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Biomedical subjects

S P Chunikhin

Publications and source records attributed to S P Chunikhin.

At least 19 recordsLinked to original sources
PubMed1996

Preliminary studies on virus and spirochete accumulation in the cement plug of ixodid ticks.

We provide evidence that tick-borne encephalitis virus and Borrelia burgdorferi s.l. are accumulated in the cement plug in the host skin within the first few hours after tick attachment. Extirpation of the tick without the cement plug, even very soon after the attachment, did not prevent the transmission by Ixodes ricinus, Ixodes persulcatus or Dermacentor reticulatus to mice. This was within 1 hour in the case of the TBE virus and after 20-22 h of attachment, in the case of Borrelia and I. persulcatus. The epidemiological significance of these findings is discussed.

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PubMed1995

Bacteriocidal qualities of ixodid tick (Acarina: Ixodidae) salivary cement plugs and their changes under the influence of a viral tick-borne pathogen.

The abundance of bacteriocidal compounds contained in the salivary cement plug of ixodid ticks was changed because of the reproduction of tick-borne encephalitis virus (TBEV) in their bodies. The size of TBEV-infected Ixodes persulcatus Shulze lytic zone surrounding the cement plug enlarged to that of naive ticks, whereas Micrococcus lysodeikticus (Cohn) lytic zones induced by the cement plugs of TBEV-infected Amblyomma hebraeum Koch nymphs or Rhipicephalus appendiculatus Neumann females were reduced, compared with those produced by noninfected specimens. It is possible that an increase of lysozyme production by the primary TBEV vectors (Ixodinae) infected salivary gland cells, compared with suppression of the bacteriocidal qualities of saliva of ticks that are not TBEV vectors in nature (Amblyomminae), is an indication of the specificity of a I. persulcatus-TBEV interface.

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PubMed1986

Peculiarities of tick-borne encephalitis virus reproduction in Haemaphysalis inermis ticks and their explants.

Virological, electron microscopic and immunomorphological investigation on the reproduction of tick-borne encephalitis (TBE) virus in Haemaphysalis inermis ticks and in tissue explants from nymphs during their metamorphosis revealed that the virus reproduced in the cells of different tissues and organs of ticks which were in different phases and stages of life cycle. During the eclipse phase of TBE virus persistence in ticks, when no virus could be demonstrated by infectivity assay, viral particles were detected by electron microscopy.

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PubMed1985

Role of macrophages in the pathogenesis of experimental tick-borne encephalitis in mice.

In vivo phagocytosis activity of macrophages (PAM) was temporarily suppressed in mice by application of a suspension of microscopic from particles. As demonstrated, a reversible block of 70% of PAM was accompanied by a marked increase of the lethality during the acute tick-borne encephalitis (TBE) virus infection. Asymptomatic persistence of TBE virus in the brain was 4 times more frequent in mice with PAM defect than in immuno-competent mice. Suppression of PAM during the first 48 hr post infection (p.i.) did not affect interaction of B-, T-lymphocytes and macrophages. Cytotoxic activity of splenocytes against TBE virus-infected mouse embryo fibroblasts (MEF) was alike irrespective of whether cytotoxic cells were collected from mice inoculated or not inoculated with microscopic iron suspension. Similarly, frequency of seroconversion did not differ in these groups of mice. Adoptively transferred peritoneal macrophages from TBE virus-infected or intact mice did not exert any protective activity. The presence of splenic macrophages was necessary neither in adoptive immunity transfer in vivo nor in cytotoxic activity of T-lymphocytes directed to virus-infected targets in vitro. It was further found that peritoneal macrophages (PM) both from TBE virus immunized and non immunized donors in the presence of antibodies to TBE virus acquired the capability to kill TBE virus-infected target cells. Antibody-dependent cytotoxicity (ADC) of macrophages was associated with population of phagocytic cels.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1985

Variability of Powassan virus cultured in tissue explants and organism of Hyalomma anatolicum ticks.

The variability of Powassan virus was studied during successive passages in Hyalomma anatolicum ticks or prolonged reproduction in their tissue explants. It had been shown that in the course of tick passages and during reproduction in the explants, pathogenicity of the virus in respect to causing acute disease in mice after peripheral inoculation was decreased, while virus ability to cause death after intracerebral (i.c.) inoculation remained unchanged. In mice infected with the original strain P-40 of Powassan virus damaging effect of the immune response prevailed, while in mice infected with the strains passaged for a long time in ticks (strain P-40Hat) or in tick tissue explants (strain P-40Haex), the protective effect of the immune response was prominent.

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PubMed1982

[Correlations of the indices of tick-borne encephalitis morbidity in the Maritime Territory with natural factors].

The comparison of the absolute figures of the tick-borne encephalitis morbidity and mortality rates in the Primorye Territory for 16-22 years with the climatic parameters and the characteristics of the natural focus in the key area has allowed one to reveal close relationship between the two above-mentioned epidemiological characteristics and such factors as the intensity of monsoon rains and the size of the population of large-toothed redback voles in the previous year. Multiple regression equations suitable for the prognosis of the morbidity and mortality levels in the territory for the coming year have been set up.

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PubMed1982

[Modeling a persistent infection by tick-borne encephalitis virus strains in a cell culture of the clawed toad].

Differences in the ability of 12 tick-borne encephalitis virus strains to induce persistent infection in the culture of clawed frog cells incubated at 26-32 degrees C were shown. In 8 strains the process of persistence was accompanied by the stable preservation of the infectious virus in the culture medium during 10 passages, while in 4 strains the virus disappeared already in passages 3-8.

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PubMed1981

Experimental characteristics of viraemia caused by two strains of tick-borne encephalitis virus in small rodents.

Two strains of tick-borne encephalitis (TBE) virus differing in virulence for subcutaneously (s.x.) inoculated adult white mice elicited different levels of viraemia in small rodents. Strain Skalica of a lowered virulence caused no detectable viraemia in adult Clethrionomys glareolus and only negligible viraemia in adult Apodemus sylvaticus, Microtus arvalis and Pitymys subterraneus species. The virulent strain 204 gave rise to higher levels of viraemia, sufficient for infection of TBE virus vectors-ixodid ticks, in most individuals of the rodent species tested. Viraemia surpassing the threshold values of infectivity for tick vectors was also found in some juvenile and adult Clethrionomys rufocanus, C. rutilus and Micromys minutus. The level of viraemia depended on rodent species and age, and exhibited individual variability.

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PubMed1979

Viraemia in Clethrionomys glareolus -- a new ecological marker of tick-borne encephalitis virus.

Viraemia was studied in adult Clethrionomys glareolus subcutaneously infected with 12 strains of tick-borne encephalitis (TBE) virus isolated in western and eastern foci of TBE. Nine strains caused viraemia regularly or irregularly, reaching titres higher than the threshold level of TBE virus infectivity for its vectors, ixodid ticks (2.5 -- 4.5 log LD50/0,03 ml) and three strains caused lower levels of hiraemia (0.4 -- 1.5 log LD50/0.03 ml). The ability or inability of various TBE virus strains to cause viraemia in adult C. glareolus in titres higher than the threshold level of infectivity for tick vectors was considered as an ecological marker of TBE virus. This marker was designated Cg: Cg+ and Cg- for TBE virus strains inducing respectively higher and lower levels of viraemia than the threshold of infectivity.

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PubMedDate not supplied

[A trial at using the systemic action of ivermectin for suppressing the vector capacity of ticks (Ixodidae) infected with the tick-borne encephalitis virus].

Adult Dermacentor marginatus hatched from nymphs infected with TBE virus and poisoned with ivermectin retain their vector abilities. Even small individuals with a 1.5-2 times lesser mass as against the reference mass contain the virus in the body in the same titers and the virions in salivary gland alveoli. Administration of an oil solution of ivermectin into the stomach of white mice, nymph feeders, in a dose surpassing threefold the dose recommended for intramuscular injection of this agent completely suppressed shedding of intact nymphs but did not suppress it in those infected. The nymph mass, size and mass of adult ticks hatched from them dropped under the effect of ivermectin dosage build-up in both intact and infected ticks, but these processes were slower in ticks infected with TBE virus. The authors suggest that the ticks infected with TBE virus are much more resistant to the process of gamma-aminobutyric acid depression, the mechanism of ivermectin action. They emphasize the necessity of bearing in mind the possible differences in the reactions to systemic poisons of intact and infected ticks when organizing vector control measures.

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PubMedDate not supplied

[Differences in the distant transmission of the tick-borne encephalitis virus by ixodid ticks of 2 subfamilies].

Simultaneous but separate feeding of ticks on nonviremic animal (guinea pig) has shown that Amblyomminae ticks are practically unable to transmit distantly tick-borne encephalitis virus (TBEV) to the specimens of their own subfamily and to Ixodinae as well. Ixodes persulcatus and I. ricinus displayed their ability as donors and recipients of TBEV (adults and nymphs) not only for their own subfamily representatives but also as donors for recipients of Amblyomminae subfamily (nymphs and adults of Dermacentor and Rhipicephalus and nymphs of Haemaphysalis). Experimental and literature data analysis permits the authors to conclude that the very important role of TBEV circulation in nature belongs to the distant virus transmission. The absence of such type of virus exchange among Amblyomminae excludes this group of ticks from active virus circulation in TBEV foci.

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PubMedDate not supplied

[Plant smells---important determinants in the behavior and rate of development of ixodid disease vectors].

Experiments with nymphs of Ixodes persulcatus and Dermacentor marginatus have shown that the rate and degree of engorgement, dropping off from the mouse, metamorphosis longevity and weight of emerging imagoes change under plant odour influence. The influence of acetone extract vapours of pepper, poplar buds, linden and aspen was tested. Under the influence of the vapour, acting as an attractant for the adults, engorgement weight of their nymphs and the weight of imagoes emerging from them increased; attractants change the nymph-imago metamorphosis duration as well. Repellent acting odours, as a rule, produce an opposite reaction. The phenomenon of the inversion of the infected D. marginatus reaction to the odour is proved in nymphs. Attractant for naive adult ticks (poplar buds) increased the time of feeding and weight of nymphs in comparison with the control. Just the opposite: nymphs infected with tick-borne encephalitis (TBE) virus produce an opposite reaction--weight decrease under influence of poplar buds as the repellent. Importance of the above phenomena for the ticks distribution and TBE epizootiology is discussed.

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