[Natural foci of tick-borne encephalitis in the Slovak Republic and its relation to the natural ecosystem].

To evaluate the incidence of natural foci of tick-borne encephalitis in the Slovak Republic data of the hygiene service on the morbidity from tick-borne encephalitis during the period from 1961-1988 were used as well as data from the literature and results of the author's field studies on the incidence of the common tick. The main foci of tick-borne encephalitis are in the West Slovakian region, in the Záhorské lowland, in the Váh valley up to the distrikt of Povázská Bystrica, in the area of the Low Carpathian mountains, Tribec, Vtácnik, the Nitra and Hron hills, and Kovácov hills, in the Central Slovakian region in the Krupin hills and in the East Slovakian region in the Slovak karst and Slanské hills. The incidence of common ticks and foci of tick-borne encephalitis is linked to the original oak grove communities. In Slovakia the latter comprise hornbean and oak forests, oak groves and thermophile oak forests. Areas of original communities of beech woods and spruces which grow in higher altitudes do not provide favourable conditions for the development of the common tick. Rare foci of tick-borne encephalitis of a mountainous type found in Slovakia survive probably due to the extremely favourable microclimatic conditions in these areas. Also the hygrophilous communities of alders, moorlands and dry steppes, original as well as cultivated ones, are not suitable for the common tick. This is why ticks are not found in central, northern and northeastern Slovakia, in the Rye island and lowland along the Tisa river.(ABSTRACT TRUNCATED AT 250 WORDS)