Esquistossomose: focos de transmissão, espécies de biomphalaria sp. envolvidas e fatores socioambientais em Pitimbu/PB, Brasil

Abstract

Classified as a neglected tropical disease because it is present in places with a tropical climate and affects poor populations, schistosomiasis is still a persistent public health problem. Snails of the genus Biomphalaria are organisms closely linked to the life cycle and transmission dynamics of Schistosoma mansoni because they behave as intermediate hosts and transmitters of the parasite. Environmental and ecosystem factors such as temperature, rainfall, salinity, pH, organic matter in the water; as well as socioeconomic variables such as sanitation, water supply, education, work, income, tourism are conditioning and determining drivers for maintaining the survival of snails and helminth and, consequently, for the spread of S. mansoni. In this perspective, the present study aimed to investigate the interference of local environmental and socioeconomic factors in the incidence and maintenance of schistosomiasis in the municipality of Pitimbu/PB, in the localities Acaú-Mucuim and Taquara. In this study, environmental and social data and samples were collected for laboratory analysis in different climatic periods - drought and rainy -. The environmental data were related to the local climate - rainfall and temperature - and to the ecosystem variables of the surveyed water collections - pH, temperature, turbidity and salinity -. The social data were information about the social, demographic, structural and economic situation of the municipality with search in databases, in addition to the application of a social questionnaire to collect information about the perception of populations about schistosomiasis. Laboratory data were obtained through physical-chemical analysis of the water, species differentiation (shell analysis) and release of cercariae from snails (exposure to light) and positivity in the observation of S. mansoni eggs in the collected faeces (Kato-Katz). The data were treated and analyzed using descriptive statistics using Microsoft Excel 2016 and PAST 4.03 software. Eight collection points were georeferenced, four in Acaú-Mucuim and four in Taquara and produced, using the QGIS 3.10 software, risk maps for each water collection, which were characterized in several items. It was found that, in general, the characteristics of water collections are conducive to the installation and survival of Biomphalaria. A higher population density of the species B. glabrata (12.24 snails/scoops) was observed with mortality rates lower than B. straminea among the 1130 specimens collected. There was no correlation between the population density of planorbids and the rainfall index (p = 0.476) and the local temperature (p = 0.235) in the different climatic periods. Three times more snails were estimated to be infected in the rainy season (n = 56). Even with the variation of the ecosystem factors temperature (p <0.001), pH (p <0.001), salinity (p> 0.05), turbidity (p = 0.010) between the studied periods, the waters of the collection stations showed that the environments are compatible with the colonization of molluscs, favorable to the life cycle of S. mansoni and further suggests that Biomphalaria manages to maintain itself in some conditions outside the theoretical survival range. Based on the results obtained, the risk maps produced warn in relation to the population density of planorbids, snail infection rates and purposes of use for each season studied. According to the database consulted, only 17% of the municipality's population has an adequate sewage network and that a large part of the population has an occupation that can boost the transmission of the parasite. 363 questionnaires were applied between the studied districts. There was an association between educational level and disease involvement (p = 0.0094), and on the other hand, there was no association between receiving professional guidance and knowledge about transmission (p = 0.6195) and prevention of schistosomiasis (p = 0.3875). The use of water collections varies between cultural use and use by necessity. Of those who use these waters, 65.8% in Taquara and 50.7% in Acaú-Mucuim use them in the early morning. 60.8 and 58.1% of those who claimed to know the transmitting agent, managed to make the visual identification correctly in Acaú-Mucuim and Taquara, respectively (p <0.05). The prevalence of positivity calculated for the coproscopic examinations performed corroborates with the data from the databases demonstrating that the Taquara area is classified as endemic (14.54%), but the Acaú- Mucuim area is outside this classification (4.48%). Efforts to control this disease must be carried out as a broad set of mitigating and aggravating factors that must be considered for the production of integrated strategies and for the taking of future public health measures.