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Abstract Background The great gerbil (Rhombomys opimus), whose ectoparasitic fleas significantly influence the transmission and prevalence of plague, was the dominant rodent species in the Junggar Basin in Northwestern China. However, the distribution pattern of fleas parasitizing the great gerbils and whether that pattern affected the intensity of plague prevalence in different regions remains unclear. Methods A total of 17,780 fleas were collected from 2258 great gerbils throughout 90 investigations. This study focused on analyzing the rate of flea infestation and the flea indices of species that parasitized the great gerbils. The aggregation patterns of fleas parasitizing the great gerbils were measured using the parameter b of Taylor’s power law, and the differences in the aggregation index of plague epidemic areas were compared. Results We observed an aggregated distribution of ectoparasitic fleas in the great gerbils. The aggregation degree of combined fleas was higher (P > 0.05) in the eastern area of the Junggar Basin than in the western area. The primary species of ectoparasitic fleas of the great gerbils were Xenopsylla skrjabini, Xenopsylla minax, Xenopsylla hirtipes, and Nosopsyllus laeviceps laiveceps. X. skrjabini exhibited the highest (P

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.

This study was aimed at investigating the viral diversity associated with marine organisms in the South China Sea, to improve understanding of the region’s viral ecosystems. Viruses profoundly influence aquatic ecosystems, by affecting marine biogeochemical cycles and posing threats to marine organisms. Nonetheless, a comprehensive study of marine organisms’ viral diversity in the South China Sea remains lacking. We collected gill and viscera tissue samples from three marine phyla ( Chordata , Arthropoda , and Mollusca ) along the South China Sea coast. High-throughput sequencing and bioinformatics analyses were conducted to identify and characterize viral communities within these samples, with a focus on both viral composition and potential zoonotic threats. We observed distinct viral composition patterns across tissues and phyla, notably involving Adintoviridae and viruses within the Herpesviridae and Dicistroviridae . The presence of zoonotic viruses in economically important aquatic organisms suggests potential risks. This study contributes to broader understanding of viral diversity, by suggesting potential epidemic causes and illustrating genetic relationships among viruses associated with marine organisms. By extending the virus distribution map for this region, our findings underscore the need to consider the viral microenvironments surrounding marine species, and their implications for marine and human health.

We report the isolation of Tamdy virus from Hyalomma asiaticum ticks in northwest China and serologic evidence of human Tamdy virus infection in the same region. These findings highlight the need to further investigate a potential causal relationship between Tamdy virus and febrile illnesses of unknown etiology in that region.

Despite few human cases of tick-borne encephalitis virus (TBEV), high rates of TBEV seroprevalence were reported among humans and animals in Xinjiang Uygur Autonomous Region in Northwestern China. In this study, the Karshi virus (KSIV) was identified and isolated from Hyalomma asiaticum ticks in Xinjiang. It belongs to the genus Flavivirus of the family Flaviviridae and is closely related to TBEV. KSIV infects cell lines from humans, other mammals and ticks, and causes encephalitis in suckling mice. High minimum infection rates (4.96%) with KSIV were detected among tick groups. KSIV infections have occurred in sheep and marmots, resulting in antibody-positive rates of 2.43 and 2.56%, respectively. We further found that, of the KSIV antibody-positive serum samples from animals, 13.9% had TBEV exposure showing cross-reaction to KSIV, and 11.1% had KSIV infection resulting in cross-reaction to TBEV; 8.3% were likely to have co-exposure to both viruses (or may be infected with one of them and present cross-reactivity with the other). The results revealed a substantial KSIV prevalence among ticks in Xinjiang, indicating exposure of animals to KSIV and TBEV. The findings implied misinterpretation of the high rates of TBEV seroprevalence among humans and animals in previous studies. There is a need to develop detection methods to distinguish KSIV from TBEV and to perform an in-depth investigation of KSIV and TBEV prevalence and incidence in Northwestern China, which would enhance our preparation to provide medical treatment of emerging diseases caused by tick-borne viral pathogens such as KSIV.

Severe Fever with Thrombocytopenia Syndrome Virus (SFTSV) was recently identified as a tick-borne pathogen that threat to human health. Since 2010, many countries including China, South Korea, and Japan have reported Human SFTS caused by SFTSV infection. The glycoprotein encoded by the SFTSV M gene is the major antigenic component on the viral surface, and responsible for the viral entry, which makes it an important viral antigen and a clinical diagnostic target. The present study aimed to map linear B cell epitopes (BCEs) on the N-terminal glycoprotein (Gn) from SFTSV strain WCH/97/HN/China/2011 using the modified biosynthetic peptide method. Five fine epitopes (E1, 196FSQSEFPD203; E2, 232GHSHKII238; E3, 256VCYKEGTGPC265; E4, 285FCKVAG290, and E5, 316SYGGM320) were identified using the rabbit antisera. Western blot analysis showed that all the five epitopes interacted with the positive serum of sheep that had been naturally infected with SFTSV. Three-dimensional structural modeling analysis showed that all identified BCEs were located on the surface of the SFTSV-Gn and contained flexible loops. The sequence alignment revealed high conservation of the identified BCEs among 13 SFTSV strains from different lineage. These mapped epitopes will escalate the understanding of the epitope distribution and pathogenic mechanism of SFTSV, and could provide a basis for the development of a SFTSV multi-epitope detection antigen.

ABSTRACTThe Xinjiang Uygur Autonomous Region locating in Northwest of China was not considered the epidemic area of severe fever with thrombocytopenia syndrome (SFTS). Here we report the first laboratory-confirmed SFTS case that a female patient had tick bite in Xinjiang and illness onset after returning to Hainan Province. Laboratory tests identified SFTS virus (SFTSV) infection, and the virus was isolated from the patient’s serum sample. Furthermore, SFTSV prevalence among tick groups was identified, and IgM response to SFTSV from febrile patients was identified. The findings suggested that there have been risks of SFTSV infection due to exposure to ticks in Xinjiang.

Ticks are a major arthropod vector of zoonotic diseases affecting both humans and domestic animals worldwide. Thus, studying tick microbiota would aid in understanding of the potential threats posed by ticks. Approximately 8,000 unfed ticks, identified as Dermacentor nuttalli , were collected from the sylvosteppe in the western Tianshan mountains. To investigate their potential pathogens, we divided the ticks into 36 groups of 200–300 individuals each for examination with culturomics and 16S rDNA amplicon sequencing. A total of 237 bacterial genera were identified with the two methods. Culturomics identified 46 bacterial species from 23 genera, predominantly Pseudomonas , Pantoea , and Bacillus , whereas 16S rDNA sequencing identified 461 OTUs from 233 genera, predominantly Pseudomonas (53.8%), Coxiella (17.2%), and Pantoea (6.4%). Coxiella , Rickettsia , and ten other genera were discovered only by sequencing, because optimal cultivating conditions were not used for their isolation, whereas Arthrobacter and three other genera were discovered only through culturomics. Several of the identified bacteria, such as line-related sepsis-causing Delftia acidovorans and the pneumonia agent Acinetobacter pittii , can cause human diseases. Thus, both sequencing and culturomics methods are crucial for comprehensive understanding of the microbiota of D. nuttalli .

Guertu virus (GTV) is a tick-borne phleboviruses (TBPVs) which belongs to the genus Banyangvirus in the family of Phenuiviridae. In vitro and in vivo studies of GTV demonstrated that it was able to infect animal and human cell lines and could cause pathological lesions in mice. Glycoproteins (GP, including Gn and Gc) on the surface of Guertu virus (GTV) could bind to receptors on host cells and induce protective immunity in the host, but knowledge is now lacking on the information of B cell epitopes (BCEs) present on GTV-GP protein. The aim of this study was to identify all BCEs on Gn of the GTV DXM strain using rabbit pAbs against GTV-Gn. Seven fine BCEs and two antigenic peptides (APs) from nine reactive 16mer-peptides were identified, which are EGn1 (2PIICEGLTHS11), EGn2 (135CSQDSGT141), EGn3 (165IP EDVF170), EGn4 (169VFQEL K174), EGn5 (187IDGILFN193), EGn6 (223QTKWIQ228), EGn7 (237CHKDGIGPC245), AP-8 (299GVRVRPKCYGFSRMMA314) and AP-9 (355CASH FCSSAESGKKNT370), of which six of mapped BCEs were recognized by the IgG-positive sheep serum obtained from sheep GTV-infected naturally. Multiple sequence alignments (MSA) based on each mapped BCE motif identified that the most of identified BCEs and APs are highly conserved among 10 SFTSV strains from different countries and lineages that share relatively close evolutionary relationships with GTV. The fine epitope mapping of the GTV-Gn would provide basic data with which to explore the GTV-Gn antigen structure and pathogenic mechanisms, and it could lay the foundation for the design and development of a GTV multi-epitope peptide vaccine and detection antigen.

Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne pathogen that causes severe disease in humans. CCHFV is widely distributed in more than 30 countries and distinct regions, which means that it poses a serious threat to human health. The nucleocapsid protein (NP) encoded by the CCHFV S gene is the primary detectable antigen in infected cells, which makes it an important viral antigen and a clinical diagnostic target. In this study, the modified biosynthetic peptide (BSP) method was used to identify the fine epitopes on the N- and C- terminals of NP from the CCHFV YL04057 strain using rabbit antiserum against CCHFV-NP. Nine epitopes were identified: E1a (178NLILNRGG185), E1b (184GGDENP189), E2 (352PLKWGKK358), E3 (363FADDS367), E4 (399NPDDAA404), E5a (447DIVASEHL454), E5b (452EHLLHQSL459), E6 (464SPFQNAY470) and E7 (475NATSANII482). Western blotting analysis showed that each epitope interacted with the positive serum of sheep that had been naturally infected with CCHFV. Amino acid sequence alignment between each epitope and their homologous proteins showed that they were almost 100% conserved among 12 CCHFV sequences from different lineages, except for epitopes E1a, E1b and E2. Three-dimensional structural modeling analysis showed that all identified epitopes were located on the surface of the NP "head" domain. This study identified fine epitopes on the N- and C- terminals of NP, which will increase the understanding of the structure and function of NP, and it could lay the foundation for the design and development of a CCHFV multi-epitope peptide vaccine and detection antigen.

Severe fever with thrombocytopenia syndrome (SFTS) is an acute infectious disease caused by a tick-borne phlebovirus, which was reported to be continuously epidemic in Japan, Korea and in 23 provinces of China since 2010. Most laboratory-confirmed SFTS cases in China have been recorded in 18 Eastern and Central provinces. A few suspected cases with SFTS-like symptoms were reported to the Chinese Disease Prevention and Control Information System from provinces including Guangxi, Guangdong, Gansu and Xinjiang Uygur Autonomous Region (XJUAR), however diagnosis was not confrimed due to lack of molecular biological and virological evidence. Here we reported the first laboratory-confirmed SFTS case in 2017. A resident of Hainan International Tourism Island (HNITI) was bitten by ticks when traveling in XJUAR and had illness onset after returning to HNITI. RT-PCR detected SFTSV RNA in the patient’s serum samples. Antibodies against SFTSV were detected from the patient and the neutralization from serum samples was evaluated. And the samples of person who had close contact to the patient were also investigated. Moreover, a new SFTSV strain was isolated from the serum sample collected from the patient during acute phase of disease. The viral properties and phylogeny were further characterized. In addition, SFTSV was detected positive in ticks collected from XJUAR in 2017, which suggested that SFTSV was more widely distributed than we recognized. Therefore, this study identified the first SFTS case from XJUAR where confirmed cases have never been reported and demonstrated the substantial risk from SFTSV infection via tick bite there. It is also the first importing SFTS case in HNITI, which showed the significant role of human transport in disease spread and indicated that the recently authorized international tourism island may face more challenges for controlling other importing cases from different areas and countries.

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. [ABSTRACT FROM AUTHOR]