Epidemiologia da esquistossomose mansoni em Minas Gerais: padrões espaço-temporais da ocorrência e mortalidade e avaliação do desempenho de métodos de diagnóstico [manuscrit

Abstract

Schistosomiasis, caused by various species of the genus Schistosoma, remains a public health problem in tropical and subtropical regions worldwide. In Brazil, the only species present is S. mansoni, which affects approximately 1.5 million people. Accurate diagnosis of individuals in endemic areas and case mapping are two fundamental pillars in the controlling this this parasitic disease, as they enable the identification and allocation of resources to priority areas. To address these two aspects, this thesis was divided into three chapters. The first chapter aimed to analyze epidemiological characteristics, temporal trends, and spatial patterns of mortality related to schistosomiasis in the State of Minas Gerais, from 2000 to 2019. For this purpose, an ecological and time-series study was conducted using spatial analysis techniques with mortality data from S. mansoni, extracted from the Mortality Information System. Between 2000 and 2019, 1,290 deaths from schistosomiasis were recorded, with an average mortality rate of 0.33 per 100,000. Although the overall mortality rate in Minas Gerais declined significantly, an increase was observed in the mesoregions of Jequitinhonha, Vale do Mucuri, and Vale do Rio Doce. Spatial analysis revealed a shift in high-risk clusters from the central region to Vale do Rio Doce, suggesting possible failures in the diagnosis and treatment of schistosomiasis in these areas. This study contributed to a deeper understanding of the spatiotemporal dynamics of schistosomiasis mortality in the evaluated period, assisting health authorities in allocating resources more efficiently in Minas Gerais. The second chapter aimed to determine the positivity rates of S. mansoni infection, evaluate the association between socioeconomic and behavioral factors and the spatial distribution of cases and identify risk areas in three rural communities in the Brejo do Amparo district, municipality of Januária, in 2014, 2015 and 2022. The Intestinal Helminthiasis Laboratory, in collaboration with other laboratories, conducted three cross-sectional studies that included parasitological and malacological surveys and application of questionnaires. Binomial generalized linear models were used to identify factors associated with infection. High-risk clusters were mapped with the Kernel Density Estimator and Flexible Spatial Scan (FleXScan). The prevalence decreased from 45.9% in 2014 to 10.38% in 2015 after intervention, but rose again in 2022 to 26.03%. Among the risk factors, the proximity of the residences to the stream (<200m) and the absence of a toilet were significant in 2014 and 2022. In 2022, the lack of water treatment was also a risk factor, while the use of water for irrigation showed marginal significant. Spatial analysis revealed a persistent cluster in one of the communities, with a relative risk ranging from 2.03 (2014) to 4.18 (2022). These findings highlights the importance of safe water infrastructure, integrated health interventions, and adequate health education to reduce schistosomiasis in the region. The third chapter aimed to evaluate the performance of different diagnostic methods and detection specific antibodies against different antigens for S. mansoni in urine and serum of infected patients. Fecal, blood and urine samples were collected from individuals living in the district of Brejo do Amparo, Januária, MG, and processed by the Kato-Katz, Helmintex, POC- CCA and ELISA methods. The sensitivity of the methods was compared to the combination of Kato-Katz (six slides) and Helmintex as a reference standard. The analysis of two Kato-Katz slides showed a sensitivity of 42.03%, while six slides increased the sensitivity to 69.57%. Helmintex exhibited the highest sensitivity at 98.55%, and excellent agreement with the reference standard (Kappa = 0.99). The POC-CCA, for detection of circulating antigen in urine, test showed a sensitivity of 50.72% (positive trace) and 23.19% (negative trace), with weak agreement (Kappa = 0.39 and 0.27, respectively). Abnormal urinary parameters did not significantly affect the POC-CCA results. The serum ELISA assay for detecting anti-SEA IgG showed the best performance, with a sensitivity of 81.97%, specificity of 60.36% and Kappa value of 0.33, indicating weak agreement compared to the reference standard (six KK slides and Helmintex). The soluble adult worm antigen (SWAP) and its fraction (SmJ1) showed a sensitivity of 75.41% and 77.05%, respectively, with specificity of 53.89% and 42.01%. The chimeric protein of S. mansoni (qSmP) exhibited a sensitivity of 80.33%, but low specificity (43.3%) and poor agreement (Kappa = 0.1634). The presence of IgG class antibodies against S. mansoni antigens in urine was also analyzed, with low reactivity in ELISA and receiver operating characteristics (ROC) showing area under the curve (AUC) between 0.53 and 0.58, indicating low discriminant power between the control and infected individuals.