Ticks infected with Crimean-Congo hemorrhagic fever virus (CCHFV): A decision approach systematic review and meta-analysis regarding their role as vectors.

BACKGROUND: There are many studies present in literature performed to isolate CCHFV from ticks. However, gaps in knowledge for estimating global annual CCHFV infection rates; global CCHFV infection rates and records; CCHFV infection trend in ticks and ticks infested animals; and lack a decision regarding the role of ticks as CCHFV vectors caused to conduct this review. METHODS: From 605 papers identified, 150 papers were selected to become the study meta-analysis (57 papers), detailed CCHFV infected ticks (63 papers), and systematic review (99 papers) parts. RESULTS: Since there are no significant differences between the annual tick CCHFV infection rates; tick CCHFV infection rates between continents; and CCHFV infection rates between tick species and gender of ticks, and ticks and tick species infested animals. Given that ticks are considered both as CCHFV reservoirs and vectors. It is possible a little burden of CCHFV in infected ticks in natural enzootic cycles to maintain and disseminate CCHFV in humans. The decision regarding the role of ticks as CCHFV vectors administrated based on the study and a separately literature search regarding the role of ticks as CCHFV vectors; CCHFV infection rates and records; and trend of CCHFV infection records in 31 tick species. The trend of CCHFV infection records in 31 tick species exhibited a decreasing trend indicating the degree and importance of their roles as CCHFV vectors. CONCLUSIONS: Among 31 CCHFV infected tick species, 15 species have been enrolled as proven vectors and 16 species are suspected as potential vectors.

Clinical Tick-Borne Encephalitis in a Roe Deer (Capreolus capreolus L.).

Tick-borne encephalitis virus (TBEV) is the causative agent of tick-borne encephalitis (TBE), a severe zoonosis occurring in the Palearctic region mainly transmitted through Ixodes ticks. In Italy, TBEV is restricted to the north-eastern part of the country. This report describes for the first time a case of clinical TBE in a roe deer (Capreolus capreolus L.). The case occurred in the Belluno province, Veneto region, an area endemic for TBEV. The affected roe deer showed ataxia, staggering movements, muscle tremors, wide-base stance of the front limbs, repetitive movements of the head, persistent teeth grinding, hypersalivation and prolonged recumbency. An autopsy revealed no significant lesions to explain the neurological signs. TBEV RNA was detected in the brain by real-time RT-PCR, and the nearly complete viral genome (10,897 nucleotides) was sequenced. Phylogenetic analysis of the gene encoding the envelope protein revealed a close relationship to TBEV of the European subtype, and 100% similarity with a partial sequence (520 nucleotides) of a TBEV found in ticks in the bordering Trento province. The histological examination of the midbrain revealed lymphohistiocytic encephalitis, satellitosis and microgliosis, consistent with a viral etiology. Other viral etiologies were ruled out by metagenomic analysis of the brain. This report underlines, for the first time, the occurrence of clinical encephalitic manifestations due to TBEV in a roe deer, suggesting that this pathogen should be included in the frame of differential diagnoses in roe deer with neurologic disease.

Recent Progress on Tick-Borne Animal Diseases of Veterinary and Public Health Significance in China.

Ticks and tick-borne diseases pose a growing threat to human and animal health, which has brought great losses to livestock production. With the continuous expansion of human activities and the development of natural resources, there are more and more opportunities for humans to contract ticks and tick-borne pathogens. Therefore, research on ticks and tick-borne diseases is of great significance. This paper reviews recent progress on tick-borne bacterial diseases, viral diseases, and parasitic diseases in China, which provides a theoretical foundation for the research of tick-borne diseases.

Evaluation of two artificial infection methods of live ticks as tools for studying interactions between tick-borne viruses and their tick vectors.

Up to 170 tick-borne viruses (TBVs) have been identified to date. However, there is a paucity of information regarding TBVs and their interaction with respective vectors, limiting the development of new effective and urgently needed control methods. To overcome this gap of knowledge, it is essential to reproduce transmission cycles under controlled laboratory conditions. In this study we assessed an artificial feeding system (AFS) and an immersion technique (IT) to infect Ixodes ricinus ticks with tick-borne encephalitis (TBE) and Kemerovo (KEM) virus, both known to be transmitted predominantly by ixodid ticks. Both methods permitted TBEV acquisition by ticks and we further confirmed virus trans-stadial transmission and onward transmission to a vertebrate host. However, only artificial feeding system allowed to demonstrate both acquisition by ticks and trans-stadial transmission for KEMV. Yet we did not observe transmission of KEMV to mice (IFNAR-/- or BALB/c). Artificial infection methods of ticks are important tools to study tick-virus interactions. When optimally used under laboratory settings, they provide important insights into tick-borne virus transmission cycles.

Simulated vector transmission differentially influences dynamics of two viral variants of deformed wing virus in honey bees (Apis mellifera).

Understanding how vectors alter the interactions between viruses and their hosts is a fundamental question in virology and disease ecology. In honey bees, transmission of deformed wing virus (DWV) by parasitic Varroa mites has been associated with elevated disease and host mortality, and Varroa transmission has been hypothesized to lead to increased viral titres or select for more virulent variants. Here, we mimicked Varroa transmission by serially passaging a mixed population of two DWV variants, A and B, by injection through in vitro reared honey bee pupae and tracking these viral populations through five passages. The DWV-A and DWV-B variant proportions shifted dynamically through passaging, with DWV-B outcompeting DWV-A after one passage, but levels of both variants becoming equivalent by Passage 5. Sequencing analysis revealed a dominant, recombinant DWV-B strain (DWV-A derived 5' IRES region with the rest of the genome DWV-B), with low nucleotide diversity that decreased through passaging. DWV-A populations had higher nucleotide diversity compared to DWV-B, but this also decreased through passaging. Selection signatures were found across functional regions of the DWV-A and DWV-B genomes, including amino acid mutations in the putative capsid protein region. Simulated vector transmission differentially impacted two closely related viral variants which could influence viral interactions with the host, demonstrating surprising plasticity in vector-host-viral dynamics.

Molecular detection of dugbe orthonairovirus in cattle and their infesting ticks (Amblyomma and Rhipicephalus (Boophilus)) in Nigeria.

Dugbe orthonairovirus (DUGV), a tick-borne zoonotic arbovirus, was first isolated in 1964 in Nigeria. For over four decades, no active surveillance was conducted to monitor the spread and genetic variation of DUGV. This study detected and genetically characterized DUGV circulating in cattle and their infesting ticks (Amblyomma and Rhipicephalus (Boophilus)) in Kwara State, North-Central Nigeria. Blood and or ticks were collected from 1051 cattle at 31 sampling sites (abattoirs and farms) across 10 local government areas of the State. DUGV detection was carried out by RT-qPCR, and positive samples sequenced and phylogenetically analysed. A total of 11824 ticks, mostly A. variegatum (36.0%) and R. (B.) microplus (63.9%), were obtained with mean tick burden of 12 ticks/cattle. Thirty-four (32 A. variegatum and two R. (B.) microplus) of 4644 examined ticks were DUGV-positive, whereas all of the cattle sera tested negative for DUGV genome. Whole genome sequence (S, M and L segments) and phylogenetic analyses indicate that the positive samples shared up to 99.88% nucleotide identity with and clustered around the Nigerian DUGV prototype strain IbAr 1792. Hence, DUGV with high similarity to the previously characterised strain has been detected in Nigeria. To our knowledge, this is the first report of DUGV in North-Central Nigeria and the most recent information after its last surveillance in 1974.

Crimean-Congo Hemorrhagic Fever Virus: Current Advances and Future Prospects of Antiviral Strategies.

Crimean-Congo hemorrhagic fever virus (CCHFV) is a widespread, tick-borne pathogen that causes Crimean-Congo hemorrhagic fever (CCHF) with high morbidity and mortality. CCHFV is transmitted to humans through tick bites or direct contact with patients or infected animals with viremia. Currently, climate change and globalization have increased the transmission risk of this biosafety level (BSL)-4 virus. The treatment options of CCHFV infection remain limited and there is no FDA-approved vaccine or specific antivirals, which urges the identification of potential therapeutic targets and the design of CCHF therapies with greater effort. In this article, we discuss the current progress and some future directions in the development of antiviral strategies against CCHFV.

An integrated overview of the bacterial flora composition of Hyalomma anatolicum, the main vector of CCHF.

The microbial flora associated with Hyalomma anatolicum ticks was investigated using culture-dependent (CD) and independent (next generation sequencing, NGS) methods. The bacterial profiles of different organs, development stages, sexes, and of host cattle skins were analyzed using the CD method. The egg and female gut microbiota were investigated using NGS. Fourteen distinct bacterial strains were identified using the CD method, of which Bacillus subtilis predominated in eggs, larval guts and in adult female and male guts, suggesting probable transovarial transmission. Bacillus velezensis and B. subtilis were identified in cattle skin and tick samples, suggesting that skin is the origin of tick bacteria. H.anatolicum males harbour lower bacterial diversity and composition than females. The NGS analysis revealed five different bacterial phyla across all samples, Proteobacteria contributing to >95% of the bacteria. In all, 56611sequences were generated representing 6,023 OTUs per female gut and 421 OTUs per egg. Francisellaceae family and Francisella make up the vast majority of the OTUs. Our findings are consistent with interference between Francisella and Rickettsia. The CD method identified bacteria, such B. subtilis that are candidates for vector control intervention approaches such paratransgenesis whereas NGS revealed high Francisella spp. prevalence, indicating that integrated methods are more accurate to characterize microbial community and diversity.

Modelling the transmission dynamics of severe fever with thrombocytopenia syndrome in Jiangsu Province, China.

BACKGROUND: Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease that is regionally distributed in Asia, with high fatality. Constructing the transmission model of SFTS could help provide clues for disease control and fill the gap in research on SFTS models. METHODS: We built an SFTS transmission dynamics model based on the susceptible-exposed-infectious-asymptomatic-recovered (SEIAR) model and the epidemiological characteristics of SFTS in Jiangsu Province. This model was used to evaluate the effect by cutting off different transmission routes and taking different interventions into account, to offer clues for disease prevention and control. RESULTS: The transmission model fits the reported data well with a minimum R2 value of 0.29 and a maximum value of 0.80, P < 0.05. Meanwhile, cutting off the environmental transmission route had the greatest effect on the prevention and control of SFTS, while isolation and shortening the course of the disease did not have much effect. CONCLUSIONS: The model we have built can be used to simulate the transmission of SFTS to help inform disease control. It is noteworthy that cutting off the environment-to-humans transmission route in the model had the greatest effect on SFTS prevention and control.

Trends and Opportunities in Tick-Borne Disease Geography.

Tick-borne diseases are a growing problem in many parts of the world, and their surveillance and control touch on challenging issues in medical entomology, agricultural health, veterinary medicine, and biosecurity. Spatial approaches can be used to synthesize the data generated by integrative One Health surveillance systems, and help stakeholders, managers, and medical geographers understand the current and future distribution of risk. Here, we performed a systematic review of over 8,000 studies and identified a total of 303 scientific publications that map tick-borne diseases using data on vectors, pathogens, and hosts (including wildlife, livestock, and human cases). We find that the field is growing rapidly, with the major Ixodes-borne diseases (Lyme disease and tick-borne encephalitis in particular) giving way to monitoring efforts that encompass a broader range of threats. We find a tremendous diversity of methods used to map tick-borne disease, but also find major gaps: data on the enzootic cycle of tick-borne pathogens is severely underutilized, and mapping efforts are mostly limited to Europe and North America. We suggest that future work can readily apply available methods to track the distributions of tick-borne diseases in Africa and Asia, following a One Health approach that combines medical and veterinary surveillance for maximum impact.

Geographical and Tick-Dependent Distribution of Flavi-Like Alongshan and Yanggou Tick Viruses in Russia.

The genus Flavivirus includes related, unclassified segmented flavi-like viruses, two segments of which have homology with flavivirus RNA-dependent RNA polymerase NS5 and RNA helicase-protease NS3. This group includes such viruses as Jingmen tick virus, Alongshan virus, Yanggou tick virus and others. We detected the Yanggou tick virus in Dermacentor nuttalli and Dermacentor marginatus ticks in two neighbouring regions of Russia. The virus prevalence ranged from 0.5% to 8.0%. We detected RNA of the Alongshan virus in 44 individuals or pools of various tick species in eight regions of Russia. The virus prevalence ranged from 0.6% to 7.8%. We demonstrated the successful replication of the Yanggou tick virus and Alongshan virus in IRE/CTVM19 and HAE/CTVM8 tick cell lines without a cytopathic effect. According to the phylogenetic analysis, we divided the Alongshan virus into two groups: an Ixodes persulcatus group and an Ixodes ricinus group. In addition, the I. persulcatus group can be divided into European and Asian subgroups. We found amino acid signatures specific to the I. ricinus and I. persulcatus groups and also distinguished between the European and Asian subgroups of the I. persulcatus group.

Experimental Infection of Amblyomma americanum (Acari: Ixodidae) With Bourbon Virus (Orthomyxoviridae: Thogotovirus).

Following the recent discovery of Bourbon virus (BRBV) as a human pathogen, and the isolation of the virus from Amblyomma americanum (L.) collected near the location of a fatal human case, we undertook a series of experiments to assess the laboratory vector competence of this tick species for BRBV. Larval ticks were infected using an immersion technique, and transstadial transmission of virus to the nymphal and then to the adult stages was demonstrated. Transstadially infected nymphs transmitted virus to adult ticks at very high rates during cofeeding, indicating the presence of infectious virus in the saliva of engorging ticks. Vertical transmission by transstadially infected females to their progeny occurred, but at a low rate. Rabbits fed on by infected ticks of all active life stages developed high titers of antibody to the virus, demonstrating host exposure to BRBV antigens/live virus during tick blood feeding. These results demonstrate that A. americanum is a competent vector of BRBV and indicate that cofeeding could be critical for enzootic maintenance.

The antiviral immunity of ticks against transmitted viral pathogens.

Ticks, being obligate hematophagous arthropods, are exposed to various blood-borne pathogens, including arboviruses. Consequently, their feeding behavior can readily transmit economically important viral pathogens to humans and animals. With this tightly knit vector and pathogen interaction, the replication and transmission of tick-borne viruses (TBVs) must be highly regulated by their respective tick vectors to avoid any adverse effect on the ticks' biological development and viability. Knowledge about the tick-virus interface, although gaining relevant advances in recent years, is advancing at a slower pace than the scientific developments related to mosquito-virus interactions. The unique and complicated feeding behavior of ticks, compared to that of other blood-feeding arthropods, also limits the studies that would further elaborate the antiviral immunity of ticks against TBVs. Hence, knowledge of molecular and cellular immune mechanisms at the tick-virus interface, will further elucidate the successful viral replication of TBVs in ticks and their effective transmission to human and animal hosts.

The complex interplay of climate, TBEV vector dynamics and TBEV infection rates in ticks-Monitoring a natural TBEV focus in Germany, 2009-2018.

BACKGROUND: Tick-borne encephalitis (TBE) is the most important tick-borne viral disease in Eurasia and causes disease in humans and in a number of animals, among them dogs and horses. There is still no good correlation between tick numbers, weather conditions and human cases. There is the hypothesis that co-feeding due to simultaneous occurrence of larvae and nymphs may be a factor for the increased transmission of the virus in nature and for human disease. Based on long-term data from a natural TBEV focus, phylogenetic results and meteorological data we sought to challenge this hypothesis. METHODS: Ticks from an identified TBE natural focus were sampled monthly from 04/2009 to 12/2018. Ticks were identified and pooled. Pools were tested by RT-qPCR. Positive pools were confirmed by virus isolation and/or sequencing of additional genes (E gene, NS2 gene). Temperature data such as the decadal (10-day) mean daily maximum air temperature (DMDMAT) were obtained from a nearby weather station and statistical correlations between tick occurrence and minimal infection rates (MIR) were calculated. RESULTS: In the study period from 04/2009 to 12/2018 a total of 15,530 ticks (2,226 females, 2,268 males, 11,036 nymphs) were collected. The overall MIR in nymphs over the whole period was 77/15,530 (0.49%), ranging from 0.09% (2009) to 1.36% (2015). The overall MIR of female ticks was 0.76% (17/2,226 ticks), range 0.14% (2013) to 3.59% (2016). The overall MIR of males was 0.57% (13/2,268 ticks), range from 0.26% (2009) to 0.97% (2015). The number of nymphs was statistically associated with a later start of spring/vegetation period, indicated by the onset of forsythia flowering. CONCLUSION: There was no particular correlation between DMDMAT dynamics in spring and/or autumn and the MIR of nymphs or adult ticks detected. However, there was a positive correlation between the number of nymphs and the number of reported human TBE cases in the following months, but not in the following year. The hypothesis of the importance of co-feeding of larvae and nymphs for the maintenance of transmission cycle of TBEV in nature is not supported by our findings.

A single mutation in Crimean-Congo hemorrhagic fever virus discovered in ticks impairs infectivity in human cells.

Crimean-Congo hemorrhagic fever (CCHF) is the most widely distributed tick-borne viral infection in the world. Strikingly, reported mortality rates for CCHF are extremely variable, ranging from 5% to 80% (Whitehouse, 2004). CCHF virus (CCHFV, Nairoviridae) exhibits extensive genomic sequence diversity across strains (Deyde et al., 2006; Sherifi et al., 2014). It is currently unknown if genomic diversity is a factor contributing to variation in its pathogenicity. We obtained complete genome sequences of CCHFV directly from the tick reservoir. These new strains belong to a solitary lineage named Europe 2 that is circumstantially reputed to be less pathogenic than the epidemic strains from Europe 1 lineage. We identified a single tick-specific amino acid variant in the viral glycoprotein region that dramatically reduces its fusion activity in human cells, providing evidence that a glycoprotein precursor variant, present in ticks, has severely impaired function in human cells.

Crimean-Congo hemorrhagic fever (CCHF) is caused by infection with a virus spread by ticks in Europe, Africa and Asia. It can cause severe disease in humans, including high fevers and bleeding. How deadly CCHF is varies with between 5% to 80% of those infected dying. Scientists suspect genetic differences in various strains of the virus may account for the differences in death rates, but they do not know the exact mutations that make the CCHF virus more or less deadly. To learn more, scientists have sorted strains of CCHF virus into different groups based on how similar they are genetically. One group called Europe 2 infects many people in the Balkans, but it rarely causes illness. In fact, only two mild cases of illness have been associated with Europe 2 strains, while other CCHF virus strains circulating in this region have caused thousands of more severe illnesses. Now, Hua et al. identified a mutation in one Europe 2 strain of the CCHF virus that may explain why this subgroup of viruses rarely causes severe human disease. The researchers collected a strain of CCHF virus from infected ticks found in Bulgaria and sequenced its genome. They named the virus strain Malko Tarnovo. Through a series of experiments, Hua et al. showed that the Malko Tarnovo strain very efficiently infects tick cells but not human cells. A single amino acid change in the genetic sequence of the virus appears to make the virus less able to infect human cells. The mutation prevents a protein on the surface of the virus from fusing with human cells, an essential step in infection. This may explain why this strain and others in the Europe 2 group do not cause severe human disease. Hua et al. also demonstrate the importance of studying viruses in the animals that spread them. By studying the CCHF virus in ticks, scientists may be able to learn more about how viruses evolve to infect new species, which may help scientists prevent future pandemics.

Vectors, molecular epidemiology and phylogeny of TBEV in Kazakhstan and central Asia.

BACKGROUND: In the South of Kazakhstan, Almaty Oblast' (region) is endemic for tick-borne encephalitis, with 0.16-0.32 cases/100,000 population between 2016-2018. The purpose of this study was to determine the prevalence and circulating subtypes of tick-borne encephalitis virus (TBEV) in Almaty Oblast' and Kyzylorda Oblast'. METHODS: In 2015 we investigated 2341 ticks from 7 sampling sites for the presence of TBEV. Ticks were pooled in 501 pools and isolated RNA was tested for the presence of TBEV by RT-qPCR. For the positive samples, the E gene was amplified, sequenced and a phylogenetic analysis was carried out. RESULTS: A total of 48 pools were TBEV-positive by the RT-qPCR. TBEV-positive ticks were only detected in three districts of Almaty Oblast' and not in Kyzylorda Oblast'. The positive TBEV pools were found within Ixodes persulcatus, Haemaphysalis punctata and Dermacentor marginatus. These tick species prevailed only in Almaty Oblast' whereas in Kyzylorda Oblast' Hyalomma asiaticum and D. marginatus are endemic. The minimum infection rates (MIR) in the sampling sites were 4.4% in Talgar, 2.8% in Tekeli and 1.1% in Yenbekshikazakh, respectively. The phylogenetic analysis of the generated sequences indicates that TBEV strains found in Almaty Oblast' clusters in the Siberian subtype within two different clades. CONCLUSIONS: We provided new data about the TBEV MIR in ticks in Almaty Oblast' and showed that TBEV clusters in the Siberian Subtype in two different clusters at the nucleotide level. These results indicate that there are different influences on the circulating TBEV strains in south-eastern Kazakhstan. These influences might be caused by different routes of the virus spread in ticks which might bring different genetic TBEV lineages to Kazakhstan. The new data about the virus distribution and vectors provided here will contribute to an improvement of monitoring of tick-borne infections and timely anti-epidemic measures in Kazakhstan.

Records of ticks (Acari: Ixodidae) on humans and distribution of spotted-fever cases and its tick vectors in Paraná State, southern Brazil.

Brazilian spotted fever (BSF) is the deadliest rickettsiosis in the world. Although the epidemiology of the disease has been established in Brazil, there are still limited data available on distribution of tick vectors and tick species parasitizing humans in the country, particularly in Paraná State. The State of Paraná is located in the southern region of the country and is covered by two biomes: Atlantic rainforest and Cerrado. Thus, the aims of this study were i) to map the distribution of SF tick vectors, ii) to describe and map the distribution of human parasitism by ticks, and iii) to map the distribution of fatal and non-fatal spotted fever (SF) cases in Paraná State, southern Brazil. Data were reviewed and compiled from previous published reports, and also from two scientific collections of Paraná State. SF cases were retrieved from the Brazilian Notifiable Diseases Information System. A total of 50 cases of human parasitism by ticks were recorded, with a total of 64 (22 males, 12 females, 30 nymphs) ticks collected. The following 12 tick species were identified: Amblyomma aureolatum, Amblyomma brasiliense, Amblyomma calcaratum, Amblyomma dubitatum, Amblyomma incisum, Amblyomma longirostre, Amblyomma ovale, Amblyomma parkeri, Amblyomma scalpturatum, Amblyomma sculptum, Haemaphysalis juxtakochi and Rhipicephalus sanguineus sensu lato (s.l.). The most prevalent tick species associated to cases of human parasitism were A. sculptum (13/50; 26 %), A. aureolatum (10/50; 20 %), A. brasiliense (5/50; 10 %), A. ovale (5/50; 10 %) and A. parkeri (4/50; 8%). A total of 51 non-fatal and five fatal SF cases were recorded. Data from this study highlights the need for monitoring ticks parasitizing humans aiming early detection of tick-borne diseases cases, particularly BSF in Paraná State, southern Brazil.

The Regulation of Flavivirus Infection by Hijacking Exosome-Mediated Cell-Cell Communication: New Insights on Virus-Host Interactions.

The arthropod-borne flaviviruses are important human pathogens, and a deeper understanding of the virus-host cell interaction is required to identify cellular targets that can be used as therapeutic candidates. It is well reported that the flaviviruses hijack several cellular functions, such as exosome-mediated cell communication during infection, which is modulated by the delivery of the exosomal cargo of pro- or antiviral molecules to the receiving host cells. Therefore, to study the role of exosomes during flavivirus infections is essential, not only to understand its relevance in virus-host interaction, but also to identify molecular factors that may contribute to the development of new strategies to block these viral infections. This review explores the implications of exosomes in flavivirus dissemination and transmission from the vector to human host cells, as well as their involvement in the host immune response. The hypothesis about exosomes as a transplacental infection route of ZIKV and the paradox effect or the dual role of exosomes released during flavivirus infection are also discussed here. Although several studies have been performed in order to identify and characterize cellular and viral molecules released in exosomes, it is not clear how all of these components participate in viral pathogenesis. Further studies will determine the balance between protective and harmful exosomes secreted by flavivirus infected cells, the characteristics and components that distinguish them both, and how they could be a factor that determines the infection outcome.

Tick-borne pathogens and their vectors in Kazakhstan - A review.

Tick-borne diseases (TBDs), in particular Crimean-Congo hemorrhagic fever (CCHF) and tick-borne encephalitis (TBE), have been found to be expanding beyond their traditional geographic locations in Kazakhstan, which led to increased awareness and concern against TBDs in recent years. The tick fauna of Kazakhstan includes more than 30 species of human-biting ixodid ticks, recognized as carriers of a number of dangerous infectious pathogens that cause CCHF, TBE, tularemia, tick-borne rickettsioses and Lyme borreliosis. This paper presents the current knowledge of the main vectors of tick-borne pathogens (TBP) occurring in Kazakhstan, as well as a review of recent studies of ticks performed with the use of molecular methods being currently developed and widely utilized by Kazakh epidemiologists.

Role of three tick species in the maintenance and transmission of Severe Fever with Thrombocytopenia Syndrome Virus.

Severe fever with thrombocytopenia syndrome virus (SFTSV) is a novel phlebovirus in the Bunyaviridae family, causing SFTS with high mortality rate. Haemaphysalis longicornis ticks has been demonstrated as a competent vector of SFTSV by experimental transmission study and field study. However, there has been query whether other tick species that infest human beings in the SFTS endemic regions are capable of transmitting the pathogen. Here by performing experimental transmission study, we compared the capable of transmitting SFTSV among Ixodes sinensis, Ixodes persulcatus and Dermacentor silvarum ticks. The transovarial transmission was seen in the I. sinensis ticks with a rate of 40%, but neither in I. persulcatus nor in D. silvarum ticks. I. sinensis ticks also have the ability to transmit SFTSV horizontally to uninfected mice at 7 days after feeding, but not for I. persalcatus or D. silvarum ticks. In the transstadial transmission of I. persulcatus and D. silvarum ticks, I. persulcatus ticks were tested negative from larvae to adults. But the D. silvarum ticks were tested positive from larvae to nymphs, with the positive rate of 100% (10/10) for engorged larval ticks and 81.25% (13/16) for molted nymphs. However, the mice bitten by SFTSV-infected D. silvarum nymphs were negative for SFTSV detection. Therefore, there is not enough evidence to prove the transstadial transmission of SFTSV in I. persalcatus and D. silvarum ticks.