Dermacentor Silvarum Research Articles

Investigation and research on ticks carrying spotted fever group rickettsia in the border area of Tumen River Basin

Objective: To understand the situation and genotype distribution of spotted fever group rickettsia (SFGR) in the border area of Tumen River Basin in free ticks in Yanbian Korean Autonomous Prefecture (Yanbian Prefecture), Jilin Province. Methods: From April to September, 2017, ticks were collected using flagging method from Hunchun, Tumen, Helong and Longjing cities in the Tumen River basin of Yanbian Prefecture. Outer membrane protein A (ompA) was detected by Polymerase Chain Reaction (PCR), then, the species were identified by gene sequencing and analyzed systematically. The positive rate of pools and MIR(minimum infection rate per 100 ticks,MIR) of SFGR were calculated, and the difference of positive rate of pools among ticks with different characteristics was compared by Chi-square test. Results: A total of 3 079 ticks were collected and divided into 536 pools. The positive rate of pools of SFGR nucleic acid was 39.7% (213 pools). The MIR of SFGR was 6.9%.The positive rate of pools of SFGR in Dermacentor silvarum, Haemaphysalis concinna, Haemaphysalis japonica, Haemaphysalis longicornis and Ixodes persulcatus were 80.4% (41/51), 14.0% (25/179), 20.2% (18/89), 78.9% (101/128) and 25.9% (21/81), and the difference was statistically significant (P<0.001). There was statistical difference in the positive rate of pools of SFGR in developmental stages of ticks (P<0.001); the positive rate of pools of female adults, male adults, nymph and larvae were 36.4% (95/261), 34.2% (67/196), 56.3% (40/71) and 7/8, and the MIR was 7.9%, 7.7%, 4.9% and 3.5%. The five genotype was detected which was Candidatus Rickettsia longicornii, Rickettsia raoultii, Rickettsia heilongjiangensis, Candidatus Rickettsia tarasevichiae,Rickettsia monacensis and have 98%-100% homology with known gene sequences. Candidatus Rickettsia longicornii, Rickettsia raoultii, Rickettsia heilongjiangensis and Candidatus Rickettsia tarasevichiae showed close evolutionary relationship with known specie (have 98%-100% homology with known gene sequences); Rickettsia monacensis showed Far from evolutionary relationship with known species (have 98% homology with known gene sequences). Conclusion: SFGR infection of ticks is common in the border areas of the Tumen River Basin. There was high diversity in SFGR species and tick species in the areas surveyed.

Microbiota assessment across different developmental stages of Dermacentor silvarum (Acari: Ixodidae) revealed stage-specific signatures

Dermacentor silvarum is an important vector of tick-borne pathogens. The microbiota of ticks has been recognized to influence their development, fitness, and reproduction as well as the acquisition, establishment and transmission of pathogens. Eggs, larvae, nymphs and adults (females and males) of D. silvarum were used in this study to evaluate microbial community and diversity across different developmental stages. The results demonstrated that some developmental stages host different bacterial species, confirming that each stage of development could have a specific associated microbiota. Proteobacteria was the dominant phylum in most stages, while Actinobacteria was the most abundant in nymphs. The abundance of Brevibacterium significantly increased from the egg stage to the following stages, and there was a sharp increase in the abundance of this genus among nymphs. Eggs showed the highest microbial richness and diversity, and the microbial community of eggs exhibited high similarity to that of females. Moreover, the high abundance of Coxiella in eggs and females further indicated that members of this genus are vertically transmitted symbionts. Nymphs showed a microbial composition distinct from those of the other stages, and the microbial community associated with males possessed higher species richness and greater bacterial diversity than that of females. Further investigations are needed to determine the functions of the microbiota and provide information enabling a better understanding of the diversity of the microbial community at different life stages.

Present-Day Epidemiological-Epizootological Peculiarities of Natural Tularemia Foci in Altai

RelevanceNatural tularemia foci are widespread in Altai Krai and Republic Altai and characterized by high functional stability.Aim.To study modern epidemiological and epizootological features of natural foci of tularemia in the Altai region Russia.Materials and MethodsThe current state of small mammal number in the region is examined. Results of complex studying of 14 Francisella tularensis strains isolated in Republic Altai from 1950 to 2015 (from the collection of Museum of live cultures in Irkutsk Antiplague Research Institute of Rospotrebnadzor) and 21 strains isolated in 2016–2018 in the Altai region are presented. For the first time the tularemia causative agent was isolated at this territory in 1940s. Water vole (Arvicola amphibius) is the most epidemiologically significant as the infection source in these foci. Ixodes ticks: Dermacentor silvarum, D. reticulatus, D. marginatus, Haemaphysalis concinna, Ixodes persulcatus are the main vectors. Now Francisella tularensis subspecies holarctica circulates at Altai territory, and since 2011 additionally F. tularensis mediasiatica.ConclusionsThe functioning of the natural center of tularemia in the territory of the Altai region in the modern period is characterized by coupled circulation of the causative agent of tularemia of two subspecies, sporadic cases of tularemia diseases and infection by the causative agent of environmental objects (bloodsucking arthropods, open water, small mammals). All this indicates a high activity of natural foci with respect to this especially dangerous natural focal infection.

A dataset of distribution and diversity of ticks in China

While tick-borne zoonoses, such as Lyme disease and tick-borne encephalitis, present an increasing global concern, knowledge of their vectors’ distribution remains limited, especially for China. In this paper, we present the first comprehensive dataset of known tick species and their distributions in China, derived from peer-reviewed literature published between 1960 and 2017. We searched for journal articles, conference papers and degree thesis published in both English and Chinese, extracted geographic information associated with tick occurrence, and applied quality-control procedures to remove duplicates and ensure accuracy. The dataset contains 5731 records of geo-referenced occurrences for 123 tick species distributed over 1141 locations distinguished at four levels of scale i.e., provincial, prefectural, county, and township and finer. The most frequently reported tick species include Haemaphysalis longicornis, Dermacentor silvarum, Ixodes persulcatus, Haemaphysalis conicinna, Rhipicephalus microplus, and Rhipicephalus sanguineus sensu lato. The geographical dataset provides an improved map of where ticks inhabit China and can be used for a variety of spatial analyses of ticks and the risk of zoonoses they transmit.

Species and Genetic Diversity of Representatives of the &lt;i&gt;Anaplasmataceae&lt;/i&gt; Family Found in the Sympatry Zone of the &lt;i&gt;Ixodes, Dermacentor&lt;/i&gt; and &lt;i&gt;Haemaphysalis&lt;/i&gt; Genera Ticks

Introduction.On the territory of the Ekhirit-Bulagatsky district of the Irkutsk region zones of sympatry of four Ixodes ticks species are found, where the species and genetic diversity of infectious agents transmitted through tick bites may be more pronounced than in foci with a mono-dominant type of ticks’ population. In this connection, the study of the species and genetic diversity of representatives of the Anaplasmataceae family in the sympatry zone of the Ixodes ticks of closely related species was of scientific interest.Objective: To study the species and genetic diversity of members of the Anaplasmataceae family in the zones of sympatry of Ixodes ticks Ixodes persulcatus, Dermacentor silvarum, D. nuttalli and Haemaphysalis concinna, to identify the main carriers and potential reservoir hosts of ehrlichia and anaplasma.Methods. In the course of the study, 1106 specimens of adult ticks and 49 samples of small mammalian livers from the Ekhirit-Bulagatsky area were analyzed. Anaplasma and ehrlichia DNA were detected by two-round PCR in the presence of genus- and species-specific primers from the 16S rRNA gene region. The nucleotide sequences of the 16S rRNA gene and the fragment of the groESL operon were identified in some samples. Sequencing was carried out according to the Sanger method. Comparative analysis was performed using the BLASTN program and ClustalW method. Epidemiological data analysis was performed using parametric methods of statistical processing of the material.Results. The DNA of Ehrlichia muris and Anaplasma phagocytophilum were detected in all studied species of ticks in their sympatry area. However, the rate of infection of taiga ticks was significantly higher than that of H. concinna and Dermacentor spp. Potential reservoir hosts of the Anaplasmataceae family members can be classified as Microtus oeconomus, M. gregalis, Myodes rutilus and Sorex spp. When analyzing the nucleotide sequences of the 16S rRNA gene, three genetic variants of anaplasma were detected. The nucleotide sequences of the A. phagocytophilum groESL operon belonged to two genetic groups.

Tick distribution in border regions of Northwestern China

Ticks are important vectors of emerging and re-emerging pathogens. The aim of this study was to determine tick species occurring in Xinjiang Uygur Autonomous Region (XUAR), especially on border regions. A total of 22,994 ticks (including 22,629 adults, 365 larvae and nymphs), belonging to six tick genera (i.e. Dermacentor, Hyalomma, Rhipicephalus, Haemaphysalis, Ixodes and Argas) and fourteen tick species, were collected from ten animal hosts in thirty-five counties (cities) in XUAR during 2011 - 2017. Rhipicephalus turanicus, Dermacentor niveus, Hyalomma asiaticum and Dermacentor marginatus were dominantly sampled from domestic animals while Dermacentor nuttalli, Haemaphysalis punctata, Haemaphysalis concinna, Rhipicephalus sanguineus sensu lato, Dermacentor silvarum, Hyalomma scupense and Argas persicus were sporadically found. Based on 16S rDNA, phylogenetic analyses showed that: i) R. turanicus genotypes in XUAR showed geographical separation, and belonged to clade I (major distribution in the Central Asian) rather than clade II (major distribution in the Mediterranean Basin); ii) Ixodes kaiseri, firstly sampled from Asian badgers (Meles leucurus), was in ancestral position compared to European tick species when combining COI haplotypes; and iii) Haemaphysalis erinacei from marbled polecats in China was a separate genotype compared with that in Mediterranean and Europe. Our findings suggest that geographical range plays a more important role than host-association in tick phylogeny, especially for R. turanicus, I. kaiseri and H. erinacei.

Rickettsia raoultii and Rickettsia sibirica in ticks from the long-tailed ground squirrel near the China\u2013Kazakhstan border

Spotted fever group (SFG) rickettsiae cause infection in humans, domestic animals and wildlife. To date, no rickettsial agents have been reported in hard ticks from the long-tailed ground squirrel (Spermophilus undulatus). A total of 50 adult ticks and 48 nymphs were collected from S. undulatus in the border region of northwestern China. Tick species (identified according to morphological and molecular characteristics) included Dermacentor nuttalli, Dermacentor silvarum and Ixodes kaiseri. Based on the cytochrome c oxidase subunit I (COI) haplotype analysis, I. kaiseri from S. undulatus belongs to an ancestral. In addition, all tick samples were analyzed for the presence of rickettsiae by PCR amplification and sequencing of six genetic markers. Rickettsia raoultii and Rickettsia sibirica subsp. sibirica were shown to occur in adults and nymphs of D. nuttalli and D. silvarum. Rickettsia sibirica subsp. sibirica was also detected in an I. kaiseri adult. Dermacentor silvarum and I. kaiseri were found for the first time on S. undulatus. Rickettsia raoultii and R. sibirica subsp. sibirica were detected in two Dermacentor and one Ixodes species, respectively, suggesting that these rickettsiae circulate in the region of the China-Kazakhstan border by hard ticks infesting S. undulatus.

Prevalence of Borrelia burgdorferi sensu lato and Borrelia miyamotoi in ixodid ticks in the Far East of Russia.

Borrelia burgdorferi sensu lato (s.l.) DNA was detected by PCR in Ixodes persulcatus Schulze, 1930, Haemaphysalis concinna Koch, 1844, Haemaphysalis japonica douglasi Nuttall et Warburton, 1915 and Dermacentor silvarum Olenev, 1932 ticks collected in the Amur region, the Jewish Autonomous region, the Sakhalin region and on the Khabarovsk territory. Infection rate of I. persulcatus with B. burgdorferi s.l. 10–69% exceeded the corresponding values of three other tick species in all examined regions during 1999–2014 despite different tick abundance and dominance structure. Bacterial loads estimated on the base of quantitative real time PCR varied from 102 to 109 genome-equivalents per a tick with maximal values for I. persulcatus and H. japonica. Phylogenetic analysis of 16S rRNA gene and 5S—23S rRNA intergenic spacer nucleotide sequences revealed two species: 1) Borrelia garinii of Asian type NT29 with several isolates of European type 20047; 2) Borrelia afzelii with identical sequences of the majority of studied isolates and VS461 reference strain in all regions except the Sakhalin Island where B. afzelii was not found. Borrelia miyamotoi of the relapsing fever group was detected as monoinfection or in combination with B. burgdorferi s.l. in 4.0 ± 0.9% and 4.8 ± 0.9% I. persulcatus ticks, respectively. Multiple locus sequence analysis of three fragments of 16S rRNA, glpQ and p66 genes proved that all the Far Eastern B. miyamotoi isolates belonged to the Asian type identical to FR64b strain (GenBank CP004217) from Japan. Wide distribution of Borrelia DNA in ticks, relative genetic homogeneity with similar sequences of the coding regions and the intergenic spacer of Borrelia wild isolates and temporal stability with high homology levels of the Far Eastern isolates of B. garinii, B. afzelii and B. miyamotoi with previously described spirochetes from the surrounding regions of Russia, China and Japan allowed us to suggest multiple ecological niches as the stability factor of the parasitic system.

Virome analysis of tick-borne viruses in Heilongjiang Province, China

Ticks are implicated in the transmission of various human and livestock pathogens worldwide. This study aimed to understand the geographical distribution of tick species, along with tick-associated viruses, in Heilongjiang Province, northeast China. Molecular methods were used to classify tick species, with next-generation sequencing and polymerase chain reaction-based analyses used to assess the viromes of ticks from four representative sampling locations in the Greater Khingan Mountains. Five species of ixodid ticks were identified, including Ixodes persulcatus, Dermacentor nuttalli, Dermacentor silvarum, Haemaphysalis longicornis, and Haemaphysalis concinna. From the 1102 ticks, 3,568,561 high-quality reads were obtained by next-generation sequencing. Following trimming, 302,540 reads were obtained, of which 6577 (2.16%) reads were annotated to viruses. Phylogenetic analysis revealed that the viral sequences shared a close relationship with Orthonairovirus, Phlebovirus, deer tick Mononegavirales-like virus, and Jingmen tick virus sequences, but the significance of these newly-identified tick-borne viruses to human and animal health requires further investigation. The results of this study provide a basis not only for further studies on the relationship between ticks and tick-borne viruses, but also for preventing future tick-borne epidemic outbreaks by means of vector control.

Some aspects on tick species in Mongolia and their potential role in the transmission of equine piroplasms, Anaplasma phagocytophilum and Borrelia burgdorferi L.

Ticks are cosmopolitan vectors of numerous diseases, and detection of various pathogens in ticks can help to assess their distribution. In the current study, 528 adult ticks were collected from grazing animals or the ground in ten different Mongolian provinces. Dermacentor nuttalli constituted 76.1% of them and was found in all ecozones except the eastern desert. Dermacentor marginatus (8.3%), Dermacentor silvarum (1.1%) and Ixodes persulcatus (3.0%) were found in the northern forest areas and Hyalomma asiaticum (11.4%) only in the southern (semi-)desert. Of these, 359 ticks were subjected to DNA extraction and PCR was carried out to detect various pathogens. Anaplasma spp. was found in D. marginatus and D. nuttalli (2.5% positive each), including flagged specimen and identified as Anaplasma phagocytophilum. Borrelia spp. were found in 2.5% of the ticks (mostly in I. persulcatus) and identified as Borrelia garinii. Babesia spp. (40%) identified as Babesia caballi were detected in all five tick species including flagged Dermacentor spp. and I. persulcatus, and 3.5% of the ticks (all species except D. silvarum) were positive for Theileria spp. identified as Theileria equi. The piroplasms were found in all provinces. Tick-borne encephalitis virus was not detected. The results highlight the high risk of equine piroplasmosis in Mongolia, which is a concern for both the nomadic population who rely on horses for transport and for conservation of Przewalski’s horses in Mongolia. In addition, zoonotic agents such as the avian B. garinii and A. phagocytophilum were also detected, outlining a high risk for exposed humans.

Genetic variability of Rickettsia spp. in Dermacentor and Haemaphysalis ticks from the Russian Far East

The Russian Far East is an endemic region for tick-borne rickettsioses. However, the prevalence and genetic variability of Rickettsia species in this region have not been extensively investigated. In this study, 188 Dermacentor silvarum, 439 Haemaphysalis concinna, and 374 Haemaphysalis japonica adult ticks were collected from four locations in Khabarovsk Province and three locations in Amur Province in the Russian Far East. These ticks were examined for the presence of Rickettsia spp. by amplifying a fragment of the gltA gene. Identified rickettsiae were genotyped by sequencing of the gltA, 16S rRNA, ompA, ompB, and sca4 genes. In the examined ticks, Rickettsia heilongjiangensis, the causative agent of Far-Eastern tick-borne rickettsiosis, was found in 10.5% of H. concinna and in 1.9% of H. japonica ticks, while Rickettsia sibirica, the agent of Siberian tick typhus, was detected in only one H. concinna tick. In addition, Rickettsia raoultii was found predominantly in D. silvarum (>70%) and significantly less frequently in Haemaphysalis ticks (<3%). “Candidatus Rickettsia tarasevichiae” was found in all examined tick species (1.6–5.3% in different species). Notably, this study is the first observation of “Candidatus R. tarasevichiae” in D. silvarum ticks. Moreover, DNA of Rickettsia canadensis was found for the first time in a H. japonica tick; DNA of Rickettsia aeschlimannii was revealed for the first time in H. concinna and H. japonica ticks. “Candidatus Rickettsia principis” and “Candidatus Rickettsia rara” were found in Haemaphysalis spp. ticks. “Candidatus R. principis” was associated with H. japonica and identified in 5.6% of the examined ticks, while “Candidatus R. rara” was found more frequently in H. concinna (3.0%) compared to H. japonica ticks (1.1%). In this study, “Candidatus R. principis” and “Candidatus R. rara” were characterized for the first time by the 16S rRNA, ompA, ompB, and sca4 genes.

Isolation and genomic characterization of lymphocytic choriomeningitis virus in ticks from northeastern China.

Lymphocytic choriomeningitis virus (LCMV) is a rodent-borne arenavirus that is considered a neglected cause of neurologic diseases in humans. In this study, we described genomic characterization of newly isolated LCMVs in Haemaphysalis longicornis, Dermacentor nuttalli, Dermacentor silvarum and Ixodes persulcatus in Jilin Province, northeastern China. The complete sequences of the small (S) and large (L) segments of LCMVs in ticks contained 3,375 and 7,235-7,241 nucleotides, respectively. Sequence comparison showed 82.1%-86.0% identity of S segment with other lineage I strains at the nucleotide level and 91.2%-97.5% at the deduced amino acid level, while a lower identity was observed in the L segment at both nucleotide (75.4%-82.2%) and amino acid (82.4%-93.4%) levels. Phylogenetic analysis grouped the tick LCMVs together with the lineage I strains, but in an isolated cluster with a high bootstrap value. Bayesian analysis indicated that the molecular evolutionary rate was estimated to be 3.3×10-4 substitutions/site/year for the S segment and 6.3×10-4 substitutions/site/year for the L segment, and the time to most recent common ancestor was 1980 and 1970years ago, respectively, showing that tick LCMVs were predicted to originate between 1970s and 1980s. A long evolutionary history and high prevalence of LCMV in H.longicornis were found compared to other tick species. This study represented the first report on isolation of LCMV in China, showing that LCMV is circulating among ticks in Jilin Province, but the role of ticks in the epidemiology of LCMV remains to be explored.

An Immunosuppressive Tick Salivary Gland Protein DsCystatin Interferes With Toll-Like Receptor Signaling by Downregulating TRAF6.

Ticks, blood-feeding arthropods, and secrete immunosuppressive molecules that inhibit host immune responses and provide survival advantages to pathogens. In this study, we characterized the immunosuppressive function of a novel tick salivary protein, DsCystatin, from Dermacentor silvarum of China. DsCystatin directly interacted with human Cathepsins L and B and inhibited their enzymatic activities. DsCystatin impaired the expression of inflammatory cytokines such as IL1β, IFNγ, TNFα, and IL6 from mouse bone marrow-derived macrophages (BMDMs) that had been stimulated with LPS or Borrelia burgdorferi. Consistently, DsCystatin inhibited the activation of mouse BMDMs and bone marrow-derived dendritic cells by downregulating the surface expression of CD80 and CD86. Mechanically, DsCystatin inhibited LPS- or B. burgdorferi-induced NFκB activation. For the first time, we identified that DsCystatin-attenuated TLR4 signaling by targeting TRAF6. DsCystatin enhanced LPS-induced autophagy, mediated TRAF6 degradation via an autophagy dependent manner, thereby impeded the downstream phosphorylation of IκBα and the nuclear transport of NFκB. Finally, DsCystatin relieved the joint inflammation in B. burgdorferi or complete Freund’s adjuvant induced mouse arthritis models. These data suggested that DsCystatin is a novel immunosuppressive protein and can potentially be used in the treatment of inflammatory diseases.

Complete Genomic Characterization of Three Tick-Borne Encephalitis Viruses Detected Along the China-North Korea Border, 2011.

Tick-borne encephalitis virus (TBEV) causes neurological infections with serious sequelae in Europe and Northeast Asia. In China, the major epidemic areas are along the borders with Russia and North Korea. Although several TBEV isolates have been reported, the biological characteristics of the Chinese strains, especially those along the China-North Korea border, are unclear. In this study, we detected seven TBEV fragment sequences in 602 adult Dermacentor silvarum collected in the Changbai Mountain area of Jilin Province on the China-North Korea border and characterized the genome of three TBEV strains (JLCB11-08, JLCB11-35, and JLCB11-40). These three TBEV strains belong to the TBEV-Far Eastern (TBEV-FE) genotype and clustered most closely with the Svetlogorie and Kavalerovo strains from Russia. In addition, the TBEV strains from Northeast China clustered geographically within the TBEV-FE subtype branch. These findings will facilitate further research on the distinct genetic groupings of TBEV strains in China.

Tick-borne encephalitis virus in arthropod vectors in the Far East of Russia

Isolates of tick-borne encephalitis virus (TBEV) from arthropod vectors (ticks and mosquitoes) in the Amur, the Jewish Autonomous and the Sakhalin regions as well as on the Khabarovsk territory of the Far East of Russia were studied. Different proportions of four main tick species of the family Ixodidae: Ixodes persulcatus P. Schulze, 1930; Haemaphysalis concinna Koch, 1844; Haemaphysalis japonica douglasi Nuttall et Warburton, 1915 and Dermacentor silvarum Olenev, 1932 were found in forests and near settlements. RT-PCR of TBEV RNA in adult ticks collected from vegetation in 1999–2014 revealed average infection rates of 7.9 ± 0.7% in I. persulcatus, of 5.6 ± 1.0% in H. concinna, of 2.0 ± 2.0% in H. japonica, and of 1.3 ± 1.3% in D. silvarum. Viral loads varied in a range from 102 to 109 TBEV genome-equivalents per a tick with the maximal values in I. persulcatus and H. japonica. Molecular typing using reverse transcription with subsequent real time PCR with subtype-specific fluorescent probes demonstrated that the Far Eastern (FE) subtype of TBEV predominated both in mono-infections and in mixed infection with the Siberian (Sib) subtype in I. persulcatus pools. TBEV strains of the FE subtype were isolated from I. persulcatus, H. concinna and from a pool of Aedes vexans mosquitoes. Ten TBEV strains isolated from I. persulcatus from the Khabarovsk territory and the Jewish Autonomous region between 1985 and 2013 cluster with the TBEV vaccine strain Sofjin of the FE subtype isolated from human brain in 1937. A TBEV strain from H. concinna collected in the Amur region (GenBank accession number KF880803) is similar to the vaccine strain 205 isolated in 1973 from I. persulcatus collected in the Jewish Autonomous region. The TBEV strain Lazo MP36 of the FE subtype isolated from a pool of A. vexans in the Khabarovsk territory in 2014 (KT001073) differs from strains isolated from 1) I. persulcatus (including the vaccine strain 205) and H. concinna; 2) mosquitoes [strain Malishevo (KJ744034) isolated in 1978 from Aedes vexans nipponii in the Khabarovsk territory]; and 3) human brain (including the vaccine strain Sofjin). Accordingly, in the far eastern natural foci, TBEV of the prevailing FE subtype has remained stable since 1937. Both Russian vaccines against TBE based on the FE strains (Sofjin and 205) are similar to the new viral isolates and might protect against infection.

Borrelia miyamotoi Infections in Humans and Ticks, Northeastern China.

We conducted an investigation of Borrelia miyamotoi infections in humans and ticks in northeastern China. Of 984 patients reporting recent tick bites, 14 (1.4%) were found to be infected with B. miyamotoi by PCR and genomic sequencing. The 14 patients had nonspecific febrile manifestations, including fever, headache, anorexia, asthenia, and arthralgia. Rash, eschar, and regional lymphadenopathy were each observed in 1 patient. Four (28.6%) patients were hospitalized because of severe disease. B. miyamotoi was detected in 3.0% (19/627) of Ixodes persulcatus, 1 (2.8%) of 36 Haemaphysalis concinna, and none of 29 Dermacentor silvarum ticks. Phylogenetic analyses based on sequences of a nearly entire 16s rRNA gene, a partial flagellin gene, and the glycerophosphodiester phosphodiesterase gene revealed that B. miyamotoi identified in patients and ticks were clustered in the group of the Siberian type. These findings indicate that B. miyamotoi is endemic in northeastern China and its public health significance deserves further investigation.

Gene expression profiling of the unfed nymphal Dermacentor silvarum (Acari: Ixodidae) in response to low temperature

The tick Dermacentor silvarum is recognized as an emerging vector of marked medical and veterinary significance. The current study investigated the gene expression profiling of the unfed nymphal D. silvarum in response to low temperature using high-throughput transcriptome sequencing. A total of approximately 12-giga base pairs were produced, which yielded 87,500 unigenes, and among them, 29,815 unigenes were successfully annotated by all available databases (NCBI nonredundant, Swissprot, UniProtKB/TrEMBL, the clusters of orthologous groups databases, the Kyoto encyclopedia of genes and genomes database, and pfam database). After low temperature treatment (4°C for 10 days), 2,241 genes, including 1,160 up-regulated and 1,081 down-regulated genes, were differentially expressed. The differentially expressed genes were further enriched to GO terms and KEGG pathways, and our results showed that 133 genes were enriched in molecular function, 90 genes were enriched in cellular components, 107 genes were enriched in biological processes and 202 genes were assigned into different KEGG pathways. This study establishes a molecular basis for gene function analysis in the tick D. silvarum, and will provide theoretical information for mechanistic studies on the overwintering adaptations of ticks.

Molecular prevalence of spotted fever group rickettsiae in ticks from Qinghai Province, northwestern China

Tick-borne rickettsioses is one of the oldest known vector-borne diseases and has been viewed as emerging or re-emerging disease in China. The causative agents have been increasingly recognized and exhibited a high degree of genetic diversity and widespread distribution. This study was conducted to determine the prevalence of spotted fever group rickettsiae in ticks from Qinghai Province, northwestern China. In total, 860 questing adult ticks representing six species were collected. The SFG rickettsiae were detected in Haemaphysalis qinghaiensis (19.6%, 79/404), Dermacentor abaensis (73.7%, 157/213), Dermacentor silvarum (50.0%, 47/94), Dermacentor nuttalli (67.4%, 97/144), and Ixodes crenulatus (100%, 3/3), with an overall infection rate of 44.5%. The infection rates of SFG rickettsiae were significantly higher in Dermacentor spp. than in Haemaphysalis spp. (p<0.05). Sequence analyses of the gltA and ompA genes revealed that five SFG rickettsiae are present in ticks in Qinghai, including R. sibirica subspecies sibirica, R. raoultii, “Candidatus Rickettsia tibetani”, and “Candidatus Rickettsia gannanii” Y27 and F107. Moreover, a potential novel Rickettsia species (Rickettsia sp. 10CYF) was identified in D. nuttalli and I. crenulatus. These findings extend our knowledge of the potential vector spectrum and distribution of rickettsiae, and provided valuable information for assessing the potential risk for public health.

Antibacterial Activity of Eggs and Egg Wax Covering of Selected Ixodid (Acari: Ixodidae) Ticks

Abstract Antimicrobial activity of eggs and the wax covering of eggs has been observed in several tick (Acari) species, but any antimicrobial activity associated with ixodid (Acari: Ixodidae) tick eggs is unknown. The antimicrobial activity associated with eggs, wax extracts from eggs, and eggs from which wax was removed of the ixodids Haemaphysalis longicornis Neumann (parthenogenetic and bisexual populations), Haemaphysalis doenitzi Warburton et Nuttal, Dermacentor silvarum Olenev, and Hyalomma asiaticum Schulze and Schlottke was assessed using an in vitro agar diffusion assay. Eggs of D. silvarum and Hy. asiaticum placed on the agar culture inhibited the growth of gram-negative bacteria but had no activity against gram-positive bacteria. Eggs of H. longicornis (parthenogenesis and bisexual population) and H. doenitzi inhibited the growth of gram-positive bacteria, but not gram-negative bacteria. All eggs from which the wax had been extracted had no activity against either gram-positive or gram-negative...

Cold tolerance and biochemical response of unfed Dermacentor silvarum ticks to low temperature

The important pathogen vector Dermacentor silvarum is widely distributed in China. However, the tick’s adaptation to low winter temperatures remains poorly understood. We therefore investigated the cold hardiness and physiological and biochemical responses of D. silvarum ticks exposed to low temperatures. The results indicated that the lower lethal temperatures (LT50s) for larvae, nymphs, females and males were −16.9°C, −15.8°C, −20.0°C and −20.1°C, respectively. The discriminating temperatures (resulting in 20% survival) for larvae, nymphs, females and males were −18.5°C, −20.0°C, −21.7°C and −22.6°C, respectively. The supercooling temperature points (at which body fluids spontaneously freeze) of larvae, nymphs, females and males averaged −20.0°C, −23.5°C, −24.2°C and −23.9°C, respectively. These results indicate that adult ticks are more tolerant to cold than the immatures. Low-temperature stress can enhance adult cold hardiness and trigger decreases in glycogen and protein in both females and males, whereas nymphs displayed different biochemical responses, including an increase in water and total fat content. An increase of glycerol observed in nymphs and females suggests that glycerol is important for cold hardiness. The findings of this study will help to define the dispersal limits for D. silvarum and thus inform the need for tick control efforts.