Changes of Conditions of Existence of the Natural Tularemia Focus in the Northern Area of the Volgo-Akhtubinsk Floodplain Area in Connection with the Construction of the Volgograd Hydroelectric Power Station

摘要

Considerable changes were noted in the biocenosis of the natural tularemia focus as a result of constructing the Volgograd Hydro-Electric Power Station and due to the changes of the hydrological regimen of the Volga river, particularly the appearance of an additional winter inundation. These biocenosis changes consisted in a marked reduction of the Arvicola terrestris L. and of other rodent population, as well as a drop of the number of D. marginatus and Rh. rossicus ticks. Bacteriological examination of 8,863 sexually mature D. marginatus and 55 sexually mature Ph. rossicus obtained from the cattle at the floodplain area (where tularemia-infected ticks of the same species were regularly revealed prior to the building of the Volgograd Hydro-Electric Power Station) gave negative results. This should be regarded as a sign of decline of the natural focus of this infection. Examination of the population of the Volgo-Akhtubinsk floodplain area, by means of the skin tularemia demonstrated that the number of persons immuned as a result of vaccination with the live tularemia vaccine averaged 70.8 per cent. The absence during the last few years of any tularemia cases among the residents of the Volgo-Akhtubinsk floodplain area was due not only to the vaccinations, but also to the decline of the natural focus of this infection. Epidemiological and epizootological observation over the Volgo-Akhtubinsk floodplain area should be continued with the data pointing to eradication of the natural focus of tularemia the vaccination should be reduced. (Author)