Detection of Alpha and Gamma-Proteobacteria in Amblyomma triste (Acari: Ixodidae) from Uruguay

Pathologic and Immunohistochemical Evidence of Possible Francisellaceae among Aborted Ovine Fetuses, Uruguay

The only genus of the Francisellaceae family known to contain species pathogenic to mammals is Francisella, for which reported cases in the Southern Hemisphere have been limited to Australia. We describe severe necrotizing and inflammatory lesions and intralesional immunohistochemical identification of Francisella sp. lipopolysaccharide among aborted ovine fetuses in Uruguay.

Rickettsia spp., Ehrlichia sp. and Candidatus Midichloria sp. associated to ticks from a protected urban area in Buenos Aires City (Argentina)

The aim of this study was to determine the infection with Rickettsiales in ticks and birds from the main protected urban area of Buenos Aires City (Argentina). One Amblyomma aureolatum (0.2%) and one Ixodes auritulus (0.1%) were positive by PCR targeting Rickettsia 23S-5S rRNA intergenic spacer. Phylogenetic analysis shows to findings in A. aureolatum are closely to Rickettsia bellii and for I. auritulus are related to 'Candidatus Rickettsia mendelii'. One I. auritulus (0.1%) and three A. aureolatum (0.6%) were positive by PCR for a fragment of the 16S rRNA gene of the Anaplasmataceae family. The sequences obtained from A. aureolatum were phylogenetically related to Midichloriaceae endosymbionts. The sequence from I. auritulus s.l. had 100% identity with Ehrlichia sp. Magellanica from Chile and two genotypes of Ehrlichia sp. from Uruguay. The results of our study show that Rickettsia and Ehrlichia are present in ticks in the main protected urban area of Buenos Aires City.

Characterization of "Candidatus Ehrlichia Pampeana" in Haemaphysalis juxtakochi Ticks and Gray Brocket Deer (Mazama gouazoubira) from Uruguay

Human ehrlichiosis are scantily documented in Uruguay. The aim of this study was to investigate the presence of Ehrlichia spp. in Haemaphysalis juxtakochi and in a gray brocket deer (Mazama gouazoubira) from Uruguay. The presence of Ehrlichia DNA was investigated in free-living H. juxtakochi in five localities of southeast and northeast Uruguay, as well as blood, spleen, and ticks retrieved from a M. gouazoubira. Ehrlichia spp. DNA was detected in six out of 99 tick pools from vegetation, in the spleen of M. gouazoubira, and in one out of five pools of ticks feeding on this cervid. Bayesian inference analyses for three loci (16S rRNA, dsb, and groEL) revealed the presence of a new rickettsial organism, named herein as "Candidatus Ehrlichia pampeana". This new detected Ehrlichia is phylogenetically related to those found in ticks from Asia, as well as Ehrlichia ewingii from USA and Cameroon. Although the potential pathogenicity of "Ca. E. pampeana" for humans is currently unknown, some eco-epidemiological factors may be relevant to its possible pathogenic role, namely: (i) the phylogenetic closeness with the zoonotic agent E. ewingii, (ii) the evidence of H. juxtakochi parasitizing humans, and (iii) the importance of cervids as reservoirs for zoonotic Ehrlichia spp. The molecular detection of "Ca. E. pampeana" represents the third Ehrlichia genotype described in Uruguay.

Survey of ticks and tick-borne agents in maned wolves (Chrysocyon brachyurus) from a natural landscape in Brazil

This study evaluated ticks and tick-borne agents in 104 captures of the maned wolf Chrysocyon brachyurus (50 different individuals and 54 recaptures) in the Serra da Canastra National Park (SCNP), a Cerrado preserved area in southeastern Brazil, from 2005 to 2012. From the 104 capture events, a total of 1,206 ticks were collected on 94 occasions (90.4 %), and identified into five species: Amblyomma tigrinum (77.3 % of all collected ticks), Amblyomma sculptum (16.6 %), Amblyomma ovale (0.1 %), Amblyomma brasiliense (0.1 %), Rhipicephalus microplus (0.1 %), and Amblyomma spp. larvae (5.8 %). Molecular analyses of A. tigrinum adult ticks revealed the presence of 'Candidatus Rickettsia andeanae', Rickettsia parkeri sensu stricto, two different haplotypes of 'Ca. Midichloria sp.', and a Hepatozoon canis haplotype. Molecular analyses of maned wolf blood samples revealed two distinct haplotypes of Hepatozoon spp., one identical to the H. canis genotype that was detected in the A. tigrinum ticks, and a Hepatozoon americanum-like haplotype. None tick or blood samples yielded amplicons through PCR assays targeting the genera Ehrlichia, Anaplasma, Babesia, Rangelia, Cytauxzoon, and Theileria. Maned wolf serum samples were tested by immunofluorescence assay against antigens of five Rickettsia species (R. parkeri, R. rickettsii, R. amblyommatis, R. rhipicephali, and R. bellii) and Ehrlichia canis. Among 78 serum samples (45 captures plus 33 recaptures), 74 (95 %) were reactive to at least one Rickettsia species, with R. parkeri eliciting the highest endpoint titers. Some maned wolves that were recaptured during the study were shown to seroconvert to R. parkeri. Serum-reactiveness to E. canis was detected in 36 % (16/45) maned wolves. During the study, general clinical signs of tick-borne diseases were not found in any of the captured animals, indicating that they were under a good health status in the SCNP, despite of been exposed to ticks (mostly A. tigrinum) and some tick-borne agents (Rickettsia, Hepatozoon, Ehrlichia). The results of the present study might represent baseline data for the conservation of the maned wolf in its natural habitat, which should be used to interpret further studies about ticks and tick-borne diseases in maned wolves within human-modified landscapes.

Microbial community of Hyalomma lusitanicum is dominated by Francisella-like endosymbiont

Exploring tick associations with complex microbial communities and single-microbial partners, especially intracellular symbionts, has become crucial to understand tick biology. Of particular interest are the underlying interactions with biological consequences i.e. tick fitness, vector competence. In this study, we first sequenced the 16S rRNA bacterial phylogenetic marker in adult male ticks of Hyalomma lusitanicum collected from 5 locations in the province of Cáceres to explore the composition of its microbial community. Overall, 16S rRNA sequencing results demonstrated that the microbial community of H. lusitanicum is mostly dominated by Francisella-like endosymbionts (FLEs) (ranging from 52% to 99% of relative abundance) suggesting it is a key taxon within the microbial community and likely a primary endosymbiont. However, further research is required to explore the mechanisms underlying the interaction between FLEs and H. lusitanicum.

A novel Ehrlichia strain (Rickettsiales: Anaplasmataceae) detected in Amblyomma triste (Acari: Ixodidae), a tick species of public health importance in the Southern Cone of America

The aim of this work was to report the detection of a putative novel Ehrlichia strain associated with the tick Amblyomma triste. Free-living adult ticks determined as A. triste were collected by drag-sampling in Argentina and Uruguay. Molecular detection of Ehrlichia agents was performed targeting three different loci: 16S rRNA gene, dsb gene and a fragment of groESL heat shock operon. In total, 164 adults of A. triste (38 from INTA E.E.A Delta del Paraná in Argentina and 126 from Toledo Chico in Uruguay) were analyzed. One tick (0.6%) collected in INTA E.E.A. Delta del Paraná (Argentina) was positive. The phylogenetic analyses show that the Ehrlichia strain found in this study (named Ehrlichia sp. strain Delta) represents an independent lineage within the genus Ehrlichia, close to E. chaffeensis and E. muris. This is also the first report of an Ehrlichia agent infecting the tick A. triste. The medical and veterinary significance of Ehrlichia sp. strain Delta remains to be demonstrated. However, it is important to mention that adults of A. triste are aggressive to humans and domestic mammals. Therefore, the potential role of A. triste in the transmission of Ehrlichia agents to humans or domestic animals across its distributional range should be highlighted, even more considering that Ehrlichia sp. strain Delta is phylogenetically related to the zoonotic E. chaffeensis, which is recognized as pathogenic to both humans and animals.

Bovine anaplasmosis and tick-borne pathogens in cattle of the Galapagos Islands

A cross-sectional study was conducted to determine the species of Anaplasma spp. and estimate its prevalence in cattle of the three main cattle-producing Galapagos Islands (Santa Cruz, San Cristóbal and Isabela) using indirect PCR assays, genetic sequencing and ELISA. Ticks were also collected from cattle and scanned for 47 tick-borne pathogens in a 48 × 48 real-time PCR chip. A mixed effects logistic regression was performed to identify potential risk factors explaining Anaplasma infection in cattle. A. phagocytophilum was not detected in any of the tested animals. Genetic sequencing allowed detection of A. platys-like strains in 11 (36.7%) of the 30 Anaplasma spp.-positive samples analysed. A. marginale was widespread in the three islands with a global between-herd prevalence of 100% [89; 100]_{95% CI} and a median within-herd prevalence of 93%. A significant association was found between A. marginale infection and age with higher odds of being positive for adults (OR = 3.3 [1.2; 9.9]_{95% Bootstrap CI} ). All collected ticks were identified as Rhipicephalus microplus. A. marginale, Babesia bigemina, Borrelia theileri and Francisella-like endosymbiont were detected in tick pools. These results show that the Galapagos Islands are endemic for A. marginale.

Patterns of Midichloria infection in avian-borne African ticks and their trans-Saharan migratory hosts

Background

Ticks are obligate haematophagous ectoparasites of vertebrates and frequently parasitize avian species that can carry them across continents during their long-distance migrations. Ticks may have detrimental effects on the health state of their avian hosts, which can be either directly caused by blood-draining or mediated by microbial pathogens transmitted during the blood meal. Indeed, ticks host complex microbial communities, including bacterial pathogens and symbionts. Midichloria bacteria (Rickettsiales) are widespread tick endosymbionts that can be transmitted to vertebrate hosts during the tick bite, inducing an antibody response. Their actual role as infectious/pathogenic agents is, however, unclear.

Methods

We screened for Midichloria DNA African ticks and blood samples collected from trans-Saharan migratory songbirds at their arrival in Europe during spring migration.

Results

Tick infestation rate was 5.7%, with most ticks belonging to the Hyalomma marginatum species complex. Over 90% of Hyalomma ticks harboured DNA of Midichloria bacteria belonging to the monophylum associated with ticks. Midichloria DNA was detected in 43% of blood samples of avian hosts. Tick-infested adult birds were significantly more likely to test positive to the presence of Midichloria DNA than non-infested adults and second-year individuals, suggesting a long-term persistence of these bacteria within avian hosts. Tick parasitism was associated with a significantly delayed timing of spring migration of avian hosts but had no significant effects on body condition, whereas blood Midichloria DNA presence negatively affected fat deposits of tick-infested avian hosts.

Conclusions

Our results show that ticks effectively transfer Midichloria bacteria to avian hosts, supporting the hypothesis that they are infectious to vertebrates. Bird infection likely enhances the horizontal spread of these bacteria across haematophagous ectoparasite populations. Moreover, we showed that Midichloria and tick parasitism have detrimental non-independent effects on avian host health during migration, highlighting the complexity of interactions involving ticks, their vertebrate hosts, and tick-borne bacteria.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-2669-z) contains supplementary material, which is available to authorized users.

The Tick Microbiome: Why Non-pathogenic Microorganisms Matter in Tick Biology and Pathogen Transmission

Ticks are among the most important vectors of pathogens affecting humans and other animals worldwide. They do not only carry pathogens however, as a diverse group of commensal and symbiotic microorganisms are also present in ticks. Unlike pathogens, their biology and their effect on ticks remain largely unexplored, and are in fact often neglected. Nonetheless, they can confer multiple detrimental, neutral, or beneficial effects to their tick hosts, and can play various roles in fitness, nutritional adaptation, development, reproduction, defense against environmental stress, and immunity. Non-pathogenic microorganisms may also play a role in driving transmission of tick-borne pathogens (TBP), with many potential implications for both human and animal health. In addition, the genetic proximity of some pathogens to mutualistic symbionts hosted by ticks is evident when studying phylogenies of several bacterial genera. The best examples are found within members of the Rickettsia, Francisella, and Coxiella genera: while in medical and veterinary research these bacteria are traditionally recognized as highly virulent vertebrate pathogens, it is now clear to evolutionary ecologists that many (if not most) Coxiella, Francisella, and Rickettsia bacteria are actually non-pathogenic microorganisms exhibiting alternative lifestyles as mutualistic ticks symbionts. Consequently, ticks represent a compelling yet challenging system in which to study microbiomes and microbial interactions, and to investigate the composition, functional, and ecological implications of bacterial communities. Ultimately, deciphering the relationships between tick microorganisms as well as tick symbiont interactions will garner invaluable information, which may aid in the future development of arthropod pest and vector-borne pathogen transmission control strategies.

"Candidatus Fokinia solitaria", a Novel "Stand-Alone" Symbiotic Lineage of Midichloriaceae (Rickettsiales)

Recently, the family Midichloriaceae has been described within the bacterial order Rickettsiales. It includes a variety of bacterial endosymbionts detected in different metazoan host species belonging to Placozoa, Cnidaria, Arthropoda and Vertebrata. Representatives of Midichloriaceae are also considered possible etiological agents of certain animal diseases. Midichloriaceae have been found also in protists like ciliates and amoebae. The present work describes a new bacterial endosymbiont, "Candidatus Fokinia solitaria", retrieved from three different strains of a novel Paramecium species isolated from a wastewater treatment plant in Rio de Janeiro (Brazil). Symbionts were characterized through the full-cycle rRNA approach: SSU rRNA gene sequencing and fluorescence in situ hybridization (FISH) with three species-specific oligonucleotide probes. In electron micrographs, the tiny rod-shaped endosymbionts (1.2 x 0.25-0.35 μm in size) were not surrounded by a symbiontophorous vacuole and were located in the peripheral host cytoplasm, stratified in the host cortex in between the trichocysts or just below them. Frequently, they occurred inside autolysosomes. Phylogenetic analyses of Midichloriaceae apparently show different evolutionary pathways within the family. Some genera, such as "Ca. Midichloria" and "Ca. Lariskella", have been retrieved frequently and independently in different hosts and environmental surveys. On the contrary, others, such as Lyticum, "Ca. Anadelfobacter", "Ca. Defluviella" and the presently described "Ca. Fokinia solitaria", have been found only occasionally and associated to specific host species. These last are the only representatives in their own branches thus far. Present data do not allow to infer whether these genera, which we named "stand-alone lineages", are an indication of poorly sampled organisms, thus underrepresented in GenBank, or represent fast evolving, highly adapted evolutionary lineages.

Coxiella-like endosymbionts

In the past two decades, many Coxiella-like bacteria have been found in hard ticks and soft ticks as well as in vertebrate hosts. It is interesting to note that many ticks harbor Coxiella-like bacteria with high prevalence. Coxiella-like bacteria and virulent Coxiella burnetii have high homology to each other; they form a monophyletic clade based on 16S rRNA sequence data and subsequent phylogenetic tree analyses. In this chapter, methods of detection, phylogeny, prevalence and density, distribution in tick organs, transmission routes, bacteria-host interactions, and putative functions of the Coxiella-like bacteria are reviewed.

Presence, genetic variability, and potential significance of "Candidatus Midichloria mitochondrii" in the lone star tick Amblyomma americanum

We used next generation sequencing to detect the bacterium "Candidatus Midichloria mitochondrii" for the first time in lone star ticks (Amblyomma americanum) from the eastern United States. 177 individuals and 11 tick pools from seven sites in four states were tested by pyrosequencing with barcoded 16S rRNA gene eubacterial primers targeting variable regions 5-3. Average infection prevalence was 0.15 across all surveyed populations (range 0-0.29) and only the site with the smallest sample size (n = 5) was negative. Three genotypes differing by 2.6-4.1 % in a 271 bp region of 16S rRNA gene were identified. Two variants co-occurred in sites in North Carolina and New York, but were not observed in the same tick at those sites. The third genotype was found only in Georgia. Phylogenetic analysis of this fragment indicated that the three variants are more closely related to "Candidatus Midichloria mitochondrii" genotypes from other tick species than to each other. This variation suggests that multiple independent introductions occurred in A. americanum which may provide insight into bacterial spread within its ecosystem and parasitism on this tick. Whether the presence of this bacterium affects acquisition or maintenance of other pathogens and symbionts in A. americanum or the survival, biology and evolution of the tick itself is unknown.

Detection of bacteria related to Candidatus Midichloria mitochondrii in tick cell lines

Many ticks have been shown to be infected with intracellular bacteria. One of these bacteria is Candidatus Midichloria mitochondrii which is the only characterized bacterium that has the ability to invade the mitochondria within ovarian cells and consume them without any effect on the female tick's reproduction. In the present study, eight cell lines derived from the ticks Ixodes ricinus, Ixodes scapularis, Rhipicephalus (Boophilus) microplus, and Rhipicephalus (Boophilus) decoloratus were examined for the presence of the bacterium Ca. Midichloria mitochondrii. PCR assays for this bacterium were carried out using two sets of primers targeting the eubacterial 16SrRNA gene and a set of primers specific for the gyrB gene of Ca. Midichloria mitochondrii. With the 16S rRNA primers, DNA was amplified from two cell lines (R. (B.) decoloratus line BDE/CTVM14 and I. ricinus line IRE/CTVM19) on one out of three occasions each. Sequencing of the PCR products showed that the two cell lines gave sequences with 100% similarity to Ca. Midichloria mitochondrii. However, all cell lines, including the two positive cell lines, were negative with the specific primers. Phylogenetic analysis shows that our sequences belong to the subclass α-proteobacteria. They were identical to the sequences amplified from the tick I. ricinus. The results suggest that two cell lines, IRE/CTVM19 and BDE/CTVM14, may contain bacteria closely related to Ca. Midichloria mitochondrii and identical with it in a 350-bp part of the 16S rRNA gene sequence. To our knowledge, this constitutes the first report of the presence of DNA similar to the DNA of Ca. Midichloria mitochondrii in tick cell lines.

"Candidatus anadelfobacter veles" and "Candidatus cyrtobacter comes," two new rickettsiales species hosted by the protist ciliate Euplotes harpa (Ciliophora, Spirotrichea)

The order Rickettsiales (Alphaproteobacteria) is a well-known group containing obligate endocellular prokaryotes. The order encompasses three families (Rickettsiaceae, Anaplasmataceae, and Holosporaceae) and a fourth, family-level cluster, which includes only one candidate species, "Candidatus Midichloria mitochondrii," as well as several unnamed bacterial symbionts. The broad host range exhibited by the members of the "Candidatus Midichloria" clade suggests their eventual relevance for a better understanding of the evolution of symbiosis and host specificity of Rickettsiales. In this paper, two new bacteria belonging to the "Candidatus Midichloria" clade, hosted by two different strains of the ciliate protist Euplotes harpa, are described on the basis of ultrastructural observations, comparative 16S rRNA gene sequence analysis, and an estimation of the percentage of infection. Ultrastructure of these bacteria shows some unusual features: one has an electron-dense cytoplasm, and the other one lacks a symbiosomal membrane. The latter was up to now considered an exclusive feature of bacteria belonging to the family Rickettsiaceae. 16S rRNA gene phylogenetic analysis unambiguously places the new bacteria in the "Candidatus Midichloria" clade, although their phylogenetic relationships with other members of the clade are not clearly resolved. This is the first report of a ciliate-borne bacterium belonging to the "Candidatus Midichloria" clade. On the basis of the data obtained, the two bacteria are proposed as two new candidate genera and species, "Candidatus Anadelfobacter veles" and "Candidatus Cyrtobacter comes."

Absence of the symbiont Candidatus Midichloria mitochondrii in the mitochondria of the tick Ixodes holocyclus

Candidatus Midichloria mitochondrii (M. mitochondrii) belongs to a novel clade of bacteria within the order Rickettsiales. Recent PCR-based screening studies indicate that it is present in a number of blood-sucking arthropods, as well as the blood of some vertebrates. Its medical and veterinary significance remains to be determined. Electron microscopic examinations of M. mitochondrii have thus far been conducted on two infected tick species. Remarkably, the bacterium was found in abundance within the mitochondria of the ovarian cells of each tick species. This makes it the only characterized bacterium able to invade the mitochondria of any multicellular organism. To examine whether mitochondrial invasion is a consistent characteristic of M. mitochondrii, we examined two tick species found in Eastern Australia. One of these species, Ixodes holocyclus, was infected with two M. mitochondrii strains; however, no bacteria were seen in the mitochondria. Comparative studies involving these strains may shed light on the unique phenomenon of mitochondrial invasion.

Francisella-like endosymbiont DNA and Francisella tularensis virulence-related genes in Brazilian ticks (Acari: Ixodidae)

Ticks are vectors of a variety of pathogens, including Francisella tularensis. Bacteria in the genus Francisella have been identified mostly in the Northern Hemisphere and include tick endosymbionts. Francisella has never been described in Brazil, where Amblyomma spp. ticks are known as the vector of many bacterial zoonotic pathogens. In the present work, we have identified bacterial DNA sequences with identity to Francisella genes in Amblyomma dubitatum Neumann Dermacentor nitens (Neumann), and Rhipicephalus microplus (Canestrini) in Brazil. DNA fragments with homology to Francisella spp. 16S rDNA and the tul4 gene were polymerase chain reaction amplified from tick DNA samples collected in Minas Gerais and Mato Grosso states. These sequences were 96-99% identical to the reported sequences for Francisella-like tick endosymbionts (FLEs). Sequences similar to the tularemia agent F. tularensis pathogenicity island gene iglC and its regulatory gene mglA also were identified in FLEs.