EUROMEDICA  Hanover 6-7  Juni 2008	Advanced methods of diagnosis, treatment and prophylactics
	European Academy of Natural Sciences, Hanover European Scientific Society, Hanover Russian Academy of Natural Sciences, Moscow

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Tick-born encephalitis (TBE) is the most important natural foci infection in Russian Federation. It has strictly seasonal character depending on a period of activity of it’s transmitters – Ixodes ticks. The main transmitter in focuses around most territory of Russia is Ixodes persulcatus, the highest disease rate is observed in May-June. Another situation exists in some European regions where Ixodes ricinus prevail: two peaks of the disease are usually registered – in spring and in the end of summer and beginning of autumn. Activity of focuses fluctuates from year to year as a result of changes in different biological and abiotic factors. Therefore number of cases of tick-borne encephalitis may vary considerably. Man is an occasional recipient of TBE virus, when undergoes an attack of infected tick being in natural or anthropourgic focuses.

Traditionally high risk of infection exists among workers of “forest professions” – forest guards, woodcutters, as well as topographists, geologists, road and pipeline builders. Workers of these professions are included into a risk group and undergo systematic vaccination. However villagers are also under threat to be infected during hunting, wood cutting, fishing, gathering mushrooms and berries. Last several years among all patients with tick-borne encephalitis townspeople prevail, who visited natural and anthropourgic focuses for picnic, tourism and work in suburb gardens.

Epidemiological situation in the time of border of ages is characterized by unprecedented increase in disease rate (up to 10 000 annually) and some other new features, requiring precise analysis in order to develop adequate strategy to deal with the disease.

Disease rate of Tick-borne encephalitis in Russia increased primarily because of Siberian and Ural territories. For example, disease rate of tick-borne encephalitis in 1999 in Russia was 6.8 per 100 000 of population, being in Udmurtia 53.0, Perm’ region – 32.4, Tyumen’ region -35.2, Kurgan region – 35.4, Krasnoyarskiy kray – 52.8 and Tomsk region – 64.2. An extremely high increase of the disease rate was detected in regions of Eastern Siberia. Only for 5 years 1994-1999 in Republic of Hakasia it increased in 4 times, Republic of Buryatia – 5 times, Irkutsk region – 6 times and Republic of Tyva – 16 times. The decrease of morbidity of TBE in beginning of 2000^ths is the result of natural cycle and probably will continue some more years.

An important feature of modern epidemiology of tick-borne encephalitis is a shift in the structure of disease rate: today 70-80% of cases are uninoculated townsmen visiting forests for recreation and sometimes with economic intentions. Mainly people get infected in anthropourgic focuses, easily arising in suburb forest massifs because of individual house-building.

Loose control of a forest exploitation leads to acceleration of anthropogenic transformation of natural taiga and forest landscapes, destroying them and often creating favorable conditions for increase of ticks’ number. Raising number of automobiles significantly influences the disease rate, increasing number of townsmen going to a countryside and leading to their intensive contacts with ticks. Inhabiting of parks and public gardens by ticks is an another one negative factor. There is a data that about 10-20% of patients get infected without crossing borders of a city. Changes and extension of areas of the infection, appearance of new endemic regions were detected either in Europe or in Asia.

It was revealed that three main genotypes of TBE virus exist, corresponding to antigen subtypes. Elucidation of primary structure of viral RNA revealed that genotype 3 (Ural-Siberian) dominates on the territory of Russia (more 60%) but not genotype 1 (Far-Eastern) as it was thought before.

New important information concerning wide spread of combined focuses of tick-borne infections of bacterial, viral, rickettsial and protozoan origin has appearance during last 10-15 years. Tick borreliosis is the most well-studied disease, which area coincides with the area of TBE and may be even wider. Main arthropod hosts of Borrelia are the same tick species as for TBE - I. persulcatus and I. ricinus. In some cases a tick may be infected with two or more pathogens, leading to appearance of a mixed-infection in humans. Circulation of several genetically different species of Borrelia was revealed in Eurasia: B. burgdorferi, B. garinii, B. afzelii. Retrospective analysis has shown that a significant number of cases, which were treated as tick-borne encephalitis in 1960-1980 were in fact Tick borreliosis (Lime’s disease). Tick-borne rickettsiosis also extends it’s borders. Wide circulation of R. sibirica, R. slovaca in Russia was shown, and also several new non-pathogenic rickettsiae were described from a group of Tick-borne spotted fever. Recently several focuses of Granulocytic and Monocytic erlichiosis were discovered and patients revealed on the territory of Russia inside the area of TBE virus. Literature of the last years describes a possibility of babeziosis in Siberia.

The strategy of prophylaxis of TBE includes complex of specific and nonspecific measures as vaccination, using immunoglobulin against TBE for urgent prophylaxis, acaricidic processing and individual prevention. Since 2008 in Russian Federation a company of mass vaccination of endemic territory population was started.