Ultrastructure and phylogenetic analysis of ‘Candidatus Neoehrlichia mikurensis' in the family Anaplasmataceae, isolated from wild rats and found in Ixodes ovatus ticks
Makoto KawaharaYasuko RikihisaEmiko IsogaiMamoru TakahashiHitoko MisumiChiharu SUTOShinichiro ShibataChunbin ZhangMasayoshi Tsuji
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A novel bacterium that infects laboratory rats was isolated from wild Rattus norvegicus rats in Japan. Transmission electron microscopy of the spleen tissue revealed small cocci surrounded by an inner membrane and a thin, rippled outer membrane in a membrane-bound inclusion within the cytoplasm of endothelial cells. Phylogenetic analysis of the 16S rRNA gene sequence of the bacterium found in R. norvegicus rats and Ixodes ovatus ticks in Japan revealed that the organism represents a novel clade in the family Anaplasmataceae , which includes the Schotti variant found in Ixodes ricinus ticks in the Netherlands and the Ehrlichia -like Rattus strain found in R. norvegicus rats from China. The novel clade was confirmed by phylogenetic analysis of groESL sequences found in R. norvegicus rats and Ixodes ovatus ticks in Japan. No serological cross-reactivity was detected between this bacterium and members of the genera Anaplasma , Ehrlichia or Neorickettsia in the family Anaplasmataceae . It is proposed that this new cluster of bacteria should be designated ‘ Candidatus Neoehrlichia mikurensis’.Keywords:
Anaplasmataceae
Ixodes scapularis
Rickettsiaceae
Ehrlichia chaffeensis
Rickettsiaceae
Anaplasmataceae
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The order Rickettsiales contains a group of vector-borne gram-negative obligate intracellular bacteria, which often cause human emerging infectious diseases and economic losses for dairy and meat industries. The purpose of this study is to investigate the distribution of the pathogens including Rickettsia spp., Anaplasma spp., and Ehrlichia spp. in the order Rickettsiales in ticks from Yueyang, a prefecture-level city of Hunan Province in Sothern China, and assess the potentiality of transovarial transmission of these rickettsial organisms.Ticks were collected from cattle in a farm in Yueyang City and the tick DNA was used as template to amplify the htrA, rrs, gltA, ompA and ompB genes of Rickettsia as well as rrs and groEL genes of Anaplasma and Ehrlichia.All ticks (465) collected were the cattle tick, Rhipicephalus microplus. PCR showed the minimum infection rate (MIR) was 1.5% (7/465) for Candidatus Rickettsia xinyangensis, 1.9% (9/465) for C. Anaplasma boleense, 1.3% (6/465) for Anaplasma platys, 0.6% (3/465) for A. marginale, and 1.17% (2/465) for each of A. bovis, Ehrlichia minasensis, and a non-classified Ehrlichia sp. A human pathogen, C. Rickettsia xinyangensis and A. platys were detected in 100% (3/3) and 33.3% (2/6) laboratory-hatched larval pools from infected females respectively.Our study revealed a diversity of pathogenic rickettsial species in R. microplus ticks from Hunan Province suggesting a threat to people and animals in China. This study also provided the first molecular evidence for the potential transovarial transmission of C. Rickettsia xinyangensis and A. platys in R. microplus, indicating that R. microplus may act as the host of these two pathogens.
Anaplasmataceae
Rhipicephalus
Rhipicephalus microplus
Transovarial transmission
Rickettsiaceae
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Anaplasma phagocytophilum
Candidatus
Anaplasmataceae
Rickettsiaceae
Tick-borne disease
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A new microorganism, tentatively named "Montezuma" was detected in ticks and in specimens (blood, bioptic specimens of the primary affect) taken from patients with an acute fever disease, etiologically linked with the bites of Ixodes ticks in the Far East of the Russian Federation. After sequencing the products of the amplification of DNA isolated from ticks with wide-spectrum primers new primers were developed, highly specific to the unusual sequence thus obtained. The study revealed that ticks of the species Ixodes persulcatus (97%) and Haemophysalis concinnae (5%) contained DNA of this microorganism. The same DNA was detected in materials taken from the patients. The phylogenetic analysis of the gene showed that this organism formed an independent and well defined branch within the order Rickettsiales. The nearest homology (89%) was observed with recently detected endosymbiotes Acanthamoeba. The similarity with their relatives from the families Rickettsiaceae and Anaplasmataceae of the order Rickettsiales was within 81-86%, which made it possible to infer the existence of, probably, only a new genus, but also a family. The isolated DNA belonged, supposedly, to the new microoganism which caused a tick-borne disease in humans, transmitted through bites of Ixodes ticks, and was, supposedly, widely spread in the southern area of the Khabarovsk Territory.
Ixodes persulcatus
Anaplasmataceae
Tick-borne disease
Ehrlichiosis
Rickettsiaceae
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Background: Anaplasma and Ehrlichia (Rickettsiales: Anaplasmataceae) are intracellular Gram-negative bacteria of medical and veterinary importance that infect monocytes, neutrophils, endothelial cells or platelets, depending upon the species involved. The capybara, Hydrochoerus hydrochaeris, is a large rodent found in tropical to temperate freshwater wetlands of South America, considered to be the most important amplifying host of the human pathogen Rickettsia rickettsii (Rickettsiales: Rickettsiaceae). In Esteros del Iberá (northeastern Argentina), capybaras are present at high densities, living close to farms and urban settlements, resulting in an extensive human-livetock-wildlife interface that may represent a potential risk to public health. Methods & Materials: We investigated the potential role played by capybaras and their ticks on the ecology of Anaplasma spp. and Ehrlichia spp. in northeastern Argentina. During 2010–2016 blood samples from 70 capybaras and more than 9400 Amblyomma dubitatum questing ticks were obtained from a ranch in Esteros del Iberá (28°36′ S 57°49′ W). Ticks were identified by using standard taxonomic keys. DNA was extracted from blood and ticks and all samples were screened for Anaplasmataceae by a real-time PCR assay targeting the 16S rRNA gene. Results: Prevalence of Anaplasma spp. infection in capybaras was high (50.0%), while Ehrlichia spp. prevalence was lower (12.8%). Interestingly, very low prevalence of both Anaplasma (0.03%) and Ehrlichia (0.07%) was observed in questing ticks. Molecular analysis using 16S rRNA gene showed that Anaplasma sp. from capybaras was closely related to Anaplasma odocoilei from North America, while Ehrlichia sp. was related to Candidatus Ehrlichia khabarensis from Eastern Russia. In addition, we observed Anaplasma sp. infecting capybaras platelets, which coincides with the tropism of A. odocoilei in deer. Conclusion: Our results showed the presence of novel rickettsial agents infecting a population of free-ranging capybaras in northeastern Argentina. The extremely low prevalence of these agents in capybara's ticks (Amblyomma dubitatum) excludes this arthropod as a competent vector, warranting further research to find the possible vectors of these bacteria.
Anaplasmataceae
Ehrlichia canis
Tick-borne disease
Rickettsiaceae
Anaplasma phagocytophilum
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Anaplasmataceae
Candidatus
Haemaphysalis
Haemaphysalis longicornis
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Candidatus
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The order Rickettsiales in the class Alphaproteobacteria comprises vector-borne pathogens of both medical and veterinary importance. Ticks, as a group, are second only to mosquitoes as vectors of pathogens to humans, playing a critical role in the transmission of rickettsiosis. In the present study, 880 ticks collected from Jinzhai County, Lu'an City, Anhui Province, China in 2021-2022 were identified as belonging to five species from three genera. DNA extracted from individual ticks was examined using nested polymerase chain reaction targeting the 16S rRNA gene (rrs), and the gene fragments amplified were sequenced to detect and identify Rickettsiales bacteria in the ticks. For further identification, the rrs-positive tick samples were further amplified by PCR targeting the gltA and groEL gene and sequenced. As a result, 13 Rickettsiales species belonging to the genera Rickettsia, Anaplasma, and Ehrlichia were detected, including three tentative species of Ehrlichia. Our results reveal the extensive diversity of Rickettsiales bacteria in ticks from Jinzhai County, Anhui Province. There, emerging rickettsial species may be pathogenic and cause under-recognized diseases. Detection of several pathogens in ticks that are closely related to human diseases may indicate a potential risk of infection in humans. Therefore, additional studies to assess the potential public health risks of the Rickettsiales pathogens identified in the present study are warranted.
Rickettsiaceae
Bartonella
Anaplasmataceae
Tick-borne disease
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Anaplasma marginale is a tick-borne pathogen that causes the disease anaplasmosis in cattle (Bram, 1975; Ristic, 1968). This pathogen is classified within the Order Rickettsiales which was recently reorganized into two families, Anaplasmataceae and Rickettsiaceae, based on genetic analyses of 16S rRNA, groELS and surface protein genes (Dumler et al., 2001) (Table 15.1). Organisms of the family Anaplasmataceae are obligate intracellular organisms that are found exclusively within membrane-bound vacuoles in the host cell cytoplasm. Phylogenetic analyses consistently supported the formation of four distinct genetic groups of the organisms: (1) Anaplasma (96.1% similarity), (2) Ehrlichia (97.7%), (3) Wolbachia (minimum of 95.6% similarity) and (4) Neorickettsia (minimum of 94.9% similarity) (Dumler et al., 2001). The genus Anaplasma currently includes the three pathogens of ruminants, A. marginale, A. centrale and A. ovis, together with A. bovis (formerly Ehrlichia bovis), A. phagocytophilum (formerly E. phagocytophilum, E. equi and the HGE agent), and A. platys (formerly E. platys). Aegyptianella, also included in this genus, was retained as a genus incertae sedis due to lack of sequence information.
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Anaplasma phagocytophilum
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The genera Anaplasma, Ehrlichia, Cowdria, Neorickettsia and Wolbachia encompass a group of obligate intracellular bacteria that reside in vacuoles of eukaryotic cells and were previously placed in taxa based upon morphological, ecological, epidemiological and clinical characteristics. Recent genetic analyses of 16S rRNA genes, groESL and surface protein genes have indicated that the existing taxa designations are flawed. All 16S rRNA gene and groESL sequences deposited in GenBank prior to 2000 and selected sequences deposited thereafter were aligned and phylogenetic trees and bootstrap values were calculated using the neighbour-joining method and compared with trees generated with maximum-probability, maximum-likelihood, majority-rule consensus and parsimony methods. Supported by bootstrap probabilities of at least 54%, 16S rRNA gene comparisons consistently clustered to yield four distinct clades characterized roughly as Anaplasma (including the Ehrlichia phagocytophila group, Ehrlichia platys and Ehrlichia bovis) with a minimum of 96.1% similarity, Ehrlichia (including Cowdria ruminantium) with a minimum of 97.7% similarity, Wolbachia with a minimum of 95.6% similarity and Neorickettsia (including Ehrlichia sennetsu and Ehrlichia risticii) with a minimum of 94.9% similarity. Maximum similarity between clades ranged from 87.1 to 94.9%. Insufficient differences existed among E. phagocytophila, Ehrlichia equi and the human granulocytic ehrlichiosis (HGE) agent to support separate species designations, and this group was at least 98.2% similar to any Anaplasma species. These 16S rRNA gene analyses are strongly supported by similar groESL clades, as well as biological and antigenic characteristics. It is proposed that all members of the tribes Ehrlichieae and Wolbachieae be transferred to the family Anaplasmataceae and that the tribe structure of the family Rickettsiaceae be eliminated. The genus Anaplasma should be emended to include Anaplasma (Ehrlichia) phagocytophila comb. nov. (which also encompasses the former E. equi and the HGE agent), Anaplasma (Ehrlichia) bovis comb. nov. and Anaplasma (Ehrlichia) platys comb. nov., the genus Ehrlichia should be emended to include Ehrlichia (Cowdria) ruminantium comb. nov. and the genus Neorickettsia should be emended to include Neorickettsia (Ehrlichia) risticii comb. nov. and Neorickettsia (Ehrlichia) sennetsu comb. nov.
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