**1. Introduction**

[86] Zlotnik, I. 1968. The reaction of astrocytes to acute virus infections of central nervous

[87] Zlotnik, I., Grant, D.P., Carter, G.B. 1976. Experimental infection of monkeys with vi‐ rus of tick-borne encephalitis complex. Degenerative cerebellar lesions following in‐ apparent form of the disease of recovery from clinical encephalitis. Bri. J. Exper. Path.

system. Brit. J. Exper. Path. Vol. 49, N 6. pp. 555-564.

Vol. 57. pp. 200-210.

144 Encephalitis

The formation natural foci of tick-borne infections is closely connected to three physical‐ ly–geographical zones in Ukraine: Ukrainian Polissya (mixed forest zone - (woodlands), Forest–Steppe zone, Steppe zone and two extra-zonal natural areas – Carpathian and Cri‐ mean mountains.

On the territory of Ukrainian Polissya there are favourable conditions for the formation of natural foci of mainly those types of arboviruses and bacterial infections, which are transmitted by ticks – tick-borne viral encephalitis, Tribec, Uukuniemi, ixodid tick-borne borreliosis, human granulocytic anaplasmosis (HGA), others.

Tick-borne viral encephalitis (TBVE), ixodid tick-borne borreliosis (ITBB) and mixed-infection (TBVE and ITBB) are the most prevalent feral herd transmissible infections in Ukraine. Numer‐ ous aspects of these infections require to be better looked into or need more accurate definitions. First of all, this refers to the regional peculiarities of epidemiology and clinical manifestations, diagnostics, treatment and also the efficiency of preventive measures taken. There is an urgent need in studies of special clinical features of late manifestations and chronic course of these neu‐ roinfections, as well as their better timely diagnostics and etio-pathogenetic therapy.
