Ixodes scapularis and Ixodes ricinus tick cell lines respond to infection with tick-borne encephalitis virus: transcriptomic and proteomic analysis

BACKGROUND

Ixodid ticks are important vectors of a wide variety of viral, bacterial and protozoan pathogens of medical and veterinary importance. Although several studies have elucidated tick responses to bacteria, little is known about the tick response to viruses. To gain insight into the response of tick cells to flavivirus infection, the transcriptomes and proteomes of two Ixodes spp cell lines infected with the flavivirus tick-borne encephalitis virus (TBEV) were analysed.

METHODS

RNA and proteins were isolated from the Ixodes scapularis-derived cell line IDE8 and the Ixodes ricinus-derived cell line IRE/CTVM19, mock-infected or infected with TBEV, on day 2 post-infection (p.i.) when virus production was increasing, and on day 6 p.i. when virus production was decreasing. RNA-Seq and mass spectrometric technologies were used to identify changes in abundance of, respectively, transcripts and proteins. Functional analyses were conducted on selected transcripts using RNA interference (RNAi) for gene knockdown in tick cells infected with the closely-related but less pathogenic flavivirus Langat virus (LGTV).

RESULTS

Differential expression analysis using DESeq resulted in totals of 43 and 83 statistically significantly differentially-expressed transcripts in IDE8 and IRE/CTVM19 cells, respectively. Mass spectrometry detected 76 and 129 statistically significantly differentially-represented proteins in IDE8 and IRE/CTVM19 cells, respectively. Differentially-expressed transcripts and differentially-represented proteins included some that may be involved in innate immune and cell stress responses. Knockdown of the heat-shock proteins HSP90, HSP70 and gp96, the complement-associated protein Factor H and the protease trypsin resulted in increased LGTV replication and production in at least one tick cell line, indicating a possible antiviral role for these proteins. Knockdown of RNAi-associated proteins Argonaute and Dicer, which were included as positive controls, also resulted in increased LGTV replication and production in both cell lines, confirming their role in the antiviral RNAi pathway.

CONCLUSIONS

This systems biology approach identified several molecules that may be involved in the tick cell innate immune response against flaviviruses and highlighted that ticks, in common with other invertebrate species, have other antiviral responses in addition to RNAi.

EPIDEMIOLOGY, CLINICAL AND LABORATORY FEATURES OF CRIMEAN-CONGO HEMORRHAGIC FEVER IN GEORGIA

Crimean-Congo hemorrhagic fever virus transmitted to humans by Hyalomma ticks or by direct contact with the blood of infected humans or domestic animals. The most common clinical signs of CCHF are fever, nausea, headache, diarrhea, myalgia, petechial rash, and bleeding. CCHF is a severe disease in humans with a fatality rate up to 15-85%. This study was undertaken to determine the predictors of fatality among patients with CCHF based on epidemiological, clinical, and laboratory findings. 34 patients were enrolled in the study, aged 4 to 77; 17 - male and 17 female. 3 of them were fatal cases. All of them were from Shua Kartli: Khashuri, Gori and Kaspi districts, involved in farming/handling livestock and the history of tick bite was present in most of patients. Evaluation of the epidemiological characteristics of this cases showed that the female to male ratio was nearly similar. The disease is common in the rural areas of the region, mostly in the actively working age group and almost all patients were farmers. The results of our study show that the most cardinal clinical and laboratory features of Crimean-Congo hemorrhagic fever are - acute beginning of disease, high fever, intoxication and hemorrhagic symptoms, thrombocytopenia, high level of aminotransferases and creatine. Predictors of fatality are: an altered mental status, in early stage of disease dramatic decreased thrombocytes count and significantly high level of aspartate aminotransferase, also longer the mean prothrombin time and INR.

Rhipicephalus rossicus, a neglected tick at the margin of Europe: a review of its distribution, ecology and medical importance

Rhipicephalus rossicus (Ixodida: Ixodidae) is a three-host tick with a broad host spectrum that includes wild animals, pets, livestock and humans. Despite its local abundance in certain areas, most of the available information on R. rossicus was published decades ago, mainly by former soviet authors. Its distribution largely overlaps the Eurasian steppe. However, its range may be more extensive than is currently known because this species may have been misidentified as Rhipicephalus sanguineus, principally in areas where the latter species is present. Although R. rossicus has been occasionally reported to feed on people, little attention has been given to its medical importance. It has been shown to have a vectorial role in the transmission of Francisella tularensis, Crimean-Congo haemorrhagic fever virus and West Nile virus. However, the vectorial importance of R. rossicus may be significantly greater, mainly as the closely related species R. sanguineus s.l. is known to transmit a very wide spectrum of pathogens. The probably underestimated vectorial role of R. rossicus may represent a hidden public health threat.

The global distribution of Crimean-Congo hemorrhagic fever

BACKGROUND

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne infection caused by a virus (CCHFV) from the Bunyaviridae family. Domestic and wild vertebrates are asymptomatic reservoirs for the virus, putting animal handlers, slaughter-house workers and agricultural labourers at highest risk in endemic areas, with secondary transmission possible through contact with infected blood and other bodily fluids. Human infection is characterized by severe symptoms that often result in death. While it is known that CCHFV transmission is limited to Africa, Asia and Europe, definitive global extents and risk patterns within these limits have not been well described.

METHODS

We used an exhaustive database of human CCHF occurrence records and a niche modeling framework to map the global distribution of risk for human CCHF occurrence.

RESULTS

A greater proportion of shrub or grass land cover was the most important contributor to our model, which predicts highest levels of risk around the Black Sea, Turkey, and some parts of central Asia. Sub-Saharan Africa shows more focalized areas of risk throughout the Sahel and the Cape region.

CONCLUSIONS

These new risk maps provide a valuable starting point for understanding the zoonotic niche of CCHF, its extent and the risk it poses to humans.

Metagenomic profile of the viral communities in Rhipicephalus spp. ticks from Yunnan, China

Besides mosquitoes, ticks are regarded as the primary source of vector-borne infectious diseases. Indeed, a wide variety of severe infectious human diseases, including those involving viruses, are transmitted by ticks in many parts of the world. To date, there are no published reports on the use of next-generation sequencing for studying viral diversity in ticks or discovering new viruses in these arthropods from China. Here, Ion-torrent sequencing was used to investigate the presence of viruses in three Rhipicephalus spp. tick pools (NY-11, NY-13, and MM-13) collected from the Menglian district of Yunnan, China. The sequencing run resulted in 3,641,088, 3,106,733, and 3,871,851 reads in each tick pool after trimming. Reads and assembled contiguous sequences (contigs) were subject to basic local alignment search tool analysis against the GenBank database. Large numbers of reads and contigs related to known viral sequences corresponding to a broad range of viral families were identified. Some of the sequences originated from viruses that have not been described previously in ticks. Our findings will facilitate better understanding of the tick virome, and add to our current knowledge of disease-causing viruses in ticks living under natural conditions.

A 4-year study of a natural tick-borne encephalitis virus focus in Hungary, 2010-2013

A tick-borne encephalitis virus focus was identified in a former goat pasture that had been associated with a milk-borne encephalitis outbreak in 2007. Ticks and rodents were sampled monthly from April 2010 to October 2013 on two separate 0.5 ha sampling sites. At site 1, three tick-borne encephalitis virus strains were isolated from a total of 7,247 sampled ticks; 28 of the 539 tested sera (5.19%) were seropositive. At site 2, from the 2,369 sampled ticks, virus was not isolated, tests of 284 rodent sera resulted in 14 positives (4.93%). For survival, the virus needs a territory with continuously dense rodent and tick population, although observed TBEV prevalence was low both in ticks and in rodents. Sampling points of positive ticks and rodents did not coincided exactly, at a certain time only some m(2) territory is dangerous, these hot spots change unpredictably as positive ticks die or move on with their hosts.

Survival dynamics of tick-borne encephalitis virus in Ixodes ricinus ticks

Biotic factors contributing to the survival of tick-borne viruses in nature are poorly understood. Using tick-borne encephalitis virus (TBEV) and its principal European vector, Ixodes ricinus, we examined the relative roles of salivary gland infection, co-feeding transmission, and moulting in virus survival. Virus titres in the salivary glands increased after blood-feeding in a time- and dose-dependent manner. This was observed in ticks infected by inoculation but not in ticks infected by the natural route of co-feeding. Amplification of infection prevalence occurred via co-feeding. However, when larvae or nymphs subsequently moulted, the infection prevalence dramatically declined although this was not observed when ticks were infected by inoculation. Trans-stadial survival is a hitherto overlooked parameter that may contribute to the low incidence of TBEV infection in field-collected I. ricinus ticks.

A virulent strain of deformed wing virus (DWV) of honeybees (Apis mellifera) prevails after Varroa destructor-mediated, or in vitro, transmission

The globally distributed ectoparasite Varroa destructor is a vector for viral pathogens of the Western honeybee (Apis mellifera), in particular the Iflavirus Deformed Wing Virus (DWV). In the absence of Varroa low levels DWV occur, generally causing asymptomatic infections. Conversely, Varroa-infested colonies show markedly elevated virus levels, increased overwintering colony losses, with impairment of pupal development and symptomatic workers. To determine whether changes in the virus population were due Varroa amplifying and introducing virulent virus strains and/or suppressing the host immune responses, we exposed Varroa-naïve larvae to oral and Varroa-transmitted DWV. We monitored virus levels and diversity in developing pupae and associated Varroa, the resulting RNAi response and transcriptome changes in the host. Exposed pupae were stratified by Varroa association (presence/absence) and virus levels (low/high) into three groups. Varroa-free pupae all exhibited low levels of a highly diverse DWV population, with those exposed per os (group NV) exhibiting changes in the population composition. Varroa-associated pupae exhibited either low levels of a diverse DWV population (group VL) or high levels of a near-clonal virulent variant of DWV (group VH). These groups and unexposed controls (C) could be also discriminated by principal component analysis of the transcriptome changes observed, which included several genes involved in development and the immune response. All Varroa tested contained a diverse replicating DWV population implying the virulent variant present in group VH, and predominating in RNA-seq analysis of temporally and geographically separate Varroa-infested colonies, was selected upon transmission from Varroa, a conclusion supported by direct injection of pupae in vitro with mixed virus populations. Identification of a virulent variant of DWV, the role of Varroa in its transmission and the resulting host transcriptome changes furthers our understanding of this important viral pathogen of honeybees.

Honeybees are the most important managed pollinating insect, contributing billions of dollars to annual global agricultural production. Over the last century a parasitic mite, Varroa, has spread worldwide, with significant impacts on honeybee colony health as a consequence of its transmission of a cocktail of viruses while feeding on honeybee ‘blood’. The most important virus for colony health is deformed wing virus (DWV), high levels of which cause developmental deformities and premature ageing resulting in high overwintering colony losses. In experiments on individual Varroa-exposed pupae we demonstrate that a single type of virulent DWV is amplified 1,000–10,000 times in the recipient pupae, despite the mite containing a high diversity of replicating DWV strains. We could recapitulate this by direct injection of pupae with mixed virus populations, showing the virulent strain is advantaged by the route of transmission. In parallel, we detected changes in the immune response and developmental gene expression of the honeybee and propose that these contribute to the characteristic pathogenesis of DWV. Identification of a virulent strain of DWV has implications for therapeutic or prophylactic interventions to improve honeybee colony health, as well as contributing to our understanding of the biology of this important honeybee viral pathogen.

Estimated effects of projected climate change on the basic reproductive number of the Lyme disease vector Ixodes scapularis

BACKGROUND

The extent to which climate change may affect human health by increasing risk from vector-borne diseases has been under considerable debate.

OBJECTIVES

We quantified potential effects of future climate change on the basic reproduction number (R0) of the tick vector of Lyme disease, Ixodes scapularis, and explored their importance for Lyme disease risk, and for vector-borne diseases in general.

METHODS

We applied observed temperature data for North America and projected temperatures using regional climate models to drive an I. scapularis population model to hindcast recent, and project future, effects of climate warming on R0. Modeled R0 increases were compared with R0 ranges for pathogens and parasites associated with variations in key ecological and epidemiological factors (obtained by literature review) to assess their epidemiological importance.

RESULTS

R0 for I. scapularis in North America increased during the years 1971-2010 in spatio-temporal patterns consistent with observations. Increased temperatures due to projected climate change increased R0 by factors (2-5 times in Canada and 1.5-2 times in the United States), comparable to observed ranges of R0 for pathogens and parasites due to variations in strains, geographic locations, epidemics, host and vector densities, and control efforts.

CONCLUSIONS

Climate warming may have co-driven the emergence of Lyme disease in northeastern North America, and in the future may drive substantial disease spread into new geographic regions and increase tick-borne disease risk where climate is currently suitable. Our findings highlight the potential for climate change to have profound effects on vectors and vector-borne diseases, and the need to refocus efforts to understand these effects.

[Middle East respiratory syndrome (MERS): bats or dromedary, which of them is responsible?]

In 2012 a new viral emergent human disease appeared in the Middle East. This entity was named MERS for' Middle East respiratory syndrome'. By January 9, 2014, the disease had already struck 178 persons of whom 75 died from respiratory failure and diarrhoea. As the new disease was very similar to the deadly SARS (2002-2003) and since it was provoked by a Betacoronavirus, chiroptera were first suspected to be at the origin of this infection. Morever, recent studies performed in Saudi Arabia showed that one individual of the bat Taphozous perforatus harbored a short nucleotide segment identical to the homologous segment present in the viral strain isolated from the index-case of the epidemic. In addition, many strains of Betacoronavirus more or less related to those responsible for the MERS disease in man have been isolated from bats in Africa, Asia and Europe. However, another hypothesis was simultaneously proposed incriminating dromedary (Camelus dromedarius L.) as a likely actor in the transmission to human beings of the disease.We then reviewed data relative to other viral zoonosis in which dromedary was possibly implicated. This led to the provisional conclusion that this large mammal might play a role in the dissemination of the MERS-COV, the etiologic agent of the disease. This is based on epidemiological data and results of several serological surveys in animals.

Comparison of the prevalence of Crimean-Congo hemorrhagic fever virus in endemic and non-endemic Bulgarian locations

BACKGROUND & OBJECTIVES

The Balkans is an endemic region for Crimean-Congo hemorrhagic fever (CCHF), caused by the CCHF virus (CCHFV). Several Bulgarian regions comprised of smaller locations are categorized either as endemic or non-endemic for CCHF. However, little is known about the dynamics that underlie the development of endemicity within the locations throughout the years.

METHODS

Seven locations categorized as endemic in one central Bulgarian region (Stara Zagora) were compared to seven non-endemic areas. During the period 2006-12, a total of 1775 blood samples from cattle, were tested for anti-CCHFV antibodies using an indirect immunofluorescence antibody assay. Also, the infestation of 617 mature ticks for CCHFV was studied using a combination of an immunofluorescence haemocytes assay and molecular-virological methods.

RESULTS

Anti-CCHFV antibodies were established in 7.89% (140/1775) of the sera. The average CCHFV-infestation in the ticks was 1.46% (9/617). CCHFV was detected in three tick species: H.m. marginatum (3.73%, 6/161), being the main vector of the infection; R. sanguineus (1.63%, 2/123); and I. ricinus (1.96%, 1/51).

INTERPRETATION & CONCLUSION

The data for the endemic and non-endemic locations did not reveal significant differences for the prevalence of CCHFV. Mosaic dispersion of the virus was determined in the studied region and the results did not vary significantly throughout the investigated years.

Virus investigation in ticks from migratory birds in Italy

The role of migratory birds in circulation tick-borne viruses needs to be better defined. In order to assess the potential role of migratory birds in exotic virus spread, we conducted a study to identify ticks collected from migratory birds in the Central Region of Italy, and performed molecular investigation for Crimea-Congo Hemorrhagic Fever (CCHFV), West Nile fever (WNFV) and Usutu (USUV) in the vectors. A total of 137 competent ticks were collected with predominance of Hyalomma species. Although, negative results were obtained for all viruses considered, the high proportion of Hyalomma ticks highlights the potential risk for the dissemination of tick-borne viruses through infested migratory birds.

Detection of lumpy skin disease virus in saliva of ticks fed on lumpy skin disease virus-infected cattle

Lumpy skin disease is an economically important disease of cattle that is caused by the lumpy skin disease virus (LSDV), which belongs to the genus Capripoxvirus. It is endemic in Africa and outbreaks have also been reported in the Middle-East. Transmission has mostly been associated with blood-feeding insects but recently, the authors have demonstrated mechanical transmission by Rhipicephalus appendiculatus as well as mechanical/intrastadial and transstadial transmission by Amblyomma hebraeum. Saliva is the medium of transmission of pathogens transmitted by biting arthropods and, simultaneously, it potentiates infection in the vertebrate host. This study aimed to detect LSDV in saliva of A. hebraeum and R. appendiculatus adult ticks fed, as nymphs or as adults, on LSDV-infected animals, thereby also demonstrating transstadial or mechanical/intrastadial passage of the virus in these ticks. Saliva samples were tested for LSDV by real-time PCR and virus isolation. Supernatants obtained from virus isolation were further tested by real-time PCR to confirm that the cytopathic effects observed were due to LSDV. Lumpy skin disease virus was detected, for the first time, in saliva samples of both A. hebraeum and R. appendiculatus ticks. At the same time, mechanical/intrastadial and transstadial passage of the virus was demonstrated and confirmed in R. appendiculatus and A. hebraeum.

Influence of laboratory animal hosts on the life cycle of Hyalomma marginatum and implications for an in vivo transmission model for Crimean-Congo hemorrhagic fever virus

Crimean-Congo hemorrhagic fever virus (CCHFV) is one of the most geographically widespread arboviruses and causes a severe hemorrhagic syndrome in humans. The virus circulates in nature in a vertebrate-tick cycle and ticks of the genus Hyalomma are the main vectors and reservoirs. Although the tick vector plays a central role in the maintenance and transmission of CCHFV in nature, comparatively little is known of CCHFV-tick interactions. This is mostly due to the fact that establishing tick colonies is laborious, and working with CCHFV requires a biosafety level 4 laboratory (BSL4) in many countries. Nonetheless, an in vivo transmission model is essential to understand the epidemiology of the transmission cycle of CCHFV. In addition, important parameters such as vectorial capacity of tick species, levels of infection in the host necessary to infect the tick, and aspects of virus transmission by tick bite including the influence of tick saliva, cannot be investigated any other way. Here, we evaluate the influence of different laboratory animal species as hosts supporting the life cycle of Hyalomma marginatum, a two-host tick. Rabbits were considered the host of choice for the maintenance of the uninfected colonies due to high larval attachment rates, shorter larval-nymphal feeding times, higher nymphal molting rates, high egg hatching rates, and higher conversion efficiency index (CEI). Furthermore, we describe the successful establishment of an in vivo transmission model for CCHFV in a BSL4 biocontainment setting using interferon knockout mice. This will give us a new tool to study the transmission and interaction of CCHFV with its tick vector.

Research on the ecology of ticks and tick-borne pathogens--methodological principles and caveats

Interest in tick-transmitted pathogens has experienced an upsurge in the past few decades. Routine application of tools for the detection of fragments of foreign DNA in ticks, together with a high degree of interest in the quantification of disease risk for humans, has led to a marked increase in the number of reports on the eco-epidemiology of tick-borne diseases. However, procedural errors continue to accumulate in the scientific literature, resulting in misleading information. For example, unreliable identification of ticks and pathogens, erroneous interpretations of short-term field studies, and the hasty acceptance of some tick species as vectors have led to ambiguities regarding the vector role of these arthropods. In this review, we focus on the ecological features driving the life cycle of ticks and the resulting effects on the eco-epidemiology of tick-transmitted pathogens. We review the factors affecting field collections of ticks, and we describe the biologically and ecologically appropriate procedures for describing tick host-seeking activity and its correlation with environmental traits. We detail the climatic variables that have biological importance on ticks and explain how they should be properly measured and analyzed. We also provide evidence to critically reject the use of some environmental traits that are being increasingly reported as the drivers of the behavior of ticks. With the aim of standardization, we propose unambiguous definitions of the status of hosts and ticks regarding their ability to maintain and spread a given pathogen. We also describe laboratory procedures and standards for evaluating the vectorial capacity of a tick or the reservoir role of a host. This approach should provide a coherent framework for the reporting of research findings concerning ticks and tick-borne diseases.

First detection of heartland virus (Bunyaviridae: Phlebovirus) from field collected arthropods

Heartland virus (HRTV), the first pathogenic Phlebovirus (Family: Bunyaviridae) discovered in the United States, was recently described from two Missouri farmers. In 2012, we collected 56,428 ticks representing three species at 12 sites including both patients' farms. Amblyomma americanum and Dermacentor variabilis accounted for nearly all ticks collected. Ten pools composed of deplete nymphs of A. americanum collected at a patient farm and a nearby conservation area were reverse transcription-polymerase chain reaction positive, and eight pools yielded viable viruses. Sequence data from the nonstructural protein of the Small segment indicates that tick strains and human strains are very similar, ≥ 97.6% sequence identity. This is the first study to isolate HRTV from field-collected arthropods and to implicate ticks as potential vectors. Amblyomma americanum likely becomes infected by feeding on viremic hosts during the larval stage, and transmission to humans occurs during the spring and early summer when nymphs are abundant and actively host seeking.

A novel virus of the genus Cilevirus causing symptoms similar to citrus leprosis

Citrus leprosis in Colombia was previously shown to be caused by cytoplasmic Citrus leprosis virus (CiLV-C). In 2011, enzyme-linked immunosorbent assay and reverse-transcription polymerase chain reaction (RT-PCR)-based diagnostic methods failed to identify CiLV-C from citrus samples with symptoms similar to citrus leprosis; however, virions similar to CiLV-C were observed in the cytoplasm of the symptomatic leaves by transmission electron microscopy. Furthermore, the causal organism was transmitted by the false spider mite, Brevipalpus phoenicis, to healthy citrus seedlings. A library of small RNAs was constructed from symptomatic leaves and used as the template for Illumina high-throughput parallel sequencing. The complete genome sequence and structure of a new bipartite RNA virus was determined. RNA1 (8,717 nucleotides [nt]) contained two open reading frames (ORFs). ORF1 encoded the replication module, consisting of five domains: namely, methyltransferase (MTR), cysteine protease-like, FtsJ-MTR, helicase (Hel), and RNA-dependent RNA polymerase (RdRp); whereas ORF2 encoded the putative coat protein. RNA2 (4,989 nt) contained five ORFs that encode the movement protein (MP) and four hypothetical proteins (p7, p15, p24, and p61). The structure of this virus genome resembled that of CiLV-C except that it contained a long 3' untranslated terminal region and an extra ORF (p7) in RNA2. Both the RNA1 and RNA2 of the new virus had only 58 and 50% nucleotide identities, respectively, with known CiLV-C sequences and, thus, it appears to be a novel virus infecting citrus. Phylogenetic analyses of the MTR, Hel, RdRp, and MP domains also indicated that the new virus was closely related to CiLV-C. We suggest that the virus be called Citrus leprosis virus cytoplasmic type 2 (CiLV-C2) and it should be unambiguously classified as a definitive member of the genus Cilevirus. A pair of CiLV-C2 genome-specific RT-PCR primers was designed and validated to detect its presence in citrus leprosis samples collected from the Casanare and Meta states in Colombia.

Detection and characterization of tick-borne encephalitis virus in Baltic countries and eastern Poland

Ticks were collected from the vegetation in the Baltic countries Estonia, Latvia, Lithuania and eastern Poland and analyzed for the presence of tick-borne encephalitis virus (TBEV) by amplification of the partial E and NS3 genes. In Estonia we found statistically significant differences in the TBEV prevalence between I. persulcatus and I. ricinus ticks (4.23% and 0.42%, respectively). In Latvia, the difference in TBEV prevalence between the two species was not statistically significant (1.02% for I. persulcatus and 1.51% for I. ricinus, respectively). In Lithuania and Poland TBEV was detected in 0.24% and 0.11% of I. ricinus ticks, respectively. Genetic characterization of the partial E and NS3 sequences demonstrated that the TBEV strains belonged to the European subtype in all countries, as well as to the Siberian subtype in Estonia. We also found that in areas where ranges of two tick species overlap, the TBEV subtypes may be detected not only in their natural vector, but also in sympatric tick species.

What is the risk for exposure to vector-borne pathogens in United States national parks?

United States national parks attract > 275 million visitors annually and collectively present risk of exposure for staff and visitors to a wide range of arthropod vector species (most notably fleas, mosquitoes, and ticks) and their associated bacterial, protozoan, or viral pathogens. We assessed the current state of knowledge for risk of exposure to vector-borne pathogens in national parks through a review of relevant literature, including internal National Park Service documents and organismal databases. We conclude that, because of lack of systematic surveillance for vector-borne pathogens in national parks, the risk of pathogen exposure for staff and visitors is unclear. Existing data for vectors within national parks were not based on systematic collections and rarely include evaluation for pathogen infection. Extrapolation of human-based surveillance data from neighboring communities likely provides inaccurate estimates for national parks because landscape differences impact transmission of vector-borne pathogens and human-vector contact rates likely differ inside versus outside the parks because of differences in activities or behaviors. Vector-based pathogen surveillance holds promise to define when and where within national parks the risk of exposure to infected vectors is elevated. A pilot effort, including 5-10 strategic national parks, would greatly improve our understanding of the scope and magnitude of vector-borne pathogen transmission in these high-use public settings. Such efforts also will support messaging to promote personal protection measures and inform park visitors and staff of their responsibility for personal protection, which the National Park Service preservation mission dictates as the core strategy to reduce exposure to vector-borne pathogens in national parks.

Wheat curl mite, Aceria tosichella, and transmitted viruses: an expanding pest complex affecting cereal crops

The wheat curl mite (WCM), Aceria tosichella, and the plant viruses it transmits represent an invasive mite-virus complex that has affected cereal crops worldwide. The main damage caused by WCM comes from its ability to transmit and spread multiple damaging viruses to cereal crops, with Wheat streak mosaic virus (WSMV) and Wheat mosaic virus (WMoV) being the most important. Although WCM and transmitted viruses have been of concern to cereal growers and researchers for at least six decades, they continue to represent a challenge. In older affected areas, for example in North America, this mite-virus complex still has significant economic impact. In Australia and South America, where this problem has only emerged in the last decade, it represents a new threat to winter cereal production. The difficulties encountered in making progress towards managing WCM and its transmitted viruses stem from the complexity of the pathosystem. The most effective methods for minimizing losses from WCM transmitted viruses in cereal crops have previously focused on cultural and plant resistance methods. This paper brings together information on biological and ecological aspects of WCM, including its taxonomic status, occurrence, host plant range, damage symptoms and economic impact. Information about the main viruses transmitted by WCM is also included and the epidemiological relationships involved in this vectored complex of viruses are also addressed. Management strategies that have been directed at this mite-virus complex are presented, including plant resistance, its history, difficulties and advances. Current research perspectives to address this invasive mite-virus complex and minimize cereal crop losses worldwide are also discussed.

Brevipalpus mites (Acari: Tenuipalpidae): vectors of invasive, non-systemic cytoplasmic and nuclear viruses in plants

Multi-directional interactions occur among plant hosts, Brevipalpus mites and the plant viruses they transmit. Such interactions should be considered when evaluating the severity of a disease such as citrus leprosis. The current understanding of Brevipalpus-transmitted viruses relies on the capability of the vector to transmit the disease, the persistence of the virus in the host plant and the ability of the disease to spread. Previously, we discussed the Citrus leprosis virus (CiLV) and its importance and spread over the past decade into new areas of South and Central America, most recently into southern Mexico and Belize. Here, we address key questions to better understand the biology of the mite vector, fitness costs, and the peculiarities of Brevipalpus mite reproduction, virus survival, transmissibility and spread, and the expansion of the host plant range of Brevipalpus species vectoring the disease.

Using the gravity model to estimate the spatial spread of vector-borne diseases

The gravity models are commonly used spatial interaction models. They have been widely applied in a large set of domains dealing with interactions amongst spatial entities. The spread of vector-borne diseases is also related to the intensity of interaction between spatial entities, namely, the physical habitat of pathogens’ vectors and/or hosts, and urban areas, thus humans. This study implements the concept behind gravity models in the spatial spread of two vector-borne diseases, nephropathia epidemica and Lyme borreliosis, based on current knowledge on the transmission mechanism of these diseases. Two sources of information on vegetated systems were tested: the CORINE land cover map and MODIS NDVI. The size of vegetated areas near urban centers and a local indicator of occupation-related exposure were found significant predictors of disease risk. Both the land cover map and the space-borne dataset were suited yet not equivalent input sources to locate and measure vegetated areas of importance for disease spread. The overall results point at the compatibility of the gravity model concept and the spatial spread of vector-borne diseases.

Tick cell lines for study of Crimean-Congo hemorrhagic fever virus and other arboviruses

Continuous cell lines derived from many of the vectors of tick-borne arboviruses of medical and veterinary importance are now available. Their role as tools in arbovirus research to date is reviewed and their potential application in studies of tick cell responses to virus infection is explored, by comparison with recent progress in understanding mosquito immunity to arbovirus infection. A preliminary study of propagation of the human pathogen Crimean-Congo hemorrhagic fever virus (CCHFV) in tick cell lines is reported; CCHFV replicated in seven cell lines derived from the ticks Hyalomma anatolicum (a known vector), Amblyomma variegatum, Rhipicephalus (Boophilus) decoloratus, Rhipicephalus (Boophilus) microplus, and Ixodes ricinus, but not in three cell lines derived from Rhipicephalus appendiculatus and Ornithodoros moubata. This indicates that tick cell lines can be used to study growth of CCHFV in arthropod cells and that there may be species-specific restriction in permissive CCHFV infection at the cellular level.

[Isolation, identification and characterization of SFTS bunyavirus from ticks collected on the surface of domestic animals]

To understand the maintenance and transmission of SFTS virus, the potential vector ticks were collected from sheep, cattle and dogs in the endemic areas of SFTSV in Shandong Province. Among the collected ticks, the dominant species was H. longicornis ticks. Real-time PCR for RNA detection, virus isolation and characterization, genomic sequencing, phylogenetic and antigenic analysis were performed in this investigation. The results showed that the SFTS viral RNA was detected in 2.14% H. longicornis, and a SFTS virus was isolated from one of viral RNA positive ticks collected from sheep. Whole genome analysis of the SFTSV isolates with 11 human-origin SFTS virus revealed a highly pairwise similarity, and the growth curve analysis showed nearly identical in virus yield and the dynamic of virus reproduction compared to human derived viral isolates. Immunofluorescence and neutralization test showed identical serological reaction character of the two different origin viral strains. In this study, the characters of a SFTSV isolate was firstly described, which suggested that the tick species H. longicornis acting important vector role in the transmission of SFTS virus.

Differential salivary gland transcript expression profile in Ixodes scapularis nymphs upon feeding or flavivirus infection

Ixodid ticks are vectors of human diseases such as Lyme disease, babesiosis, anaplasmosis, and tick-borne encephalitis. These diseases cause significant morbidity and mortality worldwide and are transmitted to humans during tick feeding. The tick-host-pathogen interface is a complex environment where host responses are modulated by the molecules in tick saliva to enable the acquisition of a blood meal. Disruption of host responses at the site of the tick bite may also provide an advantage for pathogens to survive and replicate. Thus, the molecules in tick saliva not only aid the tick in securing a nutrient-rich blood meal, but can also enhance the transmission and acquisition of pathogens. To investigate the effect of feeding and flavivirus infection on the salivary gland transcript expression profile in ticks, a first-generation microarray was developed using ESTs from a cDNA library derived from Ixodes scapularis salivary glands. When the salivary gland transcript profile in ticks feeding over the course of 3 days was compared to that in unfed ticks, a dramatic increase in transcripts related to metabolism was observed. Specifically, 578 transcripts were up-regulated compared to 151 down-regulated transcripts in response to feeding. When specific time points post attachment were analyzed, a temporal pattern of gene expression was observed. When Langat virus-infected ticks were compared to mock-infected ticks, transcript expression changes were observed at all 3 days of feeding. Differentially regulated transcripts include putative secreted proteins, lipocalins, Kunitz domain-containing proteins, anti-microbial peptides, and transcripts of unknown function. These studies identify salivary gland transcripts that are differentially regulated during feeding or in the context of flavivirus infection in Ixodes scapularis nymphs, a medically important disease vector. Further analysis of these transcripts may identify salivary factors that affect the transmission or replication of tick-borne flaviviruses.

[A case of Crimean-Congo hemorrhagic fever with long incubation period in Kocaeli, Turkey]

Crimean-Congo hemorrhagic fever (CCHF) is a viral hemorrhagic disease with high mortality rate. CCHF is endemic in Central Anatolia and East and Central Black Sea parts of Turkey, however sporadic cases have been detected in the other regions. The incubation period of the disease is between 1-3 days (maximum 12 days). In this report, a very rare CCHF case with a long incubation period of 30 days, was reported. A 40-year-old female patient living in a village of Kocaeli, Turkey was admitted to a health center in June 2010 with the complaints of headache, myalgia, nausea, vomiting, fatigue and fever. Since laboratory results revealed severe thrombocytopenia (18.300/mm3), the patient was referred to the university hospital in Kocaeli. It was learned from her history that she had been working in the garden and removed a tick from the skin of gluteal area a month ago without seeking any medical help. Physical examination of the patient revealed that her general condition was well, oriented and cooperative, body temperature was 36.6°C, pulse 82/minute, trombocyte count 69.400/mm3 and liver enzymes were elevated (ALT: 194 U/L, AST: 499 U/L, GGT: 384 U/L, LDH: 1290 U/L). Petecchial lesions were seen on hard palate and extremities and a hyperemic lesion was detected at the gluteal area where the tick had attached. In-house real-time polymerase chain reaction test for CCHF, performed at Refik Saydam National Public Health Agency, Virology Reference and Research Laboratory, revealed positive result. This case was presented to withdraw attention to a long incubation period CCHF and also of its epidemiological importance since it was the first case in Kocaeli province, Turkey.

Transmission of tick-borne pathogens between co-feeding ticks: Milan Labuda's enduring paradigm

During the 1990s, Milan Labuda's experimental results established a new paradigm for the study of tick-borne viruses that has since been strengthened by its demonstrated effectiveness in explaining the epidemiology of tick-borne encephalitis (TBE). This brief review summarizes the essential features of the transmission of tick-borne pathogens such as TBE virus. Leukocytes migrate between tick feeding sites, bearing infective virions and providing a transport route for the virus between co-feeding ticks independent of a systemic viraemia. Such tick-borne pathogens are thus transmitted from tick to tick via vertebrates; the ticks are the reservoirs as well as the vectors, while the vertebrate is the transient bridge. The aim is to bring the related but non-synonymous terms (co-feeding and non-systemic) to the attention of workers who use simple PCR screening to identify additional vertebrate reservoir hosts of vector-borne pathogens that are not in fact maintained in nature through systemic transmission.

Detection of Brevipalpus-transmitted viruses in their mite vectors by RT-PCR

The diagnosis of plant diseases caused by Brevipalpus-transmitted viruses (BrTVs) has been done through the analyses of symptoms, transmission electron microscopy, and RT-PCR of infected plant tissues. Here, we report the detection of Citrus leprosis virus C, Orchid fleck virus, Clerodendrum chlorotic spot virus and Solanum violaefolium ringspot virus in their viruliferous vectors Brevipalpus spp. using specific primer pairs for each of the viruses. The efficiency of virus transmission by Brevipalpus mites is low, so the detection of these pathogens in their vectors could constitute an important tool for studies involving virus-vector relationships, transmission, and monitoring the pathogen prior to the appearance of symptoms in the field.

Evaluation of knowledge about protection against Crimean-Congo hemorrhagic fever

This study was conducted in order to evaluate individuals' knowledge about protection against Crimean Congo hemorrhagic fever (CCHF). This descriptive study was carried out among 478 persons, to whom a Family Health Center located within boundaries of Erzurum Metropolitan Municipality, provides health service. A questionnaire form developed by the researchers was used for collecting data. Seventy-one point eight percent of individuals who participated in the study stated they had knowledge about CCHF, 25.9% stated that region was risky in terms of being bitten by ticks, 61.3% stated they could recognize ticks and 56.1% stated that not all tick bites cause the disease. Seventy-seven point eight percent stated CCHF is a virulent disease, 33.1% stated it can be transmitted from human to human and 30.3% stated it can be transmitted from animals to humans. In terms of protection from tick bites, 45, 15.3 and 11.3% of individuals stated wearing clothes to cover the whole body, carefully inspecting the body, and not touching ticks with bare hands, respectively, were good methods. Ninety-two point one percent stated it is necessary to go to a healthcare organization immediately in case of tick bite, whereas 18% of individuals stated it is necessary to remove the tick with tweezers or forceps. The results of this study show most individuals are not well informed about methods for protecting against CCHF, for removing ticks and what precautions to take to protect against tick bites.

Microclimate and the zoonotic cycle of tick-borne encephalitis virus in Switzerland

The focal distribution of tick-borne encephalitis virus (TBEV; Flaviviridae, Flavivirus) appears to depend mainly on cofeeding transmission between infected Ixodes ricinus L. nymphs and uninfected larvae. To better understand the role of cofeeding ticks in the transmission of TBEV, we investigated tick infestation of rodents and the influence of microclimate on the seasonality of questing I. ricinus ticks. A 3-yr study was carried out at four sites, including two confirmed TBEV foci. Free-living ticks and rodents were collected monthly, and microclimatic data were recorded. A decrease in questing nymph density was observed in 2007, associated with low relative humidity and high temperatures in spring. One site, Thun, did not show this decrease, probably because of microclimatic conditions in spring that favored the questing nymph population. During the same year, the proportion of rodents carrying cofeeding ticks was lower at sites where the questing nymph density decreased, although the proportion of infested hosts was similar among years. TBEV was detected in 0.1% of questing ticks, and in 8.6 and 50.0% of larval ticks feeding on two rodents. TBEV was detected at all but one site, where the proportion of hosts with cofeeding ticks was the lowest. The proportion of hosts with cofeeding ticks seemed to be one of the factors that distinguished a TBEV focus from a non-TBEV focus. The enzootic cycle of TBEV might be disrupted when dry and hot springs occur during consecutive years.

Crimean Congo hemorrhagic fever: requires vigilance and not panic

Crimean Congo hemorrhagic fever (CCHF) has been in the news with reports of its outbreak in India from Gujarat. CCHF is caused by a virus which is a member of the Nairovirus genus of the family Bunyaviridae. All of these viruses are transmitted by either ixodid or argasid ticks. Humans get this infection after a bite of an infected tick or from one infected human to another by contact with infectious blood or body fluids. Workers in livestock and agriculture industry, slaughterhouses, and veterinary practice are most prone to this infection. In severe cases after 3-6 days of the onset of symptoms hemorrhagic manifestations occur. IgG and IgM antibodies may be detected in serum by ELISA from about the sixth day of the illness. The mainstay of treatment in CCHF is supportive. Management of DIC, sepsis, shock and MODS should be undertaken. The antiviral drug Ribavirin has shown benefits. Benefits of treatment with ribavirin outweigh the fatal risks, and ribavirin may therefore be recommended. People at risk should use effective personal protective measures against tick bites. Acaricide treatment of livestock in CCHF virus endemic areas is effective in reducing the population of infected ticks.

Species diversity of ixodid ticks feeding on humans in Amasya, Turkey: seasonal abundance and presence of Crimean-Congo hemorrhagic fever virus

Ticks (Acari:Ixodidae) are important pests transmitting tick-borne diseases such as Crimean-Congo hemorrhagic fever (CCHF) to humans. Between 2002 and 2009, numerous CCHF cases were reported in Turkey, including Amasya province. In the current study, species diversity, seasonal abundance of ticks, and presence of CCHF virus (CCHFV) in ticks infesting humans in several districts of Amasya province were determined. In the survey, a total of 2,528 ixodid ticks were collected from humans with tick bite from April to November 2008 and identified to species. Hyalomma marginatum (18.6%), Rhipicephalus bursa (10.3%), Rhipicephalus sanguineus (5.7%), Rhipicephalus (Boophilus) annulatus (2.2%), Dermacentor marginatus (2.5%), Haemaphysalis parva (3.6%), and Ixodes ricinus (1.6%) were the most prevalent species among 26 ixodid tick species infesting humans in Amasya province. Hyalomma franchinii Tonelli & Rondelli, 1932, was a new record for the tick fauna of Turkey. The most abundant species were the members of Hyalomma and Rhipicephalus through summer and declined in fall, whereas relative abundances of Ixodes and Dermacentor ticks were always low on humans in the province. Of 25 Hyalomma tick pools tested, seven pools were CCHFV positive by reverse transcription-polymerase chain reaction. Results indicated diversity of ixodid tick species infesting humans was very high, abundance of ticks changed by season, and ticks infesting humans had potential for transmitting CCHFV.

Molecular epidemiology of Crimean- Congo hemorrhagic fever virus genome isolated from ticks of Hamadan province of Iran

BACKGROUND & OBJECTIVES

Crimean-Congo hemorrhagic fever (CCHF) virus is a tick-borne member of the genus Nairovirus, family Bunyaviridae. CCHFV has been isolated from at least 31 different tick species. The virus is transmitted through the bite of an infected tick, or by direct contact with CCHFV-infected patients or the products of infected livestock. This study was undertaken to study the genetic relationship and distribution of CCHFV in the tick population of Hamadan province of Iran.

METHOD

In this study, RT-PCR has been used for detection of the CCHFV genome.

RESULTS

This genome was detected in 19.2% of the ticks collected from livestock of different regions of the Hamadan province in western Iran. The infected species belonged to Hyalomma detritum, H. anatolicum, Rhipicephalus sanguineus and Argas reflexus. With one exception, genetic analysis of the virus genome isolates showed high sequence identity to each other. Even though they clustered in the same group with the strain circulating in Iran, they had a closer relationship to the Matin strain.

INTERPRETATION & CONCLUSION

Vector control programs should be applied for reducing population density of potential tick vectors in this province. Further surveys are indicated in this region to provide a better view of the distribution and epidemiology of the virus.

[Crimean-Congo hemorrhagic fever: basics for general practitioners]

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne disease described in more than 30 countries in Europe, Asia and Africa. The causative agent is the Crimean-Congo hemorrhagic fever virus (CCHFV) that is a member of the genus Nairovirus of the family Bunyaviridae. CCHFV that is characterized by a high genetic variability is transmitted to humans by tick bites or contact with fluids from an infected individual or animal. The initial symptoms of CCHF are nonspecific and gradually progress to a hemorrhagic phase that can be lethal (case-fatality rate: 10 to 50%). Characteristic laboratory findings of CCHF are thrombocytopenia, elevated liver and muscle enzymes, and coagulation defects. The pathogenesis of CCHF remains unclear but might involve excessive pro-inflammatory cytokine production and dysfunction of the innate immune response. Diagnosis of CCHF is based mainly on isolation of the virus, identification of the viral genome by molecular techniques (RT-PCR), and serological detection of anti-CCHFV antibodies. There is currently no specific treatment for CCHFV infection and the efficacy of ribavirin is controversial. In absence of an effective vaccine, prevention is based mainly on vector control, protection measures, and information to increase the awareness of the population and of healthcare workers.

African swine fever

African swine fever (ASF) is a devastating haemorrhagic fever of pigs that causes up to 100% mortality, for which there is no vaccine. It is caused by a unique DNA virus that is maintained in an ancient cycle between warthogs and argasid ticks, making it the only known DNA arbovirus. ASF has a high potential for transboundary spread, and has twice been transported from Africa to other continents--Europe and subsequently the Caribbean and Brazil (1957, 1959) and the Caucasus (2007). It is also a devastating constraint for pig production in Africa. Research at Onderstepoort Veterinary Institute has made and is making important contributions to knowledge of this disease, focusing on the cycle in warthogs and tampans and transmission from that cycle to domestic pigs, resistance to its effects in domestic pigs, and the molecular genetic characterisation and epidemiology of the virus.

Dynamics of tick-borne disease systems: minor role of recent climate change

Tick-borne disease systems are very sensitive to climate through the impact of temperature and moisture stress on rates of the demographic processes of ticks. There is no a priori reason, however, to expect tick abundance or seasonal activity patterns to respond to climate change in ways that inevitably increase the risk of infection by the transmitted pathogens. Changing host availability may be more important than climate in determining tick abundance. The credibility of any (inherently untestable) predictions of future system-specific changes will be strengthened if based on satisfactory explanations of the past. Tick-borne encephalitis (TBE) in Europe is presented as a case study: observed patterns of climate change are too similar within and between countries to provide the sole explanation for the extreme spatio-temporal heterogeneity of the marked upsurges in TBE incidence over the past two decades. Instead, a nexus of interacting factors affecting both the risk of infection and exposure of humans to that risk, and each differing in force in space and time, is a more powerful model. Many of these factors are driven by socio-economic changes, and include climate, land cover, wildlife, agricultural practices, industrial activities, (un)employment and income. The same principle may apply to the periodic epidemics of Crimean-Congo haemorrhagic fever.

[Current characteristics of natural nidality of tick-borne encephalitis: new or well forgotten?]

A number specialists' opinion as to which the rise in the incidence of tick-borne encephalitis at the turn of the centuries is due to the new features of the epidemiology of this infection and to global climatic changes is analyzed. There are no objective evidence suggesting the ongoing expansion of a natural habitat of the major vectors--taiga (Ixodes persulcatus) and wood (I. ricinis) ticks and the noticeable increase in their size and virus infection rates. The notion of the recent penetration of ticks into the metropolises where natural focuses have emerged and human beings are infected is inconsistent with the multidescribed facts. There is no significant evidence for the expansion of a nosoarea of tickborne encephalitis. The impact of reformed anthropurgic foci and that of the proportion of town-dwellers in the general structure of morbidity on the epidemic situation have been evaluated. The intensity of an epidemic manifestation of natural foci is always determined by two most important parameters: 1) the loimopotential of foci and 2) the intensity of the population's contact with them. The nature of an interaction between these factors, which has caused a rapid surge of morbidity rates and their subsequent long-time reduction, is considered.

[Detection of the West Nile Virus and its genetic typing in ixodid ticks (Parasitiformes: Ixodidae) in Tomsk City and its suburbs]

Four tick species, Ixodes persulcatus, I. pavlovskyi, I. trianguliceps, and Dermacentor reticulatus, were found in Tomsk and its suburbs in 2006. The species I. pavlovskyi was found to be dominant in the localities situated in Tomsk City, and I. persulcatus was dominant in its suburbs. Viral RNA and viral antigen of the West Nile virus (WNV) were detected in the ticks I. pavlovskyi and I. persulcatus collected in the city and its suburbs by the RT PCR method and enzyme immunoassay with monoclonal antibodies against protein E of the WNV. Average rate of the WNV infected ticks varied from 5.2 up to 11.7% in different localities. Identification of the nucleotide sequence of the protein E gene fragment allowed classifying the cDNA obtained as genotype Ia of the WNV. The sequences are proved similar to the strain LEIV-Vlg99-27889-human of the WNV isolated in Volgograd. The obtained data showed that natural foci of the WNV virus can appear in the city and its suburbs probably involving two dominant tick species. The WNV infected imagoes, larvae, and nymphs of I. persulcatus and I. pavlovskyi were collected from small mammals, lizards, and birds. Therefore we presume that these hosts can be involved in the circulation and distribution of WNV on the territory of Tomsk Region.

[Molecular and epidemiological characteristics of tick-borne encephalitis virus in the Sverdlovsk Region on the basis of genotype-specific RT-PCR]

Studies and complete awareness of the regional and epidemiological properties of tick-borne encephalitis virus (TBEV) allow one to improve methods for preventing, diagnosing, and treating its severe neurological infection. The authors have developed reverse-transcriptase polymerase chain reaction (RT-PCR) systems for the detection of RNA of TBEV and for the determination of its genotype in the ticks and clinical materials. RT-PTC was shown to have a higher sensitivity and specificity than the practically used enzyme immunoassay system. Despite significant variations in the spread of infected ticks in some districts of the Sverdlovsk Region (5-12%), the average regional value was 8% over the study period. The authors have studied more than a thousand of ticks collected from the nature and humans in the epidemic season of 2005-2006. There was a virtually complete predominance (more than 95%) of the Ural-Siberian genotype, with rare cases of the European genotype (slightly more than 4%) being detected. The Far-Eastern genotype was not detected.

Prevention of tick-borne diseases

Tick-borne diseases are on the rise. Lyme borreliosis is prevalent throughout the Northern Hemisphere, and the same Ixodes tick species transmitting the etiologic agents of this disease also serve as vectors of pathogens causing human babesiosis, human granulocytic anaplasmosis, and tick-borne encephalitis. Recently, several novel agents of rickettsial diseases have been described. Despite an explosion of knowledge in the fields of tick biology, genetics, molecular biology, and immunology, transitional research leading to widely applied public health measures to combat tick-borne diseases has not been successful. Except for the vaccine against tick-borne encephalitis virus, and a brief campaign to reduce this disease in the former Soviet Union through widespread application of DDT, success stories in the fight against tick-borne diseases are lacking. Both new approaches to tick and pathogen control and novel ways of translating research findings into practical control measures are needed to prevent tick-borne diseases in the twenty-first century.

[Development of amplification technology-based methods for tick-borne encephalitis virus detection and genotyping]

The development of methods for tick-borne encephalitis (TBE) virus genotyping, such as determination of nucleotide sequences, analysis of restriction fragment length polymorphism, polymerase chain reaction using genotype-specific probes with hybridization-fluorescence detection, is under consideration. The capacities and application area of varions typing techniques, such as TBE detection and genotyping in the field, autoptic, and cultural materials; study of circulating genotypes in different natural foci and in various viral vectors and carriers, are described. Each technique was tested using a large number of strains isolated from ill humans and ticks in different regions of the country and employed to investigate abundant materials.