identities of the individuals from this population were confirmed through morphological examination, and by means of two mitochondrial genes, cytochrome oxidase subunit I (COI) and 16S-rRNA. With both markers, phylogenetic analyses were conducted in order to compare the genetic background of individuals from the Pinturas River with previously genetically characterized strains of B. peregrina from various South-American locations. In addition, we produced a potential distribution model of B. peregrina in South America and identified the environmental variables that best predict that distribution. The model was estimated through a maximum entropy algorithm and run with occurrence points obtained from several sources, including the scientific literature and international databases, along with climatic and hydrographic variables. Different phylogenetic analyses with either the COI or 16S-rRNA sequences did not conflict, but rather gave very similar topological organizations. Two major groups were identified, with sequences from the Pinturas River grouping together with haplotypes from subtropical and temperate regions. The model developed had a satisfactory performance for the study area. We observed that the areas with higher habitat suitability were found to be mainly linked to subtropical and temperate regions of South America between 15° and 45° south latitude, with different moderate- and low-suitability areas outside this range. We also identified the coldest temperatures as the main predictors of the potential distribution of this snail. Susceptibility surveys would be required to evaluate if southern populations of B. peregrina still retain their potential as intermediate hosts of S. mansoni.