[Determination of the degree of infectiousness of adult ixodid ticks with the tick-borne encephalitis virus]. / Opredelenie stepeni infitsirovannosti vzroslykh iksodovykh kleshchei virusom kleshchevogo éntsefalita.

It was shown to be principally possible to determine the content of tick-borne encephalitis virus in ticks in a certain territory by total collection of these arthropods in permanent areas followed by individual virological examination and titration of virus in the infected ticks.

[Multi-year observations of the humoral immunity status of patients with tick-borne encephalitis in 3 endemic regions]. / Mnogoletnie nabliudeniia za sostoianiem gumoral'nogo immuniteta u bol'nykh kleshchevym éntsefalitom v trekh éndemichnykh regionakh.

Analysis of the results of the laboratory diagnosis of tick-borne encephalitis (TBE) by HI test over many years proved a statistically significant decrease by the 80's in the intensity of humoral immunity in the subjects with a history of tick-borne encephalitis in Kemerovo Province, Udmurtia and Latvia. A decrease in antihemagglutinin levels in the blood of convalescents after TBE was detected in endemic foci located in different geographical regions differing by epidemiological parameters; it did not depend on the portion of infected ticks and ratio of the clinical forms of the disease in a focus. Parallel tests by HI of the diagnostic value of several antigens of TBE virus strains isolated from different sources in different regions with sera from TBE patients revealed no differences among them. The antigenic activity of the strains in HI test did not depend on the source and region of isolation (Kemerovo Province, Udmurtia and Latvia).

[Intrapopulation differences in the infectivity of adult Ixodes persulcatus P. Sch. with the tick-borne encephalitis virus and an assessment of its total content in ticks]. / Vnutripopuliatsionnye razlichiia infitsirovannosti vzroslykh Ixodes persulcatus P. Sch. virusom kleshchevogo éntsefalita i otsenka ego summarnogo soderzhaniia v kleshchakh.

At the present stage of investigations on the role of vectors in foci of tick-borne encephalitis and of other transmissible infections it is necessary not only to operate with extensive indices of arthropod infection rate but also to take into account the degree of their infection. It has been demonstrated that adult empty Ixodes persulcatus ticks at the time of activation differ significantly by the degree of their infection with tick-borne encephalitis virus. In the Khabarovsk Territory, annual changes in the relative and absolute numbers of infected ticks did not lead to sharp variations in the virus population portion associated with ticks. It is suggested that vector individuals containing different virus doses are of different functional importance in providing long-term existence of virus population.

[Demonstration of the tick-borne encephalitis virus by a solid-phase immunoenzyme method in materials from natural foci]. / Indikatsiia virusa kleshchevogo éntsefalita tverdofaznym immunofermentnym metodom v materialakh prirodnykh ochagov.

Large-scale examinations of specimens from natural foci of tick-borne encephalitis (TBE) demonstrated that sensitivity of solid-phase enzyme immunoassay (EIA) in detecting TBE virus antigen was as high as that of the fluorescent antibody technique. The EIA takes less time and may be used for examinations of specimens after a preliminary passage in cell cultures. The EIA was also shown to be highly effective in the detection of TBE virus antigen in the cerebral tissue of patients post mortem and in the confirmation of the clinical diagnosis.

[Biological properties of tick-borne encephalitis strains isolated in different parts of its geographic range]. / Izuchenie biologicheskikh svoistv shtammov virusa kleshchevogo éntsefalita, vydelennykh v raznykh chastiakh ego areala.

A comparative study of over 200 tick-borne encephalitis (TBE) virus strains isolated from patients and ticks in different regions varying in the proportion of severe clinical forms of TBE was carried out. The strains were tested for their pathogenicity for white mice, cytopathic and plaque-forming properties as well as for the interferon-inducing capacity in SPEV cells. All the strains were found to be highly neurovirulent for mice, to produce plaques with diameters varying form less than 1 to 10 mm, and to induce interferon production in SPEV cell. Among the TBE virus strains isolated in the Baltic republics and Vologda region there occurred strains causing complete destruction of SPEV cells at later intervals than the prototype strains. No association of the examined properties of TBE virus strains with the region of isolation or with the clinical forms of human disease was established.

[The immunogenic and hemagglutinating activities of tick-borne encephalitis viral strains isolated from patients in different parts of the geographic range of the disease]. / Immunogennaia i gemaggliutiniruiushchaia aktivnost' shtammov virusa kleshchevogo éntsefalita, vydelennykh ot bol'nykh v raznykh chastiakh nozoareala.

Considerable variability of the immunogenic and antigenic (in HA test) activity of tick-borne encephalitis virus strains was shown. No correlation was observed between the hemagglutinating activity of strains and their capacity to stimulate humoral immunity in the infected animals. The results of the study did not allow one to place strains into groups according to the area of isolation in relation to their immunogenic and antigenic activity.

[The infectiousness of Ixodes persulcatus ticks with the causative agents of Lyme disease and tick-borne encephalitis simultaneously]. / Zarazhennost' kleshchei Ixodes persulcatus vozbuditeliami bolezni Laima i kleshchevogo éntsefalita odnovremenno.

By means of individual bacteriological and virological investigations of adult Ixodes persulcatus ticks and comparison of obtained results there has been established their simultaneous spontaneous infection with agents of Lyme disease and tick-borne encephalitis. A possible frequency of such mixed infection in these vectors is being discussed.

[A count of the vector portion of a population of the causative agent of tick-borne encephalitis connected with the imago of the taiga tick (Ixodes persulcatus)]. / Chislennost' vektornoi chasti populiatsii vozbuditelia kleshchevogo éntsefalita, sviazannoi s imago taezhnogo kleshcha.

The paper presents results of individual virological investigation of about 2 thousand of hungry imagoes of Ixodes persulcatus Sch., collected for the estimation of the absolute number of ticks at test sites. This approach is shown to be suitable for estimating the ratio between the vectors with various virus doses, the number of vectors, and of the vector share in a virus population in natural tick-born encephalitis foci.