Tick Virus Research Articles

Prevalence and phylogenetic analysis of Crimean-Congo hemorrhagic fever virus in ticks collected from Punjab province of Pakistan

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne zoonotic disease of human that caused by CCHF virus. To study the epidemiological distribution of CCHFV, 2183 tick samples were collected from sheep, goats, cattle and buffalo of different livestock farms of ten districts of Punjab province of Pakistan. Detection of CCHFV was done using enzyme link immunosorbent assay (ELISA) after proper identification of tick samples. The partial S-segment of CCHFV from ELISA positive tick samples was amplified by PCR and sequenced to determine the genotype of CCHFV. Out of2183 collected tick samples, 1913 ticks belonged to 5 species of genus Hyalomma as H. antolicum (48%), H. marginatum (30.2%), H. rufipes (10.82%), H. impressum (5.43%) and H. dromedarii (5.27%). While 270 ticks belonged to 3 species of genus Rhipicephalus as R. microplus (44.8%), R. sanguineus (32.22%) and R. turanicus (24.8%). The overall antigenic prevalence of CCHFV was found to be 12.13% in collected tick samples and 21 tick pools were sequenced for partial S-segment of CCHFV. All of the 21 tick pools were clustered in genotype IV (Asia-1). The highest prevalence of CCHFV was found in district Chakwal (24.13%) followed by Mianwali (23.68%), Rawalpindi (23.07%), Attock (20.0%), Rajanpur (10.52%) and Lahore (8.33%). In positive tick pools, the highest prevalence of CCHFV antigen was found in H. antolicum (39.6%) followed by H. marginatum (30.18%), H. rufipes (13.2%), H. impressum (3.77%), H. dromedarii (1.88%), R. microplus (5.66%) and R. sanguineus (5.66%). The current study confirms the presence of CCHFV in the ticks population of Punjab. The CCHF virus present in Punjab belongs to Asia-1 genotype. It is important to control the tick infestation of the animals present in these areas. So that the transmission cycle of CCHF can be inhibited.

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.

Widespread Detection of Multiple Strains of Crimean-Congo Hemorrhagic Fever Virus in Ticks, Spain.

Human cases of Crimean-Congo hemorrhagic fever (CCHF) were first detected in Spain in 2016. National human and animal health authorities organized a large, multidisciplinary study focusing on ticks as sentinels to determine the nationwide distribution of ticks with CCHF virus. Ticks were collected from animals and vegetation, samples pooled (12,584 ticks; 4,556 pools), and molecular methods used to look for the virus. We detected the virus in 135 pools from most of the regions studied, indicating that it is widespread in Spain. We found sequences of CCHF virus genotypes I, III, and IV in the tick species collected, most commonly in Hyalomma lusitanicum, suggesting this tick has a prominent role in the virus’s natural cycle. The red deer (Cervus elaphus) was the host that most frequently yielded positive ticks. Our study highlights the need for larger studies in Spain to ascertain the complete risk to public health.

Utility of a Sequence-Independent, Single-Primer-Amplification (SISPA) and Nanopore Sequencing Approach for Detection and Characterization of Tick-Borne Viral Pathogens

Currently, next generation sequencing (NGS) is the mainly used approach for identification and monitorization of viruses with a potential public health threat in clinical and environmental samples. To facilitate detection in NGS, the sequence-independent, single-primer-amplification (SISPA) is an effective tool for enriching virus sequences. We performed a preliminary assessment of SISPA-nanopore sequencing as a potential approach for screening tick-borne viruses in six specimens with detectable Crimean-Congo hemorrhagic fever virus (CCHFV) and Jingmen tick virus (JMTV) sequences. A comparison of unbiased NGS and SISPA followed by nanopore sequencing was carried out in 4 specimens with single and pooled ticks. The approach was further used for genome sequencing in culture-grown viruses. Overall, total/virus-specific read counts were significantly elevated in cell culture supernatants in comparison to single or pooled ticks. Virus genomes could be successfully characterized by SISPA with identities over 99%. Genome coverage varied according to the segment and total read count. Base calling errors were mainly observed in tick specimens and more frequent in lower viral loads. Culture-grown viruses were phylogenetically-related to previously-reported local viruses. In conclusion, the SISPA + nanopore sequencing was successful in generating data comparable to NGS and will provide an effective tool for broad-range virus detection in ticks.

Features of Reproduction of Tick-Borne Encephalitis Virus in a New Cell Line of the Siberian Bat Myotis sibiricus (Kastschenko, 1905)

Background. Tick-borne encephalitis virus (TBEV) in nature exists due to the constant circulation between vertebrate animals and tick viruses. To study the characteristics of reproduction of TBEV in the cells of vertebrate hosts of various species, it is necessary to simulate infection in the cell lines of both natural and accidental hosts of TBEV. Aim . To study the possibility of reproduction of TBEV in the cell line of the kidney of Siberian bat Myotis sibiricus (Kastschenko, 1905) – an accidental host of the virus. Materials and methods. The cell line of Siberian bat M. sibiricus was established by serial passages of primary culture of kidney cells. The SPEV line porcine kidney cells were used as reference. Cells were infected with a strain of TBEV of the Siberian subtype 92M and both cells and cell culture fluids were sampled every 2 hours during first 24 hours post infection. In addition, the samples were collected daily up to 5 days post infection. Evaluation of the amount of intracellular RNA of TBEV of positive polarity (+RNA) was performed using quantitative real-time PCR. The concentration of infectious TBEV was evaluated using the method of titration TBEV on plaque forming units. Results. The continuous cell line, designated as MdbK, was established from the kidney cell suspension of M. sibiricus and was used for experiments after 20 serial passages. MdbK cells were able to support the replication of TBEV RNA and production of infectious virus was also possible. The concentration of intracellular RNA had reached 9.1 lg copies/μl by day 3 post infection, whereas highest titer of infectious TBEV in cell culture fluid had comprised 5,5 PFU/ml and was detected by day 4. The concentration of intracellular RNA and the virus infectivity in MdbK cell line was significantly lower than in convenient SPEV line porcine kidney cell. Conclusions . The results suggest the low fitness of TBEV to the intracellular environment of an accidental host.

Powassan Virus Experimental Infections in Three Wild Mammal Species.

Powassan virus (POWV) is a tick-borne virus maintained in sylvatic cycles between mammalian wildlife hosts and ticks (primarily Ixodes spp.). There are two currently recognized lineages, POWV-lineage 1 (POWV-L1) and deer tick virus (DTV; lineage 2), both of which can cause fatal neurologic disease in humans. Increased numbers of human case reports in the northeastern and north central United States in recent years have fueled questions into POWV epidemiology. We inoculated three candidate wildlife POWV reservoir hosts, groundhogs (Marmota monax), striped skunks (Mephitis mephitis), and fox squirrels (Sciurus niger), with either POWV-L1 or DTV. Resulting viremia, tissue tropism, and pathology were minimal in most inoculated individuals of all three species, with low (peak titer range, 101.7-103.3 plaque-forming units/mL serum) or undetectable viremia titers, lack of detection in tissues except for low titers in spleen, and seroconversion in most individuals by 21 days postinoculation (DPI). Pathology was limited and most commonly consisted of mild inflammation in the brain of POWV-L1- and DTV-inoculated skunks on four and 21 DPI, respectively. These results reveal variation in virulence and host competence among wild mammalian species, and a likely limited duration of host infectiousness to ticks during enzootic transmission cycles. However, POWV can transmit rapidly from tick to host, and tick co-feeding may be an additional transmission mechanism. The rare and low-level detections of viremia in these three, common, wild mammal species suggest that vector-host dynamics should continue to be explored, along with eco-epidemiological aspects of enzootic POWV transmission in different regions and virus lineages.

Human Tacheng Tick Virus 2 Infection, China, 2019.

We used metagenomic analysis to identify Tacheng tick virus 2 infection in a patient with a history of tick bite in northwestern China. We confirmed the virus with reverse transcription-PCR, virus isolation, and genomic analysis. We detected viral RNA in 9.6% of ticks collected from the same region.

Metagenomic Profiling of Viruses Associated with Rhipicephalus microplus Ticks in Yunnan Province, China.

Ticks are well known as vectors of many viruses which usually do great harm to human and animal health. Yunnan Province, widely covered by flourishing vegetation and mainly relying on farming husbandry, is abundant with Rhipicephalus microplus ticks. Therefore, it is of great significance to characterize the viral profile present in R. microplus parasitizing on cattle in Yunnan Province. In this study, a total of 7387 R. microplus ticks were collected from cattle and buffalo in the northwest and southeast areas of Yunnan Province from 2015 to 2017. We investigated the virome of R. microplus using next-generation sequencing (NGS) and the prevalence of important identified viruses among tick groups by RT-PCR. It revealed the presence of diverse virus concerning chu-, rhabdo-, phlebo-, flavi- and parvo- viruses in Yunnan. These viruses consist of single-stranded, circular and segmented sense RNAs, showing a greatly diversity in genomic organization. Furthermore, continuous epidemiological survey among ticks reveals broad prevalence of three viruses (Yunnan mivirus 1, Wuhan tick vrius 1 and YN tick-associated phlebovirus 1) and two possible prevalent viruses including a flavivirus-like segmented virus (Jingmen tick virus) and a bovine hokovirus 2 in Yunnan. Serological investigation among cattle indicates that these identified viruses may be infectious to cattle and can elicit corresponding antibody. Our findings on R. microplus-associated viral community will contribute to the prevention of viral disease and tracking the viral evolution. Further analysis is needed to better elucidate the pathogenicity and natural circulation of these viruses.

Viromes and surveys of RNA viruses in camel-derived ticks revealing transmission patterns of novel tick-borne viral pathogens in Kenya

Tick-borne viruses (TBVs) capable of transmitting between ticks and hosts have been increasingly recognized as a global public health concern. In this study, Hyalomma ticks and serum samples from camels were collected using recorded sampling correlations in eastern Kenya. Viromes of pooled ticks were profiled by metagenomic sequencing, revealing a diverse community of viruses related to at least 11 families. Five highly abundant viruses, including three novel viruses (Iftin tick virus, Mbalambala tick virus [MATV], and Bangali torovirus [BanToV]) and new strains of previously identified viruses (Bole tick virus 4 [BLTV4] and Liman tick virus [LMTV]), were characterized in terms of genome sequences, organizations, and phylogeny, and their molecular prevalence was investigated in individual ticks. Moreover, viremia and antibody responses to these viruses have been investigated in camels. MATV, BLTV4, LMTV, and BanToV were identified as viral pathogens that can potentially cause zoonotic diseases. The transmission patterns of these viruses were summarized, suggesting three different types according to the sampling relationships between viral RNA-positive ticks and camels positive for viral RNA and/or antibodies. They also revealed the frequent transmission of BanToV and limited but effective transmission of other viruses between ticks and camels. Furthermore, follow-up surveys on TBVs from tick, animal, and human samples with definite sampling relationships are suggested. The findings revealed substantial threats from the emerging TBVs and may guide the prevention and control of TBV-related zoonotic diseases in Kenya and in other African countries.

First Detection of Tacheng Tick Virus 2 in Hard Ticks from Southeastern Kazakhstan

First Detection of Tacheng Tick Virus 2 in Hard Ticks from Southeastern Kazakhstan

Ticks of genus Ixodidae: bioecological mechanisms of adaptation to environmental conditions, medical and epidemiological significance

Considering the geographical position of Ukraine, which is located on the border of several physical and geographical zones, the country has a significant variety of parasitic invertebrates and requires constant monitoring in the current integration conditions. Nowadays climatic changes and anthropogenic effect have an impact on ecosystems organization and cause the incidence of transmissible diseases, including tick-borne infections. In order to prevent the spread of pathogens, there is a necessity to analyze modern data of Ixodidae genus ticks, as components of natural and focal humans and animals diseases, their ecological features, behavioral responses, features of biotopic spread, biological patterns, their epidemiological significance. Our review analysis revealed that all stages of tick development depend on three major natural factors: temperature, humidity, duration of the photoperiod, and the presence of a host. Particularly important is the combination of the first two factors that determines the occurrence of two peaks of the number of ticks in April - May and in August – September, the last is less extended. At this time of year the nymphs and imago density increases and their infectious agents rate is increased too. The study of the epidemiological condition proves the fact that nymphs and imago of I. ricinus are equally infected with the most common pathogens of infections: Borrelia burgdorferi sensu lato (sl) and Borrelia miyamotoi, rickettsiae bacteria (Anaplasma phagocytophilum), flaviviruses (tick-borne encephalitis virus and deer tick virus) and the protozoans (Babesia microti, Babesia duncani, Babesia divergens and Babesia venatorum). Often there is a different combination of these pathogens in the one tick. The infectious agents rate have an impact on the ticks behavior differences in the feeding duration, increasing ticks bites frequency, decreasing of blood feeding, and a prolongation of the life cycle. Therefore within the transboundary territories the urgent control of agents and vectors of infectious and invasive animals and humans diseases is required, studying changes of migrant thermophilic species habitats geography, and systematic measures for the prevention of parasites implementation is needed.

Isothermal Recombinase Polymerase Amplification-Lateral Flow Point-of-Care Diagnostic Test for Heartland Virus.

The detection of novel or re-emergent pathogens necessitates the development of rapid, easy-to-use diagnostic tests that can be readily adapted and utilized in both clinical laboratories and field settings. Heartland virus (HRTV) is the first pathogenic Phlebovirus responsible for serious and fatal cases in the United States. We developed a qualitative test based on recombinase-polymerase-amplification coupled with lateral flow reading (RPA-LF) for rapid detection of HRTV. The RPA-LF detected HRTV with a limit of detection of 1.19-1.54 plaque-forming unit equivalents/reaction. In addition, the RPA-LF was able to detect 0.6075 copies/μL of HRTV nucleoprotein gene-containing plasmid. We evaluated six clinical samples that were previously found to be real-time PCR positive for HRTV and found five out of six samples to be positive by RPA-LF, yielding 83.3% concordance with real-time PCR. All six samples had Ct values between 29 and 39 by real-time PCR. We also determined that the HRTV primers and probe do not cross-react with other tick-transmitted viruses such as Bourbon and Powassan, or other related viruses, including Lonestar tick virus and Sunday canyon virus (100% specificity). This is the first isothermal amplification test developed for a tick-borne virus, which will allow for rapid differentiation between HRTV and other pathogens producing similar clinical manifestations.

Migratory birds as disseminators of ticks and the tick-borne pathogens Borrelia bacteria and tick-borne encephalitis (TBE) virus: a seasonal study at Ottenby Bird Observatory in South-eastern Sweden

BackgroundBirds can act as reservoirs of tick-borne pathogens and can also disperse pathogen-containing ticks to both nearby and remote localities. The aims of this study were to estimate tick infestation patterns on migratory birds and the prevalence of different Borrelia species and tick-borne encephalitis virus (TBEV) in ticks removed from birds in south-eastern Sweden.MethodsTicks were collected from resident and migratory birds captured at the Ottenby Bird Observatory, Öland, Sweden, from March to November 2009. Ticks were molecularly identified to species, and morphologically to developmental stage, and the presence of Borrelia bacteria and TBEV was determined by quantitative real-time PCR.ResultsA total of 1339 ticks in the genera Haemaphysalis, Hyalomma, and Ixodes was recorded of which I. ricinus was the most abundant species. Important tick hosts were the European robin (Erithacus rubecula), Blackbird (Turdus merula), Tree pipit (Anthus trivialis), Eurasian wren (Troglodytes troglodytes), Common redstart (Phoenicurus phoenicurus), Willow warbler (Phylloscopus trochilus), and Common whitethroat (Sylvia communis). Borrelia bacteria were detected in 25% (285/1,124) of the detached ticks available for analysis. Seven Borrelia species (B. afzelii, B. burgdorferi (s.s.), B. garinii, B. lusitaniae, B. turdi, B. valaisiana, and B. miyamotoi) were identified. B. turdi was recorded for the first time in ticks in Sweden. The number of Borrelia cells per tick ranged from 2.0 × 100 to 7.0 × 105. B. miyamotoi-containing ticks contained a significantly higher median number of Borrelia cells than B. burgdorferi (s.l.)-containing ticks. B. garinii and B. miyamotoi were the most prevalent Borrelia species in tick larvae. Larvae of I. ricinus with B. garinii were removed from seven bird species, particularly S. communis and A. trivialis, which may suggest that the larvae had contracted the Borrelia bacteria from or via these birds. Also, a high percentage of tick larvae containing B. miyamotoi was removed from E. rubecula. All ticks were negative for TBEV.ConclusionsThe results corroborate the view that the contributions of birds to human disease are substantial, particularly as blood hosts for ticks and for their short-, medium-, and long-distance dispersal. Moreover, several ground-foraging bird species appear to be important for the maintenance and dispersal of Borrelia species. The absence of TBEV in the ticks conforms to other similar studies.Graphical

Identification of recently identified tick-borne viruses (Dabieshan tick virus and SFTSV) by metagenomic analysis in ticks from Shandong Province, China

The aim of this study is to systematically examine the variety of viruses maintained in ticks from Shandong Province. A total of 2522 ticks were sampled from five cities of Shandong Province and divided into 264 pools according to location and species. Viral megagenomic analysis revealed the sequences of two viruses, Dabieshan tick virus and SFTSV. Then qRT-PCR and nested PCR were performed to confirm the presence of corresponding pathogens, which showed positive results for Dabieshan tick virus and SFTSV, with a minimum infection rate of 0.67% (17/2522) and 2.5% (63/2522), respectively. Phylogenetic analysis showed that Dabieshan tick virus formed a monophyletic cluster with the Yongjia tick virus and Uukuniemi virus from China, and SFTSV shared over 95% identity with human and animal derived isolates. These findings are the first time to demonstrate molecular evidence of Dabieshan tick virus in unrecognized endemic regions and indicate the need for further investigation.

Characterization of flavivirus infection in salivary gland cultures from male Ixodes scapularis ticks.

Infected Ixodes scapularis (black-legged tick) transmit a host of serious pathogens via their bites, including Borrelia burgdorferi, Babesia microti, and tick-borne flaviviruses (TBFVs), such as Powassan virus (POWV). Although the role of female I. scapularis ticks in disease transmission is well characterized, the role of male ticks is poorly understood. Because the pathogens are delivered in tick saliva, we studied the capacity of male salivary glands (SGs) to support virus replication. Ex vivo cultures of SGs from unfed male I. scapularis were viable for more than a week and maintained the characteristic tissue architecture of lobular ducts and acini. When SG cultures were infected with the TBFVs Langat virus (LGTV) or POWV lineage II (deer tick virus), the production of infectious virus was demonstrated. Using a green fluorescent protein-tagged LGTV and confocal microscopy, we demonstrated LGTV infection within SG acinus types II and III. The presence of LGTV in the acini and lobular ducts of the cultures was also shown via immunohistochemistry. Furthermore, the identification by in situ hybridization of both positive and negative strand LGTV RNA confirmed that the virus was indeed replicating. Finally, transmission electron microscopy of infected SGs revealed virus particles packaged in vesicles or vacuoles adjacent to acinar lumina. These studies support the concept that SGs of male I. scapularis ticks support replication of TBFVs and may play a role in virus transmission, and further refine a useful model system for developing countermeasures against this important group of pathogens.

Full-length genome sequence of segmented RNA virus from ticks was obtained using small RNA sequencing data

BackgroundIn 2014, a novel tick-borne virus of the Flaviviridae family was first reported in the Mogiana region of Brazil and named the Mogiana tick virus (MGTV). Thereafter, the Jingmen tick virus (JMTV), Kindia tick virus (KITV), and Guangxi tick virus (GXTV)—evolutionarily related to MGTV—were reported.ResultsIn the present study, we used small RNA sequencing (sRNA-seq) to detect viruses in ticks and discovered a new MGTV strain in Amblyomma testudinarium ticks collected in China’s Yunnan Province in 2016. We obtained the full-length genome sequence of this MGTV strain Yunnan2016 (GenBank: MT080097, MT080098, MT080099 and MT080100) and recommended it for its inclusion in the NCBI RefSeq database for future studies on MGTV, JMTV, KITV and GXTV. Phylogenetic analysis showed that MGTV, JMTV, KITV and GXTV are monophyletic and belong to a MGTV group. Furthermore, this MGTV group of viruses may be phylogenetically related to geographical regions that were formerly part of the supercontinents Gondwana and Laurasia.ConclusionsTo the best of our knowledge, this is the first study in which 5′ and 3′ sRNAs were used to generate full-length genome sequences of, but not limited to, RNA viruses. We also demonstrated the feasibility of using the sRNA-seq based method for the detection of viruses in pooled two and even possible one small ticks. MGTV may preserve the characteristic of ancient RNA viruses, which can be used to study the origin and evolution of RNA viruses. In addition, MGTV can be used as novel species for studies in phylogeography.

Severe Fever with Thrombocytopenia Syndrome Virus in Ticks and SFTS Incidence in Humans, South Korea.

During 2016–2018, we collected 3,193 ticks from rural areas in South Korea to investigate the prevalence of severe fever with thrombocytopenia syndrome virus (SFTSV). We detected SFTSV in ticks at an infection rate (IR) of 11.1%. We noted increases in the human IR associated with the monthly SFTSV IR in ticks.

Powassan Virus Neuropathology and Genomic Diversity in Patients With Fatal Encephalitis.

BackgroundPowassan virus (POWV) is an emerging cause of severe encephalitis; very little is known about human pathogenicity due to challenges in diagnosis and viral RNA recovery. We present 3 patients with fatal encephalitis due to POWV lineage II (deer tick virus). MethodsWe obtained 27 unique samples, including from brain biopsy and autopsy, and used metagenomic sequencing, quantitative reverse transcriptase polymerase chain reaction, and a newly developed CRISPR-based diagnostic assay to perform the first detailed characterization of POWV compartmentalization and genomics between and within human subjects. ResultsIn all 3 patients, imaging and histopathology findings were notable for profound cerebellar involvement. All patients were initially diagnosed with POWV by metagenomic sequencing, and 2 of the 3 had negative clinical testing by serology. We detected POWV RNA in 13 clinical samples; levels were highest in the cerebellum, and there was very little involvement of peripheral tissue. We assembled complete POWV genomes from 8 samples, providing unique information about the strains of POWV lineage II (deer tick virus) that infect humans. ConclusionsWe demonstrate the utility of molecular assays for detecting POWV infection, including in seronegative patients, and nominate viral genomic features that may relate to human infection and neuropathogenicity. The cerebellum was identified as a key target POWV in fatal infection, by radiological and histopathological findings as well as molecular testing.

Diversity and circulation of Jingmen tick virus in ticks and mammals

Since its initial identification in ticks in 2010, Jingmen tick virus (JMTV) has been described in cattle, rodents, and primates. To better understand the diversity, evolution, and transmission of JMTV, we sampled 215 ticks, 104 cattle bloods, 216 bats, and 119 rodents in Wenzhou city, Zhejiang Province, China as well as 240 bats from Guizhou and Henan Provinces. JMTV was identified in 107 ticks (from two species), 54 bats (eleven species), 8 rodents (three species), and 10 cattle, with prevalence levels of 49.8, 11.8, 6.7, and 9.6 per cent, respectively, suggesting that bats may be a natural reservoir of JMTV. Phylogenetic analyses revealed that all the newly identified JMTVs were closely related to each other and to previously described viruses. Additionally, all tick and mammalian JMTV sampled in Wenzhou shared a consistent genomic structure, suggesting that the virus can cocirculate between ticks and mammals without observable variation in genome organization. All JMTVs sampled globally could be divided into two phylogenetic groups, Mantel tests suggested that geographic isolation, rather than host species, may be the main driver of JMTV diversity. However, the exact geographical origin of JMTV was difficult to determine, suggesting that this virus has a complex evolutionary history.

Development of a small animal model for deer tick virus pathogenesis mimicking human clinical outcome.

Powassan virus (POWV) is a tick-borne flavivirus that encompasses two genetic lineages, POWV (Lineage I) and deer tick virus (DTV, Lineage II). In recent years, the incidence of reported POWV disease cases has increased, coupled with an expanded geographic range of the DTV tick vector, Ixodes scapularis. POWV and DTV are serologically indistinguishable, and it is not known whether clinical manifestations, pathology, or disease outcome differ between the two viruses. Six-week-old male and female BALB/c mice were footpad-inoculated with DTV doses ranging from 101 to 105 FFU. Dose-independent mortality, morbidity, and organ viral loads were observed for mice inoculated with sequentially increasing doses of DTV. By study completion, all surviving mice had cleared their viremias but detectable levels of negative-sense DTV RNA were present in the brain, indicating viral persistence of infectious DTV in the central nervous system. For mice that succumbed to disease, neuropathology revealed meningoencephalitis characterized by microscopic lesions with widespread distribution of viral RNA in the brain. These findings, coupled with the rapid onset of neurological signs of disease and high viral titers in nervous tissue, highlight the neurotropism of DTV in this mouse model. Additionally, disease outcome for DTV-infected mice was not affected by sex, as males and females were equally susceptible to disease. This is the first study to comprehensively characterize the clinical disease outcome in a small animal model across a spectrum of POWV/DTV infection doses. Here, we developed a small animal model for DTV pathogenesis that mimics the manifestations of POWV disease in humans. Since it is currently not known whether DTV and POWV differ in their capacity to cause human disease, the animal model detailed in our study could be utilized in future comparative pathogenesis studies, or as a platform for testing the efficacy of vaccines, and anti-virals.