Infection with Ehrlichia canis and Anaplasma platys (Rickettsiales: Anaplasmataceae) in two lineages of Rhipicephalus sanguineus sensu lato (Acari: Ixodidae) from Argentina

Molecular detection and phylogenetic analysis of Anaplasma platys-like and Candidatus Anaplasma boleense strains from Argentina

The present study aimed at the molecular detection of Anaplasma spp. in different samples obtained from cattle, goats and free-living Rhipicephalus microplus ticks from Argentina. DNA of members of the Anaplasmataceae family was detected by different PCR assays. The phylogenetic analyses of the obtained partial DNA sequences of the 16 S rDNA gene resulted in the identification of two different Anaplasma spp.: (I) Anaplasma platys-like bacteria (in blood sample from cattle and pools of R. microplus larvae and (II) Candidatus Anaplasma boleense (in blood samples from goats and one pool of R. microplus larvae of R. microplus). Candidatus A. boleense was found in two provinces that belong to different biogeographic regions, which leads to the conclusion that this bacterium may be widely distributed in Argentina. Interestingly, both Anaplasma spp. were found in the same R. microplus population in Chaco province, indicating that these two strains of Anaplasma are circulating in the same tick population. The results of this work represent the first report of the circulation of A. platys-like bacteria and Ca. A. boleense in domestic ruminants and free-living R. microplus ticks in Argentina. Further studies to determine the prevalence of infection, dispersion, clinical impact, transmission routes and cross-reactivity in serological tests of both Anaplasma species are needed.

Molecular detection and phylogeny of Ehrlichia canis and Anaplasma platys in naturally infected dogs in Central and Northeast Thailand

Background and Aim

Ehrlichia canis and Anaplasma platys are tick-borne, Gram-negative bacteria that cause canine monocytic ehrlichiosis and canine cyclic thrombocytopenia, respectively. These diseases are of great importance and are distributed globally. This study aimed to create new primers for the identification of E. canis and A. platys in naturally infected dogs using polymerase chain reaction (PCR), DNA sequencing, and phylogenetic analysis using the 16S rDNA and gltA genes.

Materials and Methods

In total, 120 blood samples were collected from dogs in three different locations (Saraburi, Buriram, and Nakhon Ratchasima provinces) in Central and Northeast Thailand. The molecular prevalence of E. canis and A. platys was assessed using PCR targeting the 16S rDNA and gltA genes. All positive PCR amplicons were sequenced, and phylogenetic trees were constructed based on the maximum likelihood method.

Results

Ehrlichia canis had an overall molecular prevalence of 15.8% based on the 16S rDNA gene, compared to 8.3% based on the gltA gene. In addition, the overall molecular prevalence of A. platys using the 16S rDNA gene was 10.8%, while the prevalence rate was 5.8% using the gltA gene. Coinfection was 0.8% in Saraburi province. The partial sequences of the 16S rDNA and gltA genes of E. canis and A. platys in dogs in Central and Northeast Thailand showed 96.75%-100% identity to reference sequences in GenBank. Phylogenetic analysis of the 16S rDNA and gltA genes revealed that E. canis and A. platys sequences were clearly grouped into their own clades.

Conclusion

This study demonstrated the molecular prevalence of E. canis and A. platys in Central and Northeast Thailand. The 16S rDNA and gltA genes were useful for the diagnosis of E. canis and A. platys. Based on the phylogenetic analysis, the partial sequences of the 16S rDNA and gltA genes in E. canis and A. platys were related to prior Thai strains and those from other countries.

Novel Ehrlichia canis genogroup in dogs with canine ehrlichiosis in Cuba

Background

Canine monocytic ehrlichiosis (CME) is caused by the tick-borne pathogen Ehrlichia canis, an obligate intracellular Gram-negative bacterium of the family Anaplasmataceae with tropism for canine monocytes and macrophages. The trp36 gene, which encodes for the major immunoreactive protein TRP36 in E. canis, has been successfully used to characterize the genetic diversity of this pathogen in different regions of the world. Based on trp36 sequence analysis, four E. canis genogroups, United States (US), Taiwan (TWN), Brazil (BR) and Costa Rica (CR), have been identified. The aim of this study was to characterize the genetic diversity of E. canis in Cuba based on the trp36 gene.

Methods

Whole blood samples (n = 8) were collected from dogs found to be infested with the tick vector Rhipicephalus sanguineus sensu lato (s.l.) and/or presenting clinical signs and symptoms of CME. Total DNA was extracted from the blood samples and trp36 fragments were amplified by PCR. Nucleotide and protein sequences were compared using alignments and phylogenetic analysis.

Results

Four of the trp36 sequences obtained (n = 8) fall within the phylogenetic cluster grouping the US genogroup E. canis strains. The other E. canis trp36 sequences formed a separate and well-supported clade (94% bootstrap value) that is phylogenetically distant from the other major groups and thus represents a new genogroup, herein designated as the ‘Cuba (CUB) genogroup’. Notably, dogs infected with the CUB genogroup presented frequent hemorrhagic lesions.

Conclusions

The results of this study suggest that genetic diversification of E. canis in Cuba is associated with the emergence of E. canis strains with increased virulence.

Molecular detection of tick-borne pathogens in Rhipicephalus sanguineus sensu stricto collected from dogs in the steppe and high plateau regions of Algeria

Epidemiology and distributions of canine tick-borne diseases as well as their veterinary and zoonotic significance are poorly understood in Algeria. The present study describes a molecular investigation of important tick-borne pathogens in Rhipicephalus sanguineus sensu stricto collected from domestic dogs in steppe and high plateau areas of central and eastern Algeria. In total, 1,043 ticks were collected from 147 domestic dogs, including 756 ticks from 124 dogs in the steppe region of Djelfa, and 287 ticks from 23 dogs in the high plateau area of Bordj Bou Arreridj. Ticks were divided into 384 pools (309 pools from Djelfa and 75 pools from Bordj Bou Arreridj) and tested for genomic materials of Crimean-Congo hemorrhagic fever virus (CCHFV) as well as DNA for Anaplasma phagocytophilum, Anaplasma platys, Ehrlichia canis, Rickettsia spp., Babesia spp., and Hepatozoon spp. using PCR, sequencing and phylogenetic analysis. Hepatozoon spp. was most prevalent, with 160 positive pools (41.70%), and 12 of these were sequenced and identified as Hepatozoon canis. Babesia spp. was detected in 50 samples (13.0%), of which 11 were sequenced and identified as Babesia vogeli. A. platys and E. canis were detected in 92 (24.0%) and 15 (3.9%) of tested samples, respectively. Rickettsia spp. were detected in 24 (6.3%) samples, including 11 samples identified as R. massiliae, 6 samples identified as R. conorii conorii, and 7 samples could not be identified to species level. All 384 pools tested negative for CCHFV and A. phagocytophilum. In addition to detection of R. conorii conorii, R. massiliae, and E. canis, the present study provides the first molecular data for occurrence of A. platys, B. vogeli, and H. canis in Rh. sanguineus s.s. infesting dogs in Algeria. Further large scale studies should be conducted to better understand the epidemiology, distributions and importance of canine tick-borne pathogens in Algeria.

Rhipicephalus sanguineus Complex in the Americas: Systematic, Genetic Diversity, and Geographic Insights

The Rhipicephalus sanguineus group encompasses at least 12 validated species of Palearctic and Afrotropical hard ticks, which are relevant in veterinary medicine and public health. The taxonomy of R. sanguineus s.s., has been particularly intensely debated, due to its wide geographic distribution, morphological variants, parasite-host associations, and its capacity and vectorial competence for the transmission of several pathogens. By sequencing mitochondrial markers, it was possible to identify the existence of multiple lineages, among which the Tropical and the Temperate lineages stand out, particularly in America. However, the northern limit between these lineages is not clear due to the lack of extensive sampling across Mexico. For this reason, the aim of the present study was to determine the genetic diversity and structure of the R. sanguineus group in Mexico and to compare it with the populations reported in the Americas, in order to propose the northern limit of the R. sanguineus Tropical lineage and the potential regions of sympatry with R. sanguineus s.s. The findings of this study now confirm the presence of R. sanguineus s.s. in Mexico, showing a subtle genetic structure and high genetic diversity throughout its distribution in the Americas. In contrast, the Tropical lineage seems to be genetically less diverse in its overall distribution in the Americas. The genetic diversity of these two independent lineages could have important epidemiological implications in the transmission of tick pathogens.

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.

MOLECULAR INVESTIGATION AND PHYLOGENETIC ANALYSIS OF ANAPLASMOSIS IN DOGS

Anaplasmosis is a widespread vector-borne disease affecting dogs, and Anaplasma platys is the major etiological agent of the disease. The study examines anaplasmosis molecular prevalence, related risk factors, and alteration of hematological variables in Anaplasma-affected dogs. A total of 150 blood samples were collected from dogs in the district of Lahore, Pakistan. The samples were screened with PCR targeting the 16S rRNA gene of Anaplasma. Sequencing of samples that were found positive after performing PCR was conducted. A questionnaire was developed to collect epidemiological data on subject dogs, and the information was analyzed with a logistic regression model using SPSS. The current study revealed an 11.34% (17/150) prevalence of anaplasmosis in dogs based on PCR detection. Tick infestation, previous tick history, house hygiene, and tick control status were major risk factors linked with disease occurrence. Red blood cell count, packed cell volume, hemoglobin, and platelet count were decreased significantly (P < 0.05) in Anaplasma-infected dogs. Phylogenetically, the 2 isolates of the current study clustered together, and that cluster was very similar to A. platys isolates from India, Malaysia, and Thailand.

Mapping the distribution and risk factors of Anaplasmataceae in wild and domestic canines in Chile and their association with Rhipicephalus sanguineus species complex lineages

Anaplasma platys and Ehrlichia canis are members of the Anaplasmataceae family that cause disease in dogs and are mainly transmitted by Rhipicephalus sanguineus species group ticks. We performed a cross-sectional study on these pathogens across six bioclimatic regions of Chile, including 719 free-ranging rural dogs, 132 Andean foxes (Lycalopex culpaeus), and 82 South American gray foxes (Lycalopex griseus). Dog and fox blood samples were first screened for DNA of Anaplasmataceae followed by two Ehrlichia-specific protocols. Antibodies against Anaplasma sp. and E. canis were assessed by immunofluorescence in dogs. Ectoparasites were collected and identified, with the determination of the lineages of the Rhipicephalus sanguineus species group by molecular and phylogenetic analyses. Finally, potential risk factors for infection were investigated across the different bioclimatic regions and host species. All DNA amplicons obtained from the screening protocol corresponded to Anaplasma platys. The occurrence of both A. platys DNA and antibodies was confirmed in all six bioclimatic regions, except for regions at high altitude and/or without either R. sanguineus species group lineage present. Dogs infested with R. sanguineus ticks were significantly more prone to be infected and exposed to Anaplasma spp. Prevalence of DNA was significantly higher in juvenile (19%) than in adult dogs (9%), whereas the opposite was found for seroprevalence (19% versus 35%, respectively). Overall prevalence of A. platys DNA was higher in dogs (11%) than in foxes (4%), probably owing to markedly lower tick infestations in the foxes. Ehrlichia canis DNA was not detected in any sample, and antibodies against this pathogen were detected only in four dogs, in areas with both R. sanguineus lineages present. Free-ranging dogs in Chile could be favoring the maintenance of A. platys in all areas suitable for its tick vector. Although apparently infrequent, spillovers from dogs to foxes may be taking place and should be considered in management plans in Chile.

Prevalence and distribution of pathogen infection and permethrin resistance in tropical and temperate populations of Rhipicephalus sanguineus s.l. collected worldwide

The brown dog tick, Rhipicephalus sanguineus sensu lato (s.l.) Latreille (Acari: Ixodidae), is a peridomestic, cosmopolitan parasite of dogs known to vector numerous pathogens of veterinary and medical importance. Recent phylogenetic analyses separate this tick into temperate and tropical lineages. Populations of Rh. sanguineus s.l. have been reported to exhibit sodium channel target site insensitivity to permethrin and etofenprox, which is likely due to the prolonged use of pyrethroids against many pests in and around the home. In this study, populations collected in the Caribbean, Africa, Asia, Europe and North America, were tested to identify the distribution of a known resistance mechanism, pathogen-vector interactions and phylogeny in relation to latitude. Using molecular assays, populations from 29 distinct locations were simultaneously geographically typed and screened for bacterial infection by Rickettsia, Ehrlichia, Babesia and Hepatozoon species, and for the presence of a sodium channel single nucleotide polymorphism known to confer permethrin resistance. Implications of these results on Rh. sanguineus s.l. management in association with geographical distribution will be discussed.

Unbiased Characterization of the Microbiome and Virome of Questing Ticks

Due to their vector capacity, ticks are ectoparasites of medical and veterinary significance. Modern sequencing tools have facilitated tick-associated microbiota studies, but these have largely focused on bacterial pathogens and symbionts. By combining 16S rRNA gene sequencing with total RNA-sequencing methods, we aimed to determine the complete microbiome and virome of questing, female Ixodes holocyclus recovered from coastal, north-eastern New South Wales (NSW), Australia. We present, for the first time, a robust and unbiased method for the identification of novel microbes in ticks that enabled us to identify bacteria, viruses, fungi and eukaryotic pathogens. The dominant bacterial endosymbionts were Candidatus Midichloria sp. Ixholo1 and Candidatus Midichloria sp. Ixholo2. Candidatus Neoehrlichia australis and Candidatus Neoehrlichia arcana were also recovered, confirming that these bacteria encompass I. holocyclus’ core microbiota. In addition, seven virus species were detected—four previously identified in I. holocyclus and three novel species. Notably, one of the four previously identified virus species has pathogenic potential based on its phylogenetic relationship to other tick-associated pathogens. No known pathogenic eukaryotes or fungi were identified. This study has revealed the microbiome and virome of female I. holocyclus from the environment in north-eastern NSW. We propose that future tick microbiome and virome studies utilize equivalent methods to provide an improved representation of the microbial diversity in ticks globally.

Molecular detection and characterization of Anaplasma platys and Ehrlichia canis in dogs from the Caribbean

Anaplasma platys is a tick-transmitted rickettsial pathogen, which is known to be the etiologic agent for cyclic thrombocytopenia in its primary canine host. Infections with this pathogen are also reported in cats, cattle and people. Similarly, Ehrlichia canis is another tick-borne rickettsial pathogen responsible for canine monocytic ehrlichiosis and is also reported to cause infections in people. We describe infections in dogs with these two pathogens on the Caribbean island of Grenada, West Indies by detection using molecular methods. We utilized a 16S rRNA gene-based PCR assay to detect both Ehrlichia and Anaplasma species by screening 155 canine blood samples from asymptomatic dogs. We found 18.7 % of the dogs to be positive for A. platys and 16.8 % for E. canis. Samples that tested positive for A. platys were further assessed by sequence analysis targeting 16S rRNA, 23S rRNA, citrate synthase (gltA) and heat shock protein (groEL) genes. Phylogenetic analysis revealed high correlation of A. platys 16S rRNA and gltA gene sequences with the geographic origins, while 23S rRNA and groEL gene sequences clustered independent of the geographic origins. This study represents an important step in defining the widespread distribution of active rickettsial infections in Caribbean dogs with no apparent clinical signs, thus posing a high risk for canine health and to a lesser extent to humans, as most dogs in the Caribbean are free-roaming.

Comparative Proteomic Analysis of Rhipicephalus sanguineus sensu lato (Acari: Ixodidae) Tropical and Temperate Lineages: Uncovering Differences During Ehrlichia canis Infection

The tick vector Rhipicephalus sanguineus is established as a complex of closely related species with high veterinary-medical significance, in which the presence of different genetic, morphological, and biological traits has resulted in the recognition of different lineages within taxa. One of the most striking differences in the "temperate" and "tropical" lineages of R. sanguineus (s.l.) is the vector competence to Ehrlichia canis, suggesting that these ticks tolerate and react differently to pathogen infection. The present study addresses the SG and MG proteome of the R. sanguineus tropical and temperate lineages and compares their proteomic profile during E. canis infection. Batches of nymphs from the two lineages were allowed to feed on naïve and experimentally E. canis infected dogs and after molting, adults were dissected, and salivary glands and midgut tissues separated. Samples were screened for the presence of E. canis before proteomic analyses. The representation of the proteins identified in infected and non-infected tissues of each lineage was compared and gene ontology used for protein classification. Results highlight important differences in those proteomic profiles that added to previous reported genetic, biological, behavioral, and morphological differences, strengthening the hypothesis of the existence of two different species. Comparing infected and non-infected tissues, the results show that, while in midgut tissues the response to E. canis infection is similar in the salivary glands, the two lineages show a different pattern of protein representation. Focusing on the proteins found only in the infected condition, the data suggests that the cement cone produced during tick feeding may be implicated in pathogen infection. This study adds useful information to the debate on the controversial R. sanguineus systematic status, to the discussion related with the different vectorial competence occurring between the two lineages and identifies potential targets for efficient tick and tick-borne disease control.

Epidemiological link between canine monocytic ehrlichiosis caused by Ehrlichia canis and the presence of Rhipicephalus sanguineus sensu stricto in Argentina

In this work, we analyze data that support an epidemiological link between cases of canine monocytic ehrlichiosis (CME) by Ehrlichia canis and the presence of Rhipicephalus sanguineus sensu stricto as vector in an endemic area for this tick in Argentina. In a blood sample of a 1-year-old toy poodle with CME compatible clinical signs, which showed CME typical morulae in monocytes in Giemsa-stained blood smear, DNA of E. canis was detected by PCR. Further, DNA of E. canis was also detected in a female of R. sanguineus s.s. collected on the infected dog. Rhipicephalus sanguineus s.s. is the only member of the R. sanguineus group that prevails in the study area. The results of this study suggest that R. sanguineus s.s. may play a more important role in the transmission of E. canis than it was assumed so far. The epidemiological link between CME cases and R. sanguineus s.s. as vector in temperate areas of Argentina described in this work contrast previous studies which found that R. sanguineus sensu lato "tropical lineage" (which is absent in the study area) is competent to transmit E. canis but not R. sanguineus s.s.

Expansion in the latitudinal distribution of Rhipicephalus sanguineus sensu stricto (Acari: Ixodidae) to southern Chile

Rhipicephalus sanguineus is a species complex with a challenging diagnosis. There are two main lineages: a temperate lineage-now recognized as R. sanguineus sensu stricto (s.s.)-and a tropical lineage. In the Americas, several studies examined the distribution of both lineages. Meanwhile, in Chile, the distribution of the tropical lineage was reported from 18° to 22° S and R. sanguineus s.s. from 20° to 33° S; the morphological diagnosis located R. sanguineus in south-central Chile. In this study, we assessed the morphological and genetic identity of ticks collected from 47 dogs in southern Chile. Six dogs (12.8%) were parasitized by ticks that were morphologically and genetically assigned to R. sanguineus s.s. This finding would represent the southernmost record of this species in the country, located at over 308 km further south than the previous record, suggesting a latitudinal expansion of its distribution. Experimental studies are further required to understand how this tick survives extreme weather conditions when compared to other R. sanguineus s.s. from lesser latitudes.

Molecular characterization of novel Ehrlichia genotypes in Ixodes auritulus from Uruguay

Ehrlichia are small intracellular Gram-negative bacteria transmitted by ticks. These microorganisms cause ehrlichiosis, a complex of life-threatening emerging zoonoses and diseases of global veterinary relevance. The aim of this study was to investigate the presence of Ehrlichia in free-living Ixodes auritulus collected in Uruguay. Ticks were collected from vegetation in five localities from the southeast and northeast of the country between 2014 and 2017. Detection of Ehrlichia DNA was performed in pools of adults or nymphs grouped according to the collection site and date. A total of 1,548 I. auritulus ticks were collected in four of the five locations sampled. Fragments of three loci (16S rRNA, dsb and groEL) were obtained by PCR, and phylogenies inferred using Bayesian inference analysis for each gene independently. DNA of Ehrlichia spp. was found in 15 out of 42 tick pools. Based on the topology of the phylogenetic trees, our sequences represent two novel genotypes for the genus named as Ehrlichia sp. Serrana and Ehrlichia sp. Laguna Negra. Both genotypes were closely related to Ehrlichia sp. Magellanica, a species detected in Ixodes uriae and Magellanic penguins. Considering that all stages of I. auritulus and I. uriae are parasites of birds, their phylogenetic relationships, and common eco–epidemiological profiles, it is reasonable to state that these genotypes of Ehrlichia spp. may represent a natural group likely associated with birds. Our results constitute the first characterization of Ehrlichia spp. in Uruguay. Future studies on birds reported as hosts for I. auritulus are needed to further understand the epidemiological cycles of both Ehrlichia genotypes in the country. Finally, I. auritulus does not feed on humans, so the two Ehrlichia species reported herein might have no implications in human health.

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First molecular characterization of Ehrlichia in Uruguay.

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Two novel genotypes of Ehrlichia were detected in Ixodes auritulus.

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Evidence of a natural lineage of Ehrlichia associated with birds is reinforced.

Detection of tick-borne rickettsial pathogens in naturally infected dogs and dog-associated ticks in Medellin, Colombia

Tick-borne rickettsial pathogens (TBRP) are important causes of infections in both dogs and humans. Dogs play an important role as a biological host for several tick species and can serve as sentinels for rickettsial infections. Our aim was to determine the presence of TBRP in dogs and in dog-associated ticks and their potential risk to human diseases in Medellin, Colombia. DNA for E. canis (16S rRNA and dsb) and A. platys (groEl) was detected in 17.6% (53/300) and 2.6% (8/300) of dogs, respectively. Antibodies against Ehrlichia spp. 82 (27.3%) and Anaplasma spp. 8 (2.6%) were detected in dogs. Antibody reactivity against both agents were found in 16 dogs (5.3%). Eight dogs showed antibody for Rickettsia spp. with titers that suggest 3 of them had a probable exposure to R. parkeri. Rhipicephalus sanguineus s.l. (178/193) was the main tick in dogs, followed by R. microplus (15/193). The minimum infection rates (MIR) in R. sanguineus were 11.8% for E. canis and 3.4% for A. platys. E. canis and A. platys are the main TBRP infecting dogs and ticks and R. sanguineus s.l. is likely involved in the transmission of both agents. Interestingly, we found serological evidence of exposure in dogs for spotted fever group rickettsiae.

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.

Anaplasma platys-Like Infection in Goats, Beijing, China

As one of the important tick-borne zoonotic pathogens, Anaplasma has both veterinary and public health significance. Here, we performed a survey of Anaplasma infection in the goats from a farm in Beijing, China, and found 44.6% (41/92) were infected with Anaplasma capra, and 22.8% (21/92) were infected with Anaplasma sp. This Anaplasma sp. bacterium was close to a recently emerging Anaplasma platys strain based on gltA and groEL gene phylogenetic analysis. As to further understand the characteristics of Anaplasma sp., we raised a couple of positive goats (n = 2) in the laboratory with tick-free settings. We observed inappetence, vomiting, high fever, and weakness of limbs in the goat's offspring (n = 3). In addition, the blood samples from all offspring were all positive of this Anaplasma spp. We did not see any intracellular morulae in neutrophils, monocytes, and erythrocytes, but we identified some in the platelets of the blood smears from the positive goats by light microscopy. We named it A. platys-like and suggested it may infect platelets and be transmitted vertically through the placenta of goats. These findings deserve further evaluation.

Molecular Detection of Some Anaplasma Species in Blood of Dogs in Baghdad Province, Iraq

A total of 150 blood samples were collected from dogs and examined by the polymerase chain reaction (PCR) technique, which was used to detect the 16S RNA gene of Anaplasma platys and Anaplasma phagocytophilum. Subsequent analysis of the PCR amplicons was achieved by nucleotides sequencing of some positive samples. Totally, the findings show the presence of PCR products (i.e., Anaplasma spp. infection) in 12/150 (8.0%) of the dogs under study. While 5/150 (3.33%) of the cases were A. platys, 7/150 (4.66%) were A. phagocytophilum. Nucleotide sequencing confirmed the identity of the amplified genes whose sequences were compared with other references belong to 15 of 16S rRNA gene of A. platys and 14 references of 16S rRNA gene of A. phagocytophilum, and the isolate sequences of this study were deposited on the Gene Bank. The identity and similarity scores between the isolates of this study and reference strains ranged from 98 to 99%. In conclusion, canine anaplasmosis prevalence in dogs could be underestimated in Iraq, and the phylogenetic tree of the local A. platys and A. phagocytophilum isolates were found to resemble other worldwide strains of Anaplasma spp. with a high degree of similarity.

Prevalence and Risk Factors of Antibodies to Anaplasma spp. in Chile: A Household-Based Cross-Sectional Study in Healthy Adults and Domestic Dogs

Background: Pet-related tick-borne infections constitute an emerging problem in human and veterinary medicine worldwide. In Chile, two pathogens of the Anaplasmataceae family, Anaplasma platys and Ehrlichia canis, have been identified in recent years in dogs and vectors. This epidemiological survey aimed to determine the human and canine seroprevalence of Anaplasma spp. in urban and rural areas of different regions in Chile and to analyze the factors associated with seropositivity. Methods: We performed a cross-sectional household-based study in four regions, where healthy adults and their household dogs were included. Households were chosen by double stratified random sampling in urban areas and by convenience sampling in rural areas. Anaplasma seroreactivity was determined by a commercial microimmunofluorescence assay using Anaplasma phagocytophilum antigens. A questionnaire survey was applied to assess risk factors for Anaplasma seropositivity. Results: A total of 1105 persons and 905 dogs were included. The overall seroprevalence in humans was 9.4%, ranging from 5.6% in central Chile to 13.7% in the extreme north; in dogs the overall prevalence was 44.0% and ranged from 37.2% in the northern region to 61.1% in central Chile. Risk factors for human seropositivity were lower education and external deworming of dogs, whereas canine seropositivity was associated to urban site, mixed-breed, older animals, and tick infestation. Conclusions: This cross-sectional study suggests a broad exposure of both dogs and dog owners to Anaplasma or related agents in Chile. Further epidemiological and clinical studies are necessary to understand the complete spectrum and epidemiology of tick-borne zoonotic infections in the different ecoclimatic regions of Chile.

Local and regional temporal trends (2013-2019) of canine Ehrlichia spp. seroprevalence in the USA

Background

In the USA, there are several Ehrlichia spp. of concern including Ehrlichia canis, Ehrlichia ewingii, Ehrlichia chaffeensis, Ehrlichia muris eauclarensis, and “Panola Mountain Ehrlichia”. Of these, E. canis is considered the most clinically relevant for domestic dogs, with infection capable of causing acute, subclinical, and chronic stages of disease. Changes in climate, land use, habitats, and wildlife reservoir populations, and increasing contact between both human and dog populations with natural areas have resulted in the increased risk of vector-borne disease throughout the world.

Methods

A Bayesian spatio-temporal binomial regression model was applied to serological test results collected from veterinarians throughout the contiguous USA between January 2013 and November 2019. The model was used to quantify both regional and local temporal trends of canine Ehrlichia spp. seroprevalence and identify areas that experienced significant increases in seroprevalence.

Results

Regionally, increasing seroprevalence occurred within several states throughout the central and southeastern states, including Missouri, Arkansas, Mississippi, Alabama, Virginia, North Carolina, Georgia and Texas. The underlying local trends revealed increasing seroprevalence at a finer scale. Clusters of locally increasing seroprevalence were seen from the western Appalachian region into the southern Midwest, along the Atlantic coast in New England, parts of Florida, Illinois, Wisconsin and Minnesota, and in a couple areas of the Mountain region. Clusters of locally decreasing seroprevalence were seen throughout the USA including New York and the mid-Atlantic states, Texas, the Midwest, and California.

Conclusions

Canine Ehrlichia spp. seroprevalence is increasing in both endemic and non-endemic areas of the USA. The findings from this study indicate that dogs across a wide area of the USA are at risk of exposure and these results should provide veterinarians and pet owners with the information they need to make informed decisions about prevention of tick exposure.

Phylogenetic profiling for zoonotic Ehrlichia spp. from ixodid ticks in the Eastern Cape, South Africa

Ticks are obligate hematophagous parasite of vertebrate that transmit a range of pathogenic microorganisms that can cause diseases in livestock and humans. The range of tick-borne disease causative agents infecting domestic animals and humans has recently increased. Several significant zoonotic tick-borne diseases such as ehrlichiosis among others are on the increase worldwide. This study was designed to investigate the occurrence of zoonotic Ehrlichia spp. from samples collected from livestock in selected communities in the Eastern Cape Province, South Africa. Tick samples were manually collected from domesticated animals in selected homesteads. The ticks were morphologically identified to species and tested for Ehrlichia infection via polymerase chain reaction (PCR), using genus-specific disulphide bond formation protein (dsbA) gene primers. This was followed by sequence analysis of amplicons and phylogeny. Of the 1,200 ticks collected, Amblyomma hebraeum was most prevalent (n = 335; 27.9%), followed by Rhipicephalus appendiculatus (n = 274; 22.8%), Rhipicephalus decoloratus; (n = 224; 18.7%) and Rhipicephalus eversti eversti (n = 200, 16.7%). Ehrlichia DNA was detected in 19/1,200 (1.6%) of the screened DNA samples. A homology search of the generated sequences revealed a high percentage of identity between 95% and 98% with other homologous dsbA gene sequences of other Ehrlichia species in GenBank. Phylogenetic analysis showed that the obtained sequences clustered unambiguously with other Ehrlichia sequences from different geographical regions of the world. We concluded that Ehrlichial pathogens are vectored by the ticks collected from domesticated animals in the study areas, thus suggesting concern for public health, as some of the recovered pathogens are zoonotic in nature and could pose serious public health risk through human exposure to tick bites.

A putative novel strain of Ehrlichia infecting Amblyomma tigrinum associated with Pampas fox (Lycalopex gymnocercus) in Esteros del Iberá ecoregion, Argentina

The current work evaluated road-killed Pampas foxes (Lycalopex gymnocercus) and their ticks for the presence of vector-borne agents in the ecoregion Esteros del Iberá in northeastern Argentina. Spleen, lung and blood samples and Amblyomma tigrinum adult ticks collected from the foxes were tested by polymerase chain reaction (PCR) assays targeting bacteria of the genera Ehrlichia, Anaplasma, and Rickettsia. All foxes tested were negative for the three genera, but evidence of Ehrlichia and Rickettsia infection was detected in the ticks. One A. tigrinum (out of 12 tested) was infected by an ehrlichial agent, here named Ehrlichia sp. strain Iberá, related to ehrlichial agents recently detected in platypuses in Tasmania (Ornithorhynchus anatinus) and in voles (Myodes rutilus and Myodes rufocanus) and shrews (Sorex araneus) in the Russian Far East. Regarding Rickettsia, all A. tigrinum ticks (100%) were infected by ´Candidatus Rickettsia andeanae´, a member of the spotted fever group rickettsia of unknown pathogenicity. Further research is necessary to unveil the ecology of Ehrlichia sp. strain Iberá as well as its zoonotic relevance. The species of the genus Ehrlichia are known to be pathogenic to mammals, including humans and domestic animals, thus the presence of this ehrlichial agent in A. tigrinum is a potential risk for veterinary and public health, as the adults of A. tigrinum are common parasites of dogs in rural and peri-urban environments, and humans are also frequently bitten by this tick species.

Molecular identification and characterization of Anaplasma capra and Anaplasma platys-like in Rhipicephalus microplus in Ankang, Northwest China

Background

Four species within Anaplasma genus are emerging zoonotic pathogens, which are transmitted by ticks and generate veterinary and public health concerns. Here, we performed a molecular survey of Anaplasma in Ankang, Northwest China.

Methods

Hard ticks were collected and identified using morphological and molecular methods. Human-pathogenic Anaplasma species were tested using nested polymerase chain reaction. The nearly complete rrs, gltA, and groEL genes sequences from revealed Anaplasma species were amplified and sequenced to determine their molecular characteristics and their phylogeny.

Results

All ticks collected in Ankang belonged to the Rhipicephalus microplus. Novel unclassified Anaplasma strains genetically related to A. platys and A. capra were detected in these ticks. Co-infection of these two organisms was also found. The novel unclassified Anaplasma strains identified in this study formed a distinct phylogenetic lineage based on the groEL gene and two lineages based on the gltA gene within A. platys and related strains group. The revealed A. capra strains identified in this study were most closely related to those detected in humans and other vertebrate animals.

Conclusion

We revealed the presence of A. capra, a novel human pathogens in R. microplus ticks in previously unrecognized endemic regions. We also detected a novel unclassified Anaplasma species genetically related to A. platys. The epidemiology of anaplasmosis caused by these two Anaplasma species in humans should be assessed in future studies.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-4075-3) contains supplementary material, which is available to authorized users.

A review on the occurrence of companion vector-borne diseases in pet animals in Latin America

Companion vector-borne diseases (CVBDs) are an important threat for pet life, but may also have an impact on human health, due to their often zoonotic character. The importance and awareness of CVBDs continuously increased during the last years. However, information on their occurrence is often limited in several parts of the world, which are often especially affected. Latin America (LATAM), a region with large biodiversity, is one of these regions, where information on CVBDs for pet owners, veterinarians, medical doctors and health workers is often obsolete, limited or non-existent. In the present review, a comprehensive literature search for CVBDs in companion animals (dogs and cats) was performed for several countries in Central America (Belize, Caribbean Islands, Costa Rica, Cuba, Dominican Republic, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama, Puerto Rico) as well as in South America (Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, French Guiana, Guyana (British Guyana), Paraguay, Peru, Suriname, Uruguay, Venezuela) regarding the occurrence of the following parasitic and bacterial diseases: babesiosis, heartworm disease, subcutaneous dirofilariosis, hepatozoonosis, leishmaniosis, trypanosomosis, anaplasmosis, bartonellosis, borreliosis, ehrlichiosis, mycoplasmosis and rickettsiosis. An overview on the specific diseases, followed by a short summary on their occurrence per country is given. Additionally, a tabular listing on positive or non-reported occurrence is presented. None of the countries is completely free from CVBDs. The data presented in the review confirm a wide distribution of the CVBDs in focus in LATAM. This wide occurrence and the fact that most of the CVBDs can have a quite severe clinical outcome and their diagnostic as well as therapeutic options in the region are often difficult to access and to afford, demands a strong call for the prevention of pathogen transmission by the use of ectoparasiticidal and anti-feeding products as well as by performing behavioural changes.

Successful Infection of Tick Cell Cultures of Rhipicephalus sanguineus (Tropical Lineage) with Ehrlichia canis

There are two distinct lineages of ticks, Rhipicephalus sanguineus, in South America: tropical and temperate lineages. Only the tropical lineage is recognized as competent vector for Ehrlichia canis. The epidemiological data of canine monocytic ehrlichiosis is congruent with the distribution of the two lineages of R. sanguineus. Herein, we report the infection of R. sanguineus (tropical lineage) cell cultures with E. canis, after cryopreservation. R. sanguineus (tropical lineage) cell identity was confirmed by sequencing using a 16S rDNA gene fragment. Tick cell cultures were prepared in L-15B medium supplemented with 10%, 15%, and 20% Fetal Bovine Serum (FBS), and 10% of Tryptose Phosphate Broth (TPB). Cell cultures developed better at the concentration of 20% of FBS. Cultures in the fifth harvest (approximately 7 months later) were selected for the first infections. Optimal R. sanguineus cell growth and adhesion was observed (5.0 × 106 cells/mL, and the population doubling time every 57 h). Once infected with E. canis, the cultures were maintained in L-15B medium supplemented with 2% and 5% of FBS fortified with iron and 10% TPB. Infected cells were also cryopreserved. DNA was extracted from infected and noninfected cells and analyzed using quantitative real-time PCR targeting the E. canis-dsb gene. Primary culture of the fifth passage was infected by E. canis and it maintained the pathogen for at least 40 days before partial cell destruction. Subcultures of infected cells (fresh and cryopreserved cultures) onto new tick cell cultures were successful. The E. canis infection was confirmed by real-time PCR and light and transmission electron microscopy. The R. sanguineus (tropical lineage) cells infected with E. canis successfully infected new tick cell cultures, showing that these cells could be an alternative substrate for maintenance of this pathogen.

Detection of Ehrlichia sp. strain San Luis and Candidatus Rickettsia andeanae in Amblyomma parvum ticks

Owing to the sanitary importance of the tick Amblyomma parvum, this study evaluated the infection by Ehrlichia, Anaplasma and Rickettsia species of questing A. parvum collected in northwestern Argentina. Our results showed that A. parvum ticks in this region are infected with the recently reported Ehrlichia sp. strain San Luis, closely related to Ehrlichia chaffeensis. A high prevalence of Candidatus Rickettsia andeanae was observed. Most of the infected ticks presented rickettsial loads lower than those previously reported for other spotted fever group rickettsiae. The presence of Ehrlichia sp. strain San Luis in A. parvum is a potential risk for public health as the principal hosts of this tick are domestic mammals in rural areas and humans are frequently bitten by this tick species.

Molecular heterogeneity of Rhipicephalus sanguineus sensu lato and screening for Ehrlichia canis in mainland Portugal

The present study aimed to expand knowledge regarding the molecular characterization of R. sanguineus s.l. in Portugal and to screen for ticks naturally infected with E. canis. A total of 113 R. sanguineus s.l. were collected questing or attached to domestic and wild animals from the 18 administrative regions of mainland Portugal. All the ticks were analyzed for the 16S rRNA and the partial sequences obtained showed high genetic similarities with specimens belonging to the temperate lineage. These sequences revealed eight haplotypes (H1‒H8), with a genetic distance ranging from 0.3% to 1.4%. A convenience sample representing approximately 75% of all the R. sanguineus s.l. ticks collected was tested for the presence of E. canis by qPCR for the dsb gene. No ticks were found to be infected with this pathogen. Accordingly, further studies are required to determine the role of the R. sanguineus s.l. temperate lineage in E. canis maintenance and transmission, as well as to elucidate if a different R. sanguineus s.l. lineage or other tick species act as E. canis vectors for dogs in Portugal.

Molecular Evidence for Transstadial Transmission of Ehrlichia canis by Rhipicephalus sanguineus sensu lato Under Field Conditions

This study investigated possible transstadial transmission of Ehrlichia canis by Rhipicephalus sanguineus sensu lato collected from shelter dogs and the shelter grounds in Diyarbakır Province of south-eastern Turkey. Totally 225 engorged nymphs were collected from eight infected dogs with E. canis and incubated at 28°C for moulting. Unfed ticks from the shelter grounds comprising 1,800 larvae, 3,100 nymphs, and 85 adults were sorted according to sampling origin, life stage, and sex into 116 pools and screened by 16S rRNA PCR. Nine out of 26 pools of unfed adult ticks were positive for E. canis, with overall infection rate maximum likelihood estimation (MLE) of 4.83 (CI 2.39-8.87). E. canis was detected in three of 12 male pools (MLE 3.22, CI 0.86-8.83) and six of 14 female pools (MLE 6.16, CI 2.59-12.90). No adult pools collected from the shelter grounds were positive. Among 62 unfed nymph pools collected from the shelter, six were infected with E. canis (MLE 0.20, CI 0.08-0.42). No E. canis DNA was detected in any of the larva pools. Our results revealed molecular evidence for transstadial transmission of E. canis by R. sanguineus s.l. both from larva to nymph and from nymph to adult. We found no evidence of transovarial transmission.

Molecular epidemiology of Anaplasma platys, Ehrlichia canis and Babesia vogeli in stray dogs in Paraná, Brazil

ABSTRACT: Hemoparasitic infections are tick-borne diseases, which affect animals and humans. Considering the importance of canine hemoparasitic infections in veterinary clinics, this study aimed to determine the occurrence of Anaplasma platys, Ehrlichia canis and Babesia vogeli in blood samples from 182 dogs not domiciled in the city of Pato Branco, southwestern region of Paraná State, Brazil, using polymerase chain reaction (PCR). The prevalence of A. platys and B. vogeli was 32.9% and 10.9% respectively, and A. platys infection prevailed (p<0.001). The number of dogs positive for A. platys was larger in Winter (p<0.05). All blood samples were negative for E. canis. In the dogs, infestation by Amblyomma cajennense predominated over that by Rhipicephalus sanguineus (p<0.001); but there was no significant association between PCR and the variables presence of ticks, sex and age. Dogs infected by A. platys and B. vogeli showed thrombocytopenia, lymphopenia and leukocytosis; but there was no correlation between such hematological changes and infection by hemoparasites. This appears to be the first molecular study that demonstrates the existence of A. platys and B. vogeli in dogs from the southwestern region of Paraná.

Bacteria of the genera Ehrlichia and Rickettsia in ticks of the family Ixodidae with medical importance in Argentina

The aim of this study was to get an overview about the occurrence of bacteria from the genus Ehrlichia and Rickettsia in ixodid ticks with medical importance in Argentina. Therefore, in 2013 and 2014, free-living ticks were collected in different provinces of northern Argentina. These ticks were determined as Amblyomma sculptum, Amblyomma neumanni, Amblyomma parvum, Amblyomma triste, Amblyomma ovale, Amblyomma tonelliae and Haemaphysalis juxtakochi. All samples were tested to determine the infection with Ehrlichia spp. and Rickettsia spp. by PCR assays. Rickettsial DNA was detected in all tested tick species, with the exception of A. tonelliae. 'Candidatus Rickettsia amblyommii', 'Candidatus Rickettsia andeanae', and Rickettsia parkeri were found in A. neumanni, A. parvum, and A. triste, respectively. Another rickettsial species, Rickettsia bellii, was found in A. sculptum, A. ovale and H. juxtakochi. None of the tested ticks showed infection with Ehrlichia. The results of the study demonstrate that Rickettsia species belonging to the spotted fever group are associated with various species of Amblyomma throughout a wide area of northern Argentina, where cases of Amblyomma ticks biting humans are common.

Using plastic tips in artificial feeding of Rhipicephalus sanguineus sensu lato (Acari: Ixodidae) females

This study evaluated the influence of the initial weight, feeding period and temperature on weight gain and biological parameters of the non-parasitic phase of partially engorged Rhipicephalus sanguineus females that were artificially fed using plastic tips as feeding devices. The device did not alter the oviposition of the females or any other parameters evaluated. Furthermore, it was observed that the temperature of the feeding the group did not affect the weight gain and biology of ticks. This device has great potential for the development of studies on bioagent transmission because it provides higher intake of blood by ixodid ticks.

Prevalence and infection intensity of Rickettsia massiliae in Rhipicephalus sanguineus sensu lato ticks from Mendoza, Argentina

Rickettsia massiliae belongs to the spotted fever group and in the New World is commonly associated with the brown dog tick, Rhipicephalus sanguineus. Herein we investigate the presence of R. massiliae in Rh. sanguineus sensu lato ticks in a location near the Andean foothills (Mendoza, Argentina), to provide a prevalence estimate and to assess the infection intensity of this pathogen. Rickettsia massiliae infection was found in 5.1% of the Rh. sanguineus s.l ticks analyzed, all with high infection intensities. Molecular analysis determined that all R. massiliae-infected Rh. sanguineus s.l. ticks belonged to the temperate lineage.

Presence of Aedes (Stegomyia) aegypti (Linnaeus, 1762) and its natural infection with dengue virus at unrecorded heights in Colombia

INTRODUCTION

Aedes aegypti is the main vector of urban yellow fever, dengue, chikungunya and Zika viruses. The biogeographical distribution of this species has expanded due to global warming, and socioeconomic and cultural factors. The changes in the altitudinal distribution patterns of this vector and its natural infection are priority fields of research to develop entomological, virological and public health surveillance strategies. 

OBJECTIVE

To evaluate the presence of A. aegypti and its natural infection with dengue virus in altitudes above 1.800 meters above sea level in two peripheral municipalities of the Valle de Aburrá, Antioquia, Colombia. 

MATERIALS AND METHODS

Twenty-one ovitraps were set in the municipalities of Bello and San Pedro de los Milagros, at altitudes ranging from 1.882 to 2.659 masl. Emerged adults caught in the ovitraps were tested by RT-PCR for dengue virus detection. 

RESULTS

We collected 367 A. aegypti adults, seven of which were found as high as 2.302 masl in Tierradentro, Bello. We detected serotype 2 dengue infection in 12 A. aegypti specimens collected in the neighbourhood of París, in Bello, at 1.984 masl. 

CONCLUSION

We recorded A. aegypti at 2.302 masl, so far the highest altitudinal record in Colombia for this vector. Furthermore, mosquitoes collected at 1.984 masl were positive for dengue virus. These findings are significant as they identify regions in Colombia at risk of potential autochthonous transmission of dengue and other arboviruses by A. aegypti.

Molecular characterization of Ehrlichia canis infecting dogs, Buenos Aires

Canine monocytic ehrlichiosis (CME) is a worldwide potentially fatal tick-borne rickettsial disease of dogs caused by Ehrlichia canis and transmitted by Rhipicephalus sanguineus sensu lato. CME diagnosis includes indirect (serology) and direct (e.g. blood smears and PCR) methods. PCR is more sensitive and specific than direct microscopic examination and positive PCR results confirm infection, whereas positive serologic test results only confirm exposure. The aim of the present study was to perform a molecular characterization of E. canis from canine samples of the Metropolitan Area of Buenos Aires. We studied 223 blood samples of dogs submitted to our institute for CME diagnoses. The samples were initially screened for Anaplasmataceae family by PCR, resulting in 30 positive dogs (13.4%). Subsequently, positive DNAs were analyzed by nested PCR 16S rRNA specific for E. canis or Anaplasma platys, resulting in 15 (6.7%) and 16 (7.2%) positive dogs, respectively. For molecular characterization, samples positive for E. canis were subjected to amplification of a fragment of the dsb and p28 genes. The nucleotide sequences obtained for the dsb fragment resulted in 100% identity with others E. canis found in dogs from different regions of worldwide. The nucleotide sequences obtained for p28 gene resulted in 100% of identity with each other and closely with E. canis str. Jaboticabal (Brazil). Identity with others sequences of E. canis ranged from 76.9 to 79.7%. The occurrence of canine cases molecularly confirmed in Metropolitan Area of Buenos Aires highlights the need for more studies in order to understand epidemiological factors associated with CME, especially the disease transmission dynamic in South America given the existence of two lineages of R. sanguineus sensu lato with different vectorial capacity for transmission of E. canis.

Growth of Ehrlichia canis, the causative agent of canine monocytic ehrlichiosis, in vector and non-vector ixodid tick cell lines

Canine monocytic ehrlichiosis is caused by Ehrlichia canis, a small gram-negative coccoid bacterium that infects circulating monocytes. The disease is transmitted by the brown dog tick Rhipicephalus sanguineus s.l. and is acknowledged as an important infectious disease of dogs and other members of the family Canidae worldwide. E. canis is routinely cultured in vitro in the canine monocyte-macrophage cell line DH82 and in non-vector Ixodes scapularis tick cell lines, but not in cells derived from its natural vector. Here we report infection and limited propagation of E. canis in the tick cell line RSE8 derived from the vector R. sanguineus s.l., and successful propagation through six passages in a cell line derived from the experimental vector Dermacentor variabilis. In addition, using bacteria semi-purified from I. scapularis cells we attempted to infect a panel of cell lines derived from non-vector species of the tick genera Amblyomma, Dermacentor, Hyalomma, Ixodes and Rhipicephalus with E. canis and, for comparison, the closely-related Ehrlichia ruminantium, causative agent of heartwater in ruminants. Amblyomma and non-vector Dermacentor spp. cell lines appeared refractory to infection with E. canis but supported growth of E. ruminantium, while some, but not all, cell lines derived from Hyalomma, Ixodes and Rhipicephalus spp. ticks supported growth of both pathogens. We also illustrated and compared the ultrastructural morphology of E. canis in DH82, RSE8 and I. scapularis IDE8 cells. This study confirms that E. canis, like E. ruminantium, is able to grow not only in cell lines derived from natural and experimental tick vectors but also in a wide range of other cell lines derived from tick species not known to transmit this pathogen.