The Estrada Real project and endemic diseases: the case of schistosomiasis, geoprocessing and tourism

Spatial analysis of areas at risk for schistosomiasis in the Alto Tietê Basin, São Paulo, Brazil

The present study identified locations with the presence of Biomphalaria and the areas at risk for Schistosoma mansoni, the etiological agent of schistosomiasis, in the Metropolitan Region of São Paulo (MRSP), located in the Alto Tietê Basin (ATB), São Paulo, Brazil. The study area comprises floodplains of the Tietê River from its source, in Salesópolis, to Rasgão Dam, in Pirapora do Bom Jesus, covering 39 municipalities. Data from the planorbidic chart of the malacology laboratory of the Endemic Control Superintendence for 2008-2016 were used, as well as data from the notification forms of cases of human schistosomiasis in 2006-2015 made available by the Epidemiological Surveillance Groups of Mogi das Cruzes and Osasco, and by the Health and Surveillance Coordination of São Paulo. These data were used to generate maps of the distribution of Biomphalaria, of the scanning analysis, of the Gi statistics of the autochthonous and imported schistosomiasis cases, and of the flow of cases imported from other Brazilian states and municipalities in the state of São Paulo to the study area. A total of 21,618 specimens of the genus Biomphalaria were captured and six species were identified. Biomphalaria tenagophila was the predominant species in the region and of greatest epidemiological importance as it is the main responsible for the transmission of the disease in the state of São Paulo. A total of 3,623 cases of schistosomiasis were reported in the study area, and São Paulo and Guarulhos were the municipalities with the highest number of autochthonous and imported cases during the study period. The imported cases originated from 21 Brazilian states plus the Federal District and from 51 municipalities in São Paulo state located outside the study area. Autochthonous clusters with high risk for the occurrence of schistosomiasis were identified in the municipalities of São Paulo, Guarulhos, Santa Isabel/Mogi das Cruzes/Arujá, and Cotia/Itapevi. Clusters of imported cases were also identified in Itaquaquecetuba, at the border of Cotia/Itapevi and Suzano/São Paulo/Mogi das Cruzes. The presence of B. tenagophila in the ATB and in the clusters of autochthonous cases herein identified, although not carrying schistosome larvae, represents a risk for the transmission of infectious agents. The human population in the MRSP mainly occupies the lowlands of the Tietê River, which are locations with poor coverage of basic sanitation. Therefore, measures for the control and surveillance of schistosomiasis such as educational actions, improvements in basic sanitation, and the malacological and epidemiological monitoring of these areas are extremely important.

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.

Predictive risk mapping of schistosomiasis in Brazil using Bayesian geostatistical models

Schistosomiasis is one of the most common parasitic diseases in tropical and subtropical areas, including Brazil. A national control programme was initiated in Brazil in the mid-1970s and proved successful in terms of morbidity control, as the number of cases with hepato-splenic involvement was reduced significantly. To consolidate control and move towards elimination, there is a need for reliable maps on the spatial distribution of schistosomiasis, so that interventions can target communities at highest risk. The purpose of this study was to map the distribution of Schistosoma mansoni in Brazil. We utilized readily available prevalence data from the national schistosomiasis control programme for the years 2005-2009, derived remotely sensed climatic and environmental data and obtained socioeconomic data from various sources. Data were collated into a geographical information system and Bayesian geostatistical models were developed. Model-based maps identified important risk factors related to the transmission of S. mansoni and confirmed that environmental variables are closely associated with indices of poverty. Our smoothed predictive risk map, including uncertainty, highlights priority areas for intervention, namely the northern parts of North and Southeast regions and the eastern part of Northeast region. Our predictive risk map provides a useful tool for to strengthen existing surveillance-response mechanisms.

Malacological survey of Biomphalaria snails in municipalities along the Estrada Real in the southeast of the State of Minas Gerais, Brazil

INTRODUCTION

The increasing practice of ecotourism and rural tourism in the State of Minas Gerais, Brazil, highlights the importance of studies concerning the occurrence of potential intermediate hosts of Schistosoma mansoni. This study aimed to identify species of Biomphalaria snails in municipalities along the Estrada Real, an important Brazilian tourism project.

METHODS

The specimens were collected in different water collections of 36 municipalities along the Estrada Real in the southeast of the State of Minas Gerais. Biomphalaria species were characterized using both morphological and molecular approaches. The research was conducted between August 2005 and September 2009 and all the sites visited were georeferenced using GPS.

RESULTS

Six Biomphalaria species were found in 30 of the 36 municipalities studied: glabrata, tenagophila, straminea, peregrina, occidentalis and schrammi. The first three species of Biomphalaria, recognized as intermediate hosts of S. mansoni, were present in 33.3%, 47.2% and 8.3% of the municipalities studied, respectively. The mollusks were found in different types of water collections and no infection by S. mansoni was detected. The highest occurrence of Biomphalaria concentration was verified in the area covered by the Caminho Novo route (Diamantina/MG to Rio de Janeiro/RJ).

CONCLUSIONS

Considering the occurrence of schistosomiasis in the State of Minas Gerais and the socioeconomic repercussions involved in the Estrada Real Project, this work focuses on the vulnerability of water collections due to the presence of Biomphalaria mollusks and emphasizes the need for epidemiological surveillance and sanitary and educational measures integrated with the local community and tourism sectors.