Detection of new Francisella-like tick endosymbionts in Hyalomma spp. and Rhipicephalus spp. (Acari: Ixodidae) from Bulgaria

Disruption of bacterial interactions and community assembly in Babesia-infected Haemaphysalis longicornis following antibiotic treatment

BACKGROUND

A previous study highlighted the role of antibiotic-induced dysbiosis in the tick microbiota, facilitating the transstadial transmission of Babesia microti from nymph to adult in Haemaphysalis longicornis. This study builds on previous findings by analyzing sequence data from an earlier study to investigate bacterial interactions that could be linked to enhanced transstadial transmission of Babesia in ticks. The study employed antibiotic-treated (AT) and control-treated (CT) Haemaphysalis longicornis ticks to investigate shifts in microbial community assembly. Network analysis techniques were utilized to assess bacterial interactions, comparing network centrality measures between AT and CT groups, alongside studying network robustness and connectivity loss. Additionally, functional profiling was conducted to evaluate metabolic diversity in response to antibiotic treatment.

RESULTS

The analysis revealed notable changes in microbial community assembly in response to antibiotic treatment. Antibiotic-treated (AT) ticks displayed a greater number of connected nodes but fewer correlations compared to control-treated (CT) ticks, indicating a less interactive yet more connected microbial community. Network centrality measures such as degree, betweenness, closeness, and eigenvector centrality, differed significantly between AT and CT groups, suggesting alterations in local network dynamics due to antibiotic intervention. Coxiella and Acinetobacter exhibited disrupted connectivity and roles, with the former showing reduced interactions in AT group and the latter displaying a loss of connected nodes, emphasizing their crucial roles in microbial network stability. Robustness tests against node removal showed decreased stability in AT networks, particularly under directed attacks, confirming a susceptibility of the microbial community to disturbances. Functional profile analysis further indicated a higher diversity and richness in metabolic capabilities in the AT group, reflecting potential shifts in microbial metabolism as a consequence of antimicrobial treatment.

CONCLUSIONS

Our findings support that bacterial interaction traits boosting the transstadial transmission of Babesia could be associated with reduced colonization resistance. The disrupted microbial interactions and decreased network robustness in AT ticks suggest critical vulnerabilities that could be targeted for managing tick-borne diseases.

First molecular detection of Francisella tularensis in turtle (Testudo graeca) and ticks (Hyalomma aegyptium) in Northwest of Iran

Francisella tularensis, causative agent of tularemia, is a contagious zoonotic ailment. This study was aimed to molecularly detect F. tularensis in tortoise blood (n = 100) and ticks (n = 100) collected in the West Azerbaijan province, Iran suing a 16SrRNA gene of the Francisella genus through employment of the Nested-PCR technique. The identified ticks were s Hyalomma aegyptium by morphological analysis. Seven percent (with a 95% CI: 3.5%-13.75%) of animal blood samples yielded positive results for the presence of the Francisella. Meanwhile, the Francisella was identified in tick samples at a rate of fifteen percent (15%) (with a 95% CI: 9%-23%). The samples containing positive results were specifically classified as F. tularensis subsp. holarctica. The samples were taken from ticks belonging to the H. aegyptium species that were gathered in Oshnavieh, southern part of West Azerbaijan province, Iran. This research was aimed to validate the existence of F. tularensis in ticks found within the West Azerbaijan province. Consequently, it is vital to acknowledge the potential of these ticks to transmit the bacteria to both livestock and humans through tick bites in this specific area.

Molecular Detection of Francisella tularensis Isolated from Ticks of Livestock in Kurdistan Region, Iraq

Background: Francisella tularensis is a Gram-negative bacterium that causes tularemia in both human and animals. Tularemia is a potential serious zoonotic disease that is transmitted by different routes, including tick bites. Materials and Methods: This study deals with investigating the prevalence of F. tularensis in the ticks of local animal farms in Kurdistan region since the farmers are normally in close contact with livestock. We used molecular methods for this purpose. A total of 412 tick and 126 blood samples were gathered from goat, sheep, and cow flocks. The existence of F. tularensis 16Sr RNA gene was examined in the samples using nested-PCR technique. Results: In the animal blood specimens, no F. tularensis was found. The incidence of F. tularensis was 1.7% (7 out of 412) in the tick samples, representing a very lower possibility of tuleremia infection. Moreover, the two subspecies of F. tularensis novicida and holarctica were identified based on the sequencing of pdpD and RD genes, respectively. The F. tularensis subsp. novicida was isolated from four species of ticks, Hyalomma anatolicum, Rhipicephalus annulatus, Rhipicephalus sanguineus, and Ornithodoros spp., whereas the F. tularensis subsp. holarctica was isolated from Haemaphysalis parva and Hyalomma dromedarii species of ticks. Conclusion: Although its prevalence is very low, the isolation of F. tularensis subsp. holarctica from the ticks of farm animals suggests possible transmission of Tularemia through tick bite in Kurdistan region of Iraq. Ref: IR-UU-AEC-3/22.

The Biological and Ecological Features of Northbound Migratory Birds, Ticks, and Tick-Borne Microorganisms in the African-Western Palearctic

Identifying the species that act as hosts, vectors, and vehicles of vector-borne pathogens is vital for revealing the transmission cycles, dispersal mechanisms, and establishment of vector-borne pathogens in nature. Ticks are common vectors for pathogens causing human and animal diseases, and they transmit a greater variety of pathogenic agents than any other arthropod vector group. Ticks depend on the movements by their vertebrate hosts for their dispersal, and tick species with long feeding periods are more likely to be transported over long distances. Wild birds are commonly parasitized by ticks, and their migration patterns enable the long-distance range expansion of ticks. The African-Palearctic migration system is one of the world's largest migrations systems. African-Western Palearctic birds create natural links between the African, European, and Asian continents when they migrate biannually between breeding grounds in the Palearctic and wintering grounds in Africa and thereby connect different biomes. Climate is an important geographical determinant of ticks, and with global warming, the distribution range and abundance of ticks in the Western Palearctic may increase. The introduction of exotic ticks and their microorganisms into the Western Palearctic via avian vehicles might therefore pose a greater risk for the public and animal health in the future.

The control of Hyalomma ticks, vectors of the Crimean–Congo hemorrhagic fever virus: Where are we now and where are we going?

At a time of major global, societal, and environmental changes, the shifting distribution of pathogen vectors represents a real danger in certain regions of the world as generating opportunities for emergency. For example, the recent arrival of the Hyalomma marginatum ticks in southern France and the concurrent appearance of cases of Crimean–Congo hemorrhagic fever (CCHF)—a disease vectored by this tick species—in neighboring Spain raises many concerns about the associated risks for the European continent. This context has created an urgent need for effective methods for control, surveillance, and risk assessment for ticks and tick-borne diseases with a particular concern regarding Hyalomma sp. Here, we then review the current body of knowledge on different methods of tick control—including chemical, biological, genetical, immunological, and ecological methods—and the latest developments in the field, with a focus on those that have been tested against ticks from the genus Hyalomma. In the absence of a fully and unique efficient approach, we demonstrated that integrated pest management combining several approaches adapted to the local context and species is currently the best strategy for tick control together with a rational use of acaricide. Continued efforts are needed to develop and implement new and innovative methods of tick control.

Disease-bearing Hyalomma ticks are an increasingly emerging threat to humans and livestock worldwide. Various chemical, biological, genetic, and ecological methods for tick control have been developed, with variable efficiencies. Today, the best tick control strategy involves an integrated pest management approach.

Co-Occurrence of Francisella, Spotted Fever Group Rickettsia, and Midichloria in Avian-Associated Hyalomma rufipes

The migratory behavior of wild birds contributes to the geographical spread of ticks and their microorganisms. In this study, we aimed to investigate the dispersal and co-occurrence of Francisella and spotted fever group Rickettsia (SFGR) in ticks infesting birds migrating northward in the African-Western Palaearctic region (AWPR). Birds were trapped with mist nests across the Mediterranean basin during the 2014 and 2015 spring migration. In total, 575 ticks were collected from 244 birds. We screened the ticks for the species Francisella tularensis, the genus Francisella, and SFGR by microfluidic real-time PCR. Confirmatory analyses and metagenomic sequencing were performed on tick samples that putatively tested positive for F. tularensis during initial screenings. Hyalomma rufipes was the most common tick species and had a high prevalence of Francisella, including co-occurrence of Francisella and SFGR. Metagenomic analysis of total DNA extracted from two H. rufipes confirmed the presence of Francisella, Rickettsia, and Midichloria. Average nucleotide identity and phylogenetic inference indicated the highest identity of the metagenome-assembled genomes to a Francisella-like endosymbiont (FLE), Rickettsia aeschlimannii, and Midichloria mitochondrii. The results of this study suggest that (i) FLE- and SFGR-containing ticks are dispersed by northbound migratory birds in the AWPR, (ii) H. rufipes likely is not involved in transmission of F. tularensis in the AWPR, and (iii) a dual endosymbiosis of FLEs and Midichloria may support some of the nutritional requirements of H. rufipes.

Recently Evolved Francisella-Like Endosymbiont Outcompetes an Ancient and Evolutionarily Associated Coxiella-Like Endosymbiont in the Lone Star Tick (Amblyomma americanum) Linked to the Alpha-Gal Syndrome

Background

Ticks are hematophagous arthropods that transmit various bacterial, viral, and protozoan pathogens of public health significance. The lone star tick (Amblyomma americanum) is an aggressive human-biting tick that transmits bacterial and viral pathogens, and its bites are suspected of eliciting the alpha-gal syndrome, a newly emerged delayed hypersensitivity following consumption of red meat in the United States. While ongoing studies have attempted to investigate the contribution of different tick-inherent factors to the induction of alpha-gal syndrome, an otherwise understudied aspect is the contribution of the tick microbiome and specifically obligate endosymbionts to the establishment of the alpha-gal syndrome in humans.

Materials and Methods

Here we utilized a high-throughput metagenomic sequencing approach to cataloging the entire microbial communities residing within different developmental stages and tissues of unfed and blood-fed ticks from laboratory-maintained ticks and three new geographical locations in the United States. The Quantitative Insights Into Microbial Ecology (QIIME2) pipeline was used to perform data analysis and taxonomic classification. Moreover, using a SparCC (Sparse Correlations for Compositional data) network construction model, we investigated potential interactions between members of the microbial communities from laboratory-maintained and field-collected ticks.

Results

Overall, Francisellaceae was the most dominant bacteria identified in the microbiome of both laboratory-raised and field-collected Am. americanum across all tissues and developmental stages. Likewise, microbial diversity was seen to be significantly higher in field-collected ticks compared with laboratory-maintained ticks as seen with a higher number of both Operational Taxonomic Units and measures of species richness. Several potential positive and negative correlations were identified from our network analysis. We observed a strong positive correlation between Francisellaceae, Rickettsiaceae, and Midichloriaceae in both developmental stages and tissues from laboratory-maintained ticks, whereas ovarian tissues had a strong positive correlation of bacteria in the family Xanthobacteraceae and Rhizobiaceae. A negative interaction was observed between Coxiellaceae and Francisellaceae in Illinois, and all the bacteria detected from ticks from Delaware were negatively correlated.

Conclusion

This study is the first to catalog the microbiome of Am. americanum throughout its developmental stages and different tissue niches and report the potential replacement of Coxiellaceae by Francisellaceae across developmental stages and tissues tested except in ovarian tissues. These unique and significant findings advance our knowledge and open a new avenue of research to further understand the role of tick microbiome in tick-borne diseases and develop a holistic strategy to control alpha-gal syndrome.

The Symbiotic Continuum Within Ticks: Opportunities for Disease Control

Among blood-sucking arthropods, ticks are recognized as being of prime global importance because of their role as vectors of pathogens affecting human and animal health. Ticks carry a variety of pathogenic, commensal, and symbiotic microorganisms. For the latter, studies are available concerning the detection of endosymbionts, but their role in the physiology and ecology of ticks remains largely unexplored. This review paper focuses on tick endosymbionts of the genera Coxiella, Rickettsia, Francisella, Midichloria, and Wolbachia, and their impact on ticks and tick-pathogen interactions that drive disease risk. Tick endosymbionts can affect tick physiology by influencing nutritional adaptation, fitness, and immunity. Further, symbionts may influence disease ecology, as they interact with tick-borne pathogens and can facilitate or compete with pathogen development within the vector tissues. Rickettsial symbionts are frequently found in ticks of the genera of Ixodes, Amblyomma, and Dermacentor with relatively lower occurrence in Rhipicephalus, Haemaphysalis, and Hyalomma ticks, while Coxiella-like endosymbionts (CLEs) were reported infecting almost all tick species tested. Francisella-like endosymbionts (FLEs) have been identified in tick genera such as Dermacentor, Amblyomma, Ornithodoros, Ixodes, and Hyalomma, whereas Wolbachia sp. has been detected in Ixodes, Amblyomma, Hyalomma, and Rhipicephalus tick genera. Notably, CLEs and FLEs are obligate endosymbionts essential for tick survival and development through the life cycle. American dog ticks showed greater motility when infected with Rickettsia, indirectly influencing infection risk, providing evidence of a relationship between tick endosymbionts and tick-vectored pathogens. The widespread occurrence of endosymbionts across the tick phylogeny and evidence of their functional roles in ticks and interference with tick-borne pathogens suggests a significant contribution to tick evolution and/or vector competence. We currently understand relatively little on how these endosymbionts influence tick parasitism, vector capacity, pathogen transmission and colonization, and ultimately on how they influence tick-borne disease dynamics. Filling this knowledge gap represents a major challenge for future research.

Four Tick-Borne Microorganisms and Their Prevalence in Hyalomma Ticks Collected from Livestock in United Arab Emirates

Ticks and associated tick-borne diseases in livestock remain a major threat to the health of animals and people worldwide. However, in the United Arab Emirates (UAE), very few studies have been conducted on tick-borne microorganisms thus far. The purpose of this cross-sectional DNA-based study was to assess the presence and prevalence of tick-borne Francisella sp., Rickettsia sp., and piroplasmids in ticks infesting livestock, and to estimate their infection rates. A total of 562 tick samples were collected from camels, cows, sheep, and goats in the Emirates of Abu Dhabi, Dubai, and Sharjah from 24 locations. DNA was extracted from ticks and PCR was conducted. We found that Hyalomma dromedarii ticks collected from camels had Francisella sp. (5.81%) and SFG Rickettsia (1.36%), which was 99% similar to Candidatus Rickettsia andeanae and uncultured Rickettsia sp. In addition, Hyalomma anatolicum ticks collected from cows were found to be positive for Theileria annulata (4.55%), whereas H. anatolicum collected from goats were positive for Theileria ovis (10%). The widespread abundance of Francisella of unknown pathogenicity and the presence of Rickettsia are a matter of concern. The discovery of T. ovis from relatively few samples from goats indicates the overall need for more surveillance. Increasing sampling efforts over a wider geographical range within the UAE could reveal the true extent of tick-borne diseases in livestock. Moreover, achieving successful tick-borne disease control requires more research and targeted studies evaluating the pathogenicity and infection rates of many microbial species.

Analysis on the prokaryotic microbiome in females and embryonic cell cultures of Rhipicephalus sanguineus tropical and temperate lineages from two specific localities in Brazil

Two lineages of Rhipicephalus sanguineus are known in Brazil: the temperate or southern and the tropical or northern populations. The distribution patterns of both lineages of R. sanguineus have epidemiological implications that can affect vectorial competence concerning Ehrlichia canis, the agent of canine monocytic ehrlichiosis. Intending to identify the microbiomes of both lineages and compare microorganisms in R. sanguineus, we used the 16S rRNA (V4-V5 region) gene-based metataxonomic approach, through NGS sequencing on the MiSeq Illumina platform. We selected specimens of females from the environment and samples of primary embryonic cell cultures, from both lineages, and this was the first study to investigate the prokaryotic microbiome in tick cell cultures. The results showed that many bacterial taxa detected in the samples were typical members of the host environment. A significant diversity of microorganisms in R. sanguineus females and in embryonic cell cultures from both lineages was found, with emphasis on the presence of Coxiella in all samples, albeit in different proportions. The Coxiella species present in the two lineages of ticks may be different and may have co-evolved with them, thus driving different patterns of interactions between ticks and the pathogens that they can harbor or transmit to vertebrate hosts.

Multi-country investigation of the diversity and associated microorganisms isolated from tick species from domestic animals, wildlife and vegetation in selected african countries

In many areas of Africa, recent studies highlighted the great impact of ticks on animal and human health throughout the continent. On the other hand, very limited information on the bacterial endosymbionts of the African ticks and their pattern of co-infections with other bacteria are found in literature, notwithstanding their pivotal role in tick survival and vector efficiency. Thus, we investigated the distribution of selected pathogenic and symbiotic bacteria in hard ticks collected from wild, domestic animals and from vegetation in various ecological zones in Africa and their co-occurrence in the same tick host. Overall, 339 hard ticks were morphologically identified as belonging to the genera Amblyomma, Dermacentor, Hyalomma, Haemaphysalis, Ixodes and Rhipicephalus. Molecular screening provided information on pathogens circulation in Africa, detecting spotted fever group rickettsiae, Anaplasma spp., Ehrlichia ruminantium, Borrelia garinii, Babesia spp., Theileria spp. and Coxiella burnetii. Furthermore, our work provides insights on the African scenario of tick-symbiont associations, revealing the presence of Coxiella, Francisella and Midichloria across multiple tick populations. Coxiella endosymbionts were the most prevalent microorganisms, and that with the broadest spectrum of hosts, being detected in 16 tick species. Francisella was highly prevalent among the Hyalomma species tested and correlated negatively with the presence of Coxiella, showing a potential competitive interaction. Interestingly, we detected a positive association of Francisella with Rickettsia in specimens of Hy. rufipes, suggesting a synergistic interaction between them. Finally, Midichloria was the most prevalent symbiont in Rhipicephalus sanguineus sensu lato from Egypt.

Reorganized Genomic Taxonomy of Francisellaceae Enables Design of Robust Environmental PCR Assays for Detection of Francisella tularensis

In recent years, an increasing diversity of species has been recognized within the family Francisellaceae. Unfortunately, novel isolates are sometimes misnamed in initial publications or multiple sources propose different nomenclature for genetically highly similar isolates. Thus, unstructured and occasionally incorrect information can lead to confusion in the scientific community. Historically, detection of Francisella tularensis in environmental samples has been challenging due to the considerable and unknown genetic diversity within the family, which can result in false positive results. We have assembled a comprehensive collection of genome sequences representing most known Francisellaceae species/strains and restructured them according to a taxonomy that is based on phylogenetic structure. From this structured dataset, we identified a small number of genomic regions unique to F. tularensis that are putatively suitable for specific detection of this pathogen in environmental samples. We designed and validated specific PCR assays based on these genetic regions that can be used for the detection of F. tularensis in environmental samples, such as water and air filters.

Update on the intricate tango between tick microbiomes and tick-borne pathogens

The recent development of high-throughput NGS technologies, (ie, next-generation sequencing) has highlighted the complexity of tick microbial communities-which include pathogens, symbionts, and commensals-and also their dynamic variability. Symbionts and commensals can confer crucial and diverse benefits to their hosts, playing nutritional roles or affecting fitness, development, nutrition, reproduction, defence against environmental stress and immunity. Nonpathogenic tick bacteria may also play a role in modifying tick-borne pathogen colonization and transmission, as relationships between microorganisms existing together in one environment can be competitive, exclusive, facilitating or absent, with many potential implications for both human and animal health. Consequently, ticks represent a compelling yet challenging system in which to investigate the composition and both the functional and ecological implications of tick bacterial communities, and thus merits greater attention. Ultimately, deciphering the relationships between microorganisms carried by ticks as well as symbiont-tick interactions will garner invaluable information, which may aid in some future arthropod-pest and vector-borne pathogen transmission control strategies. This review outlines recent research on tick microbiome composition and dynamics, highlights elements favouring the reciprocal influence of the tick microbiome and tick-borne agents and finally discusses how ticks and tick-borne diseases might potentially be controlled through tick microbiome manipulation in the future.

Dermacentor marginatus and Dermacentor reticulatus, and Their Infection by SFG Rickettsiae and Francisella-Like Endosymbionts, in Mountain and Periurban Habitats of Northwestern Italy

We investigated the distribution of Dermacentor spp. and their infection by zoonotic bacteria causing SENLAT (scalp eschar neck lymphadenopathy) in Turin province, northwestern Italy. We collected ticks in a mountain and in a periurban park, from vegetation and different animal sources, and we sampled tissues from wild boar. Dermacentor marginatus (n = 121) was collected in both study areas, on vegetation, humans, and animals, while D. reticulatus (n = 13) was exclusively collected on wild boar from the periurban area. Rickettsia slovaca and Candidatus Rickettsia rioja infected 53.1% of the ticks, and R. slovaca was also identified in 11.3% of wild boar tissues. Bartonella spp. and Francisella tularensis were not detected, however, Francisella-like endosymbionts infected both tick species (9.2%). Our findings provide new insights on the current distribution of Dermacentor spp. and their infection with a spotted-fever group rickettsiae in the Alps region. Wild boar seem to play a major role in their eco-epidemiology and dispersion in the study area. Although further studies are needed to assess the burden of rickettsial diseases, our results highlight the risk of contracting SENLAT infection through Dermacentor spp. bites in the region.

Ticks (Acari: Ixodidae) on birds migrating to the island of Ponza, Italy, and the tick-borne pathogens they carry

Seasonal migration of birds between breeding and wintering areas can facilitate the spread of tick species and tick-borne diseases. In this study, 151 birds representing 10 different bird species were captured on Ponza Island, an important migratory stopover off the western coast of Italy and screened for tick infestation. Ticks were collected and identified morphologically. Morphological identification was supported through sequencing a fragment of the 16S mitochondrial gene. In total, 16 captured birds carried ticks from four tick species: Hyalomma rufipes (n = 14), Amblyomma variegatum (n = 1), Amblyomma sp. (n = 1), and Ixodes ventalloi (n = 2). All specimens were either larvae (n = 2) or nymphs (n = 16). All ticks were investigated for tick-borne pathogens using published molecular methods. Rickettsia aeschlimannii was detected in six of the 14 collected H. rufipes ticks. Additionally, the singular A. variegatum nymph tested positive for R. africae. In all 14 H. rufipes specimens (2 larvae and 12 nymphs), Francisella-like endosymbionts were detected. Four H. rufipes ticks tested positive for Borrelia burgdorferi sensu lato in a screening PCR but did not produce sufficient amplicon amounts for species identification. All ticks tested negative for tick-borne encephalitis virus, Crimean-Congo hemorrhagic fever virus, Coxiella burnetii, Coxiella-like organisms, Babesia spp., and Theileria spp. This study confirms the role of migratory birds in the spread and establishment of both exotic tick species and tick-borne pathogens outside their endemic range.

Ecology of Francisella tularensis

Tularemia is a Holarctic zoonosis caused by the gamma proteobacterium Francisella tularensis and is considered to be a vector-borne disease. In many regions, human risk is associated with the bites of flies, mosquitoes, or ticks. But the biology of the agent is such that risk may be fomite related, and large outbreaks can occur due to inhalation or ingestion of contaminated materials. Such well-documented human risk factors suggest a role for these risk factors in the enzootic cycle as well. Many arthropods support the growth or survival of the agent, but whether arthropods (ticks in particular) are obligately required for the perpetuation of F. tularensis remains to be demonstrated. As with most zoonoses, our knowledge of the ecology of F. tularensis has been driven with the objective of understanding human risk. In this review, we focus on the role of the arthropod in maintaining F. tularensis, particularly with respect to long-term enzootic persistence.

First molecular detection of Francisella-like endosymbionts in Hyalomma and Rhipicephalus tick species collected from vertebrate hosts from Sardinia island, Italy

Ticks are vectors of a wide variety of human and animal pathogens as well as non-pathogenic microorganisms acting as endosymbionts and whose role in ticks is still little known. Symbionts such as Francisella-like endosymbionts (FLEs) are members of Francisellaceae family with unknown pathogenicity, detected in both hard and soft ticks. A total of 236 ticks collected from several sites in Sardinia were screened for Francisella species by PCR using primers targeting a fragment of the 16S rRNA gene. DNA of Francisella was detected in 5.1% (12/236) of the ticks tested. Sequencing results revealed that seven Rhipicephalus sanguineus s.l., three Hyalomma marginatum, one Hy. lusitanicum, and one Rh. bursa ticks exhibited DNA with 99-100% similarity to Francisella-like endosymbionts isolated from different tick species all over the world. Further research is needed in order to better characterize FLE strains obtained in Sardinia and to better understand if their presence could be related to the infection with other zoonotic pathogens.

Francisella spp. detected in Dermacentor ticks in Malaysian forest reserve areas

Limited information is available on tropical ticks and tick-borne bacteria affecting the health of humans and animals in the Southeast Asia region. Francisella tularensis is a tick-borne bacterium which causes a potentially life-threatening disease known as tularemia. This study was conducted to determine the occurrence of Francisella spp. in questing ticks collected from Malaysian forest reserve areas. A total of 106 ticks (mainly Dermacentor and Haemaphysalis spp.) were examined for Francisella DNA using a Polymerase chain reaction (PCR) assay targeting the bacterial 16S rDNA. Francisella DNA was detected from 12 Dermacentor ticks. Sequence analysis of the amplified 16S rDNA sequences (1035 bp) show >99% identity with that of Francisella endosymbiont reported in a tick from Thailand. A dendrogram constructed based on the bacterial 16S rDNA shows that the Francisella spp. were distantly related to the pathogenic strains of F. tularensis. Three Francisella-positive ticks were identified as Dermacentor atrosignatus, based on sequence analysis of the tick mitochondrial 16S rRNA gene. Further screening of cattle and sheep ticks (Haemaphysalis bispinosa and Rhipicephalus microplus) and animal samples (cattle, sheep, and goats) did not yield any positive findings. Our findings provide the first molecular data on the occurrence of a Francisella strain with unknown pathogenicity in Dermacentor questing ticks in Malaysia.

Ticks and Tularemia: Do We Know What We Don't Know?

Francisella tularensis, the causative agent of the zoonotic disease tularemia, is characterized by high morbidity and mortality rates in over 190 different mammalian species, including humans. Based on its low infectious dose, multiple routes of infection, and ability to induce rapid and lethal disease, F. tularensis has been recognized as a severe public health threat—being designated as a NIH Category A Priority Pathogen and a CDC Tier 1 Select Agent. Despite concerns over its use as a bioweapon, most U.S. tularemia cases are tick-mediated and ticks are believed to be the major environmental reservoir for F. tularensis in the U.S. The American dog tick (Dermacentor variabilis) has been reported to be the primary tick vector for F. tularensis, but the lone star tick (Amblyomma americanum) and other tick species also have been shown to harbor F. tularensis. This review highlights what is known, not known, and is debated, about the roles of different tick species as environmental reservoirs and transmission vectors for a variety of F. tularensis genotypes/strains.

A Novel Francisella-Like Endosymbiont in Haemaphysalis longicornis and Hyalomma asiaticum, China

Francisella tularensis causes a highly infectious zoonotic disease tularemia. Both Haemaphysalis longicornis and Hyalomma asiaticum are widely distributed in China, but the presence of Francisella and Francisella-like endosymbionts (FLEs) in the two tick species is poorly understood. Therefore, a total of 627 H. longicornis (471 adults and 156 nymphs) and 88 Hy. asiaticum ticks (adults) were collected, of which 88 were from Bole of Xinjiang, 236 from Liaoyang, and 176 from Shenyang of Liaoning, and 215 from Wuhan of Hubei. Notably, five H. longicornis pools from Liaoyang of Liaoning province might have harbored F. tularensis, showing a minimum prevalence of 2.12% (5/236). This study should alert the health department and veterinarians working within the region to prevent and control the emergence of tularemia. After the screening of 16S rRNA and tul4 genes, the results revealed that FLEs were detected in Hy. asiaticum ticks in Bole and in H. longicornis ticks in Liaoyang and Shenyang. Their infection rate was 100% (88/88), 3.39% (8/236 is a minimum), and 8.52% (15/176), respectively. Phylogenetic analyses indicated that the sequence named bole in Hy. Asiaticum from Bole, the sequence named liaoyang1 in H. longicornis from Liaoyang, and the sequence named shanyang1 in H. longicornis from Shenyang shared consistent 16S rRNA sequence, and the difference between Chinese FLEs and the known FLEs was obvious. These findings suggest that this FLE species might be a potentially novel FLE circulating in H. longicornis and Hy. asiaticum from China.

The tick endosymbiont Candidatus Midichloria mitochondrii and selenoproteins are essential for the growth of Rickettsia parkeri in the Gulf Coast tick vector

BACKGROUND

Pathogen colonization inside tick tissues is a significant aspect of the overall competence of a vector. Amblyomma maculatum is a competent vector of the spotted fever group rickettsiae, Rickettsia parkeri. When R. parkeri colonizes its tick host, it has the opportunity to dynamically interact with not just its host but with the endosymbionts living within it, and this enables it to modulate the tick's defenses by regulating tick gene expression. The microbiome in A. maculatum is dominated by two endosymbiont microbes: a Francisella-like endosymbiont (FLE) and Candidatus Midichloria mitochondrii (CMM). A range of selenium-containing proteins (selenoproteins) in A. maculatum ticks protects them from oxidative stress during blood feeding and pathogen infections. Here, we investigated rickettsial multiplication in the presence of tick endosymbionts and characterized the functional significance of selenoproteins during R. parkeri replication in the tick.

RESULTS

FLE and CMM were quantified throughout the tick life stages by quantitative PCR in R. parkeri-infected and uninfected ticks. R. parkeri infection was found to decrease the FLE numbers but CMM thrived across the tick life cycle. Our qRT-PCR analysis indicated that the transcripts of genes with functions related to redox (selenogenes) were upregulated in ticks infected with R. parkeri. Three differentially expressed proteins, selenoprotein M, selenoprotein O, and selenoprotein S were silenced to examine their functional significance during rickettsial replication within the tick tissues. Gene silencing of the target genes was found to impair R. parkeri colonization in the tick vector. Knockdown of the selenogenes triggered a compensatory response from other selenogenes, as observed by changes in gene expression, but oxidative stress levels and endoplasmic reticulum stress inside the ticks were also found to have heightened.

CONCLUSIONS

This study illustrates the potential of this new research model for augmenting our understanding of the pathogen interactions occurring within tick hosts and the important roles that symbionts and various tick factors play in regulating pathogen growth.

Diversity of Coxiella-like and Francisella-like endosymbionts, and Rickettsia spp., Coxiella burnetii as pathogens in the tick populations of Slovakia, Central Europe

Ticks are important vectors of pathogens affecting humans and animals worldwide. They do not only carry pathogens but diverse commensal and symbiotic microorganisms are also present in ticks. A molecular screening for tick-borne pathogens and endosymbionts was carried out in Ixodes ricinus, Dermacentor reticulatus and Haemaphysalis inermis questing ticks collected in Slovakia. The presence of Rickettsia spp., Coxiella burnetii, Coxiella-like and Francisella-like microorganisms was evaluated by PCR in 605 individuals and by randomly sequencing 66 samples. Four species of rickettsiae (R. raoultii, R. slovaca, R. helvetica and R. monacensis) were identified and reported with an overall prevalence range between 0.4 and 50.3% (±8.0) depending on tick species, sex and locality. Partial sequencing of the gltA gene of 5 chosen samples in H. inermis showed 99% identity with Candidatus Rickettsia hungarica. The total prevalence of C. burnetii in ticks was 2.2 ± 1.7%; bacteria were confirmed in I. ricinus and D. reticulatus ticks. The sequences from 2 D. reticulatus males and 1 I. ricinus female ticks were compared to GenBank submissions and a 99.8% match was obtained with the pathogenic C. burnetii. Coxiella-like endosymbionts were registered in all three species of ticks from all studied sites with an average prevalence of 32.7 ± 3.7%. A phylogenetic analysis of this Coxiella sp. showed that it does not group with the pathogenic C. burnetii. The prevalence of Francisella-like microorganisms in questing ticks was 47.9 ± 3.9%, however H. inermis (n = 108) were not infested. Obtained sequences were 98% identical with previously identified Francisella-like endosymbionts in D. reticulatus and I. ricinus. Coxiella-like and Francisella-like microorganisms were identified for the first time in Slovakia, they might be considered as a non-pathogenic endosymbiont of I. ricinus, D. reticulatus and H. inermis, and future investigations could aim to assess their role in these ticks. However, this work provided further data and broadened our knowledge on bacterial pathogens and endosymbionts present in ticks in Slovakia to help understanding co-infestations, combined treatments and public health issues linked to tick bites.

Molecular survey of neglected bacterial pathogens reveals an abundant diversity of species and genotypes in ticks collected from animal hosts across Romania

Background

Ticks are transmitting a wide range of bacterial pathogens that cause substantial morbidity and mortality in domestic animals. The full pathogen burden transmitted by tick vectors is incompletely studied in many geographical areas, and extensive studies are required to fully understand the diversity and distribution of pathogens transmitted by ticks.

Results

We sampled 824 ticks of 11 species collected in 19 counties in Romania. Ticks were collected mainly from dogs, but also from other domestic and wild animals, and were subjected to molecular screening for pathogens. Rickettsia spp. was the most commonly detected pathogen, occurring in 10.6% (87/824) of ticks. Several species were detected: Rickettsia helvetica, R. raoultii, R. massiliae, R. monacensis, R. slovaca and R. aeschlimannii. A single occurrence of the zoonotic bacterium Bartonella vinsonii berkhoffii was detected in a tick collected from a dog. Anaplasma phagocytophilum occurred in four samples, and sequences similar to Anaplasma marginale/ovis were abundant in ticks from ruminants. In addition, molecular screening showed that ticks from dogs were carrying an Ehrlichia species identical to the HF strain as well as the enigmatic zoonotic pathogen “Candidatus Neoehrlichia mikurensis”. An organism similar to E. chaffeensis or E. muris was detected in an Ixodes ricinus collected from a fox.

Conclusions

We describe an abundant diversity of bacterial tick-borne pathogens in ticks collected from animal hosts in Romania, both on the level of species and genotypes/strains within these species. Several findings were novel for Romania, including Bartonella vinsonii subsp. berkhoffii that causes bacteremia and endocarditis in dogs. “Candidatus Neoehrlichia mikurensis” was detected in a tick collected from a dog. Previously, a single case of infection in a dog was diagnosed in Germany. The results warrant further studies on the consequences of tick-borne pathogens in domestic animals in Romania.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-2756-1) contains supplementary material, which is available to authorized users.

The diversity of tick-borne bacteria and parasites in ticks collected from the Strandja Nature Park in south-eastern Bulgaria

Background

Ticks are important carriers of many different zoonotic pathogens. To date, there are many studies about ticks and tick-borne pathogens (TBP), but only a few were carried out in Bulgaria. The present study intends to detect the prevalence of tick-borne bacteria and parasites occurring at the Black Sea in Bulgaria to evaluate the zoonotic potential of the tick-borne pathogens transmitted by ticks in this area.

Methods

In total, cDNA from 1541 ticks (Dermacentor spp., Haemaphysalis spp., Hyalomma spp., Ixodes spp. and Rhipicephalus spp.) collected in Bulgaria by flagging method or from hosts was tested in pools of ten individuals each for Anaplasma phagocytophilum, Babesia spp., Borrelia burgdorferi (s.l.), Rickettsia spp. and “Candidatus Neoehrlichia mikurensis” via conventional and quantitative real-time PCR. Subsequently, samples from positive pools were tested individually and a randomized selection of positive PCR samples was purified, sequenced, and analyzed.

Results

Altogether, 23.2% of ticks were infected with at least one of the tested pathogens. The highest infection levels were noted in nymphs (32.3%) and females (27.5%). Very high prevalence was detected for Rickettsia spp. (48.3%), followed by A. phagocytophilum (6.2%), Borrelia burgdorferi (s.l.) (1.7%), Babesia spp. (0.4%) and “Ca. Neoehrlichia mikurensis” (0.1%). Co-infections were found in 2.5% of the tested ticks (mainly Ixodes spp.). Sequencing revealed the presence of Rickettsia monacensis, R. helvetica, and R. aeschlimannii, Babesia microti and B. caballi, and Theileria buffeli and Borrelia afzelli.

Conclusion

This study shows very high prevalence of zoonotic Rickettsia spp. in ticks from Bulgaria and moderate to low prevalence for all other pathogens tested. One should take into account that tick bites from this area could lead to Rickettsia infection in humans and mammals.

Endosymbiont CLS-HI plays a role in reproduction and development of Haemaphysalis longicornis

Coxiella-like endosymbiont (CLS-Hl) is a primary endosymbiont of Haemaphysalis longicornis. CLS-Hl infects tick special tissues and its prevalence is 100% in ovaries and Malpighian tubules. Tetracycline was injected into females, which then fed on rabbits also treated with tetracycline. The densities of CLS-Hl were measured by semi-quantitative PCR. CLS-Hl densities in ovaries and Malpighian tubes of H. longicornis had significant effects on engorged weight, feeding time, number of eggs, oviposition period, and hatching period. These findings suggested that CLS-Hl plays a role in the reproduction and development of H. longicornis.

Francisella-Like Endosymbiont Detected in Haemaphysalis Ticks (Acari: Ixodidae) From the Republic of Korea

A total of 6,255 ticks belonging to three genera and six species (Haemaphysalis flava Neumann, Haemaphysalis longicornis Neumann, Haemaphysalis phasiana Saito, Ixodes nipponensis Kitaoka & Saito, Ixodes persulcatus Schulze, and Amblyomma testudinarium Koch) collected from May-August, 2013, at four southwestern provinces in the Republic of Korea (ROK) were submitted to the Armed Forces Research Institute of Medical Sciences and assayed for selected tick-borne pathogens. One pool each of H. flava and H. phasiana was positive by PCR and sequencing for a Francisella-like endosymbiont, while all pools were negative for Francisella tularensis, the causative agent of tularemia.

Diversity of tick species on domestic animals in Shandong Province, China, using DNA barcoding

Ticks are considered to be second only to mosquitoes as vectors of diseases. In recent years, severe fever with thrombocytopenia syndrome, a new emerging tick-borne disease has been detected in many areas of China, including Shandong Province, Eastern China. Here, we report the tick species diversity based on surveys between 2014 and 2016 covering 16 locations in seven cities of Shandong. Based on DNA barcoding, 1859 ticks belonging to three species were identified: Haemaphysalis longicornis, Rhipicephalus turanicus and Haemaphysalis verticalis. Samples of the same species clustered together in a neighbor-joining phylogenetic tree, with intraspecific distances between 0 and 3.0% and interspecific distances ranged between 15.5 and 24.3%. Goats and dogs were the major hosts of ticks and H. longicornis was regarded as predominant tick species of Shandong. In order to reduce tick populations and prevent tick-borne diseases, effective control measures should be implemented on human and domestic animals, respectively.

Francisella-Like Endosymbionts and Rickettsia Species in Local and Imported Hyalomma Ticks

Hyalomma ticks (Acari: Ixodidae) are hosts for Francisella-like endosymbionts (FLE) and may serve as vectors of zoonotic disease agents. This study aimed to provide an initial characterization of the interaction between Hyalomma and FLE and to determine the prevalence of pathogenic Rickettsia in these ticks. Hyalomma marginatum, Hyalomma rufipes, Hyalommadromedarii, Hyalommaaegyptium, and Hyalommaexcavatum ticks, identified morphologically and molecularly, were collected from different hosts and locations representing the distribution of the genus Hyalomma in Israel, as well as from migratory birds. A high prevalence of FLE was found in all Hyalomma species (90.6%), as well as efficient maternal transmission of FLE (91.8%), and the localization of FLE in Malpighian tubules, ovaries, and salivary glands in H. marginatum Furthermore, we demonstrated strong cophylogeny between FLE and their host species. Contrary to FLE, the prevalence of Rickettsia ranged from 2.4% to 81.3% and was significantly different between Hyalomma species, with a higher prevalence in ticks collected from migratory birds. Using ompA gene sequences, most of the Rickettsia spp. were similar to Rickettsiaaeschlimannii, while a few were similar to Rickettsiaafricae of the spotted fever group (SFG). Given their zoonotic importance, 249 ticks were tested for Crimean Congo hemorrhagic fever virus infection, and all were negative. The results imply that Hyalomma and FLE have obligatory symbiotic interactions, indicating a potential SFG Rickettsia zoonosis risk. A further understanding of the possible influence of FLE on Hyalomma development, as well as on its infection with Rickettsia pathogens, may lead to novel ways to control tick-borne zoonoses.IMPORTANCE This study shows that Francisella-like endosymbionts were ubiquitous in Hyalomma, were maternally transmitted, and cospeciated with their hosts. These findings imply that the interaction between FLE and Hyalomma is of an obligatory nature. It provides an example of an integrative taxonomy approach to simply differentiate among species infesting the same host and to identify nymphal and larval stages to be used in further studies. In addition, it shows the potential of imported Hyalomma ticks to serve as a vector for spotted fever group rickettsiae. The information gathered in this study can be further implemented in the development of symbiont-based disease control strategies for the benefit of human health.

Crimean-Congo Hemorrhagic Fever: Tick-Host-Virus Interactions

Crimean-Congo hemorrhagic fever virus (CCHFV) is transmitted to humans by bite of infected ticks or by direct contact with blood or tissues of viremic patients or animals. It causes to humans a severe disease with fatality up to 30%. The current knowledge about the vector-host-CCHFV interactions is very limited due to the high-level containment required for CCHFV studies. Among ticks, Hyalomma spp. are considered the most competent virus vectors. CCHFV evades the tick immune response, and following its replication in the lining of the tick's midgut, it is disseminated by the hemolymph in the salivary glands and reproductive organs. The introduction of salivary gland secretions into the host cells is the major route via which CCHFV enters the host. Following an initial amplification at the site of inoculation, the virus is spread to the target organs. Apoptosis is induced via both intrinsic and extrinsic pathways. Genetic factors and immune status of the host may affect the release of cytokines which play a major role in disease progression and outcome. It is expected that the use of new technology of metabolomics, transcriptomics and proteomics will lead to improved understanding of CCHFV-host interactions and identify potential targets for blocking the CCHFV transmission.

Symbiont dynamics of the Tibetan tick Haemaphysalis tibetensis (Acari: Ixodidae)

Background

Characterization of the microbial diversity and symbiont dynamics of ticks may help to understand the development of ticks and reveal new strategies to control tick-transmitted pathogens, which has not yet been explored in the Tibetan tick Haemaphysalis tibetensis. This tick species is widely distributed in the Tibetan Plateau, and is recognized as one of the primary parasites affecting domestic and wild animals.

Methods

In the present study, the endosymbionts of H. tibetensis were characterized using diagnostic polymerase chain reaction (diagnostic PCR), and further evaluated for tissue distribution and population dynamics at each developmental stage of ticks and in tissues at different reproductive statuses by real-time quantitative polymerase chain reaction (RT-qPCR).

Results

Two symbionts were found in H. tibetensis, and named as CLS-Ht (Coxiella-like symbiont in H. tibetensis) and RLS-Ht (Rickettsia-like symbiont in H. tibetensis). They showed 100% infection rate in both females and males of H. tibetensis. CLS-Ht and RLS-Ht can be observed within eggs, larvae, nymphs and adults, which indicates vertical transmission in H. tibetensis. CLS-Ht was specifically distributed in the female ovaries and Malpighian tubules, whereas RLS-Ht was detected within ovaries, Malpighian tubules, salivary glands and midguts of the ticks. Real-time qPCR suggested that adult ticks carried the largest amount of CLS-Ht and RLS-Ht with CLS-Ht having a significantly higher presence in females than in males (P < 0.05), whereas the presence of RLS-Ht showed no significant differences between sexes. In the ovaries, CLS-Ht distribution reached a peak at one day post-engorgement, and then gradually declined to a lower level, whereas no change was observed in RLS-Ht. In Malpighian tubules, the amount of both symbionts displayed an increasing trend with time post-engorgement. In midguts and salivary glands, the amount of RLS-Ht showed no significant differences.

Conclusion

Two novel endosymbionts (CLS-Ht and RLS-Ht) were characterized in H. tibetensis both showing a high prevalence and stable vertical transmission. The described tissue distribution and population dynamics might imply the important functions of these symbionts during the development and reproduction of ticks.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2199-0) contains supplementary material, which is available to authorized users.

Molecular Detection of Francisella spp. Among Ticks Attached to Camels in Egypt

This study was conducted to investigate the possible role of camels and attached ticks in the epidemiology of Francisella spp. including Francisella tularensis. For this purpose, a total of 319 ticks (248 Hyalomma dromedarii and 71 Amblyomma spp.) as well as 100 blood and 50 fecal samples collected from camels were screened for the presence of Francisella spp. by PCR through amplification of Francisella 16S rRNA gene. Positive samples were then tested for F. tularensis by PCR. In addition, serum samples from 75 camel abattoir workers were examined for the presence of IgG antibodies against F. tularensis using enzyme-linked immunosorbent assay (ELISA). Of the examined ticks, 15 were positive for Francisella spp. with prevalence of 4.7%, all positive results were recorded in Hyalomma dromedarii (6%). Neither blood nor fecal samples from camels yielded Francisella spp. even camels which carried Francisella spp. positive ticks. Moreover, F. tularensis could not be detected among Francisella-positive ticks. Phylogenetic analysis of some Francisella 16S rRNA gene sequences obtained in this study points out that these sequences are closely related to Francisella-like endosymbionts. In contrast, seroprevalence of F. tularensis antibodies among examined abattoir workers was 9.3% with significantly high prevalence among workers frequently exposed to tick bites (20.7%) rather than occasionally exposed workers (2.2%). In conclusion, however, F. tularensis could not be detected in this study; the high seroprevalence among camel abattoir workers especially those frequently exposed to tick bites underlines the possible role of ticks attached to camels in transmission of tularemia to humans.

Tick-Pathogen Interactions and Vector Competence: Identification of Molecular Drivers for Tick-Borne Diseases

Ticks and the pathogens they transmit constitute a growing burden for human and animal health worldwide. Vector competence is a component of vectorial capacity and depends on genetic determinants affecting the ability of a vector to transmit a pathogen. These determinants affect traits such as tick-host-pathogen and susceptibility to pathogen infection. Therefore, the elucidation of the mechanisms involved in tick-pathogen interactions that affect vector competence is essential for the identification of molecular drivers for tick-borne diseases. In this review, we provide a comprehensive overview of tick-pathogen molecular interactions for bacteria, viruses, and protozoa affecting human and animal health. Additionally, the impact of tick microbiome on these interactions was considered. Results show that different pathogens evolved similar strategies such as manipulation of the immune response to infect vectors and facilitate multiplication and transmission. Furthermore, some of these strategies may be used by pathogens to infect both tick and mammalian hosts. Identification of interactions that promote tick survival, spread, and pathogen transmission provides the opportunity to disrupt these interactions and lead to a reduction in tick burden and the prevalence of tick-borne diseases. Targeting some of the similar mechanisms used by the pathogens for infection and transmission by ticks may assist in development of preventative strategies against multiple tick-borne diseases.

Identification, Distribution and Population Dynamics of Francisella-like Endosymbiont in Haemaphysalis doenitzi (Acari: Ixodidae)

Francisella-like endosymbionts (FLEs) with significant homology to Francisella tularensis (γ-proteobacteria) have been characterized in several tick species, whereas knowledge on their distribution and population dynamics in ticks remains meager. Hence, in the current study, we identified a novel Francisella-like endosymbiont (FLEs-Hd) from the tick Haemaphysalis doenitzi and evaluated the putative functions of this symbiont. Results indicated that FLEs-Hd had 100% infection rate and a perfect vertical transmission in H. doenitzi, and that it is distributed in ovaries, malpighian tubules, salivary glands and midguts of the ticks, suggesting that FLEs-Hd presumably is a crucial symbiont of the host without specific tissue tropism. To further explore the function of the symbiont, the population dynamics of FLEs-Hd at each developmental stage of ticks and in tissues at different reproductive statuses were determined by real-time quantitative polymerase chain reaction (real-time qPCR). Results showed that the high density and regular population dynamics of FLEs-Hd appeared in female ovaries, suggesting that the symbiont may provide necessary nutrients or regulators to ensure normal ovary development of ticks.

Tick species, tick-borne pathogens and symbionts in an insular environment off the coast of Western France

Insular environments provide ideal natural conditions to study disease ecology, especially emerging diseases, due to clear differentiation between local and long-distance transmission. Such environments are of particular interest regarding tick-borne pathogens (TBP), since animal exchange with the mainland (along with any ticks they carry) is limited, and because such locations could lie on migratory routes for birds carrying ticks. Therefore both tick species and TBP may display different prevalence than those observed on the continent. As such, an epidemiological survey was performed on Belle-Ile-en-Mer, an island off the coast of Western France, in order to estimate the prevalence of tick species and the microorganisms they carried. Three tick species, Dermacentor marginatus, D. reticulatus, and Haemaphysalis punctata were collected at five different sites in 2010 and 2011. All ticks were tested for pathogen's and symbiont's DNA by (i) PCR for Anaplasma spp., Borrelia spp., Rickettsia spp.; (ii) real-time PCR for Francisella tularensis, Francisella-like endosymbionts (FLE) and Coxiella spp. and (iii) PCR-RLB for Babesia-Theileria spp. Pathogen DNA detected in D. marginatus including Borrelia spp. (18%), Rickettsia spp. (13%) which was identified as R. slovaca, Babesia spp. (8%), and Theileria spp. (1%). Pathogens detected in D. reticulatus including Rickettsia spp. (31%) identified as R. raoulti, Francisella-like endosymbiont (86%), and Babesia spp (21%). Pathogens detected in H. punctata including Rickettsia spp. (1%) identified as R. aeschlimannii, FLE (0.4%), Babesia spp. (18%), and Theileria spp. (7%). Anaplasma spp., F. tularensis, or Coxiella spp. were not detected in any of the collected ticks. This study represents the first epidemiological survey of the insular Belle-Ile-en-Mer environment. It demonstrated the presence of expected pathogens, consistent with reports from island veterinarians or physicians, as well as unexpected pathogens, raising questions about their potential introduction through infected animals and/or their dispersion by migratory birds.

Population dynamics of multiple symbionts in the hard tick, Dermacentor silvarum Olenev (Acari: Ixodidae)

Previously, we reported that Coxiella-like, Rickettsia-like and Arsenophonus-like symbionts could simultaneously coexist in Dermacentor silvarum. In this study, we examined their burdens and population dynamics in a single host during the host life cycle using quantitative PCR. Our results showed that multiple symbionts exhibited different abundances and varying trends in the tick host. Coxiella-like and Rickettsia-like symbionts were found at high densities in large quantities that fluctuated with time. This may coincide with oogenesis and mating of the host. Our findings provide insight into symbiont-tick interactions that lay the foundation for future studies.

Francisella species in ticks and animals, Iberian Peninsula

The presence of Francisella species in 2134 ticks, 93 lagomorphs and 280 small mammals from the Iberian Peninsula was studied. Overall, 19 ticks and 6 lagomorphs were positive for Francisella tularensis subsp. holarctica, suggesting, as described for other regions, that lagomorphs may have an important role in the maintenance of F. tularensis in nature. Of the 6 positive lagomorphs, 4 were identified as the European rabbit, Oryctogalus cuniculus. Additionally, 353 ticks and 3 small mammals were PCR positive for Francisella-like endosymbionts (FLEs) and one small mammal was also positive for Francisella hispaniensis-like DNA sequences. Among FLE positive specimens, a variety of sequence types were detected: ticks were associated with 5 lpnA sequence types, with only one type identified per tick, in contrast to 2 lpnA sequence types detected in a single wood mouse (Apodemus sylvaticus). To our knowledge, this is the first report of FLEs in free-living small mammals as well as the first detection of F. hispaniensis-like sequences in a natural setting.

Occurrence of Francisella spp. in Dermacentor reticulatus and Ixodes ricinus ticks collected in eastern Poland

A total of 530 questing Dermacentor reticulatus ticks and 861 questing Ixodes ricinus ticks were collected from Lublin province (eastern Poland) and examined for the presence of Francisella by PCR for 16S rRNA (rrs) and tul4 genes. Only one female D. reticulatus tick out of 530 examined (0.2%) was infected with Francisella tularensis subspecies holarctica, as determined by PCR of the rrs gene. None of 861 I. ricinus ticks were infected with F. tularensis. In contrast, the presence of Francisella-like endosymbionts (FLEs) was detected in more than half of the D. reticulatus ticks (50.4%) and 0.8% of the I. ricinus ticks. The nucleotide sequences of the FLEs detected in D. reticulatus exhibited 100% homology with the nucleotide sequence of the FLE strain FDrH detected in Hungary in D. reticulatus. In conclusion, our results suggest a low contribution of D. reticulatus and I. ricinus ticks to the circulation of F. tularensis in eastern Poland. This finding, however, needs to be confirmed by further studies in other areas. Our study confirmed the common infection of D. reticulatus with Francisella-like endosymbionts (FLEs) of unknown pathogenic potential and revealed, for the first time, a low grade of infection of I. ricinus with FLEs.

Detection of Francisella-like endosymbiont in Hyalomma rufipes from Ethiopia

The expanding family of Francisellaceae includes the genus Francisella, where several pathogen bacteria, e.g. the zoonotic F. tularensis, and different Francisella-like agents belong to. Francisella-like endosymbionts (FLEs) are widespread in hard and soft ticks and their pathogenicity is unknown. The examination of 296 ticks collected in Ethiopia was performed for the detection of F. tularensis and FLEs using polymerase chain reaction (PCR) assays based on the amplification of 16S rRNA, sdhA and tul4 gene fragments. FLE was described in one Hyalomma rufipes tick based on the 16S rRNA and sdhA gene sequences. The 16S rRNA gene fragment was identical with the ones detected previously in Rhipicephalus sanguineus and Hyalomma marginatum marginatum in Bulgaria. The presence of endosymbionts with identical 16S rRNA gene sequence in both Rhipicephalus and Hyalomma species further supports the hypotheses, that certain FLEs had independent evolution from their tick hosts.

Comparative review of Francisella tularensis and Francisella novicida

Francisella tularensis is the causative agent of the acute disease tularemia. Due to its extreme infectivity and ability to cause disease upon inhalation, F. tularensis has been classified as a biothreat agent. Two subspecies of F. tularensis, tularensis and holarctica, are responsible for tularemia in humans. In comparison, the closely related species F. novicida very rarely causes human illness and cases that do occur are associated with patients who are immune compromised or have other underlying health problems. Virulence between F. tularensis and F. novicida also differs in laboratory animals. Despite this varying capacity to cause disease, the two species share ~97% nucleotide identity, with F. novicida commonly used as a laboratory surrogate for F. tularensis. As the F. novicida U112 strain is exempt from U.S. select agent regulations, research studies can be carried out in non-registered laboratories lacking specialized containment facilities required for work with virulent F. tularensis strains. This review is designed to highlight phenotypic (clinical, ecological, virulence, and pathogenic) and genomic differences between F. tularensis and F. novicida that warrant maintaining F. novicida and F. tularensis as separate species. Standardized nomenclature for F. novicida is critical for accurate interpretation of experimental results, limiting clinical confusion between F. novicida and F. tularensis and ensuring treatment efficacy studies utilize virulent F. tularensis strains.

Tularaemia: a challenging zoonosis

In recent years, several emerging zoonotic vector-borne infections with potential impact on human health have been identified in Europe, including tularaemia, caused by Francisella tularensis. This remarkable pathogen, one of the most virulent microorganisms currently known, has been detected in increasingly new settings and in a wide range of wild species, including lagomorphs, rodents, carnivores, fish and invertebrate arthropods. Also, a renewed concern has arisen with regard to F. tularensis: its potential use by bioterrorists. Based on the information published concerning the latest outbreaks, the aim of this paper is to review the main features of the agent, its biology, immunology and epidemiology. Moreover, special focus will be given to zoonotic aspects of the disease, as tularaemia outbreaks in human populations have been frequently associated with disease in animals.

An insight into the microbiome of the Amblyomma maculatum (Acari: Ixodidae)

The aim of this study was to survey the bacterial diversity of Amblyomma maculatum Koch, 1844, and characterize its infection with Rickettsia parkeri. Pyrosequencing of the bacterial 16S rRNA was used to determine the total bacterial population in A. maculatum. Pyrosequencing analysis identified Rickettsia in A. maculatum midguts, salivary glands, and saliva, which indicates successful trafficking in the arthropod vector. The identity of Rickettsia spp. was determined based on sequencing the rickettsial outer membrane protein A (rompA) gene. The sequence homology search revealed the presence of R. parkeri, Rickettsia amblyommii, and Rickettsia endosymbiont ofA. maculatum in midgut tissues, whereas the only rickettsia detected in salivary glands was R. parkeri, suggesting it is unique in its ability to migrate from midgut to salivary glands, and colonize this tissue before dissemination to the host. Owing to its importance as an emerging infectious disease, the R. parkeri pathogen burden was quantified by a rompB-based quantitative polymerase chain reaction (qPCR) assay and the diagnostic effectiveness of using R. parkeri polyclonal antibodies in tick tissues was tested. Together, these data indicate that field-collected A. maculatum had a R. parkeri infection rate of 12-32%. This study provides an insight into the A. maculatum microbiome and confirms the presence of R. parkeri, which will serve as the basis for future tick and microbiome interaction studies.

Microbial communities and symbionts in the hard tick Haemaphysalis longicornis (Acari: Ixodidae) from north China

Background

Close relationships between ticks and microbial communities are important for tick fitness and pathogen colonization and transmission. Haemaphysalis longicornis, distributed widely in China, can carry and transmit various pathogens and pose serious damages to public health and economics. However, little is known about the broader array of microbial communities and symbionts in H. longicornis under natural conditions. In the present study, we investigated the composition of bacterial communities associated with H. longicornis and evaluated the putative symbionts.

Methods

The eubacterial 16S rRNA gene clone libraries of H. longicornis were constructed and analyzed by restriction fragment length polymorphism (RFLP) and DNA sequencing. In addition, diagnostic PCR was performed to assess the prevalence, vertical transmission and infection sites of the symbionts in H. longicornis.

Results

Vertically-transmitted symbionts, potential pathogens and allochthonous nonpathogenic bacteria were identified from the field-collected H. longicornis. Three types of symbionts (Coxiella-like, Arsenophonus-like and Rickettsia-like symbionts) were identified in a single host simultaneously. A series of analyses revealed the vertical transmission, prevalence, and infection sites of these symbionts. However, only Coxiella-like bacteria were transmitted stably in the laboratory-reared ticks. In addition, we identified a novel Coxiella-like agent with 95.31% sequence similarity to the taxon described previously.

Conclusions

The present study demonstrated that natural H. longicornis harboured a diverse array of microbial communities. Three types of symbionts were identified in a single host simultaneously. Moreover, high prevalence, vertical transmission and the infection sites supported an obligate symbiotic association between Coxiella symbiont and its host. The role of Coxiella symbiont in the host fitness and the interaction among microbial communities remained to be elucidated. Our investigation of microbial communities in the ticks revealed the complexity of ecological interactions between host and microbe and provided insight for the biological control of ticks.

Prevalence of Francisella tularensis and Francisella-like endosymbionts in the tick population of Hungary and the genetic variability of Francisella-like agents

Several new taxa belonging to the genus Francisella have been described recently. The present study describes the prevalence of Francisella tularensis and Francisella-like endosymbionts (FLE) in ticks collected from Hungary from 2007 to 2009 and characterizes the genetic variability of FLEs. A total of 5402 Ixodid ticks (Ixodes ricinus, I. acuminatus, Dermacentor marginatus, D. reticulatus, Haemaphysalis inermis, H. concinna, H. punctata) were collected from vegetation and animal hosts and tested with conventional PCR, detecting the 16S rRNA and tul4 genes. F. tularensis ssp. holarctica was found in 2 pools of H. concinna and 1 pool of D. reticulatus, both representing minimum prevalence (calculated with 1 infected tick per pool) of 0.27% whereas the sequences of a FLE were detected in 11 pools of D. reticulatus showing a minimum prevalence of 3%. Although the tul4 gene sequence of this FLE was identical to all Hungarian and Portuguese FLEs found earlier, and the 16S rRNA sequence was also identical to the sequence of the endosymbiont of D. reticulatus described in Bulgaria, these 16S rRNA gene coding sequences differed in 2 nucleotides from the one found earlier in this tick species in Hungary. This divergence may appear to be a minor difference between the sequences, potentially even resulting from a technical failure, but it could also indicate a significant difference stemming from the conservative genetic character of Francisellaceae. Thus, it raises a question about the number of FLE variants circulating in D. reticulatus in Europe and indicates the need for further data about the FLEs described in other parts of the continent and new FLE genotyping markers.

Discriminating Francisella tularensis and Francisella-like endosymbionts in Dermacentor reticulatus ticks: evaluation of current molecular techniques

Francisella tularensis, the causative agent of tularemia, is commonly transmitted by ticks. To ensure accurate F. tularensis reporting rates in epidemiological surveys, specific discrimination between F. tularensis and Francisella-like tick endosymbionts (FLEs) is absolutely critical. Four molecular available techniques capable of distinguishing Francisella spp. were compared here for the first time in French Dermacentor reticulatus ticks in order to estimate their specificity as well as their ease and speed of use. Results showed that tul4 and fopA real-time PCR assays can easily and effectively discriminate between F. tularensis and FLEs in D. reticulatus. In addition, a high prevalence of FLEs in D. reticulatus collected in France was reported by the use of fopA real-time PCR assay (79%). Finally, phylogenetic analysis showed that FLEs isolated from D. reticulatus correspond to a well-defined group compared to FLEs originating from various tick species.