Spatial analysis of areas at risk for schistosomiasis in the Alto Tiete Basin, Sao 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 Sao Paulo (MRSP), located in the Alto Tiete Basin (ATB), Sao Paulo, Brazil. The study area comprises floodplains of the Tiete River from its source, in Salesopolis, to Rasgao 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 Sao 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 Sao 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 Sao Paulo. A total of 3,623 cases of schistosomiasis were reported in the study area, and Sao 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 Sao Paulo state located outside the study area. Autochthonous clusters with high risk for the occurrence of schistosomiasis were identified in the municipalities of Sao Paulo, Guarulhos, Santa Isabel/Mogi das Cruzes/Aruja, and Cotia/Itapevi. Clusters of imported cases were also identified in Itaquaquecetuba, at the border of Cotia/Itapevi and Suzano/Sao 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 Tiete 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.