Administration of standardized drinking water containing 10 mg/liter silicon for 2 months adlibitum induced structural reorganization of the cortical and medullary layers of the thymiclobules in laboratory rats accompanied by functional activation of monocyte/macrophage cells and antigen-presenting cells was changed in morphological structures of the thymus. A possible mechanism of development of autoimmune processes under the effect of silicon is discussed.

The study of the structural and functional features of the thymus is relevant, since lymphopoiesis takes place in it, it is responsible for the effectiveness of the cellular immune response of both innate and acquired immunity. The purpose of this work was to study the morphological structures of CD3-positive structures of the thymus in laboratory animals when using calcium salt supplied with drinking water. Quantitative indicators of CD3-positive thymus cells were studied using the immunohistochemical method. For the general histological characteristics of the thymus, hematoxylin and eosin staining was used. During the experiment, the animals received daily an average of 8.1–10.2 mg /kg of calcium with drinking water. It can be stated that intake of drinking water with a calcium concentration of 235 mg / l leads to an increase in the average size of the lobular area, mainly due to the cortical substance. An increase in the relative number of large lymphocytes in the cortical substance of the thymus lobes occurs due to a decrease in the number of medium and small cell forms. As for the percentage of large and small CD3-positive cells in thymus structures, in the experimental group of animals the authors observed a decrease in small cells in the medulla and at the border between the cortical and the medullary substances due to an increase in the number of large and medium thymus cells, respectively.

The analysis of ascariasis prevalence in the Chuvash Republic for the period 1997-2017 was carried out depending on natural and anthropogenic environmental factors. As a result of multiple regression analysis including 61 factors integrated into the matrix for regression analysis, 19 factors were selected which were statistically significantly associated with the incidence of ascariasis depending on the administrative-territorial structure of the Republic. The chosen factors are divided into six groups: group 1 – factors reflecting the characteristics of water balance and the distribution of water masses in the area: (a) average annual flow (coefficient = 0.761), determining the amount of water flowing along river beds per year; b) the number of drilled wells (coefficient = 0.5133); c) the average snow cover height (coefficient = 0.2940); d) 4) the average amount of precipitation for the winter period (coefficient = 0.0073); e) the average number of sources whoch do not conform to sanitary standards and regulations (coefficient = -0.3309); f) drainage network density in km per km2 (coefficient = –0.0152), i.e. water balance and distribution of water masses in the territory of the region determine the direct impact on the incidence of ascariasis; group 2 – factors created by agricultural human activities related to soil: (a) the average annual number of poultry per 100 hectares of crops (coefficient = 0.2265); b) the specific weight of agricultural livestock areas in the entire area of agricultural land,% (coefficient = 0.2537); c) sheep stock per 100 hectares of agricultural land (coefficient = 0.1838), as it is known, livestock objects maintain viable helminth eggs for a long time; group 3 – ecological-climatic factors: a) fluctuations within the limits of baseline radiation background (coefficient = -0.2537); b) average year-round temperature (coefficient = –0,1103); c) depth of soil freezing (coefficient = –0.0412) – this group of factors is a deterrent in the spread of ascariasis because it directly affects to slow down the maturation of eggs and contributes to the early loss of vitality. As a result of cartography, a high incidence of ascariasis is noted in areas with prevalence of typical gray forest soils in combination with light gray and dark gray forest soils, in areas with gray cespitose- cryptopodzol soils. It is Krasnochetaisky region – 171,17±108,36 cases per 100 thousand population, Alikovsky region – 118,5±74.4 and Shumerlinsky region – 70,5±47,8. The minimum morbidity is in Yalchiksky region – 12,10±9,14. Conclusions: 1) the incidence of ascariasis in the territory of the Chuvash Republic is of a mosaic character. The incidence of ascariasis prevails in administrative-territorial regions located in the western part of the Chuvash Republic; 2) it is statistically proved that such a hydro-geological feature of the territory as annual runoff, including spring flooding, has a significant negative impact on morbidity; 3) such environmental and climatic factors as annual average temperature and the depth of soil freezing, have a deterrent effect on the incidence of ascariasis.

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