ABSTRACT
Potential epidemiological valency (PEV) of the natural foci of tick-borne encephalitis was characterized by the quantity of the infected ticks per unit of the area of the focal territory, and also by the section of the pathway of man's passage along this territory, at which encounter of a single viroforic tick is possible. PEV indices reflected the epidemiological intensity of the natural foci of infection both in the mastered and in the poorly developed areas, and therefore could be used for the epidemiological prognosis on tick-borne encephalitis and in epidemiological search of this infection on the newly-developing territories. The extent of PEV reduction as a result of anti-tick treatment of forests endemic by tick-borne encephalitis which as caricides with a prolonged residual action of the tick-vectors offered a possibility of assessing the epidemiological efficacy of the measures carried out the most objectively.
