Under the effect of human economic activity in the natural plague foci there occurred changes in the structures of local biocenoses. The extent and the direction of these changes were determined by the character and the scale of the economic activity. The final outcome of ploughing up, irrigation and supply with water of the vast areas is elimination of the focus or of its autonomic areas, but excessive exploitation of the desert pastures not infrequently leads to the opposite result. Large industrial construction and building of means of communications decreased the territories of the natural foci of plague only slightly, although no significant action was produced by them on the structure of biocenoses and the state of the foci.