[Schistosomiasis prevalence in Tutóia village, Maranhão, Brazil]

Spatial distribution of the positivity of Schistosomiasis mansoni in Maranhao State, Northeastern Brazil, from 2007 to 2016

Schistosomiasis is considered one of the Neglected Tropical Diseases (NTDs), which affects around 240 million people worldwide. In Brazil, Schistosomiasis mansoni has been registered in 19 states, predominantly in rural areas. This study aimed to analyze the spatial distribution of Schistosomiasis mansoni cases in the Maranhao State from 2007 to 2016, as well as the temporal trend over this period. The data were obtained from secondary sources: Schistosomiasis Control Program of Maranhao (PCE-MA) and Information System for Notifiable Diseases (SINAN). The State Health Regions (HRs) were considered analysis units. Maranhao had a positivity rate of 3.8 for the period. The Regions that presented the highest percentages of positivity in the state were Pinheiro (7.92), Ze Doca (3.30), and Viana (3.10). Municipalities such as Bacuri, Serrano do Maranhao, and Bequimao, located in the Pinheiro HR, showed positivity rates of 16.56, 13.31, and 11.01 respectively. The spatial analysis of schistosomiasis cases showed that Maranhao has two main centers for the spread of the disease, both located in the northern portion of the state, namely the Baixada Maranhense and the east coast. This study concluded that the positivity of Schistosomiasis mansoni in Maranhao was stable over the analyzed period. The state still maintains the Baixada Maranhense micro-region as an important area for the spread of the disease reaching socially vulnerable population groups.

Socioenvironmental factors associated with Schistosoma mansoni infection and intermediate hosts in an urban area of northeastern Brazil

Schistosomiasis, which is caused by trematodes of the genus Schistosoma and by the species Schistosoma mansoni in Brazil, is transmitted primarily by Biomphalaria glabrata mollusks. Infections occur in humans and mollusks in freshwater environments contaminated with feces from infected humans. This study aimed to evaluate potential foci of schistosomiasis based on the identification of infection sites for the snails, factors that increased the human infection probability of S. mansoni infection, and the relationship of the disease with abiotic, biotic, and sociocultural factors. The study was conducted in an urban area on the northeast coast of Brazil; this location was chosen based on the following factors: the presence of B. glabrata, nearby freshwater, and the absence of sewer treatment. A parasitological analysis was performed to evaluate infections of the mollusks and residents inside the perimeter defined by the collection points. Questionnaires were applied to obtain demographic data and to identify behaviors that led to human infection. To verify the contamination of freshwater by human feces, a microbiological analysis of the water was performed at the mollusk collection points to determine the rate of contamination with fecal coliforms. A total of 10,270 B. glabrata mollusks were collected between August 2013 and August 2014, of which 8.8% were positive for S. mansoni; the prevalence ranged from 0 to 34.5% over the study period. A total of 232 coprological samples from the residents were analyzed. The S. mansoni infection prevalence rate was 16.4%, and the S. mansoni parasitic load in the infected residents was 54.9 eggs per gram of feces on average. Males were more affected by the parasite, especially in the 8-17-year-old age range. Thermotolerant coliforms were observed at the mollusk collection sites, which indicated that freshwater and sewage were in continuous contact. This contamination indicated poor sanitary conditions, as was previously observed, which could be combined with detrimental behavior due to the residents' habits. These conditions cause a predisposition for both intermediate and definitive infections of the hosts by creating a socioenvironmental scenario that is conducive to the formation and maintenance of potential schistosomiasis foci. This and similar areas deserve special attention from the government with an aim of improving sanitation services and local resident knowledge to prevent future contamination.

Spatial distribution and seasonality of Biomphalaria spp. in São Luís (Maranhão, Brazil)

Two of the three vector species of Schistosoma mansoni Sambon, 1907 in Brazil occur in the state of Maranhão: Biomphalaria glabrata (Say, 1818) and Biomphalaria straminea (Dunker, 1848). For the implementation of effective measures to combat schistosomiasis, it is necessary to identify the spatial and seasonal dynamics of these snails. Therefore, this work brought together information from malacological survey carried out in São Luís (Maranhão, Brazil) to identify the spatial and seasonal distribution patterns of Biomphalaria spp. snails. We used data from malacological surveys of the Municipal Health Secretary of São Luís, conducted between 2006 and 2013 in 23 neighborhoods. We also used data from the mollusk surveys that we conducted for 2 years (2012-2014) in four of these neighborhoods. During the 8-year period (2006-2013), 15,990 specimens of Biomphalaria spp. were collected. There was a positive association between precipitation and the abundance of mollusks of the genus Biomphalaria. During 2012-2014, a total of 2487 snail specimens were obtained (B. glabrata: 1046 specimens; B. straminea: 1426 specimens). There was a positive correlation between precipitation and B. straminea abundance. High density of human occupation and high precipitation are two factors that affect the distribution and density of Biomphalaria spp.

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