[Quantitative assessment of the level of the causative agent of tick-borne rickettsiosis in a population of the main vector]. / Kolichestvennaia otsenka soderzhaniia vozbuditela kleshchevogo rikketsioza v populiatsii osnovnogo perenoschika.

It was first demonstrated that the method of individual titration of ticks from natural population, using animals sensitive to tick rickettsiosis agent, helps accurately estimate their infection level and define the level of infection of individual samples. It is shown that in natural focus of tick rickettsiosis infected hungry adult ixodes specimens differ in the quantity of rickettsia contained in them in different years. Possibility to estimate the size of the agent population connected with the imago of the major carrier is demonstrated.

[Characteristics of the transphase and transovarial transmission of Rickettsia sibirica by ixodid and argasid ticks]. / Osobennosti transfaznoi i transovarial'noi peredach Rickettsia sibirica iksodovymi i argasovymi kleshchami.

Both the specific vector Dermacentor silvarum and the nonspecific one Ornithodoros papillipes are shown to become Rickettsia sibirica infected while sucking blood on the infected guinea pigs. Meanwhile, the specific vector D. silvarum is more sensitive to R. sibirica than the nonspecific. O papillipes. The infectivity of D. silvarum and O. papillipes ticks by R. sibirica was found to be dependent on the intensity of guinea pigs' rickettsemia. Transovarial transmission of Rickettsia has been established for the D. silvarum and O. papillipes ticks, but the Rickettsia titer in the infested D. silvarum larvae exceeded that O. papillipes. Survival of D. silvarum ticks infected by various concentrations of the R. sibirica microbial bodies was found to exceed that of O. papillipes.

[Tick-borne encephalitis viral titers of engorged adult Ixodes persulcatus ticks]. / Titry virusa kleshchevogo éntsefalita u napitavshikhsia vzroslykh kleshchei Ixodes persulcatus.

The results of titration of adult virus infected ticks of Ixodes persulcatus are given. The ticks were collected in various natural nidi of tick-borne encephalitis and individually fed on laboratory animals. The results of titration of ticks of the same species primarily infected on laboratory animals during virusemia are given as well. Changes of the virus titer in engorged ticks were observed till the egg production. A role of the presence of virus in engorged ticks for the process of the agent circulation in natural nidi is discussed.

Biological properties of strains of tick-borne encephalitis virus isolated in the natural foci of the eastern part of the Russian plain.

Strains of tick-borne encephalitis virus isolated in the natural foci of infection in the eastern part of the Russian Plain (the Kirov region) were examined for their biological properties. The strains examined were 69 strains isolated from ticks Ixodes persulcatus, 62 strains obtained from patients with the clinically manifest form of tick-borne encephalitis and 56 strains isolated from the blood of patients with the inapparent form of infection. Comparative studies on laboratory animals (albino mice, golden hamsters, suckling guinea pigs and other mammals) as well as comparative serologic studies provided evidence which suggested that all virus isolates from the Kirov region were antigenically identical with the strain "Sofin" isolated in the Far East and represent thus a single causative agent of the tick-borne encephalitis virus infection. This strain of virus is supposed to exist in two variants, in dependence on ecological conditions: one of these variants is the eastern variant (strain Sofin and strains from the Kirov region) and the other one is the western variant of tick-borne encephalitis virus.

Consistent patterns in the contact of small mammals with tick-borne encephalitis virus in foci of the eastern part of the Russian plain.

The pattern of contact between small terrestrial mammals and tick-borne encephalitis virus was studied in dependence on year, yearly season and the age of the largest animal populations. The animal-virus contact was assessed by the appearance, persistence and loss of antibodies in the animals examined. A total of 9256 sera of small rodents were collected and tested in this study.

Contact of birds with tick-borne encephalitis virus in the eastern part of the Russian plain.

A total of 706 native blood sera of birds representing 44 most common bird species in the southern parts of the Kirov region were examined for antibodies against tick-borne encephalitis virus. Some serologic tests were found positive, but the birds appeared to constitute a secondary and nonessential link in the circulation of virus in the natural environment of this area.

Consistent patterns in the contact of domestic animals with tick-borne encephalitis virus in the eastern part of the Russian plain.

Hemagglutination inhibition test (HIT), neutralization test (NT) and complement fixation test (CFT) were used to serologically examine goats and cows in the southern area of the Kirov region and in the Udmurt ASSR. A total of 1641 sera of goats and 1414 sera of cows were examined for the presence on antibodies against tick-borne encephalitis virus. The tests showed a relatively intensive contact of goats and cows with TBE virus in the forests of the eastern part of the Russian Plain: HIT was positive in 27% of goat sera and 17% of cow sera, virus-neutralizing antibodies were detected in 25% of sera of goats and the positivity of CFT was recorded in 32% of goat sera and 29% of cow sera. The relative number of immune animals differed considerably from locality to locality. The localities with great numbers of immune animals were characterized by a distinct increase in the incidence of adult ticks Ixodes persulcatus. The immunization of domestic animals in the natural foci of infection was found to be season-dependent: the highest immunity rates were observed at the end of summer and in the autumn. The seasonal variations in animal immunity are demonstrated in detail on adult goats. Towards the spring time some serum antibodies, namely virus neutralizing antibodies and antihemagglutinins, tended to disappear in a certain number of animals. A similar, but somewhat different pattern of immunization could be observed in cows. In contrast to goats, cows appeared to be less susceptible to the tick-borne encephalitis virus infection, which was substantiated by both serologic data obtain in this study and the data reported in the literature. In the natural foci of TBE virus infection grazing goats and cows had the most intensive contact with the pathogenic agent in the first year of their lives.