[Pathogenetic criteria for evaluating the virulence of tick-borne encephalitis strains isolated in the southern part of the Far East]. / Patogeneticheskie kriterii otsenki virulentnosti shtammov virusa kleshchevogo éntsefalita, izolirovannykh na iuge dal'nego vostoka.

A comparative virological, immunological, and pathohistological study of 5 tick-borne encephalitis (TBE) strains differing by virulence was carried out in golden hamsters. The authors characterize the TBE virus pathogenicity sign, denoted as Pmaic genetic marker (pathogenicity for hamsters at intracerebral inoculation), which helps understand the essence of immunopathogenetic mechanisms of the TBE infectious process in man.

[An assessment of the immunoepidemiological efficacy of a liquid cultured killed vaccine against tick-borne encephalitis virus strain 205 in the Maritime Territory]. / Otsenka immunoépidemiologicheskoi éffektivnosti zhidkoi kul'tural'noi ubitoi vaktsiny protiv kleshchevogo éntsefalita shtamm 205 v usloviiakh Primorskogo kraia.

Inactivated vaccine against tick-borne encephalitis (TBE), prepared on the basis of strain 205, is characterized by epidemiological (53%) and immunobiological activity. The appearance of a few TBE cases among the vaccinees is probably due to different maturation rate of immune response to various strains (different specificity of immune response). A suggestion has been made that no inactivated vaccine prepared from a single strain can produce a reliable protective effect because of pronounced heterogeneity of the population of TBE virus.

[The clinico-epidemiological characteristics of Powassan encephalitis in the southern Soviet Far East]. / Kliniko-épidemiologicheskie osobennosti éntsefalita Povassan na iuge Sovetskogo Dal'nego Vostoka.

The present communication deals with the analysis of 14 cases of Powassan encephalitis. As shown in this study, the course of this infection may be accompanied by symptoms indicating the presence of cerebral and meningeal lesions (in 7 cases meningoencephalitic forms with one fatal outcome and in 2 cases meningeal forms were registered) or take febrile and inapparent forms (5 cases). Powassan encephalitis was found to give characteristic symptoms of cerebellovestibular lesions, differentiating this disease from tick-borne encephalitis (TBE). The cases of mixed infections caused by TBE virus, Powassan encephalitis virus and tick-born Borrelia were found to be possible.

[A virulence study of tick-borne encephalitis virus strains isolated in the southern Soviet Far East]. / Izuchenie virulentnosti shtammov virusa kleshchevogo éntsefalita, izolirovannykh na iuge Sovetskogo Dal'nego Vostoka.

Study of virulence for white mice and Syrian hamsters of 115 tick-borne encephalitis virus strains isolated in Maritime Territory showed virulence to be a complex biological manifestation of pathogenic properties of tick-borne encephalitis virus. The virulent properties of strains may have individual manifestations in each species of specific causative agent hosts and susceptible experimental biological models.

[The role of ixodid ticks in the epizootic process of tick-borne encephalitis in the Maritime Territory]. / Rol' iksodovykh kleshchei v épizooticheskom protsesse kleshchevogo éntsefalita v Primorskom krae.

Relative significance of Ixodidae in tick-borne encephalitis epizootic process in the Maritime Territory was determined from many years' data on the carriage of viruses by Ixodidae and results of experimental studies of the selective role of Ixodidae main species. Causes of low rates ow carriage of viruses by Ixodidae in the area under study are revealed.

[The spatial-temporal structure of fluctuations in tick-borne encephalitis morbidity in the Maritime Territory]. / Prostranstvenno-vremennaia struktura kolebanii zabolevaemosti kleshchevym éntsefalitom v Primorskom krae.

The annual dynamics of the epidemic process in tick-borne encephalitis and its spread in the Maritime Territory, endemic for this infection, have been studied. The study has shown that in the central mountainous regions grown with boreal forest, in contrast to the rest of this focal area, a higher morbidity level and more severe outcomes of this infection are observed. This indicates that in those regions more ancient nuclei of the endemic area of this infection with the main stable elements of the natural focus are preserved.

[Clinico-epidemiological characteristics of tick-borne encephalitis in the Maritime Territory]. / Kliniko-épidemiologicheskie osobennosti kleshchevogo éntsefalita v Primorskom krae.

Clinico-epidemiological analysis of tick-borne encephalitis (TBE) incidence rate in the Primorski Territory for 25 years has revealed the prevalence of focal forms of this infection (on the average, 50%) and its high mortality rate (on the average, 33% for the focal forms and 6.4% for the meningeal form). Such course and termination of this infection depend not only on the reactive capacity of the patient's body, but, to a great extent, on the virulence of TBE virus circulating in the area under study.

[The role of wild murine rodents in the selection of different strains of tick-borne encephalitis and Powassan viruses]. / Rol' dikikh myshevidnykh gryzunov v selektsii razlichnykh shtammov virusov kleshchevogo éntsefalita i Povassan.

The study demonstrated the role of wild murine rodents in selection of different strains of tick-borne encephalitis and Powassan viruses, determined their ecological characteristics reflected in the epidemiological features of tick-borne encephalitis and Powassan encephalitis in southern Far East.

[Clinico-immunological study of the effectiveness of vaccination against tick-borne encephalitis in the Maritime Territory]. / Kliniko-immunologicheskoe izuchenie éffektivnosti vaktsinatsii protiv kleshchevogo éntsefalita v Primorskom krae.

Analysis of the severity of the clinical course of tick-borne encephalitis (TBE) in the Maritime Territory, 1966-1983, showed a decline in the incidence of the disease by 20% in the group of subjects vaccinated against TBE, whereas the severity of the disease showed no statistically significant difference from that among nonvaccinated subjects. The causes of the poor protective effect of the liquid tissue culture vaccine produced by the Research Institute of Vaccines and Sera, Ministry of Health of the USSR, Tomsk, were demonstrated alongside with the advantages of the lyophilized concentrated vaccine manufactured by the Institute for Poliomyelitis and Viral Encephalitides of the USSR Academy of Medical Sciences, which should be used for prophylactic vaccinations of subjects working in forests who comprised 29% of the vaccines. In this way, TBE incidence in the region could be reduced considerably.

[Role of Powassan virus in the etiological structure of tick-borne encephalitis in the Primorsky Kray]. / Izuchenie roli virusa Povassan v étiologicheskoi strukture kleshchevogo entsefalita v Primorskom krae.

Composite studies conducted annually in the Primorsky kray showed the tick-borne encephalitis virus to play the main etiological role in the group of encephalites with the spring-summer incidence. In 1976--1978, virological studies of 69 cases of the disease yielded 11 strains of tick-borne encephalitis virus. In 1978, from the blood of clinically normal woman after a tick bite strain 555 was first isolated which was identified as Powassan virus, and antigenemia was observed for 53 days using the fluorescent antibody technique. In the same period, serological examinations of the blood sera from 117 patients demonstrated antibody to tick-borne encephalitis virus in 69.2%, to Powassan virus in 4,3% and to both viruses simultaneously in 4.3%. Besides, antibody to tick-borne encephalitis virus, Powassan virus and both viruses simultaneously was found in patients with progredient forms of tick-borne encephalitis and in subjects with the history of tick attachment.