Diversity of spotted fever group rickettsiae and their association with host ticks in Japan

Distribution of ticks and their possession of spotted fever group Rickettsia in Ibaraki prefecture

INTRODUCTION

Tick-borne diseases (TBDs) are a growing threat in Japan. However, distribution of ticks and their possession of human pathogens remain poorly understood.

METHODS

In the present study, we collected 3477 ticks at 6 remote, woodland sites in Ibaraki prefecture between May 23 and November 4, 2021, and investigated the distribution and the possession of spotted fever group Rickettia (SFGR).

RESULTS

The collected ticks included Haemaphysalis flava (78.3 %), Haemaphysalis longicornis (9.0 %), Haemaphysalis hystricis (4.6 %), Ixodes turdus (4.3 %), Amblyomma testudinarium (2.1 %), Haemaphysalis cornigera (0.9 %), Haemaphysalis formosensis (0.9 %), Haemaphysalis megaspinosa (0.2 %), Ixodes ovatus (0.1 %), Ixodes nipponensis (0.09 %), and Ixodes columnae (0.03 %). Of 2160 DNA samples extracted from the ticks, the gltA gene and the 17-kDa antigen gene of SFGR were detected in 67 samples. Among 1682 samples from adult and nymph ticks, the positive rate of SFGR was 2.7 %. Sequence analyses of the partial 17-kDa antigen gene demonstrated that the detected SFGR were classified into 8 groups (G1 to G8). The sequences of G2, G4, G5, G6, and G7 were either identical to or differed by one base pair from those of Rickettsia asiatica, Rickettsia tamurae, Rickettsia monacensis, Rickettsia canadensis, and Rickettsia felis, respectively.

CONCLUSION

The present study revealed a diverse tick fauna in Ibaraki prefecture, including detection of species commonly found in southwestern Japan. Although the prevalence of SFGR in ticks was lower than in previous studies, several SFGR causing human infection may be present.

The case of Mediterranean spotted fever of the traveler returned from Zambia

We report the case of a traveler who returned from Zambia and was diagnosed with Mediterranean spotted fever (MSF), an infectious disease caused by Rickettsia conorii conorii. The patient presented to Sapporo City General Hospital with symptoms of fever, malaise, headache, and rash. The pathogen was identified by Polymerase Chain Reaction assays and subsequent analyses. The patient improved with 10-day treatment of oral doxycycline. Although some cases of MSF have been reported in sub-Saharan Africa, none have been reported in Zambia. Rhipicephalus sanguineus sensu lato, the vector of the Rickettsia conorii conorii, has been found in various areas of Zambia. Our case report highlights the potential threat of Mediterranean spotted fever in urban areas of Zambia.

Distribution and pathogen prevalence of field-collected ticks from south-western Korea: a study from 2019 to 2022

Hard ticks are known vectors of various pathogens, including the severe fever with thrombocytopenia syndrome virus, Rickettsia spp., Coxiella burnetii, Borrelia spp., Anaplasma phagocytophilum, and Ehrlichia spp. This study aims to investigate the distribution and prevalence of tick-borne pathogens in southwestern Korea from 2019 to 2022. A total of 13,280 ticks were collected during the study period, with H. longicornis accounting for 86.1% of the collected ticks. H. flava, I. nipponensis and A. testudinarium comprised 9.4%, 3.6%, and 0.8% of the ticks, respectively. Among 983 pools tested, Rickettsia spp. (216 pools, 1.6% MIR) were the most prevalent pathogens across all tick species, with R. japonica and R. monacensis frequently detected in I. nipponensis and Haemaphysalis spp., respectively. Borrelia spp. (28 pools, 0.2% MIR) were predominantly detected in I. nipponensis (27 pools, 13.8% MIR, P < 0.001). Co-infections, mainly involving Rickettsia monacensis and Borrelia afzelii, were detected in I. nipponensis. Notably, this study identified R. monacensis for the first time in A. testudinarium in South Korea. These findings offer valuable insights into the tick population and associated pathogens in the region, underscoring the importance of tick-borne disease surveillance and prevention measures.

Unraveling the phylogenetics of genetically closely related species, Haemaphysalis japonica and Haemaphysalis megaspinosa, using entire tick mitogenomes and microbiomes

Ticks have a profound impact on public health. Haemaphysalis is one of the most widespread genera in Asia, including Japan. The taxonomy and genetic differentiation of Haemaphysalis spp. is challenging. For instance, previous studies struggled to distinguish Haemaphysalis japonica and Haemaphysalis megaspinosa due to the dearth of nucleotide sequence polymorphisms in widely used barcoding genes. The classification of H. japonica japonica and its related sub-species Haemaphysalis japonica douglasi or Haemaphysalis jezoensis is also confused due to their high morphological similarity and a lack of molecular data that support the current classification. We used mitogenomes and microbiomes of H. japonica and H. megaspinosa to gain deeper insights into the phylogenetic relationships and genetic divergence between two species. Phylogenetic analyses of concatenated nucleotide sequences of protein-coding genes and ribosomal DNA genes distinguished H. japonica and H. megaspinosa as monophyletic clades, with further subdivision within the H. japonica clade. The 16S rRNA and NAD5 genes were valuable markers for distinguishing H. japonica and H. megaspinosa. Population genetic structure analyses indicated that genetic variation within populations accounted for a large proportion of the total variation compared to variation between populations. Microbiome analyses revealed differences in alpha and beta diversity between H. japonica and H. megaspinosa: H. japonica had the higher diversity. Coxiella sp., a likely endosymbiont, was found in both Haemaphysalis species. The abundance profiles of likely endosymbionts, pathogens, and commensals differed between H. japonica and H. megaspinosa: H. megaspinosa was more diverse.

Seasonal pattern of questing ticks and prevalence of pathogenic Rickettsia and Anaplasmataceae in Khao Yai national park, Thailand

BACKGROUND

Tick-borne diseases (TBD) are considered neglected diseases in Thailand with disease burden likely underestimated. To assess risk for emerging TBD in Thailand, the seasonality of questing tick and pathogen prevalence were studied in Khao Yai National Park, a top tourist destination.

METHODS

During 2019, questing ticks around tourist attractions were systematically collected bimonthly and analyzed for Rickettsia and Anaplasmataceae bacterial species by polymerase chain reaction and DNA sequencing.

RESULTS

Larvae and nymphs of questing ticks peaked in Khao Yai National Park during the late rainy-winter season, though no specific trends were observed in adult ticks. Winter (November to February) was the highest risk for human tick-bites due to higher numbers of both ticks and visitors. Of the total 5916 ticks analyzed (651 pools), Anaplasma phagocytophilum, Neoehrlichia mikurensis, Ehrlichia ewingii, and Ehrlichia chaffeensis were detected at low rates (≤0.05%). There was a higher prevalence of human rickettsioses (0.2-7%) in ticks surveyed with Rickettsia tamurae, Rickettsia raoultii, and Rickettsia montana the major species. Amblyomma ticks had the highest prevalence of Rickettsia (85%, 35/44 Amblyomma adults), in which only R. tamurae and R. raoultii were found in Amblyomma with mixed species infections common. We report the first detection of R. africae-like and N. mikurensis in Ixodes granulatus adults in Thailand, suggesting I. granulatus as a potential vector for these pathogens.

CONCLUSION

This study demonstrated the risk of emerging TBD in Thailand and underscores the need for tick-bite prevention among tourists in Thailand.

Complicated Japanese Spotted Fever With Meningitis in an Older Patient: A Case Report

Japanese spotted fever (JSF) poses a significant public health challenge, mainly due to its atypical presentation in specific demographics. This report details a unique case of JSF in an 89-year-old female who was admitted to a rural hospital exhibiting generalized pain and rapid cognitive decline but no rash. Initially misdiagnosed as polymyalgia rheumatica, her condition was complicated by thrombocytopenia and altered mental state, prompting consideration of tick-borne illnesses. Subsequent serological analysis confirmed JSF despite the absence of its hallmark rash. The patient's condition escalated to include bacteremia and aseptic meningitis. Treatment involved a regimen of minocycline and meropenem, along with endoscopic cauterization of a bleeding rectal ulcer. After treatment, the patient showed improvement and was transferred for rehabilitation. This case highlights the criticality of considering JSF in elderly patients within endemic areas, even when classic symptoms like erythema and petechiae are absent. It underscores the necessity for broad diagnostic perspectives, especially in atypical presentations, and the integration of comprehensive care approaches. The involvement of caregivers and relatives in early detection and seeking medical care promptly is crucial. The report illustrates the complexities in diagnosing and managing advanced JSF cases and stresses the importance of early serological testing and adaptive treatment strategies in managing such challenging cases.

Molecular Detection of Rickettsia hoogstraalii in Hyalomma anatolicum and Haemaphysalis sulcata: Updated Knowledge on the Epidemiology of Tick-Borne Rickettsia hoogstraalii

Ticks are hematophagous ectoparasites that transmit pathogens to animals and humans. Updated knowledge regarding the global epidemiology of tick-borne Rickettsia hoogstraalii is dispersed, and its molecular detection and genetic characterization are missing in Pakistan. The current study objectives were to molecularly detect and genetically characterize Rickettsia species, especially R. hoogstraalii, in hard ticks infesting livestock in Pakistan, and to provide updated knowledge regarding their global epidemiology. Ticks were collected from livestock, including goats, sheep, and cattle, in six districts of Khyber Pakhtunkhwa (KP) Pakistan. Overall, 183 hosts were examined, of which 134 (73.2%), including goats (number = 39/54, 72.2%), sheep (23/40, 57.5%), and cattle (71/89, 80%) were infested by 823 ticks. The most prevalent tick species was Rhipicephalus microplus (number = 283, 34.3%), followed by Hyalomma anatolicum (223, 27.0%), Rhipicephalus turanicus (122, 14.8%), Haemaphysalis sulcata (104, 12.6%), Haemaphysalis montgomeryi (66, 8.0%), and Haemaphysalis bispinosa (25, 3.03%). A subset of 210 ticks was selected and screened for Rickettsia spp. using PCR-based amplification and subsequent sequencing of rickettsial gltA and ompB fragments. The overall occurrence rate of R. hoogstraalii was 4.3% (number = 9/210). The DNA of Rickettsia was detected in Hy. anatolicum (3/35, 8.5%) and Ha. sulcata (6/49, 12.2%). However, no rickettsial DNA was detected in Rh. microplus (35), Rh. turanicus (35), Ha. montgomeryi (42), and Ha. bispinosa (14). The gltA and ompB fragments showed 99-100% identity with R. hoogstraalii and clustered phylogenetically with the corresponding species from Pakistan, Italy, Georgia, and China. R. hoogstraalii was genetically characterized for the first time in Pakistan and Hy. anatolicum globally. Further studies should be encouraged to determine the role of ticks in the maintenance and transmission of R. hoogstraalii in different hosts.

Quantifying the direct and indirect effects of sika deer (Cervus nippon) on the prevalence of infection with Rickettsia in questing Haemaphysalis megaspinosa: A field experimental study

Sika deer (Cervus nippon) are important hosts for all life stages of Haemaphysalis megaspinosa, a suspected Rickettsia vector. Because some Rickettsia are unlikely to be amplified by deer in Japan, the presence of deer may decrease the prevalence of Rickettsia infection in questing H. megaspinosa. As sika deer decrease vegetation cover and height and thereby indirectly cause changes in the abundance of other hosts, including reservoirs of Rickettsia, the prevalence of Rickettsia infection in questing ticks can also change. We investigated these possible effects of deer on the prevalence of infection with Rickettsia in questing ticks in a field experiment in which deer density was manipulated at three fenced sites: a deer enclosure (Deer-enclosed site); a deer enclosure where deer had been present until 2015 and only indirect effects remained (Indirect effect site); and a deer exclosure in place since 2004 (Deer-exclosed site). Density of questing nymphs and the prevalence of infection with Rickettsia sp. 1 in questing nymphs at each site were compared from 2018 to 2020. The nymph density at the Deer-exclosed site did not significantly differ from that at the Indirect effect site, suggesting that the deer herbivory did not affect the nymph density by reducing vegetation and increasing the abundance of other host mammals. However, the prevalence of infection with Rickettsia sp. 1 in questing nymphs was higher at the Deer-exclosed site than at the Deer-enclosed site, possibly because ticks utilized alternative hosts when deer were absent. The difference in Rickettsia sp. 1 prevalence between the Indirect effect and Deer-exclosed sites was comparable to that between the Indirect effect and Deer-enclosed sites, indicating that the indirect effects of deer were as strong as the direct effects. Examining the indirect effects of ecosystem engineers in the study of tick-borne diseases may be more important than previously recognized.

Tick Species Diversity and Molecular Identification of Spotted Fever Group Rickettsiae Collected from Migratory Birds Arriving from Africa

The role of migratory birds in the spread of ticks and tick-borne pathogens along their routes from Africa to Europe is increasingly emerging. Wild birds can host several tick species, often infected by bacteria responsible for zoonoses. The aim of the study is to assess the possible introduction of exotic ticks carried by migratory birds into Italy from Africa and to detect the presence of Rickettsia species and Coxiella burnetii they may harbor. During a two-year survey, we collected ticks from migratory birds captured during their short stop-over on Ventotene Island. Specimens were first identified by morphology or sequencing molecular targets when needed, and then tested by real-time PCR for the presence of selected pathogens. A total of 91% of the collection consisted of sub-Saharan ticks, more than 50% of which were infected by Rickettsia species belonging to the spotted fever group, mainly represented by R. aeschlimannii. In contrast, the suspected C. burnetii detected in two soft ticks were confirmed as Coxiella-like endosymbionts and not the pathogen. Although there are still gaps in the knowledge of this dispersal process, our findings confirm the role of migratory birds in the spread of ticks and tick-borne pathogens, suggesting the need for a continuous surveillance to monitor the potential emergence of new diseases in Europe.

Summer collection of multiple southern species of ticks in a remote northern island in Japan and literature review of the distribution and avian hosts of ticks

Expansion of ticks and tick-borne diseases is of increasing concern worldwide. To decrease the risk of ticks and tick-borne diseases to public health, understanding the mechanisms of their current distribution and future expansion is needed. Although tick distribution has been studied globally on continents and large islands that are inhabited by large mammals, less attention has been paid to remote islands. However, small islands are often important stopover sites for migratory birds that may contribute to long-distance dispersal of ticks. Therefore, islands would be a suitable system to rule out potential effects of mammals and to evaluate the contribution of birds to the expansion of ticks and tick-borne diseases. We collected questing ticks by dragging cloths over vegetation on Tobishima Island, northern Japan, in summer 2021, and conducted a literature search of the distribution and avian hosts of hard tick. We found several southern species of ticks (Haemaphysalis hystricis, H. formosensis, H. cornigera, Amblyomma testudinarium, and Dermacentor bellulus) on the island. These species have rarely or never been reported from the mainland of Japan at similar latitudes or higher, where large mammals are found. They are known vectors of tick-borne diseases, such as severe fever with thrombocytopenia syndrome. The present study suggests that migratory birds may contribute to the expansion of ticks and tick-borne diseases, and a remote island may function as a front line and/or a hub for their expansion. Evaluating tick fauna on remote islands used by migratory birds might be useful to monitor the expansion.

Molecular analysis of Rickettsia spp. and related tick-borne pathogens detected in dogs in Korea

Ticks are widespread in nature and serve as primary vectors for several tick-borne pathogens (TBPs). Ticks and TBPs cause considerable harm to humans and animals and have emerged as a major global public health concern. Domestic dogs are the major reservoirs of zoonotic agents owing to their constant interaction with humans. This study aimed to assess the prevalence and risk factors of canine TBPs, such as Rickettsiales, Coxiella burnetii, hepatozoa, and Borrelia spp., using molecular analyses. A total of 906 dogs were examined and 4 TBPs were identified: Anaplasma phagocytophilum (5; 0.6%), Hepatozoon canis (9; 1.0%), Candidatus Rickettsia longicornii (2; 0.2%), and Rickettsia tamurae (1; 0.1%). Ehrlichia spp., C. burnetii, and Borrelia spp. were not detected. To the best of our knowledge, this is the first study to perform a phylogenetic analysis of Candidatus R. longicornii and R. tamurae in dogs. These findings can help determine the potential public health risks by enhancing our understanding of the geographical and vector distributions of TBPs in Korea.

Detection of Rickettsia tamurae-like and other spotted fever group rickettsiae in ticks (Acari: Ixodidae) associated with wild birds in the Western Amazon, Brazil

Ticks are vectors for several pathogens, including bacteria belonging to the Rickettsia genus, such as Rickettsia rickettsii and Rickettsia parkeri, the causative agents of spotted fever. The aim of the present study was to investigate the tick species richness and rickettsial agents associated with wild birds captured in the Humaita Forest Reserve, Acre, in the Western Amazon region. Wild birds were captured with ornithological nets for visual inspection with the purpose of collecting ticks, which were identified through morphological analyses and molecular tests for several genes (12S rDNA, 16S rDNA, gltA, ompA, and sca4). A total of 607 wild birds were captured, 12% of which were parasitized by 268 ticks of the Amblyomma genus, with new host-parasite associations reported for Amblyomma calcaratum, Amblyomma geayi, Amblyomma longirostre, Amblyomma naponense, Amblyomma nodosum, and Amblyomma varium. Of the total ticks collected, 113 were tested for the presence of rickettsial DNA fragments, with 19 testing positive for R. parkeri in A. geayi, Rickettsia tamurae-like in Amblyomma sp., and Rickettsia amblyommatis in A. geayi, A. longirostre, and Amblyomma sp. We detected R. tamurae-like in Amblyomma larvae for the first time in the Western Brazilian Amazon biome, and registered spotted fever group rickettsiae, although the relevance of the detected species in a public health context should be further explored in South America, as well as new host-parasite interactions in this underexplored region.

Increasing Risk of Tick-Borne Disease through Growth Stages in Ticks

Rickettsia and Coxiella spp. are pathogens transmitted by ticks to humans. However, the developmental stage of the tick carrying the greatest risk of infection is unknown. Detection of pathogen-specific genes proves that ticks carrying Rickettsia or Coxiella spp. constitute a reservoir of infection. However, conventional PCR methods are unable to quantitate the pathogens within ticks. In the present study, we collected ticks in the endemic area of Japanese spotted fever, caused by Rickettsia japonica, and determined the rate of tick-borne pathogens carried by the ticks. As a method of evaluation, next-generation sequencing was used to estimate the proportion of pathogens in 10 adult and 10 larval ticks. Ticks were identified Haemaphysalis longicornis (H.L) from the results of the sequencing of PCR products amplified using tick identification-specific primers. The gene detection rates were 10/10 for Rickettsia sp. and 10/10 for Coxiella sp. among the adult ticks. For the larval ticks, the ratios were 7/10 and 5/10 for Rickettsia sp. and Coxiella sp., respectively. The largest proportion of Coxiella sp.-specific DNA reached 96% in one adult tick. The proportion of Rickettsia sp. genes ranged from 1.76% to 41.81% (mean, 15.56%) in the adult ticks. The proportions of Coxiella and Rickettsia spp. genes in the larvae ranged from 0% to 27.4% (mean 5.86%) and from 0% to 14.6% (mean 3.38%), respectively. When the percentage of Rickettsia sp., out of all pathogens detected via next-generation sequencing, was analyzed between the adult and larval stages of the ticks, a significant difference was observed at p = 0.0254. For Coxiella sp., a highly significant difference (p < 0.0001) was found between the adult and larval stages of the ticks. In conclusion, the detection rates and proportions of Rickettsia and Coxiella spp. genes were highest in adult H.L ticks. The risk of contracting tick-borne infections may increase with bites from adult ticks, especially those harboring Coxiella sp.

Phylogenetic Position of Haemaphysalis kashmirensis and Haemaphysalis cornupunctata, with Notes on Rickettsia spp

Despite high diversity in the Oriental region, ticks of the genus Haemaphysalis have been neglected regarding their genetic data and vector potential. This study aimed to genetically characterize three species of the genus Haemaphysalis: Haemaphysalis cornupunctata, Haemaphysalis kashmirensis, and Haemaphysalis montgomeryi infesting goats and sheep, and Rickettsia spp. associated with these tick species in the Hindu Kush Himalayan range of Pakistan. Altogether, 834 ticks were collected by examining 120 hosts including goats (64/120, 53.3%) and sheep (56/120, 46.6%), in which 86 (71.6%) hosts were found to be tick-infested. The morphologically identified ticks were subjected to DNA extraction and PCR for the amplification of partial 16S rDNA and cox fragments. Rickettsia spp. associated with the collected ticks were detected through the amplification of gltA, ompA and ompB partial fragments. The 16S rDNA of H. cornupunctata and H. montgomeryi showed a maximum identity of 100% with the sequences of the same species, whereas the 16S rDNA of H. kashmirensis showed the highest identity of 93-95% with Haemaphysalis sulcata. The cox sequence of H. montgomeryi displayed 100% identity with the same species. In comparison, the cox sequences of H. cornupunctata and H. kashmirensis showed maximum identities of 87.65-89.22% with Haemaphysalis punctata and 89.34% with H. sulcata, respectively. The gltA sequence of Rickettsia sp. from H. kashmirensis showed the highest identity of 97.89% with Rickettsia conorii subsp. raoultii, while the ompA and ompB fragments from the same DNA samples revealed 100% and 98.16% identity with Rickettsia sp. and "Candidatus Rickettsia longicornii", respectively. Another gltA sequence amplified from H. montgomeryi ticks showed 100% identity with Rickettsia hoogstraalii, while the attempts to amplify ompA and ompB for R. hoogstraalii were unsuccessful. In the phylogenetic tree, the 16S rDNA of H. cornupunctata clustered with the corresponding species while its cox clustered with H. punctata. Both 16S rDNA and cox sequences of H. kashmirensis clustered with H. sulcata. The gltA sequence of Rickettsia sp. was clustered individually in the spotted fever (SF) group of Rickettsia, while the gltA sequence of R. hoogstraalii was clustered with the same species in the transition group of Rickettsia. In the SF group, the rickettsial ompA and ompB sequence clustered with undetermined Rickettsia sp. and "Candidatus Rickettsia longicornii", respectively. This is the earliest study regarding the genetic characterization of H. kashmirensis. This study indicated that ticks belong to the genus Haemaphysalis have the potential of harboring and/or transmitting Rickettsia spp. in the region.

Comparative mitogenomics elucidates the population genetic structure of Amblyomma testudinarium in Japan and a closely related Amblyomma species in Myanmar

Ticks are the second most important vector capable of transmitting diseases affecting the health of both humans and animals. Amblyomma testudinarium Koch 1844 (Acari: Ixodidae), is a hard tick species having a wide geographic distribution in Asia. In this study, we analyzed the composition of A. testudinarium whole mitogenomes from various geographical regions in Japan and investigated the population structure, demographic patterns, and phylogeographic relationship with other ixodid species. In addition, we characterized a potentially novel tick species closely related to A. testudinarium from Myanmar. Phylogeographic inference and evolutionary dynamics based on the 15 mitochondrial coding genes supported that A. testudinarium population in Japan is resolved into a star‐like haplogroup and suggested a distinct population structure of A. testudinarium from Amami island in Kyushu region. Correlation analysis using Mantel test statistics showed that no significant correlation was observed between the genetic and geographic distances calculated between the A. testudinarium population from different localities in Japan. Finally, demographic analyses, including mismatch analysis and Tajima’s D test, suggested a possibility of recent population expansion occurred within Japanese haplogroup after a bottleneck event. Although A. testudinarium has been considered widespread and common in East and Southeast Asia, the current study suggested that potentially several cryptic Amblyomma spp. closely related to A. testudinarium are present in Asia.

Molecular Survey of Vector-Borne Pathogens in Ticks, Sheep Keds, and Domestic Animals from Ngawa, Southwest China

Vector-borne pathogens are mainly transmitted by blood-feeding arthropods such as ticks, mosquitoes, fleas, lice, mites, etc. They pose a significant threat to animal and human health due to their worldwide distribution. Although much work has been performed on these pathogens, some neglected areas and undiscovered pathogens are still to be further researched. In this study, ticks (Haemaphysalis qinghaiensis), sheep keds (Melophagus ovinus), and blood samples from yaks and goats were collected in Ngawa Tibetan and Qiang Autonomous Prefecture located on the eastern edge of the Qinghai–Tibet Plateau, Southwest China. Several vector-borne bacterial pathogens were screened and studied. Anaplasma bovis strains representing novel genotypes were detected in ticks (8.83%, 37/419), yak blood samples (45.71%, 64/140), and goat blood samples (58.93%, 33/56). Two spotted fever group (SFG) Rickettsiae, Candidatus Rickettsia jingxinensis, and a novel Rickettsia species named Candidatus Rickettsia hongyuanensis were identified in ticks. Another Rickettsia species closely related to the Rickettsia endosymbiont of Polydesmus complanatus was also detected in ticks. Furthermore, a Coxiella species was detected in ticks (3.34%, 14/419), keds (1.89%, 2/106), and yak blood (0.71%, 1/140). Interestingly, another Coxiella species and a Coxiella-like bacterium were detected in a tick and a goat blood sample, respectively. These results indicate the remarkable diversity of vector-borne pathogens circulating in this area. Further investigations on their pathogenicity to humans and domestic animals are still needed.

Phylogenetic Studies of Coxiella-Like Bacteria and Spotted Fever Group Rickettsiae in Ticks Collected From Vegetation in Chaiyaphum Province, Thailand

Ticks can transmit a wide variety of pathogens, including bacteria. Here, we report the detection of tick-associated bacteria in Chaiyaphum Province, northeastern Thailand. There have been few reports of tick-borne bacterial pathogens in the study areas, which are evergreen forests dominated by plateaus at elevations of approximately 1,000 m. In total, 94 ticks were collected from vegetation. They were screened for the presence of Coxiella, Francisella, Rickettsia, and Borrelia bacteria using PCR assays. In this study, we found ticks from two genera, Haemaphysalis and Amblyomma, that were positive for Coxiella-like bacteria (CLB) and Rickettsia. Francisella and Borrelia spp. were not detected in these two tick genera. The results revealed the evolutionary relationships of CLB in Amblyomma testudinarium, Haemaphysalis lagrangei, and Haemaphysalis obesa ticks using the 16S rRNA and rpoB markers, which clustered together with known isolates of ticks from the same genera. In contrast, the groEL marker showed different results. On the basis of the groEL phylogenetic analysis and BLAST results, three groups of CLB were found: (1) CLB from A. testudinarium grouped as a sister clade to CLB from Ixodes ricinus; (2) CLB from Haemaphysalis lagrangei was distantly related to CLB from Haemaphysalis wellingtoni; and (3) CLB from A. testudinarium grouped as sister clade to CLB from Amblyomma from French Guiana and Brazil. For Rickettsia studies, phylogenetic trees of the gltA, ompB, and sca4 genes revealed two groups of Spotted Fever Group (SFG) Rickettsiae: (1) SFG Rickettsiae that formed a sister clade with Rickettsia tamurae AT-1 (belong to the Rickettsia helvetica subgroup) in A. testudinarium and (2) SFG Rickettsiae that formed a distantly related group to Rickettsia rhipicephali 3-7-female6-CWPP (belong to the Rickettsia massiliae subgroup) in A. testudinarium. This study expanded our knowledge of the diversity of tick-borne Coxiella and Rickettsia bacteria. The pathogenic roles of these bacteria also need to be investigated further.

Molecular detection of Borrelia burgdorferi (sensu lato) and Rickettsia spp. in hard ticks distributed in Tokachi District, eastern Hokkaido, Japan

Ticks transmit various pathogens, including parasites, bacteria and viruses to humans and animals. To investigate the ticks and the potentially zoonotic pathogens that they may carry, questing ticks were collected in 2017 from 7 sites in Tokachi District, eastern Hokkaido, Japan. A total of 1563 ticks including adults (male and female), nymphs and larvae were collected. Four species of ticks were identified: Ixodes ovatus, Ixodes persulcatus, Haemaphysalis japonica and Haemaphysalis megaspinosa. Of the 1563 ticks, 1155 were used for DNA extraction. In total, 527 individual tick DNA samples prepared from adults (n = 484), nymphs (n = 41) and larvae (n = 2); and 67 pooled tick DNA samples prepared from larval stages (n = 628) were examined using PCR methods and sequencing to detect Borrelia burgdorferi (sensu lato) and Rickettsia spp. The phylogenetic analysis of Borrelia spp. flaB gene sequences showed the presence of the human pathogenic B. burgdorferi (s.l.) species (Borrelia garinii, Borrelia bavariensis and Borrelia afzelii) in I. persulcatus, whereas the non-pathogenic species Borrelia japonica was found only in I. ovatus. In I. persulcatus, B. garinii and/or its closely related species B. bavariensis was detected in both adults and nymphs at a prevalence of 21.9% whereas B. afzelii was found only in adults (1.8%). The prevalence of B. japonica in adult I. ovatus was 21.8%. Rickettsia species were identified through phylogenetic analysis based on gltA, 16S rRNA, ompB and sca4 genes. Four genotypes were detected in the samples which were classified into three species. The prevalence of human pathogenic Rickettsia helvetica was 26.0% in I. persulcatus adults and nymphs, 55.6% in I. persulcatus larval pools, and 1.7% in H. megaspinosa larval pools. The prevalence of “Candidatus R. tarasevichiae” was 15.4% in I. persulcatus adults and nymphs and 33.3% in I. persulcatus larval pools. The prevalence of “Candidatus R. principis” in H. megaspinosa adults and nymphs was 11.1% whereas it was detected in 3.4% of the H. megaspinosa larval pools. These results indicate that most of the risks of Lyme borreliosis and spotted fever group rickettsiosis infection in eastern Hokkaido, Japan, are restricted to I. persulcatus.

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Four species of ticks were collected in Tokachi District, eastern Hokkaido, Japan.

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Tick DNA samples were subjected to PCR to detect Borrelia spp. and Rickettsia spp.

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Borrelia garinii/Borrelia bavariensis and Borrelia afzelii were detected in Ixodes persulcatus.

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Rickettsia helvetica and “Candidatus R. tarasevichiae” were detected in I. persulcatus.

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First molecular detection of “Candidatus R. principis” in larvae of Haemaphysalis megaspinosa.

Serological and molecular survey of tick-borne zoonotic pathogens including severe fever with thrombocytopenia syndrome virus in wild boars in Miyazaki Prefecture, Japan

Background

Miyazaki Prefecture is one of the hotspots of severe fever with thrombocytopenia syndrome (SFTS) cases and related deaths in Japan since 2013 and other pathogens of tick‐borne diseases (TBDs). Japanese spotted fever and scrub typhus are also endemic in this region.

Objectives

A total of 105 wild boars, hunted in 2009, were serologically examined as sentinels for TBDs to indirectly demonstrate the potential hazard of ticks transmitting pathogens to humans in the studied area.

Methods

The collected blood and spleens of the wild boars underwent serological and molecular tests for SFTSV, Rickettsia japonica (Rj) [antibody to spotted fever group rickettsiae (SFGR) were tested by using species‐common antigen], and Orientia tsutsugamushi (Ot).

Results

Seroprevalences of SFTSV, SFGR, and Ot were 41.9%, 29.5%, and 33.3%, respectively. SFTS viral RNA was identified in 7.6% of the sera, whereas DNA of Rj or Ot was not detected in any sample. In total, 43.8% of the boars possessed an infection history with SFTSV (viral gene and/or antibody). Of these, 23.8% had multiple‐infection history with SFGR and/or Ot.

Conclusions

The high prevalence of SFTSV in wild boars might reflect the high risk of exposure to the virus in the studied areas. In addition, SFTSV infection was significantly correlated with Ot infection, and so were SFGR infection and Ot infection, indicating that these pathogens have common factors for infection or transmission. These data caution of the higher risk of SFTSV infection in areas with reported cases of other TBDs.

Identification of Rickettsia spp., Anaplasma spp., and an Ehrlichia canis-like agent in Rhipicephalus microplus from Southwest and South-Central China

Rhipicephalus microplus is considered to be the most important tick infesting cattle, buffalo, horse, goats as well as other animals. They transmit diseases between domestic animals and act as vectors of a variety of zoonotic pathogens. Although pathogens harbored by R. microplus have been extensively studied, the Rickettsiales pathogens vectored by R. microplus in some areas of China remained largely unexplored. From August to October 2020, a total of 291 R. microplus ticks were collected from goats and cattle in three Southern China provinces, Guangxi (n = 138), Sichuan (n = 120) and Hubei (n = 33) provinces. Phylogenetic analysis based on COI gene sequences shows that these ticks are divided into three distinct clades, indicating the remarkable genetic diversity of R. microplus ticks in China. These samples were subsequently screened for the presence of Rickettsia, Anaplasma and Ehrlichia using conventional PCR and sequencing. Subsequently, five bacterial species were identified. Out of the 120 tick DNA samples from Sichuan province, 35.83% (43/120) were positive for Rickettsia sp. belonging to spotted fever group (SFG), 12.50% (15/120) were positive for Anaplasma marginale and 0.83% (1/120) was identified as A. platys. From the 138 DNA samples from Guangxi province, an Ehrlichia canis-like and Rickettsia sp. were detected, with a positive rate of 11.59% (16/138) and 2.17% (3/138), respectively. A. capra DNA was detected in 4 out of 33 (12.12%) samples from Hubei province. Notably, the 16S, gltA and groEL sequences of the E. canis-like are closely related to the E. canis strain previously identified from China, and form a distinct cluster in the phylogenetic trees. Collectively, our results expand the knowledge on tick-borne Rickettsiales pathogens in China. Because the state of engorgement of ticks was not recorded, it is not clear at this stage whether these pathogens are infecting the ticks or are simply present in the blood meal. Given the public health significance of SFG Rickettsia, A. capra, A. platys and E. canis, a thorough investigation of the diversity and presence of pathogens in R. microplus in areas with tick-associated diseases are needed.

Molecular Evidence for Flea-Borne Rickettsiosis in Febrile Patients from Madagascar

Rickettsiae may cause febrile infections in humans in tropical and subtropical regions. From Madagascar, no molecular data on the role of rickettsioses in febrile patients are available. Blood samples from patients presenting with fever in the area of the capital Antananarivo were screened for the presence of rickettsial DNA. EDTA (ethylenediaminetetraacetic acid) blood from 1020 patients presenting with pyrexia > 38.5 °C was analyzed by gltA-specific qPCR. Positive samples were confirmed by ompB-specific qPCR. From confirmed samples, the gltA amplicons were sequenced and subjected to phylogenetic analysis. From five gltA-reactive samples, two were confirmed by ompB-specific qPCR. The gltA sequence in the sample taken from a 38-year-old female showed 100% homology with R. typhi. The other sample taken from a 1.5-year-old infant was 100% homologous to R. felis. Tick-borne rickettsiae were not identified. The overall rate of febrile patients with molecular evidence for a rickettsial infection from the Madagascan study site was 0.2% (2/1020 patients). Flea-borne rickettsiosis is a rare but neglected cause of infection in Madagascar. Accurate diagnosis may prompt adequate antimicrobial treatment.

Characterization of a novel transitional group Rickettsia species (Rickettsia tillamookensis sp. nov.) from the western black-legged tick, Ixodes pacificus

A previously unrecognized Rickettsia species was isolated in 1976 from a pool of Ixodes pacificus ticks collected in 1967 from Tillamook County, Oregon, USA. The isolate produced low fever and mild scrotal oedema following intraperitoneal injection into male guinea pigs (Cavia porcellus). Subsequent serotyping characterized this isolate as distinct from recognized typhus and spotted fever group Rickettsia species; nonetheless, the isolate remained unevaluated by molecular techniques and was not identified to species level for the subsequent 30 years. Ixodes pacificus is the most frequently identified human-biting tick in the western United States, and as such, formal identification and characterization of this potentially pathogenic Rickettsia species is warranted. Whole-genome sequencing of the Tillamook isolate revealed a genome 1.43 Mbp in size with 32.4 mol% G+C content. Maximum-likelihood phylogeny of core proteins places it in the transitional group of Rickettsia basal to both Rickettsia felis and Rickettsia asembonensis. It is distinct from existing named species, with maximum average nucleotide identity of 95.1% to R. asembonensis and maximum digital DNA-DNA hybridization score similarity to R. felis at 80.1%. The closest similarity at the 16S rRNA gene (97.9%) and sca4 (97.5%/97.6% respectively) is to Candidatus 'Rickettsia senegalensis' and Rickettsia sp. cf9, both isolated from cat fleas (Ctenocephalides felis). We characterized growth at various temperatures and in multiple cell lines. The Tillamook isolate grows aerobically in Vero E6, RF/6A and DH82 cells, and growth is rapid at 28 °C and 32 °C. Using accepted genomic criteria, we propose the name Rickettsia tillamookensis sp. nov., with the type strain Tillamook 23. Strain Tillamook 23 is available from the Centers for Disease Control and Prevention Rickettsial Isolate Reference Collection (WDCM 1093), Atlanta, GA, USA (CRIRC accession number RTI001^T) and the Collection de Souches de l'Unité des Rickettsies (WDCM 875), Marseille, France (CSUR accession number R5043). Using accepted genomic criteria, we propose the name Rickettsia tillamookensis sp. nov., with the type strain Tillamook 23 (=CRIRC RTI001=R5043).

Applications of Blocker Nucleic Acids and Non-Metazoan PCR Improves the Discovery of the Eukaryotic Microbiome in Ticks

Ticks serve as important vectors of a variety of pathogens. Recently, the viral and prokaryotic microbiomes in ticks have been explored using next-generation sequencing to understand the physiology of ticks and their interactions with pathogens. However, analyses of eukaryotic communities in ticks are limited, owing to the lack of suitable methods. In this study, we developed new methods to selectively amplify microeukaryote genes in tick-derived DNA by blocking the amplification of the 18S rRNA gene of ticks using artificial nucleic acids: peptide nucleic acids (PNAs) and locked nucleic acids (LNAs). In addition, another PCR using non-metazoan primers, referred to as UNonMet-PCR, was performed for comparison. We performed each PCR using tick-derived DNA and sequenced the amplicons using the Illumina MiSeq platform. Almost all sequences obtained by conventional PCR were derived from ticks, whereas the proportion of microeukaryotic reads and alpha diversity increased upon using the newly developed method. Additionally, the PNA- or LNA-based methods were suitable for paneukaryotic analyses, whereas the UNonMet-PCR method was particularly sensitive to fungi. The newly described methods enable analyses of the eukaryotic microbiome in ticks. We expect the application of these methods to improve our understanding of the tick microbiome.

Screening of tick-borne pathogens in argasid ticks in Zambia: Expansion of the geographic distribution of Rickettsia lusitaniae and Rickettsia hoogstraalii and detection of putative novel Anaplasma species

Ticks (Ixodidae and Argasidae) are important arthropod vectors of various pathogens that cause human and animal infectious diseases. Many previously published studies on tick-borne pathogens focused on those transmitted by ixodid ticks. Although there are increasing reports of viral pathogens associated with argasid ticks, information on bacterial pathogens they transmit is scarce. The aim of this molecular study was to detect and characterize Rickettsia and Anaplasmataceae in three different argasid tick species, Ornithodoros faini, Ornithodoros moubata, and Argas walkerae collected in Zambia. Rickettsia hoogstraalii and Rickettsia lusitaniae were detected in 77 % (77/100) of Ar. walkerae and 10 % (5/50) of O. faini, respectively. All O. moubata pool samples (n = 124) were negative for rickettsial infections. Anaplasmataceae were detected in 63 % (63/100) of Ar. walkerae and in 82.2 % (102/124) of O. moubata pools, but not in O. faini. Phylogenetic analysis based on the concatenated sequences of 16S rRNA and groEL genes revealed that Anaplasma spp. detected in the present study were distinct from previously validated Anaplasma species, indicating that the current knowledge on the diversity and vector range of Anaplasma spp. is incomplete. Our findings highlight new geographical records of R. lusitaniae and R. hoogstraalii and confirm that the wide geographic distribution of these species includes the African continent. The data presented here increase our knowledge on argasid tick-borne bacteria and contribute toward understanding their epidemiology.

Molecular detection of Rickettsia raoultii, Rickettsia tamurae, and associated pathogens from ticks parasitizing water deer (Hydropotes inermis argyropus) in South Korea

Most defined Rickettsiales, which can be transmitted by ticks, are known to be important zoonotic pathogens. Some of these pathogens can cause severe diseases in humans, including anaplasmosis, rickettsioses, and ehrlichiosis. Previous studies in South Korea have investigated tick-borne pathogens (TBPs) residing in ticks found on grassy vegetation and animals. However, there is limited phylogenetic information on TBPs in ticks parasitizing Korean water deer (KWD; Hydropotes inermis argyropus). This study evaluated the prevalence, risk factors (regions, tick stages, and tick species), and coinfections of TBPs in ticks parasitizing KWD. Were collected a total of 283 hard ticks, including Haemaphysalis longicornis, Haemaphysalis flava, and Ixodes nipponensis from KWD in South Korea from 2013 to 2017. In 173 tested tick pools, genes for seven TBPs, namely Rickettsia raoultii (20 %), Rickettsia tamurae (1 %), Candidatus Rickettsia longicornii (31 %), Ehrlichia canis (3 %), Anaplasma capra (3 %), Anaplasma bovis (2 %), and Anaplasma sp. (1 %), were detected. The unidentified Anaplasma sp. isolates revealed a 98.4 %-99.3 % sequence identity with Anaplasma sp. in GenBank sequences obtained from ticks. To the best of our knowledge, this is the first study to report the presence of the emerging human pathogen R. tamurae in South Korea. These results should increase awareness about the need for continued development of epidemiological control measures, and medical and veterinary communities must be informed of their high infection potential and clinical complexity in humans.

Spiroplasma Infection among Ixodid Ticks Exhibits Species Dependence and Suggests a Vertical Pattern of Transmission

Members of the genus Spiroplasma are Gram-positive bacteria without cell walls. Some Spiroplasma species can cause disease in arthropods such as bees, whereas others provide their host with resistance to pathogens. Ticks also harbour Spiroplasma, but their role has not been elucidated yet. Here, the infection status and genetic diversity of Spiroplasma in ticks were investigated using samples collected from different geographic regions in Japan. A total of 712 ticks were tested for Spiroplasma infection by PCR targeting 16S rDNA, and Spiroplasma species were genetically characterized based on 16S rDNA, ITS, dnaA, and rpoB gene sequences. A total of 109 samples originating from eight tick species were positive for Spiroplasma infection, with infection rates ranging from 0% to 84% depending on the species. A linear mixed model indicated that tick species was the primary factor associated with Spiroplasma infection. Moreover, certain Spiroplasma alleles that are highly adapted to specific tick species may explain the high infection rates in Ixodes ovatus and Haemaphysalis kitaokai. A comparison of the alleles obtained suggests that horizontal transmission between tick species may not be a frequent event. These findings provide clues to understand the transmission cycle of Spiroplasma species in wild tick populations and their roles in host ticks.

Rickettsia spp. and Ehrlichia spp. in Amblyomma ticks parasitizing wild amphibious sea kraits and yellow-margined box turtles in Okinawa, Japan

Recently, several tick-borne pathogens were detected in reptile-associated ticks. However, studies on the microorganisms in reptile-associated ticks in Japan are limited. This molecular survey thus aimed to identify and characterize tick-borne pathogens (Rickettsiaceae and Anaplasmataceae) in reptile-associated ticks in Japan. In total, 77 Amblyomma nitidum and 104 Amblyomma geoemydae were collected from wild amphibious sea kraits (Laticauda semifasciata, Laticauda colubrina, and Laticauda laticaudata) and from yellow-margined box turtles (Cuora flavomarginata evelynae), respectively. Conventional polymerase chain reaction was performed using the DNA extracted from the ticks to detect the selected pathogens. Sequencing analysis of four Rickettsia genes (gltA, ompA, ompB, and sca4) led to the identification of a putative novel Rickettsia sp. and Rickettsia aeschlimannii-like rickettsia in A. nitidum and A. geoemydae, respectively. Sequencing analysis of gltA and groEL of Anaplasmataceae revealed that the Ehrlichia spp. in these ticks were novel and related to Candidatus Ehrlichia occidentalis. This is the first study on the microorganisms in A. nitidium and the first record of Rickettsia and Ehrlichia in A. geoemydae. Further studies are required to understand their pathogenicity to humans and animals and their life cycle in the wild.

Genetic diversity of Rickettsia africae isolates from Amblyomma hebraeum and blood from cattle in the Eastern Cape province of South Africa

Rickettsia africae is a re-emerging tick-borne pathogen causing African tick bite fever (ATBF) in humans. Amblyomma variegatum is the principal vector in most sub-Sahara African countries, whereas in South Africa it is A. hebraeum. Reports of high genetic heterogeneity among R. africae isolates in southern Africa have prompted the need for molecular investigations of isolates form South Africa. Therefore, this study aimed to determine the prevalence and genetic diversity of R. africae in A. hebraeum collected from cattle, grazing pasture, as well as from blood of cattle in the Eastern Cape Province of South Africa. Amblyomma hebraeum and blood from cattle were screened by PCR and the gltA, ompA, ompB, sca4, and 17kDa genes were sequenced for R. africae from samples collected from Caquba in Port St. Johns along the coastal region in the Eastern Cape province of South Africa. The overall proportion of adult A. hebraeum that were positive for the gltA and ompA genes was 0.63 (108/180). The overall proportion of nymphs positive for the gltA and ompA genes was 0.62 (23/37) and 0.22 (20/90) from cattle blood. A positive R. africae infection was inferred by analysis of 26 sequences of the ompA, gltA, ompB, 17kDa and sca4 genes. Neighbour-joining and Maximum Likelihood analysis revealed that the study isolates were closely related to R. africae isolates from South Africa deposited in GenBank, forming a clade that was separate from north, east and west African strains. This study provides new information on the epidemiology and phylogeny of R. africae isolated from A. hebraeum ticks in the Eastern Cape province of South Africa. The heterogeneity observed between R. africae isolates from South Africa deposited in GenBank and R. africae isolates from Africa retrieved from Genbank highlight the importance of differentiation and tracking of the genetic movement among R. africae isolates in southern Africa for the better characterisation of ATBF cases, especially in rural communities and travellers visiting the region.

Expansion of Tick-Borne Rickettsioses in the World

Tick-borne rickettsioses are caused by obligate intracellular bacteria belonging to the spotted fever group of the genus Rickettsia. These infections are among the oldest known diseases transmitted by vectors. In the last three decades there has been a rapid increase in the recognition of this disease complex. This unusual expansion of information was mainly caused by the development of molecular diagnostic techniques that have facilitated the identification of new and previously recognized rickettsiae. A lot of currently known bacteria of the genus Rickettsia have been considered nonpathogenic for years, and moreover, many new species have been identified with unknown pathogenicity. The genus Rickettsia is distributed all over the world. Many Rickettsia species are present on several continents. The geographical distribution of rickettsiae is related to their vectors. New cases of rickettsioses and new locations, where the presence of these bacteria is recognized, are still being identified. The variety and rapid evolution of the distribution and density of ticks and diseases which they transmit shows us the scale of the problem. This review article presents a comparison of the current understanding of the geographic distribution of pathogenic Rickettsia species to that of the beginning of the century.

Amblyomma testudinarium infestation on a brown bear (Ursus arctos yesoensis) captured in Hokkaido, a northern island of Japan

The tick Amblyomma testudinarium Koch, 1844 (Acari: Ixodidae) is known as a vector of several pathogens such as Rickettsia tamurae and severe fever with thrombocytopenia syndrome (SFTS) virus. This tick species is present in many Asian countries, including Japan, where its distribution is limited to the warm areas of Kanto region and the southwestern region. The present study reports the recovery of a partially engorged A. testudinarium from a wild brown bear captured in Shari town, Hokkaido. In addition to morphological identification, the specimen was genetically characterized by the complete mitochondrial genome sequencing. The results showed that the length of the obtained mitogenome is 14,835 bp that encodes 13 protein-coding, two ribosomal RNA (rRNA) (12S and 16S), and 22 transfer RNA genes with two non-coding control regions. The phylogenetic analysis indicated that our sample clustered with A. testudinarium from Nara, Japan, but separated from A. testudinarium from China. Although the introduction of the tick through livestock transportation cannot be ruled out, the detection of A. testudinarium in Hokkaido prefecture, which is separated from the main island where A. testudinarium is present in the south, may suggest the introduction by migratory birds. This study provides important insights on the distribution and host range of A. testudinarium. This will be useful for the future taxonomic analysis of ticks based on the complete mitogenome sequencing. To our knowledge, this is the northernmost detection point of the tropical tick A. testudinarium.

Associations between Japanese spotted fever (JSF) cases and wildlife distribution on the Boso Peninsula, Central Japan (2006-2017)

Populations of large mammals have been dramatically increasing in Japan, resulting in damage to agriculture, forestry, and ecosystems. However, their effects on tick-borne diseases have been poorly studied. Here, we focused on the relationship between Japanese spotted fever (JSF), a tick-borne disease caused by Rickettsia japonica, and populations of large mammals. To explore factors that affected the area in which JSF cases occur, we used generalized linear mixed models (GLMMs). We demonstrated that the expansion of the area of JSF occurrence can be predicted by deer density and geographical factors, which is likely due to differences in landscape structure. However, the associated models have limitations because of the lack of information about the distribution of vectors and reservoirs. To reduce the risk of humans contracting JSF, potential reservoirs should be confirmed.

Growth Characteristics of Rickettsia Species LON Strains Closely Related to Rickettsia japonica Isolated from Haemaphysalis longicornis Ticks in Mouse Derived L929 and Human-Derived THP-1 Host Cell Lines

Non-pathogenic Rickettsia species LON strains closely related to an agent of Japanese spotted fever (JSF), R. japonica, were isolated in Japan from Haemaphysalis longicornis ticks in 2001. However, the biological properties of LONs in mammalian host cells are poorly understood. In this study, microscopic analysis showed that LONs in a mouse-derived L929 host cell line were rod shaped with sizes of 0.3-0.5 × 0.5-2.0 μm. Molecular analysis revealed the existence of a LON-specific disrupted open reading frame in R. japonica-related group-specific DNA regions. Growth kinetics of LON-2 and LON-13 strains analyzed by a quantitative real-time PCR showed 100-fold or more increment of LONs cultured in L929 host cells at 30°C and slightly less increment at 33°C, and 25-fold increment in human-derived THP-1 host cells at 35°C on day 7 (168 h) post infection. The generation times of the two LON strains cultured in L929 and THP-1 were estimated to be 9.4-12.9 h and 9.6-10.9 h, respectively. To our knowledge, this is the first report on the biological characteristics of Rickettsia sp. LON strains in mammalian cells, which may provide significant information for the experimental approaches for other rickettsiae.

Detection of Tick-Borne Pathogens in Ticks from Dogs and Cats in the Yamagata Prefecture of Japan in 2018

Companion animals can become infected with tick-borne diseases (TBDs) becoming a reservoir for human transfer, thereby damaging human health. To evaluate whether companion animals are infested with ticks harboring human TBD pathogens, we detected TBD pathogens in ticks collected from dogs and cats brought to animal hospitals in the Yamagata prefecture of Japan. An investigation of 164 adult ticks collected from 88 dogs and 41 cats between March and July 2018 revealed that this region was dominated by three tick species, Ixodes ovatus (n = 95, 57.9%), Ixodes nipponensis (n = 37, 22.6%) and Haemaphysalis flava (n = 10, 6.1%). To evaluate their pathogenic potential, we went on to test each tick for spotted fever group rickettsiae, Lyme disease borreliae, relapsing fever borreliae, tick-borne encephalitis virus, and Huaiyangshan banyangvirus (formerly SFTS virus). Our results identified two I. ovatus ticks infected with Borrelia miyamotoi, which causes emerging relapsing fever; several I. nipponensis ticks infected with Rickettsia monacensis, which cause rickettsiosis; and several Ixodes persulcatus ticks infected with Rickettsia helvetica, which can also cause rickettsiosis. These results suggest that dogs and cats, and veterinary professionals and pet owners, in the Yamagata prefecture have some risk of exposure to several TBDs. This means that there should be continuous monitoring and reporting of TBDs, even those known to be uncommon in Japan, in both companion animals and humans to ensure the health and safety of both humans and animals in Japan.

Predictive variables for hemodialysis and death in Japanese spotted fever, and the association between distance from rivers and incidence

The number of patients with Japanese spotted fever (JSF) and its case fatality rate have been increasing in Japan and other East Asian countries. Better clinical and laboratory biomarkers are needed to avoid misdiagnosing JSF and to predict severe cases. In addition to determining these predictors, we aimed to examine the association between the incidence of JSF and the distance from rivers, in Hiroshima Prefecture, one of the most JSF prevalent areas in Japan. Patients diagnosed with JSF from 2009 to 2017 in two hospitals in Onomichi City in Hiroshima Prefecture were studied, and their clinical characteristics and laboratory data were collected retrospectively from medical charts. A random forest was used to identify predictors of severe JSF leading to hemodialysis or death. A multivariable negative binomial regression model was utilized to analyze the association between the cumulative incidence in each postal code area and the distance from the residential postal code area to the closest river. Out of 82 patients with JSF (mean age at diagnosis, 74.1 ± 10.6 years; 34 (41.5 %) men), 6 cases were regarded as severe (among them 5 hemodialysis patients and 3 deaths). Twenty-eight (34.1 %) patients were misdiagnosed at least once at the initial hospital visit. Laboratory examination showed 34.5 % had atypical lymphocytes, 73.8 % had no eosinophils, 75.6 % had an elevated aspartate aminotransferase (AST) level, and 69.5 % had hyponatremia. Among cases without urine leucocytes, 63.3 % had proteinuria and 63.3 % had hematuria. Low serum total protein was the strongest predictor of severe JSF, followed by high blood urea nitrogen (BUN) and low albumin. Geospatial analysis showed a significant negative association between the cumulative incidence of JSF cases and the distance from rivers in an adjusted model: the cumulative incidence decreased by 0.51 times (95 % CI: 0.30 to 0.86) for every kilometer of distance from the residential postal code area to the closest river. Some laboratory data may be useful in averting misdiagnosis of JSF and in predicting severe cases. Additional studies should be done in order to clarify the mechanism and association of the incidence of JSF with the distance from the nearest river.

Detection of tick-borne pathogens in Rhipicephalus sanguineus sensu lato and dogs from different districts of Portugal

Dogs are highly exposed to pathogens transmitted by ectoparasites. The Mediterranean climate of Southern Europe, together with the presence of stray and/or neglected pets in close proximity with humans, contribute for tick expansion and stand for increased risk to infections in humans due to the zoonotic potential of many of these agents. The aim of this study was to perform a molecular survey in dogs (suspected of tick-borne disease and/or infested with ticks), as well as in ticks collected from those animals, from 12 districts of Portugal to investigate the occurrence of Rickettsia spp. and other tick-borne pathogens (Babesia, Ehrlichia, Anaplasma and Hepatozoon). Additionally, a serological survey of spotted fever group Rickettsia in Portuguese dogs was performed using an in-house immunofluorescence assay (IFA). A total of 200 whole-blood samples and 221 Rhipicephalus sanguineus s. l. ticks were collected from dogs. A total of 14 (7 %) blood samples and 10 (4.5 %) ticks yielded presumptively positive 420-bp amplicons using the Rickettsia spp. partial ompB nested PCR. Screening of the ompB-positive samples using the gltA gene showed 8 positive ticks. All Rickettsia ompB and gltA sequences had the highest identity with R. massiliae. The Rickettsia-positive dogs were further tested for other tick-borne pathogens and were found to be infected with Babesia spp. (n = 5), but not with Ehrlichia, Anaplasma or Hepatozoon. Of the 149 dog serum specimens tested in the serological assay, 103 (69 %) were positive for IgG antibodies against spotted fever group Rickettsia. Antibodies were found in dogs from all the studied districts, in 55 (53 %) of the stray and in 48 (47 %) of the owned dogs. Our study detected and characterized for the first time R. massiliae in dogs from Portugal, broadening the geographical range of this canine pathogen and adding knowledge to the impact of this disease in dogs.

Rickettsia africae an Agent of African Tick Bite Fever in Ticks Collected from Domestic Animals in Eastern Cape, South Africa

Background: Ticks transmit a plethora of pathogens of zoonotic implications. Their distribution, diversity and the pathogens they transmit differ from one ecological location to another. Rickettsia africae is the agent of African tick bite fever found in South Africa, a zoonotic infection that is frequently reported among travelers who have visited many sub-Saharan African countries where the pathogen is prevalent. Methods: Ticks were collected from domestic animals in Raymond Nkandla Municipality, Eastern Cape, South Africa. The ticks were identified morphologically prior to DNA extraction followed by molecular identification of randomly selected ticks from the morphologically delineated groups. To assess for the presence of tick-borne pathogens belonging to Rickettsia spp. by PCR (polymerase chain reaction), we used specific primer pairs targeting the gltA, ompA and ompB genes. The selected amplified ticks, all positive ompB and forty three ompA amplicons were sequenced in a commercial sequencing facility. The obtained nucleotide sequences were edited and subjected to BLASTn for homology search and phylogenetic analyses were performed with MEGA 7 Version for genetic relationships with curated reference sequences in GenBank. Results: A total of 953 ticks collected in the study were delineated into three genera consisting of Amblyomma, Rhipicephalus and Hyalomma in decreasing order of abundance. The presence of rickettsial DNA was detected in 60/953 (6.3%) from the three genera of ticks screened. Genetic analyses of the DNA sequences obtained showed that they have phylogenetic relationship to members of the spotted fever group rickettsiae with R. africae, being the predominant SFGR (spotted fever group rickettsiae) detected in the screened ticks. Conclusion: This report shows that R. africae is the predominant spotted fever group rickettsiae in ticks collected from domestic animals in the study area and the human health impacts are not known.

Detection of Rickettsia spp. in Fleas Collected from Small Mammals in Slovakia, Central Europe

This survey is aimed at investigation of species composition of fleas removed from small terrestrial mammals captured in rural, suburban, and urban types of habitat and molecular screening of the presence and diversity of Rickettsia species in collected ectoparasites. In total, 279 fleas (Siphonaptera) belonging to 9 species of 2 families, Ceratophyllidae and Hystrichopsyllidae, were collected from 115 (46%) out of 250 trapped small mammals of eight species (Apodemus agrarius, Apodemus flavicollis, Apodemus uralensis, Myodes glareolus, Microtus arvalis, Microtus subterraneus, Crocidura leucodon, and Sorex minutus). Rickettsia spp. were found in 2.5% (7/279) of tested fleas, namely in Ctenophthalmus agyrtes, Ctenophthalmus solutus, Ctenophthalmus uncinatus, Megabothris turbidus, and Amalareus penicilliger. Rickettsia felis, Rickettsia helvetica, and unidentified Rickettsia species were detected in fleas infesting small mammals in Eastern Slovakia. The results of the study suggest that some species of rickettsiae have a different range of arthropod vectors.

Complete Genome Sequence of Rickettsia asiatica Strain Maytaro1284, a Member of Spotted Fever Group Rickettsiae Isolated from an Ixodes ovatus Tick in Japan

This is the first report of the complete genome sequence of Rickettsia asiatica strain Maytaro1284, isolated from an Ixodes ovatus tick in Japan. The genome contains a 1,344,324-bp circular chromosome and one plasmid of 74,761 bp. There was no outer membrane protein A (ompA) gene encoded in the genome.

This is the first report of the complete genome sequence of Rickettsia asiatica strain Maytaro1284, isolated from an Ixodes ovatus tick in Japan. The genome contains a 1,344,324-bp circular chromosome and one plasmid of 74,761 bp. There was no outer membrane protein A (ompA) gene encoded in the genome.

Molecular Detection of Spotted-Fever Group Rickettsiae in Ticks Collected from Domestic and Wild Animals in Corsica, France

To obtain a better understanding of the current magnitude of tick-borne rickettsioses in Corsica, we used molecular methods to characterize the occurrence of Rickettsia spp. in ixodid ticks collected from domestic and wild animals. The presence of Rickettsia spp. was evaluated using real-time polymerase chain reaction targeting the gltA gene and by sequencing of gltA and ompA partial genes for species identification and phylogenetic analysis. Infection rates were calculated as the maximum-likelihood estimation (MLE) with 95% confidence intervals (CI). In total, 1117 ticks belonging to four genera (Rhipicephalus, Hyalomma, Ixodes, and Dermacentor) were collected from cattle, sheep, wild boars, and companion animals during July-August 2017 and July 2018-January 2019. Overall, Rickettsia DNA was detected in 208 of 349 pools of ticks (MLE = 25.6%, 95% CI: 22.6-28.8%). The molecular analysis revealed five different rickettsial species of the spotted-fever group (SFG). We highlighted the exclusive detection of Candidatus Ri. barbariae in R. bursa and of Ri. aeschlimanii in H. marginatum. Rickettsia slovaca was detected in D. marginatus collected from wild boars. This study provides the first evidence of the presence of Ri. monacensis in I. ricinus ticks isolated from a dog in Corsica. In conclusion, our data revealed wide dispersal of SFG Rickettsiae and their arthropod hosts in Corsica, highlighting the need for surveillance of the risk of infection for people living and/or working close to infected or infested animals.

Isolation of Rickettsia, Rickettsiella, and Spiroplasma from Questing Ticks in Japan Using Arthropod Cells

Ticks are blood-sucking ectoparasites that transmit zoonotic pathogens to humans and animals. Ticks harbor not only pathogenic microorganisms but also endosymbionts. Although some tick endosymbionts are known to be essential for the survival of ticks, their roles in ticks remain poorly understood. The main aim of this study was to isolate and characterize tick-borne microorganisms from field-collected ticks using two arthropod cell lines derived from Ixodes scapularis embryos (ISE6) and Aedes albopictus larvae (C6/36). A total of 170 tick homogenates originating from 15 different tick species collected in Japan were inoculated into each cell line. Bacterial growth was confirmed by PCR amplification of 16S ribosomal DNA (rDNA) of eubacteria. During the 8-week observation period, bacterial isolation was confirmed in 14 and 4 samples using ISE6 and C6/36 cells, respectively. The sequencing analysis of the 16S rDNA PCR products indicated that they were previously known tick-borne pathogens/endosymbionts in three different genera: Rickettsia, Rickettsiella, and Spiroplasma. These included four previously validated rickettsial species namely Rickettsia asiatica (n = 2), Rickettsia helvetica (n = 3), Rickettsia monacensis (n = 2), and Rickettsia tamurae (n = 3) and one uncharacterized genotype Rickettsia sp. LON (n = 2). Four isolates of Spiroplasma had the highest similarity with previously reported Spiroplasma isolates: Spiroplasma ixodetis obtained from ticks in North America and Spiroplasma sp. Bratislava 1 obtained from Ixodes ricinus in Europe, while two isolates of Rickettsiella showed 100% identity with Rickettsiella sp. detected from Ixodes uriae at Grimsey Island in Iceland. To the best of our knowledge, this is the first report on successful isolation of Rickettsiella from ticks. The isolates obtained in this study can be further analyzed to evaluate their pathogenic potential in animals and their roles as symbionts in ticks.