Avaliação do controle da transmissão e reinfecção por Schistosoma mansoni em área endêmica após intensa prospecção de casos de infecção e tratamento quimioterápico

Abstract

A search for cases of schistosomiasis was conducted among the 203 residents of village of Pedra Preta, municipality of Montes Claros, Minas Gerais, in the period of 2013-2016, of individuals who had already participated in a thorough survey of cases through the conjugation of parasitological methods in 2008 (n=175). In 2013, two studies were consolidated based on the actions taken. In study 1, the objective was to evaluate, after seven years, the impact of the actions carried out in 2008, the incidence of cases, the infection intensity and freshwater planorbis malacofauna. An association of Kato-Katz diagnostic methods (24 slides of 1 g feces) and two procedures with the Saline Gradient technique (1 g feces) were carried out. The 66 patients infected and treated in 2008 and 12 children born in 2007-2012 presented negative results. A negative infection rate of 93.93% (66 to 4) and an incidence rate of 2.29% (4/175) were found among individuals with a negative result in 2008. These four showed low amounts of eggs per gram of feces (1, 6, 7 and 19). All subjects answered epidemiological questionnaires about risk behavior by contact with natural waters at risk. All households had dry pits and domestic water supply coming from a tubular well. A severe drought in the region during the period studied led to the complete loss of the water from the main transmission focus (pond) in several months of each year considered. The malacological surveys showed a gradual reduction of Biomphalaria glabrata specimens and a clear dominance of B. straminea was verified at the end of the experiment, and none was shedding cercariae. It can be inferred that there was a remarkable decrease in the transmission strength of the disease after an intense search for reinfection cases of the subjects treated in 2008, under the ecoepidemiological conditions of the focus studied and in the period observed. In study 2, a cross-sectional study from a cohort (2013-2016), the objective was to identify the prevalence and risk factors associated with S. mansoni infection. The prevalence of S. mansoni infection was 3.9% (8/203), being that 78.8% of the population had contact with the natural water collection at risk. The following behaviors were associated with the infection: fetching water at the river/pond (OR=11.846) and crossing the dam or the Buruti Seco river (OR=8.366). The identification of the fingerprint of the area studied has contributed to the control of the disease and could contribute to the planning of preventive actions regarding S. mansoni infection.