The paper considers the trends of morbidity due to tick-borne encephalities (TBE) and lxodes tick-borne borrelioses (lTBB) in Udmurtia during 35 years (1965-2000) and evaluates the long-term influence of measures aimed at suppressing natural foci by eliminating the basic vector on this process. For this, data on 1062 cases of fevers occurring after the bite of a tick in Udmurtia in 1965-1968, the similar data on 1509 cases in 1983-1987, and the official data on the incidence of these infections in 1996-2000 have been retrospectively analyzed. It has been shown that in Udmurtia the natural foci of lTBB coexisted with those of TBE long before the pathogens of borrelioses were described and notification of the infection of this group was initiated. In the 1990s, there was a drastic rise in the incidence of TBE and lTBB as compared with the 1960s and 1980s, which was due to an increase in the rate of contacts of the population with natural foci and to the better diagnosis of these infections. The prevalence of lTBB coincides with that of TBE. There is a long (more than 30 years) epidemiological effect in eliminating the vector Ixodes persulcatus.