Characterization of the natural foci of Congo-Crimean hemorrhagic fever on the territory of Ukraine

The natural foci of the Congo-Crimean hemorrhagic fever (CCHF) in Ukraine were characterized by their geographical factors. The circulation of CCHF virus was found to occur mainly in forest and forest-steppe zones irrespective of the location of administrative regions. The territories found to be most favorable for the prolonged existence of the focus of CCHF were those having high humidity. The possibility of using geoinformation technologies for the correction of the boundaries of natural foci, the evaluation of the influence of geographical factors on the circulation of the virus was shown.     

Activation of natural tularemia foci of the field-meadow and steppe types on the territory of Tula Province 1977-1978

Natural tularemia foci of the meadow and steppe type are extremely stable and become active in those years when the most favourable living conditions for rodents appear. For the first time during the last 30 years a great increase in the number of common voles, accompanied by widely spread epizooty covering the whole territory of the Tula region, was observed. House mice, common field mice, harvest mice and black rats were also involved in this epizooty and 235 tularemia patients with all clinical forms of the disease were registered, the pulmonary form of the disease being prevalent. The cases of the disease were observed among both urban and rural population. In spite of a high morbidity rate, no cases of group infection were registered in domestic conditions and among agricultural workers due to the existence of the numerous immune layer among the population. The formation of this layer resulted from planned vaccinal prophylaxis covering, on the average, 86.3% of the rural population of the region.     

Tularemia in inactive natural foci

The data on the epidemiological and epizootological manifestations of tularemia on the territory of the Ulyanovsk region are presented. The characteristics describing the process of the of Francisella tularensis circulation as well as the environmental objects, most important for the manifestations of tularemia infection, are given.     

Natural foci of leptospirosis on the territory of Moscow in 1995 - 2004

The results of ten-year observations of the natural foci of leptospirosis on the territory of Moscow are presented. Information on the foci, the main species of small mammals (the reservours of the infection), the etiological structure of leptospires, circulating among rodents and insectivores, is given.     

Occurrence of natural tularemia foci in Kamchatka

The focus of tularemia in the Ust-Kamchatsky region belongs probably to the flood-plain and swamp type with muskrats and tundra voles being the main carriers. In autumn 1980 for the first time three cultures were isolated in this region: 1 from a tundra vole and 2 from muskrats. The presence of antibodies to tularemia antigen in Norway rats was revealed in the passive hemagglutination test.     

Methodological aspects in the study of the natural foci of zoonoses

Conceptions of different authors on the natural focus of zoonosis infections are analysed and an improved definition of this phenomenon is proposed. The natural focus of disease is the antropoecosystem of certain hierarchic level (biosocial system), where the existence and appearance of the infection agent is supported and the disease is realized in people at certain infection rate.     

Modern problems in the study of tick-born encephalitis natural foci

A new conception of natural focus as anthropo-parasitic system is given by an example of tick-born encephalitis. Problems of natural foci classification and zoning of focal territories, as well as patterns of ecological relations in these systems, are considered. Causes and factors affected expansion of the infection are analyses.     

The self-maintenance of natural foci of leptospirosis

The specificity of infection of individual species of small mammals with definite serogroups of leptospires has been shown. The intensity of the epizootic process has been found to depend on the number of animals in the population. The mechanisms of the self-regulation of the epizootic process in natural foci are explained.     

The types of the epidemic manifestations of cholera on the territory of the USSR

On the basis of the analysis of cholera cases for the period of 1965-1989 three main main types of epidemic manifestations of this infection on the territory of the USSR were determined with due attention to the complex of data, characterizing the intensity and types of the epidemic process, the danger of the outbreak and spread of cholera. This made it possible to differentiate and decrease the complex of prophylactic measures, depending on the type of the territory.     

Determination of natural foci of tularemia in the Tuva ASSR]

Eleven strains of tularemia causative agents were isolated in 1974 in bacteriological study of ixodes ticks Dermacentor nuttalli (13088 in all) by biotests on albino mice. Tularemia was confirmed retrospectively in two humans who contracted the disease from ondatra cadavers. Skin allergic test with tularin was used to examine 1733 residents of seven populated localities; a positive result was obtained in 2 persons. Finally, in examination of 240 sera of cattle agglutination reaction proved to be positive in 6 cases in titres of from 1:20 to 1:80. Thus, natural nidality of tularemia in Tuva was established for the first time.