Ixodes tick-borne borreliosis and tick-borne encephalitis in the Udmurt republic: retrospective analysis of their spread

The primary clinical-anamnestic and laboratory data on 1,062 cases, registered in Udmurtia in 1965-1968 and caused by the bites of taiga ticks (ixodes persulcatus), were retrospectively analyzed. The study revealed that not less than 27% of these cases could be regarded as cases of Ixodes tick-borne borreliosis (ITBB); formerly they were classified with tick-born encephalitis (TBE) or diseases of unclear etiology. The spread of ITBB on the territory of the Udmurt Republic was shown to be similar to that of TBE.     

The structure of tick-borne encephalitis (TBE) foci in Central Europe

Summary The investigations on the structure of TBE foci were carried out in the localities Jívová (northern Moravia), Topolianky and írany (Tribe Mountains), and environs of Debreczén (Pannonian lowland, Hungary). The biphasic activity curve of Ixodes ricinus, characteristic for the central European conditions was confirmed in all three types.In some localities two or three tick species as vectors come into consideration and the unequal seasonal occurrence of individual species results in a permanent presence of virus-harbouring ticks in nature throughout the year.The average population density of ticks per hectare in a focus near topolianky in mid-April, 1969, reached 46,000 nymphae and 50,000 adults. About 1% of the tick population were found to be viruliferous.Great differences were found in the composition of plant communities, mammalian synusies and in the population density of small mammals and ticks within the regions studied.Each elementary focus consists of many microfoci where the territories of individual host species overlap in space and time. Nests in tree holes and underground probably also belong to these microfoci. The maintenance hosts and indicators in each type of focus are mentioned. Free-living Carnivora can be considered as incidental hosts in each type of focus.     

First experience with ELISA serosurvey for tick-borne borreliosis (Lyme disease) in Czechoslovakia

Antibodies to Borrelia burgdorferi were searched for in the sera from two groups of hospital patients and one group of healthy agricultural workers. The antibody response was measured by the authors' own modification of the ELISA method employing the antigen prepared from Borrelia recurrentis strain propagated in laboratory mice. Positive antibody titres to Borrelia were demonstrated in 5 out of the 44 patients admitted to the Infectious Diseases Clinic, in 8 out of the 32 patients from the Neurologic Clinic and in 16 out of the 52 healthy agricultural workers living in areas infested with ticks. These findings are interpreted as showing the topicality of the Lyme disease problem in Czechoslovakia.     

Treatment of Lyme borreliosis

Borrelia burgdorferi sensu lato is the causative agent of Lyme borreliosis in humans. This inflammatory disease can affect the skin, the peripheral and central nervous system, the musculoskeletal and cardiovascular system and rarely the eyes. Early stages are directly associated with viable bacteria at the site of inflammation. The pathogen-host interaction is complex and has been elucidated only in part. B. burgdorferi is highly susceptible to antibiotic treatment and the majority of patients profit from this treatment. Some patients develop chronic persistent disease despite repeated antibiotics. Whether this is a sequel of pathogen persistence or a status of chronic auto-inflammation, auto-immunity or a form of fibromyalgia is highly debated. Since vaccination is not available, prevention of a tick bite or chemoprophylaxis is important. If the infection is manifest, then treatment strategies should target not only the pathogen by using antibiotics but also the chronic inflammation by using anti-inflammatory drugs.     

Viral zoonoses in Europe

A number of new virus infections have emerged or re-emerged during the past 15 years. Some viruses are spreading to new areas along with climate and environmental changes. The majority of these infections are transmitted from animals to humans, and thus called zoonoses. Zoonotic viruses are, as compared to human-only viruses, much more difficult to eradicate. Infections by several of these viruses may lead to high mortality and also attract attention because they are potential bio-weapons. This review will focus on zoonotic virus infections occurring in Europe.     

The infectiousness of Ixodes persulcatus ticks with the causative agents of Lyme disease and tick-borne encephalitis simultaneously

By means of individual bacteriological and virological investigations of adult Ixodes persulcatus ticks and comparison of obtained results there has been established their simultaneous spontaneous infection with agents of Lyme disease and tick-borne encephalitis. A possible frequency of such mixed infection in these vectors is being discussed.     

Review The ecology of ticks transmitting Lyme borreliosis

The main vectors of Borrelia burgdorferi sensu lato, the cause of Lyme borreliosis, are ixodid ticks of the Ixodes persulcatus species complex. These ticks, which occur throughout the northern temperate zone, have very similar life cycles and ecological requirements. All are three-host ticks, with the immature stages mainly parasitizing small to medium-sized mammals and birds and the adult females parasitizing large mammals such as deer, cattle, sheep and hares. The host-seeking stages show a distinct seasonality, which is regulated by diapause mechanisms and there appear to be major differences in this respect between the Old World and New World species. Most cases of human borreliosis are transmitted in the summer by the nymphal stages, with the exception of the Eurasian species, I. persulcatus, in which the adult females are mainly responsible. The ticks acquire the spirochaetes from a wide variety of mammals and birds but large mammals do not seem to be infective, so that t icks that feed almost exclusively on large mammals, for example in some agricultural habitats, are rarely infected. The greatest tick infection prevalences occur in deciduous woodland harbouring a diverse mix of host species and the diversity of the different genospecies of B. burgdorferi s.l. is also greatest in such habitats. There is evidence that these genospecies have different host predilections but, apart from the fact that I. persulcatus does not seem to be infected by B. burgdorferi sensu stricto, they do not seem to be adapted to different tick strains or species. © Rapid Science Ltd. 1998     

Lyme borreliosis situation in North Africa

Many epidemiological studies were conducted for studying Lyme borreliosis (LB) which represents a new global public health problem. It is now the most common vector-borne disease in Europe and North America. The causative agent Borrelia burgdorferi sl is a bacterial species complex comprising 12 delineated and named species. In North Africa, few studies based on clinical and serological features, have suggested that LB could occur. Indeed, recent studies conducted in Tunisia, Algeria and Morocco have showm that Ixodes ricinus is present in cooler and humid area of these regions. These studies also revealed that this species is a vector of B. burgdorferi sl with high prevalence of infection. Using IFI and PCR tests, the mean rate of Borrelia-infection ranged from 50 to 60% in I. ricinus adult collected in Tunisia and Morocco and from 30 to 40% in nymphs; in contrast, the prevalence in larvae is less than 2.5%. Several strains of B. burgdorfer were isolated from adult and nymph I ricinus collected in Tunisia and Morocco. The identification of these strains and DNAs directly extracted from Ixodes was done by PCR-RFLP and sequence analysis. The results showed that B. lusitaniae (genotypes Poti B2 and Poti B3) is the predominant species circulating in I. ricinus in Tunisia and Morocco, B. garinii and B. burgdorferi ss and B lusitaniae were also present but very rare. These results provide the evidence for the existence of B. burgdorferi sl in North Africa; however, the impact of LB in the human population seem to be negligible and the seroprevalence of Borrelia in forest workers (considered as population at high risk) in Tunisia is less than 4%.     

Prognosis in tick-borne encephalitis

The paper presents a review of suggested and used methods of predicting the number of the main vector and its infection with the tick-borne encephalitis virus. It has been suggested that most practically important are long-term prognoses of tendencies in the changes of the parasitic system on the basis of retrospective estimation of the recurrence of its changes, that is, the definition of probability of recurrence of most important characters (states) of a parasitic system in the presence of appropriate external conditions.     

Microbiological and serological diagnosis of Lyme borreliosis

In Europe, Lyme borreliosis is caused by Borrelia burgdorferi sensu stricto, B. afzelii, B. garinii and the recently described species B. spielmanii. For the development of diagnostic tools, the heterogeneity of the causative agents must be considered. The serological diagnosis should follow the principle of a two-step procedure: a sensitive enzyme-linked immunosorbent analysis as the first step, followed by immunoblot (IgM and IgG) if reactive. The sensitivity and standardization of immunoblots have been enhanced by the use of recombinant antigens instead of whole cell lysates. Improved sensitivity has resulted from the use of recombinant proteins primarily expressed in vivo (e.g. VlsE) and the combination of homologous proteins from different strains (e.g. DbpA). At present, detection rates for serum antibodies are 20-50% in localized, 70-90% in disseminated early and nearly 100% in late disease. Detection of the borreliae by culture or PCR should be confined to specific indications. The best results are obtained from skin biopsies (50-70% with culture or PCR) and synovial tissue or fluid (50-70% with PCR). Cerebrospinal fluid is positive in only 10-30%. Methods that are not recommended for diagnostic purposes include antigen tests in body fluids, PCR of urine and lymphocyte transformation tests.     

森林脑炎病毒分子生物学研究进展

森林脑炎(TBE)病毒属黄病毒科,基因姐RNA含有单个开放阅读框架,5′端编码病毒的结构蛋白,3′端编码非结构蛋白。翻译成聚蛋白后,通过细胞和病毒编码的蛋白酶裂解产生单个的病毒蛋白。成熟的病毒是由两个相关的E和M膜蛋白脂质包膜所包围的立体对称的核衣壳组成。包膜E蛋白在病毒的感染周期中对细胞的识别和穿入细胞具有极其重要的功能,同时E蛋白诱导保护性的免疫反应,E蛋白内某一位点单个氨基酸的改变可引起病毒毒力的改变。因此,对TBE病毒分子生物学的研究有助于了解病毒与宿主细胞相互作用的机理,为病毒感染的特异性诊断、疫苗的研制和抗病毒药物的设计提供理论依据。     

Cutting edge: T cell-mediated pathology in murine Lyme borreliosis

Even in the absence of an appropriate model or direct evidence, T cells have been hypothesized to exacerbate the manifestations of Lyme disease. To define definitely the role of T cells in Lyme disease, the course of disease in immunocompetent and B cell-deficient mice was compared. By 8 wk postinoculation, immunocompetent mice resolved both carditis and arthritis, whereas foci of myocarditis and severe destructive arthritis characterized disease of B cell-deficient mice. Cell transfer experiments using infected B6-Rag1 knock out mice demonstrated that: 1) innate immunity mediated the initial sequelae of infection, 2) transferring both naive T cells and B cells induced resolution of carditis and arthritis, 3) infected mice reconstituted with T cells developed myocarditis and severe destructive arthritis, and 4) CD4+ T cells were responsible for the observed immune-mediated pathology. These data demonstrate directly the deleterious effect of T cells in Lyme disease.     

Lyme borreliosis: host responses to Borrelia burgdorferi.

The chronic inflammatory condition that develops after infection by B. burgdorferi is a complex process resulting from host responses to a limited number of organisms. Amplification mechanisms driven by potent proinflammatory molecules, i.e., IL-1, may explain the vigorous response to a paucity of organisms. Spirochete dissemination to distant locations involves adherence to and penetration across endothelium and may be facilitated by host responses that increase vessel permeability. The apparent lack of tissue tropism in Lyme disease is reflected in the organism's ability to adhere to different eucaryotic cell types in vitro and the wide distribution of B. burgdorferi in various organs of infected humans and experimentally infected animals. While phagocytosis and complement activation have been observed in vitro, the specific immune response that develops in humans is inefficient in eradicating the organisms, which may possess some mechanism(s) to evade this response. There is significant evidence for host autoreactivity based on antigenic cross-reactivity between the 41-kDa flagellar subunit and stress proteins of the spirochetes and endogenous host cell components. Although the outer surface proteins appear to be suitable candidates as targets for vaccination in animal studies, fundamental differences in the immune response to spirochetal components may preclude their use in humans.