[Interrelations between Ixodes persulcatus ticks and the tick-borne encephalitis virus of the red vole (Clethrionomys rutilis) in western Siberia]. / Vzaimootnosheniia kleshchei Ixodes persulcatus i virusa kleshchevogo éntsefalita s krasnoi polevkoi (Clethrionomys rutilus) v zapadnoi ibiri.

We present the data of 12-year survey (1989-2001) of the red vole population in southeastern West Siberia, including estimation of host relative numbers, abundance of immature taiga ticks, and percentage of animals with antigemagglutitnins against tick-borne encephalitis (TBE) virus. We discuss the role of demographic groups of voles as tick's hosts and their participation in the maintenance of TBE causative agent population. The estimation of spontaneous TBE infection rate in summer as well as in winter and early spring seasons, which have been made using a set of molecular-biological, serological and virological methods, demonstrates that a high proportion of red voles maintain non-pathogenic TBE causative agent over a long time, presumably, in the form of persistent infection.

[Involvement of the common shrew, Sorex araneus (Insectivora, Soricidae), in circulation of the tick-borne encephalitis virus in south-western Siberia]. / Uchastie obyknovennoi burozubki Sorex araneus (Insectivora, Sorcidae) v tsirkuliatsii virusa kleshchevogo entsefalita na iuge zapadnoi Sibiri.

We presented the data on the abundance of immature instars of the taiga tick Ixodes persulcatus Schuize on the common shrews Sorex araneus L. in natural foci of tick-borne encephalitis in the south of Western Siberia. Basing on the results of virological and serological studies we demonstrated a low effectiveness of this host species as a donor of disease agent strains, which are predominant in the territory under study, for ticks feeding on shrews. The analysis of samples taken from the young shrews in winter and spring using reverse RNA transcription with polymerase chain reaction and ELISA revealed occurRence of subvirion components of the tick-borne encephalitis (RNA and capsid protein E) ether in brain, liver or spleen in 90 percent of shrews (n = 42). Neither hemagglutination antigen nor infectious virus have been detected. We discussed a possible epizootic role of the maintenance of non-infectious tick-borne encephalitis virus in overwintering animals.

[An analysis of the space-time changes in tick-borne encephalitis morbidity in Novosibirsk Province]. / Analiz prostranstvenno-vremennykh izmenenii zabolevaemosti kleshchevym éntsefalitom v Novosibirskoi oblasti.

The authors analyzed data on space and time changes in tick-borne encephalitis (TBE) morbidity in Novosibirsk Province from 1955 to 1995 by using the method of principal components (PCs). The first PC (26.0% of total variance) was linearly represented. Judging the the loading scores, this component can be interpreted as redistribution of TBE morbidity rates between southeastern taiga foci in Salair foothills and northern forest-steppe foci in vicinity of the Ob' River valley. The second PC (22.6% of total variance) can be read as regional differences with long-term cyclic changes. The first PC correlated with the annual average temperature (r = 0.45; P < 0.05) and this correlation can be determined by global climate warming-up.

[Endo- and ectoparasites as factors influencing variability of the humoral immunity response in a natural population of red vole (Clethrionomys rutilus)]. / Endo- i éktoparazity kak faktory izmenchivosti reaktsi gumoral'nogo immuniteta krasnykh polevok (Clethrionomys rutilus) v prirodnoi populiatsii.

Based on the five-year population study of red voles Clethrionomys rutilus Pallas in southern West Siberia, we analysed the distribution of two predominating species of parasites (tapeworms Hymenolepis horrida and immature instars of ticks Ixodes persulcatus) in different demographic groups of the host, and seasonal changes of their incidence in the population. We assessed primary humoral immune response of the voles (splenic antibody-forming cells) to antigenic challenge (injection of sheep erythrocytes) in respect to occurrence of these parasites. It was revealed that infection with H. horrida significantly reduced the numbers of antibody-forming cells in immature summer-born voles. In contrast, immune responses in immature and mature voles, which where parasitized by I. persulcatus at the moment of capture, were significantly higher as compared to non-infected hosts. The possible mechanisms of influence of parasites on variability of immune reactions of voles in the population under study are discussed.

[Characteristics of the distribution of Ixodes persulcatus in the forest-park area of Novosibirsk]. / Osobennosti raspredeleniia Ixodes persulcatus v lesoparkovoi zone g. Novosibirska.

Only one species of ixodid ticks Ixodes persulcatus occurs in the forest-park zone. Conditions of foliage forests with high grass, where occur hosts of all developmental phases of ticks (elks, hares, rodents, insectivores), are most favourable for I. persulcatus. Preimaginal phases of I. persulcatus feed, in general, on dominant species (common shrew, redbacked and narrow-skulled voles, field mouse and northern birch mouse).