[Leptospira distribution in the soil of a natural focus of the infection (an attempt at the radioisotopic labelling of infected voles)].

The mass radioisotope (32P) labelling of all tundra voles excreting Zeptospira, infected urine was carried out over the area of 1 ha, and the results of the experiment analyzed by the method of planar coherent graphs, showed the irregular (spotted) distribution of "infected spots", i. e. soil patches contaminated by Zeptospira. The borders of individual small foci of infection did not coincide with the outlines of soil and vegetational divisions of the area. The spatial structure of the "extraorganismic" part of the Zeptospira population was originally formed by the carriers and thus determined by their mobility, their manner of using the territory. Later this structure was changed by selective elimination under the influence of living conditions for Zeptospira in the soil. The "infected spots", subjected to such selection, seem to be capable of constantly sustaining Zeptospira; the presence of these organisms is also due to the fact that they are regularly added into the soil with urine excreted by the carriers visiting the same spots of their territory.