Identification of a new orthonairovirus associated with human febrile illness in China

Alongshan virus: An emerging arboviral challenge in regional health security

The Alongshan virus (ALSV), classified within the Flaviviridae family and belonging to the Jingmenvirus group, is a segmented RNA virus that was first identified in China in 2017. Since then, it has been reported in several Eurasian countries. Although no confirmed fatal cases have been documented, the potential public health risks associated with ALSV are significant and warrant serious attention. The emergence of ALSV has not only broadened the array of tick-borne diseases but has also enriched the research landscape surrounding segmented flaviviruses. Despite these advancements, our understanding of ALSV is still nascent, and its complex infection pathways remain largely unexplored. This review seeks to offer an in-depth examination of ALSV, addressing its biological properties, molecular features, epidemiological data, clinical presentations, and diagnostic methodologies. Our objective is to promote progress in the formulation of preventive, diagnostic, and therapeutic measures for this emerging segmented flavivirus.

Tamdy virus pathogenesis in immunocompetent and immunocompromised mouse models

Tamdy virus (TAMV) is one of the zoonotic tick-borne bunyaviruses that have emerged as global public health threats in recent decades. To date, however, TAMV pathogenesis remains poorly understood. In the present study, we have established different mouse infection models to enable investigation of TAMV pathogenesis. Adult BALB/c mice did not exhibit obvious clinical symptoms or signs post-TAMV infection. In contrast, adult type I interferon receptor knockout (IFNAR-/-) A129 mice were found to be susceptible to high-doses of TAMV (6 × 102 and 6 × 104 FFU) and all developed severe clinical symptoms and signs, including weight loss and immobility, and reached the euthanasia criteria at 4/5-day post-infection (dpi). Viral RNA was detected in peripheral blood and different tissues (heart, liver, spleen, lung, kidney, intestine, and brain) of the high-dose infected adult A129 mice, with the highest viral loads in the liver (approximately 108.3 copies/μL). Pathological examination also revealed severe liver damage in the high-dose infected A129 mice. In addition, the titres of TAMV-specific IgM and IgG antibodies increased rapidly 4-5 dpi. Analysis of cytokine and chemokine expression changes demonstrated that type I IFN may play an important role in the host defence against viral infection by enhancing IL-10 production. Gene ontology and KEGG analyses showed that liver injury may be associated with virus-induced expression of inflammatory cytokines and chemokines. Together, we have investigated TAMV pathogenesis using immunocompetent and immunocompromised mouse models, which will facilitate the development of TAMV-specific antivirals and vaccines.

Genetic diversity and expanded epidemic area of novel tick-borne pathogen wetland virus in ticks, wild and domestic animals, and patient in China

Wetland virus (WELV) is a recently identified segmented orthonairovirus associated with human febrile illness in northeastern China. To elucidate its ecological drivers and transmission patterns, we conducted multi-host surveillance in seven eco-climate regions across China through an integrated approach combining molecular and serological profiling. Over 33,000 questing and feeding ticks representing 11 species were systematically screened WELV-RNA alongside 1,493 wild small mammals, while 2,578 domestic animals and 3,921 patients presenting with outdoor field or tick exposure history underwent both WELV specific molecular and serological evaluation. WELV-RNA detection via real-time RT-PCR revealed low but widespread infection, including 0.54% (8/1,493) in wild rodents (Apodemus chevrieri, Rattus norvegicus), 1.12% (29/2,578) in domestic animals, and 0.86% (275/33,091) in ticks, including five newly confirmed vector species. Serological analysis via enzyme-linked immunosorbent assay (ELISA) demonstrated 2.44% (63/2,578) IgG seroprevalence in livestock. Clinical surveillance identified acute WELV infections in 1.81% (71/3,921) of febrile patients, predominantly as monoinfections (77.46%, 55/71). Coinfected patients exhibited elevated disease severity markers, with hospitalization rates doubling compared to single-infection cases (87.50% vs. 36.36%). Spatiotemporal analysis showed spring-summer predominance of WELV for both ticks and human patients. Phylogenetic analyses revealed remarkable genetic conservation patterns of WELV strains across diverse hosts and tick vectors; and clustering across geographical regions. These findings establish WELV as an emerging tick-borne virus with trans-regional spread across heterogeneous landscapes in China. The intersecting transmission cycles among wildlife reservoirs, domestic amplifier hosts, and expanding tick vectors underscore the imperative for integrated surveillance strategies to mitigate this growing public health threat.

Virome of Hyalomma and Rhipicephalus ticks from desert of Northwestern China

Ticks are important vectors for pathogen transmission, yet studies on the diversity and distribution of viruses carried by ticks in desert regions remain limited. This study investigated the tick virome in desert areas of Xinjiang, China, and identified two tick species, Hyalomma asiaticum and Rhipicephalus turanicus. A total of 30 meta-transcriptome sequencing libraries were constructed from ticks pooled by location, tick species, sex, and host. The proportion of viral reads ranged from 0.004% to 0.165%, and significant differences in viral alpha- and beta-diversity were observed between the two tick species. A total of 125 complete or nearly complete viral genomes were classified into 5 families of positive-sense single-stranded RNA viruses, 6 families of negative-sense single-stranded RNA viruses, and 2 families of double-stranded RNA viruses. Twenty-eight viral species were identified, including 20 known viruses and 8 novel viruses from the genera Orthonairovirus, Quaranjavirus, and Mitovirus, and families Peribunyaviridae and Narnaviridae. Notably, the discovery of Desert orthonairovirus, Desert quaranjavirus, and Desert peribunya-like virus revealed a potential new role for desert ticks as viral vectors. Among the other 25 viruses, 12 were specific to H. asiaticum, and 9 were specific to R. turanicus. This study highlights the diversity of tick-borne viruses in Xinjiang's desert regions, their distribution across different tick species, and underscores the importance of these tick species in pathogen transmission. These findings provide scientific evidence for further research into viral circulation in desert ecosystems and the potential public health threats posed by tick-borne pathogens.

A series of patients infected with the emerging tick-borne Yezo virus in China: an active surveillance and genomic analysis

BACKGROUND

Yezo virus (YEZV) is an emerging tick-borne pathogen, which was initially reported in Japan in 2021. Only one patient had been reported in China so far. We aimed to describe the epidemiological, clinical, and laboratory findings of a series of patients, and to characterise the viral genomes of YEZV.

METHODS

In this active surveillance and genomic analysis, we conducted active surveillance at Mudanjiang Forestry Central Hospital, Heilongjiang Province of northeast China. Participants were eligible for inclusion if they sought medical care for a recent tick bite between May 1 and July 31, in 2022 and 2023, and between May 1 and July 10, in 2024. We collected sera from participants to detect YEZV infection by meta-transcriptomic sequencing, real-time RT-PCR, and indirect immunofluorescence assay. We isolated YEZV by cell culture and characterised the pathogen by morphological and phylogenetic analyses.

FINDINGS

A series of 18 patients with YEZV infection (12 male and six female; median age 53 years, IQR 45-60) were identified among 988 participants. The patients presented with fever (18 patients, 100%), headache (ten patients, 56%), dizziness (nine patients, 50%), malaise (three patients, 17%), lumbago (three patients, 17%), and cough (three patients, 17%). Nine (50%) patients had rash around the tick bite site and four (22%) had lymphadenopathy. Nine (50%) patients had gastrointestinal symptoms, and five (28%) had neurological symptoms. We observed leukopenia in ten (63%) and thrombocytopenia in five (31%) of 16 assessed patients. Elevated hepatic transaminase concentrations were identified in 13 (72%) of all 18 patients, lactate dehydrogenase or α-hydroxybutyric dehydrogenase in nine (50%), serum amyloid protein A in 13 (72%), and hypersensitive C-reactive protein in ten (56%). Eight (7%) of 119 Ixodes persulcatus ticks removed from participants were positive for YEZV. Three YEZV strains were isolated from the sera of patients. Ten viral genomes were obtained from five patients, a blood-sucking I persulcatus removed from a participant, and four host-questing tick samples collected in the areas where patients were identified or in the adjacent region. Phylogenetic analyses revealed that YEZVs in either patients or ticks were divided into two clades, each with distinct mutations.

INTERPRETATION

Awareness of YEZV infection is important and clinicians should consider the virus when diagnosing patients with suitable symptoms.

FUNDING

National Key Research and Development Program of China.

TRANSLATION

For the Chinese translation of the abstract see Supplementary Materials section.

Effectiveness of nucleoside analogs against Wetland virus infection

Wetland virus (WELV), a newly identified Orthonairovirus phylogenetically related to the Crimean-Congo hemorrhagic fever virus (CCHFV), has recently been shown to cause human infections. A portion of patients infected with WELV usually present with febrile diseases, accompanied by hemorrhagic and neurological symptoms. Currently, there are no reports demonstrating effective therapeutic drugs for the treatment of WELV. In this study, we evaluated the anti-WELV efficacy of five nucleoside analogs: four clinically approved drugs-ribavirin, remdesivir, molnupiravir, and sofosbuvir; and a clinical candidate 4'-fluorouridine. Ribavirin and 4'-fluorouridine strongly inhibited WELV replication in vitro. Remdesivir and molnupiravir showed limited antiviral activity against WELV in Huh7 cells but not in Vero cells, while sofosbuvir did not exhibit inhibitory effects. Utilizing a lethal immunocompetent mouse model of WELV infection, we found that oral administration of relatively low doses of ribavirin (25 mg/kg/day) or 4'-fluorouridine (2.5 mg/kg/day) significantly reduced the mortality of WELV-infected mice by decreasing viral titers in tissues and alleviating pathological damage. This treatment strategy retained significant efficacy even when initiated 2-4 days after infection. Additionally, we identified mutations G3033R and A3756V in the C-terminal region of the WELV L protein, which may be associated with viral resistance to ribavirin and 4'-fluorouridine. This study revealed varying degrees of anti-WELV efficacy among different nucleoside analogs and identified 4'-fluorouridine as a promising therapeutic candidate and ribavirin as a priority treatment option for WELV infection.

Analysis of the Microbial Community Structure of Ixodes persulcatus at Each Developmental Stage

Ticks are the second most significant vector of pathogens worldwide. Ixodes persulcatus is one of the dominant tick species in Inner Mongolia that can carry and transmit various pathogenic microorganisms. However, only one specific pathogen has been detected in a particular developmental stage of I. persulcatus, moreover metagenomic analysis has been conducted only in the adult tick stage. In this study, we used I. persulcatus at different developmental stages (first-generation female adult ticks, eggs, larval ticks, engorged larval ticks, nymphal ticks, engorged nymphal ticks, and second-generation adult ticks) from Inner Mongolia as materials for nucleic acid extraction. Subsequently, we constructed Illumina PE250 and Illumina PE150 libraries and sequenced them on the Illumina NovaSeq 6000 platform. Finally, we used molecular biology software and sequence analysis platform to analyze microbial community structures. Illumina PE250 sequencing revealed that the seven developmental stages of I. persulcatus were annotated to 21 phyla, 43 classes, 104 orders, 188 families, 391 genera, and 556 species of bacteria. Among them, 4 phyla and 14 genera were present at all developmental stages, with Proteobacteria being the dominant phylum and Rickettsia spp. being the dominant genus. In addition, Rickettsia had the highest relative abundance in the seven developmental stages. All developmental stages were annotated to a certain abundance of Brucella spp. Illumina PE150 sequencing revealed that the three samples (X-I-YDCP: first-generation adult ticks; X-I-MIX: mixed samples of eggs, larval ticks, and nymphal ticks; X-I-EDCP: second-generation adult ticks) of I. persulcatus were annotated to six orders, 28 families, 72 genera, and 158 species of viruses, of which 46 genera and 80 species were found in all three sample species. To the best of our knowledge, this is the first study that comprehensively analyzed the microbial community composition of I. persulcatus at different developmental stages. Based on the study outcomes, certain abundance of Rickettsia japonica, bovine viral diarrhea virus, and African swine fever virus were annotated to I. persulcatus.

Molecular Detection of Tick-Borne Bacterial Pathogens in Ticks and Rodents from the China-Vietnam Border

Ticks and tick-borne diseases constitute a crucial focus for the health of both humans and animals worldwide. Although numerous studies on tick-borne diseases have been conducted in China, reports on tick-borne pathogens in ticks and rodents from the China-Vietnam border are scarce. In this study, we investigated tick-borne bacterial pathogens, including Rickettsia, Anaplasmataceae, and Borrelia, in nine rodents (Rattus norvegicus) and 88 ticks collected from cattle and rodents in Jingxi, a city at the China-Vietnam border. Through molecular detection and sequence analysis, four known tick-borne pathogens were identified. Specifically, Rickettsia japonica was detected in 46.3% (37/80) of Haemaphysalis cornigera; Anaplasma phagocytophilum and Candidatus Neoehrlichia mikurensis were identified in one Ixodes granulatus and one rodent, respectively; and Borrelia valaisiana was detected in two I. granulatus. Additionally, a potentially novel species of Rickettsia, provisionally named Rickettsia sp. JX, was detected in 41.3% (33/80) of Ha. cornigera, one Rhipicephalus microplus, three I. granulatus, and nine rodents, whereas a potentially novel species of Borrelia, tentatively named Borrelia sp. JX, was detected in one I. granulatus. To the best of our knowledge, this is the first report on tick-borne bacterial pathogens in ticks and rodents from the China-Vietnam border. These results expand the knowledge of the geographical distribution and vector diversity of tick-borne bacterial pathogens in China and are conducive to the evaluation of thee potential public health risk.

Virome specific to tick genus with distinct ecogeographical distribution

BACKGROUND

The emergence of tick-borne pathogens poses a serious threat to both human and animal health. There remains controversy about virome diversity in relation to tick genus and ecogeographical factors.

RESULTS

We conducted the meta‑transcriptomic sequencing of 155 pools of ticks encompassing 7 species of 3 genera collected from diverse geographical fauna of Ningxia Province, China. Two species of Dermacentor genus were distributed in the predominantly grassland areas of the central and eastern regions, with the lowest viral diversity. Two species of Hyalomma ticks were found in the predominantly desert areas of the northern regions, with intermediate viral diversity. Three species of Haemaphysalis ticks were concentrated in the predominantly forested areas of the southern regions, exhibiting the highest viral diversity. We assembled 348 viral genomes of 63 species in 14 orders, including 26 novel viruses. The identified viruses were clearly specific to tick genus: 22 virus species were exclusive to Dermacentor, 12 to Hyalomma, and 27 to Haemaphysalis.

CONCLUSIONS

The associations between tick genera and geographical distribution, viral richness, and composition provide new insights into tick-virus interactions, offering clues to identify high-risk regions for different tick-borne viruses. Video Abstract.

Characteristics of viral ovarian tumor domain protease from two emerging orthonairoviruses and identification of Yezo virus human infections in northeastern China as early as 2012

Emerging tick-borne orthonairovirus infections pose a growing global concern, with limited understanding of the viral ovarian tumor-like cysteine proteases (vOTUs) encoded by novel orthonairoviruses. These vOTUs, a group of deubiquinylases (DUBs), disrupt the innate immune response. Yezo virus (YEZV), a recently discovered pathogenic orthonairovirus, was first reported in Japan in 2021. In this study, we successfully isolated and identified YEZV and a new orthonairovirus, Jiànchuān tick virus (JCTV), from Ixodes persulcatus and Haemaphysalis montgomeryi ticks, respectively, in China. We found that the vOTU domains encoded by YEZV and JCTV exhibited both DUB and deISGylase activities, though with potentially less broad deISGylation compared to that of Crimean-Congo hemorrhagic fever virus (CCHFV) during natural infection. Phylogenetic analysis of global vOTUs, including 83 new sequences, revealed a high diversity of this domain. Interestingly, retrospective screening of tick-bite patients from 2012 to 2016 in northeastern China traced YEZV infections as far back as 2012, identifying four cases. Additionally, YEZV primarily infected I. persulcatus (31.4%) and Dermacentor nuttalli (10.5%) in northern China, while JCTV exhibited high infection rates in H. montgomeryi (81.3%) in southern China. In summary, our work emphasizes the active surveillance of orthonairovirus infections and the imperative need for the development of vOTU domain-targeted anti-virals, offering potential therapeutic solutions for a broad spectrum of orthonairoviruses.IMPORTANCEThe vOTUs, a group of DUBs, mimic the functions of host DUBs to enhance viral infectivity and may serve as potential drug targets. vOTUs from different orthonairoviruses exhibit distinct preferences toward ubiquitin (Ub) and ubiquitin-like protein interferon stimulated gene 15 (ISG15). In this study, we investigated the deubiquitinase and deISGylase functions of various orthonairoviral vOTUs using both an overexpression system and natural viral infections in vitro. Our findings illustrate that the vOTUs from YEZV and JCTV can cleave both Ub and ISG15 in an overexpression system, but these viruses exhibit potentially narrower deISGylation capacity than CCHFV during natural infection. This suggests that the diversity of vOTUs may have a potential relationship with the pathogenesis.

Prevalence of three important tick-borne pathogens in ticks and humans in Shaanxi Province, Northwest China

The investigation of important prevalent tick-borne pathogens is central to the control of tick-borne diseases. To understand the prevalence of Borrelia burgdorferi s.l., Borrelia miyamotoi, and the Alongshan virus in ticks and patients in Shaanxi Province, China, a total of 670 adult ticks and 524 patient blood samples were collected in the region between 2022 and 2023. In this study, PCR was used to estimate the prevalence of the three pathogens. The results revealed that the overall positive rates of B. burgdorferi s.l, B. miyamotoi, and ALSV infection in the collected ticks were 13.58 %, 2.46 %, and 4.17 %, respectively. Three genospecies of B. burgdorferi s.l. were detected in this study, namely, B. garinii, B. afzelii, and B. bavariensis, with positive rates of 4.63 %, 3.58 %, and 5.37 %, respectively. The prevalence rates of B. miyamotoi, ALSV  and B. burgdorferi s.l. in the patients were 0.38 %, 0.95 %, and 15 %, respectively. Moreover, B. burgdorferi s.l. and ALSV coinfection was also detected in three patients. Evolutionary analysis revealed that the isolate of B. miyamotoi belongs to the Asian type (Siberian type) and that of ALSV is closely related to that of Finland. To our knowledge, this is the first report on B. miyamotoi and ALSV detection in both ticks and humans in Shaanxi Province; the prevalence indicates that the regions in this province might be endemic areas. The results also suggest that humans in these regions are at risk of infection with these three tick-borne diseases.

Nation-wide surveillance of tick (Acari: Ixodidae) infestations of humans in Singapore

Ticks are an increasingly important threat to public health in Southeast Asia, due to the role of many tick species as parasites of humans and as vectors of zoonotic pathogens. Singapore is a densely populated Southeast Asian nation with a rich tick fauna and a significant mosaic of city and greenspace. However, apart from occasional case reports, the human-biting ticks in Singapore have received little attention from researchers. Based on an ongoing nationwide tick surveillance program beginning in 2018 and literature records (since 2002), we present data from 51 cases of tick infestation in humans in Singapore involving 128 individual ticks of 11 species. The genera Dermacentor, Haemaphysalis, Ixodes, and Amblyomma were all found to bite humans in Singapore. The most common species infesting humans in Singapore was Dermacentor auratus which was responsible for more than half of all infestations. The first records of Haemaphysalis papuana in Singapore are also presented, with 3 cases of human infestation by this tick species. Finally, we highlight the Singapore National Tick Reference Collection (SNTRC) as an invaluable resource for the identification and study of ticks in Singapore.

Metatranscriptomic analysis reveals the diversity of RNA viruses in ticks in Inner Mongolia, China

BACKGROUND

Ticks are widely distributed throughout China and are the second most prevalent pathogen vectors in the world, following only mosquitoes. Tick bites can lead to Lyme disease, forest encephalitis, and other illnesses that may result in death under severe circumstances. Materials and methods: Ticks collected from March 2021 to May 2023 were pooled and used in metatranscriptomic analyses to gain insight into the diversity and distribution of tick-borne viruses in Inner Mongolia. Next-generation sequencing (NGS) outcomes were validated, and viral prevalence across distinct tick species was determined through the application of polymerase chain reaction (PCR) paired with Sanger sequencing.

RESULTS

A total of 20 RNA viruses belonging to at least 8 families, including Chuviridae, Flaviviridae, Solemoviridae, Nairoviridae, Partitiviridae, Phenuiviridae, Rhabdoviridae, and Totiviridae, and to unclassified families were identified by NGS. Five of the identified RNA viruses (Nuomin virus, Yezo virus, tick-borne encephalitis virus, Alongshan virus, and Beiji nairovirus) are considered human pathogens. A potential human pathogen, Mukawa virus, was also among the identified viruses. Ixodes persulcatus carried a significantly greater number of viral species than did Dermacentor nuttalli, Hyalomma marginatum, and Haemaphysalis concinna. The prevalence of coinfection with multiple viruses differed in I. persulcatus from Hinggan League and Hulun Buir, and Beiji nairovirus was the codominant virus species.

CONCLUSIONS

There is a remarkable diversity of RNA viruses harboured by ticks in Inner Mongolia, with variations observed in the distribution of these tick-borne viruses across different regions and tick hosts.

Real-time quantitative reverse transcription PCR assay for the detection of Nuomin virus - An emerging tick-borne virus

Nuomin virus (NOMV), an emerging tick-borne virus (TBVs) identified in 2020, has been associated with fever, headache, and potential liver dysfunction in infected individuals. This study presents a novel TaqMan real-time quantitative PCR method designed for the rapid, sensitive, and specific detection of NOMV, facilitating early diagnosis. Utilizing Beacon Designer software 8.0, we optimized the PCR assay including the development of primers and probes to precisely target the conserved region of the NOMV genome, followed by optimization of primer and probe concentrations and annealing temperature. The resulting assay demonstrated robust performance, with standard curve represented by the equation y=-3.29x+39.42, a high correlation coefficient (R2 = 0.995) and an efficiency 99.53 %. Importantly, the method exhibited exceptional specificity, which did not yield cross-reacting signals from other TBVs, including Songling virus (SGLV), Beiji virus (BJNV), tick-borne encephalitis virus (TBEV), Yezo virus (YEZV), Alongshan virus (ALSV), and severe fever with thrombocytopenia syndrome bunyavirus (SFTSV). The assay's detection limit was remarkably low, reaching 10 copies/μL, representing a 100-fold increase compared to semi-nested RT-PCR. Additionally, it demonstrated excellent repeatability, with coefficients of variation for intra- and inter-group tests consistently below 3 %. Clinical evaluations confirmed the assay's superior performance, highlighting its high specificity, sensitivity, and reproducibility for NOMV detection. In conclusion, the method developed in this study provides a valuable tool to support timely management of NOMV infections, with significant implications for clinical practice.

Molecular epidemiological study on tick-borne pathogens in Qinghai Province, Northwestern China

Recently, there has been a continuous stream of reports on emerging tick-borne pathogens affecting humans. Qinghai Province, located in the northweastern region, is one of China's major pastoral areas, providing a suitable environment for ticks' survival and transmitting tick-borne pathogens. Here, we collected 560 free-living and parasitic ticks from 11 locations in Qinghai Province using the flag-drag method or tweezers, identifying them as belonging to 4 species of ticks. The overall positivity rate for tick-borne pathogens was 51.61 %, comprising Rickettsia (34.64 %), Anaplasma (5.00 %), Ehrlichia (2.14 %), Borrelia burgdorferi sensu lato (BBSL) (7.50 %), Babesia (0.18 %), and Theileria (5.89 %). Sequencing revealed the presence of 7 species of Rickettsia, 4 species of Anaplasma, 2 species of Ehrlichia, 2 species of BBSL, 1 species of Babesia, and 3 species of Theileria. Among the ticks, 6.43 % were co-infected with 2 pathogens, while 0.36 % exhibited co-infection with 3 pathogens. Significant correlations (P < 0.05) were observed between the prevalence of tick-borne pathogens and factors including tick species, sex, developmental stages, parasitic status, and blood-feeding status. The results highlight the diverse distribution of tick-borne pathogens in Qinghai Province, posing a significant threat to both local animal husbandry and human health. It underscores the need to enhance systematic monitoring of tick-borne pathogens in the local population and livestock.

The Known and Unknown of Global Tick-Borne Viruses

Ticks are crucial vectors for various pathogens associated with human and animal diseases, including viruses. Nevertheless, significant knowledge gaps prevail in our understanding of tick-borne viruses (TBVs). We here examined existing studies on TBVs, uncovering 870 documented virus species across 28 orders, 55 families, and 66 genera. The discovery history, vector ticks, and hosts of TBVs, as well as the clinical characteristics of TBV-induced diseases, are summarized. In total, 176 tick species from nine tick genera were confirmed as vectors for TBVs. Overall, 105 TBVs were associated with infection or exposure to humans and animals. Of them, at least 40 were identified to cause human or animal diseases. This review addresses the current challenges associated with TBV research, including the lack of knowledge about the identification of novel and emerging TBVs, the spillover potentials from ticks to hosts, and the pathogenicity and infection mechanisms of TBVs. It is expected to provide crucial insights and references for future studies in this field, while specifically focusing on expanding surveys, improving TBV identification and isolation, and enhancing the understanding of TBV-vector-host interactions. All of these findings will facilitate the preparation for preventing and treating diseases caused by emerging and novel TBVs.

Development of a LAMP assay for the rapid visual detection of the emerging tick-borne Songling virus

BACKGROUND

Songling virus (SGLV) within the genus Orthonairovirus, family Nairoviridae, is an emerging tick-borne virus associated with human febrile illness. However, no rapid detection method for SGLV has been established.

METHODS

In this study, four primer sets targeting the nucleocapsid protein gene of SGLV were designed for use in the LAMP assay and evaluated to identify the optimal primer set. Recombinant plasmids were constructed and utilized for assessing the sensitivity of the assay. Tacheng tick virus 1 (TcTV-1)-, Beiji nairovirus (BJNV)-, Yezo virus (YEZV)-, severe fever with thrombocytopenia syndrome virus (SFTSV)-, and tick-borne encephalitis virus (TBEV)-positive tick samples were utilized to assess the specificity. Field-collected ticks were also evaluated as biological specimens to validate the assay.

RESULTS

A SGLV-specific LAMP assay was established with a detection limit of 1 × 10-2 copies/μl and could be visually confirmed by a color change from purple to blue in SGLV-positive samples. No cross-reactivity was observed in the detection of TcTV-1, BJNV, YEZV, SFTSV, and TBEV using the LAMP assay. In addition to the detection of the same seven high-copy numbers of SGLV as the SYBR Green quantitative RT-PCR assay within a reduced timeframe, the developed LAMP method also effectively identified an additional sample with a low copy number in the field-collected tick samples.

CONCLUSIONS

We successfully developed a sensitive, specific, and cost-effective visual method for the rapid detection of SGLV using the LAMP assay, which can be applied in pathogenesis and epidemiological surveillance studies of SGLV.

A wide distribution of Beiji nairoviruses and related viruses in Ixodes ticks in Japan

Beiji nairovirus (BJNV), in the family Nairoviridae, the order Bunyavirales, was recently reported as a causative agent of an emerging tick-borne zoonotic infection in China. This study investigated the prevalence of BJNV in ticks in Japan. Screening of over 2,000 ticks from multiple regions revealed a widespread distribution of BJNV and BJNV-related viruses in Japan, particularly in the northern island, and in other high altitude areas with exclusive occurrence of Ixodes ticks. Phylogenetic analysis identified three distinct groups of nairoviruses in ticks in Japan: BJNV, Yichun nairovirus (YCNV) and a newly identified Mikuni nairovirus (MKNV). BJNV and YCNV variants identified in ticks in Japan exhibited high nucleotide sequence identities to those in China and Russia with evidence of non-monophyletic evolution among BJNVs, suggesting multiple cross-border transmission events of BJNV between the Eurasian continent and Japan. Whole genome sequencing of BJNV and MKNV revealed a unique GA-rich region in the S segment, the significance of which remains to be determined. In conclusion, the present study has shown a wide distribution and diversity of BJNV-related nairoviruses in Ixodes ticks in Japan and has identified unique genomic structures. The findings demonstrate the significance of BJNV as well as related viruses in Japan and highlight the necessity of monitoring emerging nairovirus infections and their potential risks to public health.

Lipoprotein receptors: A little grease for enveloped viruses to open the lock?

Several studies recently highlighted the role of lipoprotein receptors in viral entry. These receptors are evolutionarily ancient proteins, key for the transport of lipids as well as other signaling molecules across the plasma membrane. Here, we discuss the different families of lipoprotein receptors and how they are hijacked by enveloped viruses to promote their entry into infected cells. While the usage of lipoprotein receptors was known for members of the Flaviviridae family and vesicular stomatitis virus, the last 4 years have seen the discovery that these receptors are used by many genetically unrelated viruses. We also emphasize how viral particles interact with these receptors and the possible targeting of these host factors as antiviral strategies.

A New Orthonairovirus Associated with Human Febrile Illness

BACKGROUND

In June 2019, a patient presented with persistent fever and multiple organ dysfunction after a tick bite at a wetland park in Inner Mongolia. Next-generation sequencing in this patient revealed an infection with a previously unknown orthonairovirus, which we designated Wetland virus (WELV).

METHODS

We conducted active hospital-based surveillance to determine the prevalence of WELV infection among febrile patients with a history of tick bites. Epidemiologic investigation was performed. The virus was isolated, and its infectivity and pathogenicity were investigated in animal models.

RESULTS

WELV is a member of the orthonairovirus genus in the Nairoviridae family and is most closely related to the tickborne Hazara orthonairovirus genogroup. Acute WELV infection was identified in 17 patients from Inner Mongolia, Heilongjiang, Jilin, and Liaoning, China, by means of reverse-transcriptase-polymerase-chain-reaction assay. These patients presented with nonspecific symptoms, including fever, dizziness, headache, malaise, myalgia, arthritis, and back pain and less frequently with petechiae and localized lymphadenopathy. One patient had neurologic symptoms. Common laboratory findings were leukopenia, thrombocytopenia, and elevated d-dimer and lactate dehydrogenase levels. Serologic assessment of convalescent-stage samples obtained from 8 patients showed WELV-specific antibody titers that were 4 times as high as those in acute-phase samples. WELV RNA was detected in five tick species and in sheep, horses, pigs, and Transbaikal zokors (Myospalax psilurus) sampled in northeastern China. The virus that was isolated from the index patient and ticks showed cytopathic effects in human umbilical-vein endothelial cells. Intraperitoneal injection of the virus resulted in lethal infections in BALB/c, C57BL/6, and Kunming mice. The Haemaphysalis concinna tick is a possible vector that can transovarially transmit WELV.

CONCLUSIONS

A newly discovered orthonairovirus was identified and shown to be associated with human febrile illnesses in northeastern China. (Funded by the National Natural Science Foundation of China and the Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences.).

Microglia Caspase11 non-canonical inflammasome drives fever

AIM

Animals exhibit physiological changes designed to eliminate the perceived danger, provoking similar symptoms of fever. However, a high-grade fever indicates poor clinical outcomes. Caspase11 (Casp11) is involved in many inflammatory diseases. Whether Casp11 leads to fever remains unclear. In this study, we investigate the role of the preoptic area of the hypothalamus (PO/AH) microglia Casp11 in fever.

METHODS

We perform experiments using a rat model of LPS-induced fever. We measure body temperature and explore the functions of peripheral macrophages and PO/AH microglia in fever signaling by ELISA, immunohistochemistry, immunofluorescence, flow cytometry, macrophage depletion, protein blotting, and RNA-seq. Then, the effects of macrophages on microglia in a hyperthermic environment are observed in vitro. Finally, adeno-associated viruses are used to knockdown or overexpress microglia Casp11 in PO/AH to determine the role of Casp11 in fever.

RESULTS

We find peripheral macrophages and PO/AH microglia play important roles in the process of fever, which is proved by macrophage and microglia depletion. By RNA-seq analysis, we find Casp11 expression in PO/AH is significantly increased during fever. Co-culture and conditioned-culture simulate the induction of microglia Casp11 activation by macrophages in a non-contact manner. Microglia Casp11 knockdown decreases body temperature, pyrogenic factors, and inflammasome, and vice versa.

CONCLUSION

We report that Casp11 drives fever. Mechanistically, peripheral macrophages transmit immune signals via cytokines to microglia in PO/AH, which activate the Casp11 non-canonical inflammasome. Our findings identify a novel player, the microglia Casp11, in the control of fever, providing an explanation for the transmission and amplification of fever immune signaling.

The Diel Activity Pattern of Haemaphysalis longicornis and Its Relationship with Climatic Factors

Haemaphysalis longicornis is one of the most medically important carriers of various pathogens. Although H. longicornis is an important vector, only basic ecological and biological information has been obtained, primarily focusing on its abundance and distribution. This study determined the most active time and meteorological conditions for the diel activity of H. longicornis. The diel activity pattern of H. longicornis was the highest between 10:00 and 14:00, and the lowest between 22:00 and 02:00. The major activity temperature of H. longicornis was between 25 °C and 40 °C, with the highest activity at 35 °C. The relative humidity was between 30% and 70% during the active period. Temperature had the highest correlation with diel activity (R = 0.679), followed by humidity (R = -0.649) and light intensity (R = 0.572). Our results provide basic information for the development of tick-borne disease vector control programs and tick surveillance.

Novel clades of tick-borne pathogenic nairoviruses in Europe

Members of the Orthonairovirus genus (family Nairoviridae) include many tick-borne viruses of significant human and animal health impact, with several recently-documented pathogenic viruses lacking sufficient epidemiological information. We screened 215 adult ticks of seven species collected in Bulgaria, Georgia, Latvia and Poland for orthonairoviruses, followed by nanopore sequencing (NS) for genome characterization. Initial generic amplification revealed Sulina virus (SULV, Orthonairovirus sulinaense), for which an updated amplification assay was used, revealing an overall prevalence of 2.7% in Ixodes ricinus ticks from Latvia. Three complete and additional partial SULV genomes were generated, that consistently formed a separate, distinct clade with further intragroup divergence in the maximum likelihood analyses. Comparisons with previously described viruses from Romania exhibited similar genome topologies, albeit with divergent motifs and cleavage sites on the glycoprotein precursor. Preliminary evidence of recombination involving the S segment was documented, in addition to variations in predicted viral glycoproteins. Generic screening further identified Tacheng tick virus 1 (TCTV1, Orthonairovirus tachengense), with documented human infections, in Dermacentor reticulatus ticks from Poland, with a prevalence of 0.9%. Subsequent NS and assembly provided the first complete TCTV1 genome outside of China, where it was originally described. Phylogenetic analysis of virus genome segments revealed TCTV1-Poland as a discrete taxon within the TCTV1 cluster in the Orthonairovirus genus, representing a geographically segregated clade. Comparable genome topology with TCTV1 from China was observed, aside from minor variations in the M segment. Similar to SULV, TCTV1 exhibited several mismatches on previously described screening primer binding sites, likely to prevent amplification. These findings indicate presence of novel TCTV1 and SULV clades in Eastern Europe, confirming the expansion of orthonairoviruses with pathogenic potential.

Molecular characterization of plasma virome of hepatocellular carcinoma (HCC) patients

Hepatocellular carcinoma (HCC) stands as the most common cancer type, arising from various causes, and responsible for a substantial number of cancer-related fatalities. Recent advancements in viral metagenomics have empowered scientists to delve into the intricate diversity of the virosphere, viral evolution, interactions between viruses and their hosts, and the identification of viral causes behind disease outbreaks, the development of specific symptoms, and their potential role in altering the host's physiology. The present study had the objective of "Molecular Characterization of HBV, HCV, anelloviruses, CMV, SENV-D, SENV-H, HEV, and HPV viruses among individuals suffering from HCC." A total of 381 HCC patients contributed 10 cc of blood each for this study. The research encompassed the assessment of tumor markers, followed by molecular characterization of HBV, HCV, Anelloviruses (TTV, TTMV, and TTMDV), SENV-H and SENV-D viruses, HEV, CMV, and HPV, as well as histopathological examinations. The outcomes of this study revealed that majority of the HCC patients 72.4% (276/381) were male as compared to females. HCV infection, at 76.4% (291 out of 381), exhibited a significant association (p < 0.05) with HCC. Most patients displayed singular lesions in the liver, with Child Pugh Score Type B being the predominant finding in 45.2% of cases. Plasma virome analysis indicated the prevalence of TTMDV (75%), followed by TTMV (70%) and TTV (42.1%) among anelloviruses in HCC patients. Similarly, SENV-H (52%) was followed by SENV-D (20%), with co-infections at 15%. The presence of CMV and HEV among the HCC patients was recorded 5% each however 3.5% of the patients showed the presence of HPV. In conclusion, this study underscores that HCC patients serve as reservoirs for various pathogenic and non-pathogenic viruses, potentially contributing to the development, progression, and severity of the disease.

Viromes of Haemaphysalis longicornis reveal different viral abundance and diversity in free and engorged ticks

Haemaphysalis longicornis ticks, commonly found in East Asia, can transmit various pathogenic viruses, including the severe fever with thrombocytopenia syndrome virus (SFTSV) that has caused febrile diseases among humans in Hubei Province. However, understanding of the viromes of H. longicornis was limited, and the prevalence of viruses among H. longicornis ticks in Hubei was not well clarified. This study investigates the viromes of both engorged (fed) and free (unfed) H. longicornis ticks across three mountainous regions in Hubei Province from 2019 to 2020. RNA-sequencing analysis identified viral sequences that were related to 39 reference viruses belonging to unclassified viruses and seven RNA viral families, namely Chuviridae, Nairoviridae, Orthomyxoviridae, Parvoviridae, Phenuiviridae, Rhabdoviridae, and Totiviridae. Viral abundance and diversity in these ticks were analysed, and phylogenetic characteristics of the Henan tick virus (HNTV), Dabieshan tick virus (DBSTV), Okutama tick virus (OKTV), and Jingmen tick virus (JMTV) were elucidated based on their full genomic sequences. Prevalence analysis demonstrated that DBSTV was the most common virus found in individual H. longicornis ticks (12.59%), followed by HNTV (0.35%), whereas JMTV and OKTV were not detected. These results improve our understanding of H. longicornis tick viromes in central China and highlight the role of tick feeding status and geography in shaping the viral community. The findings of new viral strains and their potential impact on public health raise the need to strengthen surveillance efforts for comprehensively assessing their spillover potentials.

Establishment of a lethal mouse model of emerging tick-borne orthonairovirus infections

Emerging and reemerging tick-borne virus infections caused by orthonairoviruses (family Nairoviridae), which are genetically distinct from Crimean-Congo hemorrhagic fever virus, have been recently reported in East Asia. Here, we have established a mouse infection model using type-I/II interferon receptor-knockout mice (AG129 mice) both for a better understanding of the pathogenesis of these infections and validation of antiviral agents using Yezo virus (YEZV), a novel orthonairovirus causing febrile illnesses associated with tick bites in Japan and China. YEZV-inoculated AG129 mice developed hepatitis with body weight loss and died by 6 days post infection. Blood biochemistry tests showed elevated liver enzyme levels, similar to YEZV-infected human patients. AG129 mice treated with favipiravir survived lethal YEZV infection, demonstrating the anti-YEZV effect of this drug. The present mouse model will help us better understand the pathogenicity of the emerging tick-borne orthonairoviruses and the development of specific antiviral agents for their treatment.

Diversity of species and geographic distribution of tick-borne viruses in China

Introduction

Tick-borne pathogens especially viruses are continuously appearing worldwide, which have caused severe public health threats. Understanding the species, distribution and epidemiological trends of tick-borne viruses (TBVs) is essential for disease surveillance and control.

Methods

In this study, the data on TBVs and the distribution of ticks in China were collected from databases and literature. The geographic distribution of TBVs in China was mapped based on geographic locations of viruses where they were prevalent or they were detected in vector ticks. TBVs sequences were collected from The National Center for Biotechnology Information and used to structure the phylogenetic tree.

Results

Eighteen TBVs from eight genera of five families were prevalent in China. Five genera of ticks played an important role in the transmission of TBVs in China. According to phylogenetic analysis, some new viral genotypes, such as the Dabieshan tick virus (DTV) strain detected in Liaoning Province and the JMTV strain detected in Heilongjiang Province existed in China.

Discussion

TBVs were widely distributed but the specific ranges of viruses from different families still varied in China. Seven TBVs belonging to the genus Orthonairovirus of the family Nairoviridae such as Nairobi sheep disease virus (NSDV) clustered in the Xinjiang Uygur Autonomous Region (XUAR) and northeastern areas of China. All viruses of the family Phenuiviridae except Severe fever with thrombocytopenia syndrome virus (SFTSV) were novel viruses that appeared in the last few years, such as Guertu virus (GTV) and Tacheng tick virus 2 (TcTV-2). They were mainly distributed in the central plains of China. Jingmen tick virus (JMTV) was distributed in at least fourteen provinces and had been detected in more than ten species of tick such as Rhipicephalus microplus and Haemaphysalis longicornis, which had the widest distribution and the largest number of vector ticks among all TBVs. Parainfluenza virus 5 (PIV5) and Lymphatic choriomeningitis virus (LCMV) were two potential TBVs in Northeast China that could cause serious diseases in humans or animals. Ixodes persulcatus carried the highest number of TBVs, followed by Dermacentor nuttalli and H. longicornis. They could carry as many as ten TBVs. Three strains of Tick-borne encephalitis (TBEV) from Inner Mongolia Province clustered with ones from Russia, Japan and Heilongjiang Province, respectively. Several SFTSV strains from Zhejiang Province clustered with strains from Korea and Japan. Specific surveillance of dominant TBVs should be established in different areas in China.

Genomic and phylogenetic profiling of RNA of tick-borne arboviruses in Hainan Island, China

Ticks act as vectors and hosts of numerous arboviruses. Examples of medically important arboviruses include the tick-borne encephalitis virus, Crimean Congo hemorrhagic fever, and severe fever with thrombocytopenia syndrome. Recently, some novel arboviruses have been identified in blood specimens of patients with unexplained fever and a history of tick bites in Inner Mongolia. Consequently, tick-borne viruses are a major focus of infectious disease research. However, the spectrum of tick-borne viruses in subtropical areas of China has yet to be sufficiently characterized. In this study, we collected 855 ticks from canine and bovine hosts in four locations in Hainan Province. The ticks were combined into 18 pools according to genus and location. Viral RNA-sequence libraries were subjected to transcriptome sequencing analysis. Molecular clues from metagenomic analyses were used to classify sequence reads into virus species, genera, or families. The diverse viral reads closely associated with mammals were assigned to 12 viral families and important tick-borne viruses, such as Jingmen, Beiji nairovirus, and Colorado tick fever. Our virome and phylogenetic analyses of the arbovirus strains provide basic data for preventing and controlling human infectious diseases caused by tick-borne viruses in the subtropical areas of China.

Epidemiological surveys revealed the risk of TAMV spill-over from ticks to hosts

BACKGROUND

Tick-borne viral diseases have become an increasingly important public health concern. Tamdy virus (TAMV) is a tick-borne virus of the genus Orthonairovirus in the family Nairoviridae. While some studies have suggested that TAMV is a pathogen associated with human febrile illness, its epidemiology and the risk of TAMV spill-over remain poorly understood.

METHODS

Ticks were collected in Xinjiang, China, and grouped into pools. RT-PCR assays were used to detect TAMV RNA in these pools. The seroprevalence of TAMV was investigated using Immunofluorescence assays, Western blotting, and Luciferase immunoprecipitation system (LIPS) assays.

RESULTS

TAMV RNA was detected in 17 out of 363 tick pools, resulting in a minimum infection rate (MIR) of 4.7%. Hyalomma asiaticum and Dermacentor nuttalli were identified as major tick vectors of TAMV. Phylogenetic analysis demonstrated that TAMV strains from Xinjiang are closely related to strains from other countries. Seroprevalence studies showed that TAMV exposure has been occurring in Xinjiang since at least 2006. Antibody responses to TAMV were detected in 1.1% (26/2296) of animals, including domestic animals and wild rodents. The seropositivity rates were as follows: sheep (1.7%), dog (2.3%), Marmota monax (0.8%), Meriones meridianus (3.5%).

CONCLUSIONS

The research findings reveal that TAMV can be transmitted by ticks to various animal species, posing a significant public health risk. The wide distribution of TAMV and its tick vectors emphasise the importance of early preparedness and control measures. This study highlights the necessity for maintaining vigilance in addressing emerging zoonotic diseases transmitted by ticks.

Characterisation of putative novel tick viruses and zoonotic risk prediction

Tick-associated viruses remain a substantial zoonotic risk worldwide, so knowledge of the diversity of tick viruses has potential health consequences. Despite their importance, large amounts of sequences in public data sets from tick meta-genomic and -transcriptomic projects remain unannotated, sequence data that could contain undocumented viruses. Through data mining and bioinformatic analysis of more than 37,800 public meta-genomic and -transcriptomic data sets, we found 83 unannotated contigs exhibiting high identity with known tick viruses. These putative viral contigs were classified into three RNA viral families (Alphatetraviridae, Orthomyxoviridae and Chuviridae) and one DNA viral family (Asfarviridae). After manual checking of quality and dissimilarity towards other sequences in the data set, these 83 contigs were reduced to five contigs in the Alphatetraviridae from four putative viruses, four in the Orthomyxoviridae from two putative viruses and one in the Chuviridae which clustered with known tick-associated viruses, forming a separate clade within the viral families. We further attempted to assess which previously known tick viruses likely represent zoonotic risks and thus deserve further investigation. We ranked the human infection potential of 133 known tick-associated viruses using a genome composition-based machine learning model. We found five high-risk tick-associated viruses (Langat virus, Lonestar tick chuvirus 1, Grotenhout virus, Taggert virus and Johnston Atoll virus) that have not been known to infect human and two viral families (Nairoviridae and Phenuiviridae) that contain a large proportion of potential zoonotic tick-associated viruses. This adds to the knowledge of tick virus diversity and highlights the importance of surveillance of newly emerging tick-associated diseases.

Metatranscriptomics Reveals the RNA Virome of Ixodes Persulcatus in the China-North Korea Border, 2017

In recent years, numerous viruses have been identified from ticks, and some have been linked to clinical cases of emerging tick-borne diseases. Chinese northeast frontier is tick infested. However, there is a notable lack of systematic monitoring efforts to assess the viral composition in the area, leaving the ecological landscape of viruses carried by ticks not clear enough. Between April and June 2017, 7101 ticks were collected to perform virus surveillance on the China-North Korea border, specifically in Tonghua, Baishan, and Yanbian. A total of 2127 Ixodes persulcatus were identified. Further investigation revealed the diversity of tick-borne viruses by transcriptome sequencing of Ixodes persulcatus. All ticks tested negative for tick-borne encephalitis virus. Transcriptome sequencing expanded 121 genomic sequence data of 12 different virus species from Ixodes persulcatus. Notably, a new segmented flavivirus, named Baishan Forest Tick Virus, were identified, closely related to Alongshan virus and Harz mountain virus. Therefore, this new virus may pose a potential threat to humans. Furthermore, the study revealed the existence of seven emerging tick-borne viruses dating back to 2017. These previously identified viruses included Mudanjiang phlebovirus, Onega tick phlebovirus, Sara tick phlebovirus, Yichun mivirus, and three unnamed viruses (one belonging to the Peribunyaviridae family and the other two belonging to the Phenuiviridae family). The existence of these emerging tick-borne viruses in tick samples collected in 2017 suggests that their history may extend further than previously recognized. This study provides invaluable insights into the virome of Ixodes persulcatus in the China-North Korea border region, enhancing our ongoing efforts to manage the risks associated with tick-borne viruses.

Meta-transcriptomics for the diversity of tick-borne virus in Nujiang, Yunnan Province

Ticks, an arthropod known for transmitting various pathogens such as viruses, bacteria, and fungi, pose a perpetual public health concern. A total of 2,570 ticks collected from Nujiang Prefecture in Yunnan Province between 2017 and 2022 were included in the study. Through the meta-transcriptomic sequencing of four locally distributed tick species, we identified 13 RNA viruses belonging to eight viral families, namely, Phenuiviridae, Nairoviridae, Peribunyaviridae, Flaviviridae, Chuviridae, Rhabdoviridae, Orthomyxoviridae, and Totiviridae. The most prevalent viruses were members of the order Bunyavirales, including three of Phenuiviridae, two were classified as Peribunyaviridae, and one was associated with Nairoviridae. However, whether they pose a threat to human health still remains unclear. Indeed, this study revealed the genetic diversity of tick species and tick-borne viruses in Nujiang Prefecture based on COI gene and tick-borne virus research. These data clarified the genetic evolution of some RNA viruses and furthered our understanding of the distribution pattern of tick-borne pathogens, highlighting the importance and necessity of monitoring tick-borne pathogens.

Diversity analysis of tick-associated viruses in northeast China

•This study identified eleven tick-borne viruses in Liaoning Province and Inner Mongolia. •Tacheng tick virus 2 is for the first time detected outside Xinjiang and in a novel tick species D. niveus. •The Alongshan virus and Tacheng tick virus 2 identified in this study can be considered as novel species.

Genomic annotation for vaccine target identification and immunoinformatics-guided multi-epitope-based vaccine design against Songling virus through screening its whole genome encoded proteins

Songling virus (SGLV), a newly discovered tick-borne orthonairovirus, was recently identified in human spleen tissue. It exhibits cytopathic effects in human hepatoma cells and is associated with clinical symptoms including headache, fever, depression, fatigue, and dizziness, but no treatments or vaccines exist for this pathogenic virus. In the current study, immunoinformatics techniques were employed to identify potential vaccine targets within SGLV by comprehensively analyzing SGLV proteins. Four proteins were chosen based on specific thresholds to identify B-cell and T-cell epitopes, validated through IFN-γ epitopes. Six overlap MHC-I, MHC-II, and B cell epitopes were chosen to design a comprehensive vaccine candidate, ensuring 100% global coverage. These structures were paired with different adjuvants for broader protection against international strains. Vaccine constructions' 3D models were high-quality and validated by structural analysis. After molecular docking, SGLV-V4 was selected for further research due to its lowest binding energy (-66.26 kcal/mol) and its suitable immunological and physiochemical properties. The vaccine gene is expressed significantly in E. coli bacteria through in silico cloning. Immunological research and MD simulations supported its molecular stability and robust immune response within the host cell. These findings can potentially be used in designing safer and more effective experimental SGLV-V4 vaccines.

The expanding range of emerging tick-borne viruses in Eastern Europe and the Black Sea Region

We analysed both pooled and individual tick samples collected from four countries in Eastern Europe and the Black Sea region, using metagenome-based nanopore sequencing (NS) and targeted amplification. Initially, 1337 ticks, belonging to 11 species, were screened in 217 pools. Viruses (21 taxa) and human pathogens were detected in 46.5% and 7.3%, respectively. Tick-borne viral pathogens comprised Tacheng Tick Virus 2 (TTV2, 5.9%), Jingmen Tick Virus (JMTV, 0.9%) and Tacheng Tick Virus 1 (TTV1, 0.4%). An association of tick species with individual virus taxa was observed, with the exception of TTV2, which was observed in both Dermacentor and Haemaphysalis species. Individual ticks from pools with pathogen detection were then further screened by targeted amplification and then NS, which provided extensive genome data and revealed probable pathogen Haseki Tick Virus (HTV, 10.2%). Two distinct TTV2 clades were observed in phylogenetic analysis, one of which included closely related Dermacentor reticulatus Uukuviruses. JMTV detection indicated integrated virus sequences. Overall, we observed an expansion of newly documented pathogenic tick-borne viruses into Europe, with TTV1 being identified on the continent for the first time. These viruses should be included in the diagnostic assessment of symptomatic cases associated with tick bites and vector surveillance efforts. NS is shown as a useful tool for monitoring tick-associated pathogens in pooled or individual samples.

The current distribution of tick species in Inner Mongolia and inferring potential suitability areas for dominant tick species based on the MaxEnt model

BACKGROUND

Ticks are known to transmit a wide range of diseases, including those caused by bacteria, viruses, and protozoa. The expansion of tick habitats has been intensified in recent years due to various factors such as global warming, alterations in microclimate, and human activities. Consequently, the probability of human exposure to diseases transmitted by ticks has increased, leading to a higher degree of risk associated with such diseases.

METHODS

In this study, we conducted a comprehensive review of domestic and international literature databases to determine the current distribution of tick species in Inner Mongolia. Next, we employed the MaxEnt model to analyze vital climatic and environmental factors influencing dominant tick distribution. Subsequently, we predicted the potential suitability areas of these dominant tick species under the near current conditions and the BCC-CSM2.MR model SSP245 scenario for the future periods of 2021-2040, 2041-2060, 2061-2080, and 2081-2100.

RESULTS

Our study revealed the presence of 23 tick species from six genera in Inner Mongolia, including four dominant tick species (Dermacentor nuttalli, Ixodes persulcatus, Dermacentor silvarum, and Hyalomma asiaticum). Dermacentor nuttalli, D. silvarum, and I. persulcatus are predominantly found in regions such as Xilin Gol and Hulunbuir. Temperature seasonality (Bio4), elevation (elev), and precipitation seasonality (Bio15) were the primary variables impacting the distribution of three tick species. In contrast, H. asiaticum is mainly distributed in Alxa and Bayannur and demonstrates heightened sensitivity to precipitation and other climatic factors. Our modeling results suggested that the potential suitability areas of these tick species would experience fluctuations over the four future periods (2021-2040, 2041-2060, 2061-2080, and 2081-2100). Specifically, by 2081-2100, the centroid of suitable habitat for D. nuttalli, H. asiaticum, and I. persulcatus was predicted to shift westward, with new suitability areas emerging in regions such as Chifeng and Xilin Gol. The centroid of suitable habitat for H. asiaticum will move northeastward, and new suitability areas are likely to appear in areas such as Ordos and Bayannur.

CONCLUSIONS

This study provided a comprehensive overview of the tick species distribution patterns in Inner Mongolia. Our research has revealed a significant diversity of tick species in the region, exhibiting a wide distribution but with notable regional disparities. Our modeling results suggested that the dominant tick species' suitable habitats will significantly expand in the future compared to their existing distribution under the near current conditions. Temperature and precipitation are the primary variables influencing these shifts in distribution. These findings can provide a valuable reference for future research on tick distribution and the surveillance of tick-borne diseases in the region.

Diversity Analysis of Tick-Borne Viruses from Hedgehogs and Hares in Qingdao, China

Tick-borne viruses (TBVs) have attracted increasingly global public health attention. In this study, the viral compositions of five tick species, Haemaphysalis flava, Rhipicephalus sanguineus, Dermacentor sinicus, Haemaphysalis longicornis, and Haemaphysalis campanulata, from hedgehogs and hares in Qingdao, China, were profiled via metagenomic sequencing. Thirty-six strains of 10 RNA viruses belonging to 4 viral families, including 3 viruses of Iflaviridae, 4 viruses of Phenuiviridae, 2 viruses of Nairoviridae, and 1 virus of Chuviridae, were identified in five tick species. Three novel viruses of two families, namely, Qingdao tick iflavirus (QDTIFV) of the family of Iflaviridae and Qingdao tick phlebovirus (QDTPV) and Qingdao tick uukuvirus (QDTUV) of the family of Phenuiviridae, were found in this study. This study shows that ticks from hares and hedgehogs in Qingdao harbored diverse viruses, including some that can cause emerging infectious diseases, such as Dabie bandavirus. Phylogenetic analysis revealed that these tick-borne viruses were genetically related to viral strains isolated previously in Japan. These findings shed new light on the cross-sea transmission of tick-borne viruses between China and Japan. IMPORTANCE Thirty-six strains of 10 RNA viruses belonging to 4 viral families, including 3 viruses of Iflaviridae, 4 viruses of Phenuiviridae, 2 viruses of Nairoviridae, and 1 virus of Chuviridae, were identified from five tick species in Qingdao, China. A diversity of tick-borne viruses from hares and hedgehogs in Qingdao was found in this study. Phylogenetic analysis showed that most of these TBVs were genetically related to Japanese strains. These findings indicate the possibility of the cross-sea transmission of TBVs between China and Japan.

Identification of novel Jingmen tick virus from parasitic ticks fed on a giant panda and goats in Sichuan Province, southwestern China

Introduction

Tick-borne viruses (TBVs) pose a significant risk to the health of humans and other vertebrates. A class of multisegmented flavi-like viruses, Jingmen tick virus (JMTV) was first discovered in Rhipicephalus microplus ticks collected from Jingmen of Hubei Province, China in 2010. JMTV has been confirmed to have a relatively wide distribution in vectors and hosts and is associated with human diseases.

Methods

Parasitic and host-seeking ticks were collected in Wolong Nature Reserve, Sichuan Province. Total RNA was extracted and then enriched the viral RNA. The DNA library was constructed and then were sequenced with MGI High-throughput Sequencing Set (PE150). After the adaptor sequences,low-quality bases and host genome were removed, resulting reads classified as a virus were subsequently de novo assembled into contigs, which were then compared to the NT database. Those annotated under the kingdom virus were initially identified as potential virus-associated sequences. Phylogenetic and Reassortment analysis of sequences were performed using MEGA and SimPlot software, respectively.

Results and discussion

Two host-seeking ticks and 17 ticks that fed on giant pandas and goats were collected. Through high-throughput sequencing, whole virus genomes were attained from four tick samples (PC-13, PC-16, PC-18, and PC-19) that shared 88.7-96.3% similarity with known JMTV. Phylogenetic tree showed that it was a novel JMTV-like virus, referred to as Sichuan tick virus, which also had the signals of reassortment with other JMTV strains, suggesting a cross-species transmission and co-infection of segmented flavi-like viruses among multiple tick hosts.

Conclusion

We discovered and confirmed one new Jingmen tick virus, Sichuan tick virus. Further investigation is required to determine the pathogenicity of Sichuan tick virus to humans and animals, as well as its epidemiological characteristics in nature.

Novel Orthonairovirus Isolated from Ticks near China-North Korea Border

We isolated a new orthonairovirus from Dermacentor silvarum ticks near the China-North Korea border. Phylogenetic analysis showed 71.9%-73.0% nucleic acid identity to the recently discovered Songling orthonairovirus, which causes febrile illness in humans. We recommend enhanced surveillance for infection by this new virus among humans and livestock.

Virome diversity of ticks feeding on domestic mammals in China

Ticks are considered the second most common pathogen vectors transmitting a broad range of vital human and veterinary viruses. From 2017 to 2018, 640 ticks were collected in eight different provinces in central and western China. Six species were detected, including H.longicornis, De.everestianus, Rh.microplus, Rh.turanicus, Rh.sanguineous, and Hy.asiaticum. Sixty-four viral metagenomic libraries were constructed on the MiSeq Illumina platform, resulting in 13.44 ​G (5.88 ​× ​10⁷) of 250-bp-end reads, in which 2,437,941 are viral reads. We found 27 nearly complete genome sequences, including 16 genome sequences encoding entire protein-coding regions (lack of 3' or 5' end non-coding regions) and complete viral genomes, distributed in the arboviral family (Chuviridae, Rhabdoviridae, Nairoviridae, Phenuiviridae, Flaviviridae, Iflaviridae) as well as Parvoviridae and Polyomaviridae that cause disease in mammals and even humans. In addition, 13 virus sequences found in Chuviridae, Nairoviridae, Flaviviridae, Iflaviridae, Hepeviridae, Parvoviridae, and Polyomaviridae were identified as belonging to a new virus species in the identified viral genera. Besides, an epidemiological survey shows a high prevalence (9.38% and 15.63%) of two viruses (Ovine Copiparvovirus and Bovine parvovirus 2) in the tick cohort.

DNA virome of ticks in the Northeast and Hubei provinces of China reveals diverse single-stranded circular DNA viruses

BACKGROUND

Ticks are medically important vectors capable of transmitting a variety of pathogens to and between host species. Although the spectrum of tick-borne RNA viruses has been frequently investigated, the diversity of tick-borne DNA viruses remains largely unknown.

METHODS

A total of 1571 ticks were collected from forests and infested animals, and the diversity of the viruses they harbored was profiled using a DNA-specific virome method. The viromic data were phylogenetically analyzed and validated by PCR assays.

RESULTS

Although diverse and abundant prokaryotic viruses were identified in the collected ticks, only eukaryotic DNA viruses with single-stranded circular genomes covering the anelloviruses and circular replication-associated (Rep) protein-encoding single-stranded (CRESS) DNA viruses were recovered from ticks. Anelloviruses were detected only in two tick pools, but CRESS DNA viruses were prevalent across these ticks except in one pool of Dermacentor spp. ticks. Phylogenetic analyses revealed that these tick-borne CRESS DNA viruses were related to viruses recovered from animal feces, tissues and even environmental samples, suggesting that their presence may be largely explained by environmental factors rather than by tick species and host blood meals.

CONCLUSIONS

Based on the results, tick-borne eukaryotic DNA viruses appear to be much less common than eukaryotic RNA viruses. Investigations involving a wider collection area and more diverse tick species are required to further support this speculation.

Diversity of RNA viruses of three dominant tick species in North China

Background

A wide range of bacterial pathogens have been identified in ticks, yet the diversity of viruses in ticks is largely unexplored.

Methods

Here, we used metagenomic sequencing to characterize the diverse viromes in three principal tick species associated with pathogens, Haemaphysalis concinna, Dermacentor silvarum, and Ixodes persulcatus, in North China.

Results

A total of 28 RNA viruses were identified and belonged to more than 12 viral families, including single-stranded positive-sense RNA viruses (Flaviviridae, Picornaviridae, Luteoviridae, Solemoviridae, and Tetraviridae), negative-sense RNA viruses (Mononegavirales, Bunyavirales, and others) and double-stranded RNA viruses (Totiviridae and Partitiviridae). Of these, Dermacentor pestivirus-likevirus, Chimay-like rhabdovirus, taiga tick nigecruvirus, and Mukawa virus are presented as novel viral species, while Nuomin virus, Scapularis ixovirus, Sara tick-borne phlebovirus, Tacheng uukuvirus, and Beiji orthonairovirus had been established as human pathogens with undetermined natural circulation and pathogenicity. Other viruses include Norway mononegavirus 1, Jilin partitivirus, tick-borne tetravirus, Pico-like virus, Luteo-like virus 2, Luteo-likevirus 3, Vovk virus, Levivirus, Toti-like virus, and Solemo-like virus as well as others with unknown pathogenicity to humans and wild animals.

Conclusion

In conclusion, extensive virus diversity frequently occurs in Mononegavirales and Bunyavirales among the three tick species. Comparatively, I. persulcatus ticks had been demonstrated as such a kind of host with a significantly higher diversity of viral species than those of H. concinna and D. silvarum ticks. Our analysis supported that ticks are reservoirs for a wide range of viruses and suggested that the discovery and characterization of tick-borne viruses would have implications for viral taxonomy and provide insights into tick-transmitted viral zoonotic diseases.

Analysis of the diversity of tick-borne viruses at the border areas in Liaoning Province, China

Ticks play a significant role in transmitting arboviruses, which pose a risk to human and animal health. The region of Liaoning Province, China, with abundant plant resources with multiple tick populations, has reported several tick-borne diseases. However, there remains a scarcity of research on the composition and evolution of the tick virome. In this study, we conducted the metagenomic analysis of 561 ticks in the border area of Liaoning Province in China and identified viruses related to known diseases in humans and animals, including severe fever with thrombocytopenia syndrome virus (SFTSV) and nairobi sheep disease virus (NSDV). Moreover, the groups of tick viruses were also closely related to the families of Flaviviridae, Parvoviridae, Phenuiviridae, and Rhabdoviridae. Notably, the Dabieshan tick virus (DBTV) of the family Phenuiviridae was prevalent in these ticks, with the minimum infection rate (MIR) of 9.09%, higher than previously reported in numerous provinces in China. In addition, sequences of tick-borne viruses of the family Rhabdoviridae have first been reported from the border area of Liaoning Province, China, after being described from Hubei Province, China. This research furthered the insight into pathogens carried by ticks in the northeastern border areas of China, offering epidemiological information for possible forthcoming outbreaks of infectious diseases. Meanwhile, we provided an essential reference for assessing the risk of tick bite infection in humans and animals, as well as for exploring into the evolution of the virus and the mechanisms of species transmission.

[Research on tick-borne bunyaviruses]

Since the identification of severe fever with thrombocytopenia syndrome (SFTS) and its pathogen, a tick-borne bunyavirus, SFTS virus, there has been increasing interest in emerging viral infections caused by previously unknown viruses in ticks. This study aims to develop a comprehensive detection method for tick-borne bunyaviruses, conduct genetic analysis, isolate the detected viruses, and perform biological characterization. Through these studies, novel tick-borne bunyaviruses that have caused or may cause emerging infectious diseases were discovered. Tick-borne infections often occur sporadically, making their occurrence difficult to recognize. Therefore, continuous exploration of viruses in ticks and assessment of their potential risks causing human and animal diseases is required.

Discovery of a small-molecule inhibitor targeting the ovarian tumor domain of a novel Tamdy orthonairoviruse associated with human febrile illness

Tick-borne orthonairoviruses have been characterized as a global health threat to humans and animals. Tacheng Tick virus 1 (TcTV-1) from this family was provided as evidence that is associated with the febrile illness syndrome. Here, we first identify and demonstrate that the ovarian tumor (OTU) domain of TcTV-1 has remarkable deubiquitinating activity both in vitro and in vivo. By solving the crystal structure of TcTV-1 OTU (tcOTU) domain and comparing it to that of human deubiquitinating enzymes, we found that overall structures of tcOTU and human OTU family are similar, but the residues involved in the catalytic pocket vary widely. Based on the tcOTU domain we screened 5090 bioactive compounds and found mecobalamin had a good effect on suppressing the deubiquitinating activity. The structural model of tcOTU and mecobalamin suggests that mecobalamin occupies the site of the substrate Ub, by blocking the substrate binding to the enzyme. Thus, our results showed OTU domain of TcTV-1 has a robust deubiquitinating activity and mecobalamin or its derivatives might be promising candidates for the treatment or prevention of disease caused by the TcTV-1 virus.

Extensive diversity of RNA viruses in ticks revealed by metagenomics in northeastern China

BACKGROUND

Ticks act as important vectors of infectious agents, and several emerging tick-borne viruses have recently been identified to be associated with human diseases in northeastern China. However, little is known about the tick virome in northeastern China.

METHODS

Ticks collected from April 2020 to July 2021 were pooled for metagenomic analysis to investigate the virome diversity in northeastern China.

RESULTS

In total, 22 RNA viruses were identified, including four each in the Nairoviridae and Phenuiviridae families, three each in the Flaviviridae, Rhabdoviridae, and Solemoviridae families, two in the Chuviridae family, and one each in the Partitiviridae, Tombusviridae families and an unclassified virus. Of these, eight viruses were of novel species, belonging to the Nairoviridae (Ji'an nairovirus and Yichun nairovirus), Phenuiviridae (Mudanjiang phlebovirus), Rhabdoviridae (Tahe rhabdovirus 1-3), Chuviridae (Yichun mivirus), and Tombusviridae (Yichun tombus-like virus) families, and five members were established human pathogens, including Alongshan virus, tick-borne encephalitis virus, Songling virus, Beiji nairovirus, and Nuomin virus. I. persulcatus ticks had significant higher number of viral species than H. japonica, H. concinna, and D. silvarum ticks. Significant differences in tick viromes were observed among Daxing'an, Xiaoxing'an and Changbai mountains.

CONCLUSIONS

These findings showed an extensive diversity of RNA viruses in ticks in northeastern China, revealing potential public health threats from the emerging tick-borne viruses. Further studies are needed to explain the natural circulation and pathogenicity of these viruses.

Prevalence of Spotted Fever Group Rickettsia and Candidatus Lariskella in Multiple Tick Species from Guizhou Province, China

Rickettsiales (Rickettsia spp., Ehrlichia spp., and Anaplasma spp., etc.) are generally recognized as potentially emerging tick-borne pathogens. However, some bacteria and areas in China remain uninvestigated. In this study, we collected 113 ticks from mammals in Guizhou Province, Southwest China, and screened for the Rickettsiales bacteria. Subsequently, two spotted fever group Rickettsia species and one Candidatus Lariskella sp. were detected and characterized. "Candidatus Rickettsia jingxinensis" was detected in Rhipicephalus microplus (1/1), Haemaphysalis flava (1/3, 33.33%), Haemaphysalis kitaokai (1/3), and Ixodes sinensis (4/101, 3.96%), whereas Rickettsia monacensis was positive in H. flava (1/3), H. kitaokai (2/3), and I. sinensis ticks (74/101, 73.27%). At least two variants/sub-genotypes were identified in the R. monacensis isolates, and the strikingly high prevalence of R. monacensis may suggest a risk of human infection. Unexpectedly, a Candidatus Lariskella sp. belonging to the family Candidatus Midichloriaceae was detected from Ixodes ovatus (1/4) and I. sinensis (10/101, 9.90%). The gltA and groEL gene sequences were successfully obtained, and they show the highest (74.63-74.89% and 73.31%) similarities to "Candidatus Midichloria mitochondrii", respectively. Herein, we name the species "Candidatus Lariskella guizhouensis". These may be the first recovered gltA and groEL sequences of the genus Candidatus Lariskella.