[Life cycle of the taiga tick ixodes persulcatus in taiga forests of the eastern Sayan Plateau].

The Ixodes persulcatus life cycle has been studied in natural environments of taiga fo- rests in The Eastern Sayan Plateau (56 10' N, 91 30' E). Engorged larvae and nymphs de- velop with a morphogenetic diapause or without diapause, with ratio of these two ways of development for larvae and nymphs 77.25/22.75% and 43.43/56.57%, respectively. The hypothetic season hemipopulation consists of 34.5 +/- 4.5, 50.1 +/- 1.3, 13.2 +/- 4.0 n 2.2% of unfed imagoes, completing 3-year, 4-year, 5-year, and 6-year life cycles, respectively. Mean life span is 3.83 +/- 0.10 years per generation. The "life table" predicting the probability to complete life cycle through phases from egg to adult, was developed.

[Variability of the life cycle duration in the taiga tick from mixed coniferous-broad-leaved forests of the Udmurt Republic].

Seasonal cohorts of the unfed Ixodes persulcatus imago in the study area were found to consist of the ticks passed through three-, four-, and five-year life cycles, in the ratio 72.6, 26.4, and 2.0% respectively, on the base of mean long-term values. Such ratio is established if 91.7% of larvae and 79.9% of nymphs develop without diapause, while the rest of larvae and nymphs develop with diapause. Mean duration of the tick generation is 3.3 years, with the fluctuations in certain of the years within the limits of 3.15-3.36 years.

[Spatial and temporal variability of Ixodes ricinus and Ixodes persulcatus infection with the Lyme disease agent in Moscow Region].

Analysis of long-term data on the infection rated of the taxonomic complex Borrelia burgdorferi s. l. in Ixodes persulcatus and I. ricinus from Moscow Region is carried out. More than 14 000 tick specimens were examined by dark-field microscopy and 704 specimens were investigated by PCR. Two borrelia genospicies, B. afzelii (6.3%) and B. garinii (20%) proved the most prevalent. The genospecies could form a mixtinfection (11%). Borrelia miyamotoi, B. valaisiana, and B. burgdorferi s. s. were also found in the studied territory, with the total ratio lesser than 6%. Acarotropism of Borrelia proved 2.4 times higher with respect to I. persulcatus, than to I. ricinus. Average long-term infection rates of these tick species were 27.3 and 11.3% respectively. Spatial variability of the infection rate in ticks significantly exceeds interannual fluctuations with the variation coefficients 66 and 26% respectively.

[Tick-borne encephalitis virus as an amplifier of the metamorphosis of Ixodes ricinus (Acari: Ixodidae) tick nymphs under long-day photoperiodic conditions].

The metamorphosis of tick-borne encephalitis virus (TBEV)-induced I. ricinus nymphs under long-day photoperiodic conditions (18 light hours and 6 darkness hours) occurs more rapidly than in uninfected specimens. The infected nymphs begin to develop to the imagoes 25-33 days earlier than do uninfected ones. The first imagoes from the infected nymphs emerge on day 24 after saturation whereas those from the uninfected nymphs appear on day 43. The interval from nymphal saturation to imago development in 50% specimens is 27.7 +/- 2.0 and 52.2 +/- 0.7 days, respectively. Reasons for geographical differences in the intensity of amplification of the metamorphosis of saturated I. nicinus nymphs are discussed in the paper.

[Gradual variability of the parasitic system of tick-borne encephalitis].

It has been shown that the temperature conditions of hibernation in the major vectors of tick-borne encephalitis viruses (TBEV) the ticks Ixodes ricinus and Ixodes persulcatus occupy a special place among a lot of factors that determine the spatial distribution and the specific features of functioning of the parasitic system of tick-borne encephalitis. These conditions determine the borders of distribution of the major vectors of TBEV, their sympatric zone, and the physiological features of individual races of the ticks. The conditions of hibernation in the vectors also affect the properties of circulating RBEV strains. The reasons for variability in TBEV virulence in different landscape and climatic zones are discussed.

[Methods for estimating the demographic structure of the taiga tick (Ixodidae) based on results of standard parasitological observations]. / Metody otsenki demograficheskoi struktury taezhnogo kleshcha (Ixodidae) po rezul'tatam standartnykh parazitologicheskikh nabliudenii.

A retrospective estimation of the abundance dynamics of the taiga tick Ixodes persulcatus in mixed coniferous and leaf-bearing forests of the Udmurtia Republic in the period 1957-1986 was carried out. A possibility to estimate the absolute number of all stages of I. persulcatus based on relative indices. Females of I. persulcatus lay 20,250 eggs per 1 hectare, and this number of eggs gives birth to 15,000 larvae. From this number, 7870 larvae hibernate and 6550 individuals became fed. The number of nymphs is 5930, among which 5110 individuals live up to spring, and 1390 became fed. The number of adult mites in autumn is 1250; in subsequent spring this number decreases to 780. The mean number of engorged females is 8. The mortality rate of ticks caused by the deficit of hosts increases from preimaginal stages to adults; for larvae, nymphs and imago this index is 16.6, 72.8, and 97.9%, respectively. Quotas of individuals with 3-, 4- and 5-year life cycle among the unfed imago are 70.4, 28.0, and 1.6%, respectively.

[Reason for fluctuation in the demographic structure of the taiga tick population (Ixodidae) in dark conifer-leaf forests of Kemchug Upland]. / Prichiny kolebanii demograficheskoi struktury taezhnogo kleshcha (Ixodidae) v temnokhvoino-listvennykh lesakh Kemchugskogo Nagor'ia.

It was found out, that mean ratio of unfed taiga ticks Ixodes persulcatus having a life cycle of 3-5 and 6 years counts respectively (N = 6) 33.6, 52.8, 13.2 and 0.4%. Data on absolute number of I. persulcatus individuals in the process of onthogenesis is given. It is shown, that mortality of different unfed stages increases from larva to imago. In the autumn-winter period, the mean ratio of eliminated individuals counted 16% of larvae, 20% of nymphs, and 38 of imago. The mortality in the spring-summer period caused mainly by the deficit of hosts and counted for these stages 3, 82 and 98% respectively. Engorged ticks successfully undertake unfavorable conditions both in the spring-summer and autumn-winter periods. Their mean mortality in the period from feeding to moulting does not exceed 12%.

[Forest tick Ixodes ricinus (Ixodidae) in the foci of tick-borne borreliosis of the northwestern part of the Moscow region]. / Lesnoi kleshch Ixodes ricinus (Ixodidae) v ochagakh iksodovykh kleshchevykh borreliozov severo-zapada Podmoskov'ia.

Monitoring studies during 1996-2001 have shown a natural foci of tick-borne borreliosis with high abundance of Ixodes ricinus and high infection rate with an agent: 19.5-38.4 tick individuals per 1 km of route, infection rate 18.0 +/- 1.7-22.5 +/- 1.5%. A risk to be infected with the Lyme disease in the ricinus focus of the tick-borne borreliosis during the epizootic season did not vary much during the period of study, 3.5-8.2 in different year, mean 6.0 infected ticks per 1 km of route.

[Demographic structure of the population of taiga tick (Ixodidae) in coniferous forests of the Kemchug upland in 1986-1991]. / Demograficheskaia struktura populiatsii taezhnogo kleshcha (Ixodidae) v dolinnykh temnokhvoinykh lesakh Kemchugskogo nagor'ia po sostoianiiu na 1986-1991.

It is recovered, that full engorged females of Ixodes persulcatus lay average of 25,250 eggs per 1 ha during the season in the test area. It produces 13,750 larvae. The abundance of hungry larvae is reduced up to 12,500 during the winter period. 11,643 larvae become engorged. The total abundance of hungry nymphs counts: 10,933 in autumn, and 9895 in spring. The total abundance of hungry adults, half of which is represented by females, makes 1774 in autumn, and 1084 in spring. About 10 females found their hosts and became successfully engorged.

[Hantavirus infection in bank voles in the natural reservoir. Part 1. Characteristics of an infection process in bank voles]. / Khantavirusnaia infektsiia u ryzhikh polevok v prirodnom ochage. Soobshchenie 1. Osobennosti infektsionnogo protsessa v organizme polevok.

The specific features of hantavirus infection in naturally infected bank voles (Clethrionomys glareolus), the principal host of hantavirus of the serotype Puumala, were studied during long-term observation of individually marked animals in the active focus of hemorrhagic fever with renal syndrome (HFRS) in the south of Udmurtia. The infection time in the bank voles was defined by paired serum seroconversion tests. In the natural focus, hantavirus was shown to cause asymptomatic persistent infection in the bank voles with the body's peak accumulation of the virus and its environmental discharge within the first month of infection. In this period the animals present the greatest epidemic and epizootic hazards. Hantavirus infection has no negative impact on the viability of bank voles.

[The impact of electromagnetic radiation at microwave frequency (9.8 HhZ)on the embryonic and postembryonic development of the tick Hyalomma asiaticum (Acarina, Ixodidae)]. / Vliianie élektromagnitnogo izlucheniia svch diapazona (9.8 ggts) na émbrional'noe i postémbrional'noe razvitie kleshcha Hyalomma asiaticum (Acarina, Ixodidae).

Low-power (20 microW/cm2) microwave-modulated radiation at a carrier frequency of 9.8 Hhz is shown to affect the course and specific features of ontogenesis of the ick H. asiaticum. The actin of microwave radiation on the development of H. asiaticum substantially depends on the frequency of microwave modulation of a signal and on the temperatures of an experiment. When the temperature is 22 degrees C, there is a significant suppression of development of fed larvae and nymphs after exposure to microwave radiation at modulated signal frequencies of 3 and 5 Hz/ The whole range of the tested modulation frequencies was 2 to 16 Hz. The hungry species of all developmental phases in H. asiaticum were virtually unresponsive to exposures. At 14 degrees C (a perithreshold temperature of H. asiaticum development), the action of microwave radiation changed from inhibitory to stimulating. At modulation frequencies of 3, 5 and 7 Hz, the proportion of hatching larvae was 42.5, 67.5 and 80.0%, respectively, and that of controls was 2.5%. Whether the size of a H.asiaticum population can be controlled by a radar that provokes the development of ticks before winter by its radiation is discussed.

[The chronological structure of the population count of the taiga tick in the Maritime Territory]. / Khronologicheskaia struktura chislennosti taezhnogo kleshcha v Primorskom krae.

A time series analysis of 23-years observations of the Ixodes persulcatus imago dynamics was carried out. The tick were counted in forests of the western Sikhote-Alin' foothills near Ussuriysk. The fluctuations of the ticks number are quasiperiodical. They are formed by near 3-years oscillations, long-term non linear trend and accidental component. The observed process was described by means of a statistic model. This model combines the harmonic regression analysis with linear regression analysis. The determination coefficients are 90.8% and 92.7% for the descriptive and prognostic models respectively. The difference between two groups of environmental factors, which influence on the tick number, is discussed. These factors are: 1) the directly influencing factors (functional factors), 2) the factors influencing by dint of natural rhythms being general for a biocoenosis (synchronizing factors).

[Cyclic processes in the dynamics of the population count of the taiga tick and their relation to weather and climatic conditions]. / Tsiklicheskie protsessy v dinamike chislennosti taezhnogo kleshcha i ikh sviaz' s pogodnymi i klimaticheskimi usloviiami.

The paper continues the discussion of published materials on the dynamic of Ixodes persulcatus number in mountain forests of the central part of the Krasnoyarsk region during 1958-1990 (Korotkov e. a., 1992). An unstationarity and polycyclicity of examined processus is confirmed. It is shown, that long-term and middle-term quasi-periodical fluctuations of the tick number are determined by successive changing in forest biocenoses going under the influence of respective fluctuations of the climate. The synchronization of climatic and biocenotic processes is complicatedly organized in time and is not indicated phenomenologically. Certain quasi-periodical components in their indices of the tick number and climate are quite different by their amplitude, value of phase displacement, and longevity of terms. However, these structural differences are natural and determined by peculiarities of the response reaction of I. persulcatus to different intensivity of acting factor. This reaction under extreme environment conditions, both minimal and maximal ones, leads to the same result, the decreasing of the vital activity and the tick number.

[Distribution of hungry and engorged Ixodes persulcatus (Ixodidae) imagos on squares for absolute enumeration]. / Raspredelenie golodnykh i sytykh imago taezhnogo kleshcha (Ixodidae) na ploshchadkakh absoliutnogo ucheta chislennosti.

It was found out by the methods of large scale cartography and mathematics modelling, that the distribution of Ixodes persulcatus ticks around the point of clutch is still aggregated both on stages of hungry larvae and nymphs and on a stage of hungry imago. It is proposed to use the number of hungry imago aggregates as the criterium for the estimation of clatch number per square unit. Wild animals living in foothill taiga forests of the central part of Krasnoyarsk region support 9-10 female ticks per 10,000 square meters, and among them 5-6 females rise in full-bodied offspring, which completes the life cycle.

[The results of the serological examination of medium-sized mammals in the natural foci of arbovirus infections in central Siberia]. / Rezul'taty serologicheskogo obsledovaniia srednikh mlekopitaiushchikh v prirodnykh ochagakh arbovirusnykh infektsii Srednei Sibiri.

The serological survey of white hares (n = 8), squirrels (n = 118), and Asian chipmunks (n = 486) in the dark coniferous forests of Middle Siberia revealed tick-borne encephalitis virus antihemagglutinins only in the former two species (37.5 +/- 17.1 and 7.6 +/- 2.4%, respectively) and in the squirrel, there is a close seasonal relation between the parameters of immune interbred and those virophoricity of taiga tick nymphs.

[The reaction of the tick Hyalomma asiaticum (Acarina, Ixodidae) to 1- to 4-GHz microwaves]. / Reaktsiia kleshscha Hyalomma asiaticum (Acarina, Ixodidae) na mikrovolny 1--4 GGts.

Low-energy microwave radiation in the frequency range in question was found to exert a noticeable biological action on H. asiaticum. Radiation delayed larval hatch by 3-20 days, increased the activity duration of newly moulted larvae by 17-24 days, reduces the survival of hungry larvae and nymphs by 4-10 days. The efficiency of the biological action of microwaves is enhanced by impairments in the natural developmental rhythm of the tick.

[The correlation of light and hygrothermal factors in the determination of the morphogenetic diapause of the larvae and nymphs of the taiga tick in the northwestern spurs of the eastern Sayan]. / Sootnoshenie svetovogo i gigrotermicheskogo faktorov v determinatsii morfogeneticheskoi diapauzy lichinok i nimf taezhnogo kleshcha na severo-zapadnykh otrogakh Vostochnogo Saiana.

In the taiga of the region in question at the latitude 56 degrees N the photoperiod regimens of 25 June and 21 July determine 50% diapause in engorged larvae and nymphs of Ixodes persulcatus. The durations of the day time on these dates are 17 h 34 min and 16 h 45 min respectively. Seasonal fluctuations of temperature and precipitation in May-June are the main reasons for the modification of the critical photoperiod. In some years the critical dates for larvae and nymphs vary under these factors within the limits 11-28 July and 19 June-6 July respectively. The critical durations of the day time for these date limits are 16 h 20 min-17 h 12 min and 17 h 23 min-17 h 37 min respectively.

[The absolute and relative abundance of imagoes of the taiga tick (Ixodidae) in the dark coniferous-deciduous valley forests of the northwestern spurs of the eastern Sayan]. / Absoliutnoe i otnositel'noe obilie imago taezhnogo kleshcha (Ixodidae) v dolinnykh temnokhvoino-listvennykh lesakh severo-zapadnykh otrogov Vostochnogo Saiana.

Additions to the method of estimating the absolute and relative numbers of the pasture ticks in test areas are proposed. Additions take in attention the influence of ticks immigrating to the test area in dependence upon the isolation rate of that area. It has been stated that in the period 1987-1991 the mean relative number of I. persulcatus (mean tick number per 1 flag-kilometer of three decades) was 48, 27, 57, 29 and 38; the absolute tick number on test area (tick number per 1 hectare)--1590, 691, 1194, 641 and 668; the absolute tick number near the field station--1402, 647, 1496, 668 and 1108 respectively.