[The present knowledge of tick-borne encephalitis vectors]

The most important aspects of the relationships of tick-borne encephalitis virus and its vectors--Ixodes ticks. These include the establishment of a rule of viral exchange between the co-fed ticks, which makes its reverse transfer from nymphs to larvae possible; enhancement of tick aggressiveness under the influence of the incremental concentrations of the virus increasing their epidemiological danger; the association of the spread of viral genospecies with the genetic structure of tick populations; the emergence of phenotypically different vector subpopulations with new vector properties (under the influence of anthropogenic factors); and the elucidation of a possible role of the virus as an enhancer in mixed viral and bacterial infections of tick vectors.