Anaplasma phagocytophilum is a Gram-negative bacterium that replicates obligate intracellularly in neutrophils. It is transmitted by Ixodes spp. ticks and causes acute febrile disease in humans, dogs, horses, cats, and livestock. Because A. phagocytophilum is not transmitted transovarially in Ixodes spp., it is thought to depend on reservoir hosts to complete its life cycle. In Europe, A. phagocytophilum was detected in roe deer, red deer, wild boars, and small mammals. In contrast to roe deer, red deer and wild boars have been considered as reservoir hosts for granulocytic anaplasmosis in humans, dogs, and horses according to groESL- and ankA-based genotyping. A. phagocytophilum variants infecting small mammals in Europe have not been characterized extensively to date.
We amplified the total ankA open reading frames of 27 strains from voles and shrews. The analysis revealed that they harboured A. phagocytophilum strains that belonged to a distinct newly described ankA gene cluster. Further, we provide evidence that the heterogeneity of ankA gene sequences might have arisen via recombination.
Based on ankA-based genotyping voles and shrews are unlikely reservoir hosts for granulocytic anaplasmosis in humans, dogs, horses, and livestock in Europe.
Anaplasma phagocytophilum; Voles; Shrews; Genotyping; ankA gene; Recombination
Anaplasma phagocytophilum is a Gram-negative, tick-transmitted, obligate intracellular bacterium that elicits acute febrile diseases in humans and domestic animals. In contrast to the United States, human granulocytic anaplasmosis seems to be a rare disease in Europe despite the initial recognition of A. phagocytophilum as the causative agent of tick-borne fever in European sheep and cattle. Considerable strain variation has been suggested to occur within this species, because isolates from humans and animals differed in their pathogenicity for heterologous hosts. In order to explain host preference and epidemiological diversity, molecular characterization of A. phagocytophilum strains has been undertaken. Most often the 16S rRNA gene was used, but it might be not informative enough to delineate distinct genotypes of A. phagocytophilum. Previously, we have shown that A. phagocytophilum strains infecting Ixodes ricinus ticks are highly diverse in their ankA genes. Therefore, we sequenced the 16S rRNA and ankA genes of 194 A. phagocytophilum strains from humans and several animal species. Whereas the phylogenetic analysis using 16S rRNA gene sequences was not meaningful, we showed that distinct host species correlate with A. phagocytophilum ankA gene clusters.
Ticks act as vectors of many pathogens of domestic animals and humans. Anaplasma phagocytophilum in Europe is transmitted by the ixodid tick vector Ixodes ricinus. A. phagocytophilum causes a disease with diverse clinical signs in various hosts. A great genetic diversity of the groESL operon of A. phagocytophilum has been found in ticks elsewhere. In Slovenia, the variety of the groESL operon was conducted only on deer samples. In this study, the prevalence of infected ticks was estimated and the diversity of A. phagocytophilum was evaluated. On 8 locations in Slovenia, 1924 and 5049 (6973) I. ricinus ticks were collected from vegetation in the years 2005 and 2006, respectively. All three feeding stages of the tick's life cycle were examined. The prevalence of ticks infected with A. phagocytophilum in the year 2005 and in the year 2006 was 0.31% and 0.63%, respectively, and it did not differ considerably between locations. The similarity among the sequences of groESL ranged from 95.6% to 99.8%. They clustered in two genetic lineages along with A. phagocytophilum from Slovenian deer. One sequence formed a separate cluster. According to our study, the prevalence of A. phagocytophilum in ticks is comparable to the findings in other studies in Europe, and it does not vary considerably between locations and tick stages. According to groESL operon analysis, two genetic lineages have been confirmed and one proposed. Further studies on other genes would be useful to obtain more information on genetic diversity of A. phagocytophilum in ticks in Slovenia.
Anaplasma phagocytophilum is an emerging pathogen of humans, dogs and other animals, and it is transmitted by ixodid ticks. The objective of the current study was a) detect A. phagocytophilum in dogs and ixodid ticks using real-time Polymerase Chain Reaction (qPCR); and b) Determine important variables associated to host, environment and potential tick vectors that are related to the presence of A. phagocytophilum in dogs domiciled in Rio de Janeiro, Brazil.
We tested blood samples from 398 dogs and samples from 235 ticks, including 194 Rhipicephalus sanguineus sensu lato, 15 Amblyomma cajennense, 8 Amblyomma ovale and 18 pools of Amblyomma sp. nymphs. A semi-structured questionnaire was applied by interviewing each dog owner. Deoxyribonucleic acid obtained from ticks and dog buffy coat samples were amplified by qPCR (msp2 gene). The sequencing of 16S rRNA and groESL heat shock operon genes and a phylogenetic analysis was performed. The multiple logistic regression model was created as a function of testing positive dogs for A. phagocytophilum.
Among the 398 blood samples from dogs, 6.03% were positive for A. phagocytophilum. Anaplasma phagocytophilum was detected in one A. cajennense female tick and in five R. sanguineus sensu lato ticks (four males and one female). The partial sequences of the 16S rRNA, and groESL genes obtained were highly similar to strains of A. phagocytophilum isolated from wild birds from Brazil and human pathogenic strains. The tick species collected in positive dogs were R. sanguineus sensu lato and A. cajennense, with A.cajennense being predominant. Tick infestation history (OR = 2.86, CI = 1.98-14.87), dog size (OR = 2.41, IC: 1.51-12.67), the access to forest areas (OR = 3:51, CI: 1.52-16.32), hygiene conditions of the environment in which the dogs lived (OR = 4.35, CI: 1.86-18.63) and Amblyomma sp. infestation (OR = 6.12; CI: 2.11-28.15) were associated with A. phagocytophilum infection in dogs.
This is the first report of A. phagocytophilum in ixodid ticks from Brazil. The detection of A. phagocitophylum in A. cajennense, an aggressive feeder on a wide variety of hosts, including humans, is considered a public health concern.
Anaplasma phagocytophilum; Dogs; Ticks; Epidemiology; Emerging zoonoses
Anaplasma phagocytophilum is an intracellular tick-borne rickettsial pathogen, which causes granulocytic anaplasmosis in various species of livestock and companion animals and also in humans. Previously A. phagocytophilum has been isolated and propagated in cell lines derived from the tick Ixodes scapularis and in the human promyelocytic cell line HL60. In this study we used the Ixodes ricinus-derived cell line IRE/CTVM20 to isolate and propagate two new canine strains of A. phagocytophilum.
Blood samples were collected by veterinarians from two dogs, one from Germany and the other from Austria. Suspicion of clinical canine granulocytic anaplasmosis was raised by the treating veterinarians and after confirmation of A. phagocytophilum infection by real-time PCR, buffy coat cells were isolated and co-cultivated with IRE/CTVM20 cells maintained at 28 °C in L15/L15B medium.
In the tick cells, rickettsial inclusions were first recognised after 86 days of incubation. Electron microscopic examination of tick cells infected with one of the isolates revealed cytoplasmic vacuoles containing pleomorphic organisms with individual bacteria enveloped by a bilayer membrane. Sequencing of 16S rRNA genes confirmed the isolation of A. phagocytophilum and showed the highest identity to the A. phagocytophilum human HZ strain. The two A. phagocytophilum isolates were passaged several times in IRE/CTVM20 cells and transferred to the I. scapularis cell line ISE6. This confirms for the first time the successful establishment and continuous cultivation of this pathogen in I. ricinus cells as well as infectivity of these canine strains for I. scapularis cells.
Tick cell lines; Anaplasma phagocytophilum; IRE/CTVM20; Dog; Electron microscopy
Human granulocytic anaplasmosis (HGA) and human monocytic ehrlichiosis (HME) are emerging, tick-borne, zoonotic infectious diseases caused by Anaplasma phagocytophilum and Ehrlichia chaffeensis, respectively. Early diagnosis is essential for rapid clinical treatment to avoid misdiagnosis and severe patient outcomes. Simple, sensitive and reliable diagnostic methods are urgently needed. In this study, we developed a duplex real-time PCR assay targeting the A. phagocytophilum ankA gene and the E. chaffeensis TRP120 gene, respectively. The lowest limit of detection of the duplex real-time PCR assay was 100 copies of the targeted A. phagocytophilum ankA gene and the E. chaffeensis TRP120 gene per reaction, and the specificity was 100%. Detection in blood DNA samples from the acute stage of illness for 22 HGA cases and 8 HME cases indicated that the duplex real-time PCR assay was more sensitive than the nested PCR assay. The infection of Citellusundulatus Pallas with A. phagocytophilum and E. chaffeensis was first confirmed in Xinjiang Province and the positive rate was 3.1% for A. phagocytophilum, 6.3% for E. chaffeensis and 3.1% for co-infection with both pathogens. The rates of A. phagocytophilum and E. chaffeensis infection of D. silvarum ticks collected from Shanxi Province were 8.2% and 14.8%, respectively, and the co-infection rate was 3.3%. The rates of A. phagocytophilum and E. chaffeensis infection in H. longicornis ticks collected from Shandong Province were 1.6% and 6.3%, respectively, and the co-infection rate was 1.6%.
We report the isolation and partial genetic characterization of two equine strains of granulocytic Ehrlichia of the genogroup Ehrlichia phagocytophila. Frozen whole-blood samples from two Swedish horses with laboratory-verified granulocytic ehrlichiosis were inoculated into HL-60 cell cultures. Granulocytic Ehrlichia was isolated and propagated from both horses. DNA extracts from the respective strains were amplified by PCR using primers directed towards the 16S rRNA gene, the groESL heat shock operon gene, and the ank gene. The amplified gene fragments were sequenced and compared to known sequences in the GenBank database. With respect to the 16S rRNA gene, the groESL gene, and the ank gene, the DNA sequences of the two equine Ehrlichia isolates were identical to sequences found in isolates from clinical cases of granulocytic ehrlichiosis in humans and domestic animals in Sweden. However, compared to amplified DNA from an American Ehrlichia strain of the E. phagocytophila genogroup, differences were found in the groESL gene and ank gene sequences.
Equine Granulocytic Anaplasmosis (EGA) is caused by Anaplasma phagocytophilum, a tick-transmitted, obligate intracellular bacterium. In Europe, it is transmitted by Ixodes ricinus. A large number of genetic variants of A. phagocytophilum circulate in nature and have been found in ticks and different animals. Attempts have been made to assign certain genetic variants to certain host species or pathologies, but have not been successful so far. The purpose of this study was to investigate the causing agent A. phagocytophilum of 14 cases of EGA in naturally infected horses with molecular methods on the basis of 4 partial genes (16S rRNA, groEL, msp2, and msp4).
All DNA extracts of EDTA-blood samples of the horses gave bands of the correct nucleotide size in all four genotyping PCRs. Sequence analysis revealed 4 different variants in the partial 16S rRNA, groEL gene and msp2 genes, and 3 in the msp4 gene. One 16S rRNA gene variant involved in 11 of the 14 cases was identical to the "prototype" variant causing disease in humans in the amplified part [GenBank: U02521]. Phylogenetic analysis revealed as expected for the groEL gene that sequences from horses clustered separately from roe deer. Sequences of the partial msp2 gene from this study formed a separate cluster from ruminant variants in Europe and from all US variants.
The results show that more than one variant of A. phagocytophilum seems to be involved in EGA in Germany. The comparative genetic analysis of the variants involved points towards different natural cycles in the epidemiology of A. phagocytophilum, possibly involving different reservoir hosts or host adaptation, rather than a strict species separation.
The presence of granulocytic ehrlichiae was demonstrated by PCR in Ixodes ricinus ticks and wild small mammals in Switzerland in two areas of endemicity for bovine ehrlichiosis. Six ticks (three females and three nymphs) (1.4%) of 417 I. ricinus ticks collected by flagging vegetation contained ehrlichial DNA. A total of 201 small mammals from five species, wood mouse (Apodemus sylvaticus), yellow-necked mouse (Apodemus flavicollis), earth vole (Pitymys subterraneus), bank vole (Clethrionomys glareolus), and common shrew (Sorex araneus), were trapped. The analysis of I. ricinus mammals collected on 116 small mammals showed that nine C. glareolus voles and two A. sylvaticus mice hosted infected tick larvae. In these rodents, granulocytic ehrlichia infection was also detected in blood, spleen, liver, and ear samples. Further examinations of 190 small mammals without ticks or with noninfected ticks showed the presence of ehrlichial DNA in spleen and other tissues from six additional C. glareolus, three A. flavicollis, and one S. araneus mammals. This study suggests that A. sylvaticus, A. flavicollis, S. araneus, and particularly C. glareolus are likely to be natural reservoirs for granulocytic ehrlichiae. Partial 16S rRNA gene sequences of granulocytic ehrlichiae from ticks and rodents showed a high degree of homology (99 to 100%) with granulocytic ehrlichiae isolated from humans. In contrast, groESL heat shock operon sequence analysis showed a strong divergence (approximately 5%) between the sequences in samples derived from rodents and those derived from samples from questing ticks or from other published ehrlichia sequences. Dual infections with granulocytic ehrlichia and Borrelia burgdorferi were found in ticks and small mammals.
The aims of this study were to evaluate the host-tick-pathogen interface of Babesia spp. and Anaplasma phagocytophilum in restored areas in both questing and host-attached Ixodes ricinus and Dermacentor reticulatus and their small mammalian hosts.
Questing ticks were collected from 5 sites within the city of Leipzig, Germany, in 2009. Small mammals were trapped at 3 of the 5 sites during 2010 and 2011. DNA extracts of questing and host-attached I. ricinus and D. reticulatus and of several tissue types of small mammals (the majority bank voles and yellow-necked mice), were investigated by PCR followed by sequencing for the occurrence of DNA of Babesia spp. and by real-time PCR for A. phagocytophilum. A selected number of samples positive for A. phagocytophilum were further investigated for variants of the partial 16S rRNA gene. Co-infection with Rickettsia spp. in the questing ticks was additionally investigated.
4.1% of questing I. ricinus ticks, but no D. reticulatus, were positive for Babesia sp. and 8.7% of I. ricinus for A. phagocytophilum. Sequencing revealed B. microti, B. capreoli and Babesia spp. EU1 in Leipzig and sequence analysis of the partial 16S RNA gene of A. phagocytophilum revealed variants either rarely reported in human cases or associated with cervid hosts. The statistical analysis revealed significantly less ticks infected with A. phagocytophilum in a city park in Leipzig as compared to the other sampling sites. A. phagocytophilum-DNA was detected in 2 bank voles, DNA of B. microti in 1 striped field-mouse and of Babesia sp. EU1 in the skin tissue of a mole. Co-infections were detected.
Our results show the involvement of small mammals in the natural endemic cycles of tick-borne pathogens. A more thorough understanding of the interactions of ticks, pathogens and hosts is the essential basis for effective preventive control measures.
Babesia spp; Anaplasma phagocytophilum; Ixodes ricinus; Dermacentor reticulatus; Bank vole; Yellow-necked mouse; Recreational area; Host survey; Vector-host relation
Molecular epidemiology represents a powerful approach to elucidate the complex epidemiological cycles of multi-host pathogens, such as Anaplasma phagocytophilum. A. phagocytophilum is a tick-borne bacterium that affects a wide range of wild and domesticated animals. Here, we characterized its genetic diversity in populations of French cattle; we then compared the observed genotypes with those found in horses, dogs, and roe deer to determine whether genotypes of A. phagocytophilum are shared among different hosts. We sampled 120 domesticated animals (104 cattle, 13 horses, and 3 dogs) and 40 wild animals (roe deer) and used multilocus sequence analysis on nine loci (ankA, msp4, groESL, typA, pled, gyrA, recG, polA, and an intergenic region) to characterize the genotypes of A. phagocytophilum present. Phylogenic analysis revealed three genetic clusters of bacterial variants in domesticated animals. The two principal clusters included 98% of the bacterial genotypes found in cattle, which were only distantly related to those in roe deer. One cluster comprised only cattle genotypes, while the second contained genotypes from cattle, horses, and dogs. The third contained all roe deer genotypes and three cattle genotypes. Geographical factors could not explain this clustering pattern. These results suggest that roe deer do not contribute to the spread of A. phagocytophilum in cattle in France. Further studies should explore if these different clusters are associated with differing disease severity in domesticated hosts. Additionally, it remains to be seen if the three clusters of A. phagocytophilum genotypes in cattle correspond to distinct epidemiological cycles, potentially involving different reservoir hosts.
Electronic supplementary material
The online version of this article (doi:10.1186/s13567-014-0114-7) contains supplementary material, which is available to authorized users.
Tick-transmitted rickettsial diseases, such as ehrlichiosis and spotted fever rickettsiosis, are significant sources of morbidity and mortality in the southern United States. Because of their exposure in tick-infested woodlands, outdoor workers experience an increased risk of infection with tick-borne pathogens. As part of a double blind randomized-controlled field trial of the effectiveness of permethrin-treated clothing in preventing tick bites, we identified tick species removed from the skin of outdoor workers in North Carolina and tested the ticks for Rickettsiales pathogens.
Ticks submitted by study participants from April-September 2011 and 2012 were identified to species and life stage, and preliminarily screened for the genus Rickettsia by nested PCR targeting the 17-kDa protein gene. Rickettsia were further identified to species by PCR amplification of 23S-5S intergenic spacer (IGS) fragments combined with reverse line blot hybridization with species-specific probes and through cloning and nucleotide sequence analysis of 23S-5S amplicons. Ticks were examined for Ehrlichia and Anaplasma by nested PCR directed at the gltA, antigen-expressing gene containing a variable number of tandem repeats, 16S rRNA, and groESL genes.
The lone star tick (Amblyomma americanum) accounted for 95.0 and 92.9% of ticks submitted in 2011 (n = 423) and 2012 (n = 451), respectively. Specimens of American dog tick (Dermacentor variabilis), Gulf Coast tick (Amblyomma maculatum) and black-legged tick (Ixodes scapularis) were also identified. In both years of our study, 60.9% of ticks tested positive for 17-kDa. “Candidatus Rickettsia amblyommii”, identified in all four tick species, accounted for 90.2% (416/461) of the 23S-5S-positive samples and 52.9% (416/787) of all samples tested. Nucleotide sequence analysis of Rickettsia-specific 23S-5S IGS, ompA and gltA gene fragments indicated that ticks, principally A. americanum, contained novel species of Rickettsia. Other Rickettsiales, including Ehrlichia ewingii, E. chaffeensis, Ehrlichia sp. (Panola Mountain), and Anaplasma phagocytophilum, were infrequently identified, principally in A. americanum.
We conclude that in North Carolina, the most common rickettsial exposure is to R. amblyommii carried by A. americanum. Other Rickettsiales bacteria, including novel species of Rickettsia, were less frequently detected in A. americanum but are relevant to public health nevertheless.
Electronic supplementary material
The online version of this article (doi:10.1186/s13071-014-0607-2) contains supplementary material, which is available to authorized users.
Ticks; Rickettsiales pathogens; Rickettsia; Ehrlichia; Reverse line blot hybridization
Transmission of tick-borne pathogens requires transition between distinct host environments with infection and replication in host-specific cell types. Anaplasma marginale illustrates this transition: in the mammalian host, the bacterium infects and replicates in mature (nonnucleated) erythrocytes, while in the tick vector, replication occurs in nucleated epithelial cells. We hypothesized that proteins containing ankyrin motifs would be expressed by A. marginale only in tick cells and would traffic to the infected host cell nucleus. A. marginale encodes three proteins containing ankyrin motifs, an AnkA orthologue (the AM705 protein), AnkB (the AM926 protein), and AnkC (the AM638 protein). All three A. marginale Anks were confirmed to be expressed during intracellular infection: AnkA is expressed at significantly higher levels in erythrocytes, AnkB is expressed equally by both infected erythrocytes and tick cells, and AnkC is expressed exclusively in tick cells. There was no evidence of any of the Ank proteins trafficking to the nucleus. Thus, the hypothesis that ankyrin-containing motifs were predictive of cell type expression and nuclear localization was rejected. In contrast, AnkA orthologues in the closely related A. phagocytophilum and Ehrlichia chaffeensis have been shown to localize to the host cell nucleus. This difference, together with the lack of a nuclear localization signal in any of the AnkA orthologues, suggests that trafficking may be mediated by a separate transporter rather than by endogenous signals. Selection for divergence in Ank function among Anaplasma and Ehrlichia spp. is supported by both locus and allelic analyses of genes encoding orthologous proteins and their ankyrin motif compositions.
Anaplasma phagocytophilum is the etiological agent of granulocytic anaplasmosis in humans and animals. Wild animals and ticks play key roles in the enzootic cycles of the pathogen. Potential ecotypes of A. phagocytophilum have been characterized genetically, but their host range, zoonotic potential and transmission dynamics has only incompletely been resolved.
The presence of A. phagocytophilum DNA was determined in more than 6000 ixodid ticks collected from the vegetation and wildlife, in 289 tissue samples from wild and domestic animals, and 69 keds collected from deer, originating from various geographic locations in The Netherlands and Belgium. From the qPCR-positive lysates, a fragment of the groEL-gene was amplified and sequenced. Additional groEL sequences from ticks and animals from Europe were obtained from GenBank, and sequences from human cases were obtained through literature searches. Statistical analyses were performed to identify A. phagocytophilum ecotypes, to assess their host range and their zoonotic potential. The population dynamics of A. phagocytophilum ecotypes was investigated using population genetic analyses.
DNA of A. phagocytophilum was present in all stages of questing and feeding Ixodes ricinus, feeding I. hexagonus, I. frontalis, I. trianguliceps, and deer keds, but was absent in questing I. arboricola and Dermacentor reticulatus. DNA of A. phagocytophilum was present in feeding ticks and tissues from many vertebrates, including roe deer, mouflon, red foxes, wild boar, sheep and hedgehogs but was rarely found in rodents and birds and was absent in badgers and lizards. Four geographically dispersed A. phagocytophilum ecotypes were identified, that had significantly different host ranges. All sequences from human cases belonged to only one of these ecotypes. Based on population genetic parameters, the potentially zoonotic ecotype showed significant expansion.
Four ecotypes of A. phagocytophilum with differential enzootic cycles were identified. So far, all human cases clustered in only one of these ecotypes. The zoonotic ecotype has the broadest range of wildlife hosts. The expansion of the zoonotic A. phagocytophilum ecotype indicates a recent increase of the acarological risk of exposure of humans and animals.
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Anaplasma phagocytophilum; Zoonoses; Ixodes ricinus; Wildlife; Epidemiology
The occurrence of Anaplasma phagocytophilum was investigated in spleen and serum samples from Swedish moose (Alces alces) in southern Sweden (island and mainland). Samples were analysed for presence of A. phagocytophilum DNA by real-time PCR (n = 263), and for Anaplasma antibodies with ELISA serology (n = 234). All serum samples had antibodies against A. phagocytophilum. The mean DNA-based prevalence was 26·3%, and significant (P < 0·01) temporal, and spatial variation was found. Island moose had significantly (P < 0·001) higher prevalence of A. phagocytophilum DNA than moose from the mainland areas. Two samples were sequenced to determine genetic variation in the 16S rRNA and groESL genes. Genetic sequence similarity with the human granulocytic anaplasmosis agent, equine granulocytic ehrlichiosis agent, and different wildlife-associated A. phagocytophilum variants were observed in the 16S rRNA and groESL genes. Our study shows that moose are exposed to A. phagocytophilum in Sweden, and represent a potential wildlife reservoir of the pathogen.
Ehrlichia; epidemiology; HGA; moose; PCR; serology; tick-borne fever
Adult Ixodes ricinus (Acari: Ixodidae) ticks collected near Ljubljana, Slovenia, were tested for the agent of human granulocytic ehrlichiosis (HGE) by using PCR assays based on the 16S rRNA gene. Three (3.2%) of 93 ticks were found to contain granulocytic ehrlichiae. Nucleotide sequences of portions of the bacterial groESL heat shock operon amplified from these ticks were identical or nearly (99.8%) identical to those previously determined for human patients with HGE from Slovenia, providing additional evidence that the ticks were infected with the HGE agent. This study identified I. ricinus as the likely vector for these ehrlichial pathogens of humans in this part of Europe.
Neoehrlichia mikurensis s an emerging and vector-borne zoonosis: The first human disease cases were reported in 2010. Limited information is available about the prevalence and distribution of Neoehrlichia mikurensis in Europe, its natural life cycle and reservoir hosts. An Ehrlichia-like schotti variant has been described in questing Ixodes ricinus ticks, which could be identical to Neoehrlichia mikurensis.
Three genetic markers, 16S rDNA, gltA and GroEL, of Ehrlichia schotti-positive tick lysates were amplified, sequenced and compared to sequences from Neoehrlichia mikurensis. Based on these DNA sequences, a multiplex real-time PCR was developed to specifically detect Neoehrlichia mikurensis in combination with Anaplasma phagocytophilum in tick lysates. Various tick species from different life-stages, particularly Ixodes ricinus nymphs, were collected from the vegetation or wildlife. Tick lysates and DNA derived from organs of wild rodents were tested by PCR-based methods for the presence of Neoehrlichia mikurensis. Prevalence of Neoehrlichia mikurensis was calculated together with confidence intervals using Fisher's exact test.
The three genetic markers of Ehrlichia schotti-positive field isolates were similar or identical to Neoehrlichia mikurensis. Neoehrlichia mikurensis was found to be ubiquitously spread in the Netherlands and Belgium, but was not detected in the 401 tick samples from the UK. Neoehrlichia mikurensis was found in nymphs and adult Ixodes ricinus ticks, but neither in their larvae, nor in any other tick species tested. Neoehrlichia mikurensis was detected in diverse organs of some rodent species. Engorging ticks from red deer, European mouflon, wild boar and sheep were found positive for Neoehrlichia mikurensis.
Ehrlichia schotti is similar, if not identical, to Neoehrlichia mikurensis. Neoehrlichia mikurensis is present in questing Ixodes ricinus ticks throughout the Netherlands and Belgium. We propose that Ixodes ricinus can transstadially, but not transovarially, transmit this microorganism, and that different rodent species may act as reservoir hosts. These data further imply that wildlife and humans are frequently exposed to Neoehrlichia mikurensis-infected ticks through tick bites. Future studies should aim to investigate to what extent Neoehrlichia mikurensis poses a risk to public health.
Vector-borne disease; Emerging zoonoses; Candidatus N. mikurensis; I. ricinus; Anaplasma phagocytophylum
The first tissue culture isolates of the unique Anaplasma phagocytophilum strain, Ap-Variant 1, were obtained in the Ixodes scapularis tick-derived cell line ISE6. Two isolates were from goat blood samples: one from a goat infected with I. scapularis ticks from Rhode Island and a second from a goat infected by serial passage of blood from the first infected goat. Eight isolates were made directly from I. scapularis ticks collected from white-tailed deer in Minnesota and represent the first isolations of an Anaplasma species directly from ticks. Each of the 10 isolates had a 16S rRNA gene sequence identical to that previously described for Ap-Variant 1, but differences within the ank gene were found that suggest natural variation. Prevalence of Anaplasma in the Minnesota ticks was 63.9%; 23 of 36 ticks tested by PCR were positive. Six of the tick-derived isolates were obtained from a set of 18 PCR-positive ticks, for a 33.3% isolation success rate. The conservation of host tropism among the Rhode Island and Minnesota isolates of Ap-Variant 1 was examined by use of experimental infections of mice and a goat. A Minnesota tick-derived isolate (MN-61-2) was used to inoculate naïve animals, and this isolate was able to infect a goat but unable to infect each of five mice, confirming that the Minnesota isolates have the same host tropism as Ap-Variant 1 from the northeastern United States. Light and electron microscopy of the Ap-Variant 1 isolate MN-61-2 in ISE6 cells showed cytoplasmic inclusions characteristic of A. phagocytophilum with pleomorphic bacteria in membrane-bound vacuoles and both electron-dense and electron-lucent forms.
Anaplasma phagocytophilum is an emerging tick-borne pathogen that infects humans, domestic animals and wildlife throughout the Holarctic. In the far-western United States, multiple rodent species have been implicated as natural reservoirs for A. phagocytophilum. However, the presence of multiple A. phagocytophilum strains has made it difficult to determine which reservoir hosts pose the greatest risk to humans and domestic animals. Here we characterized three genetic markers (23S–5S rRNA intergenic spacer, ank and groESL) from 73 real-time TaqMan PCR-positive A. phagocytophilum strains infecting multiple rodent and reptile species, as well as a dog and a horse, from California. Bayesian and maximum-likelihood phylogenetic analyses of all three genetic markers consistently identified two major clades, one of which consisted of A. phagocytophilum strains infecting woodrats and the other consisting of strains infecting sciurids (chipmunks and squirrels) as well as the dog and horse strains. In addition, analysis of the 23S–5S rRNA spacer region identified two unique and highly dissimilar clades of A. phagocytophilum strains infecting several lizard species. Our findings indicate that multiple unique strains of A. phagocytophilum with distinct host tropisms exist in California. Future epidemiological studies evaluating human and domestic animal risk should incorporate these distinctions.
We examined 11 naturally occurring isolates of Ehrlichia equi in horses and two human granulocytic ehrlichiosis agent isolates in California for sequence diversity in three genes. Ehrlichia equi isolates were from Sierra (n = 6), Mendocino (n = 3), Sonoma (n = 1), and Marin (n = 1) counties, and human granulocytic ehrlichiosis (HGE) agent isolates were obtained from Humboldt county. PCR with specific primers for 16S rRNA, 444 Ep-ank and groESL heat shock operon genes successfully produced amplicons for all 13 clinical samples. The 444 Ep-ank gene of the HGE agent and E. equi isolates from northern California is different from the eastern U.S. isolates BDS and USG3. The translated amino acid sequence of the groESL heat shock operon gene fragment is identical among E. equi, the HGE agent, and E. phagocytophila, with the exception of the northern Californian equine CASOLJ isolate. Microheterogeneity was observed in the 16S rRNA gene sequences of HGE agent and E. equi isolates from northern California. These results suggest that E. equi and the HGE agent found in California are similar or identical but may differ from the isolates of equine and human origin found in the eastern United States.
Wild deer are one of the important natural reservoir hosts of several species of Ehrlichia and Anaplasma that cause human ehrlichiosis or anaplasmosis in the United States and Europe. The primary aim of the present study was to determine whether and what species of Ehrlichia and Anaplasma naturally infect deer in Japan. Blood samples obtained from wild deer on two major Japanese islands, Hokkaido and Honshu, were tested for the presence of Ehrlichia and Anaplasma by PCR assays and sequencing of the 16S rRNA genes, major outer membrane protein p44 genes, and groESL. DNA representing four species and two genera of Ehrlichia and Anaplasma was identified in 33 of 126 wild deer (26%). DNA sequence analysis revealed novel strains of Anaplasma phagocytophilum, a novel Ehrlichia sp., Anaplasma centrale, and Anaplasma bovis in the blood samples from deer. None of these have been found previously in deer. The new Ehrlichia sp., A. bovis, and A. centrale were also detected in Hemaphysalis longicornis ticks from Honshu Island. These results suggest that enzootic cycles of Ehrlichia and Anaplasma species distinct from those found in the United States or Europe have been established in wild deer and ticks in Japan.
Although anaplasmosis cases have been nationally identified in China, no human isolates of A. phagocytophilum have been obtained, which limits the analysis of any molecular and genetic contributions to patients' severe clinical manifestations and the study of the bacteria's pathogeneses in China. Given this situation, a joint project was conducted in 2009–2010. A total of 421 febrile cases of unknown etiology were collected and the patients' blood samples were collected for laboratory diagnoses including serologic diagnosis based on the four-fold rise in the anti- A. phagocytophilum IgG titer by indirect micro-immunofluorescence assay (IFA), positive PCR assay and confirmation of A. phagocytophilum DNA and positive culture of A. phagocytophilum and confirmed by amplification and sequencing of the 16S rRNA and ank A genes of the A. phagocytophilum isolates. A total of 570 ticks were collected from the patients' domestic animals (456) and from wild fields (114) for culturing and amplifying and sequencing the 16S rRNA gene of A. phagocytophilum. Phylogenetic analyses were performed on the 16S rRNA and ank A gene sequences of the isolates and the ticks tested in the study. A total of 46 (10.9%) confirmed and 16 (3.8%) probable cases were diagnosed and severe clinical features and higher mortality rates were observed in these Chinese patients. Five isolates were obtained and the 16S rRNA genes of the 5 isolates were conserved but variety for ank A genes. Two human isolates and 1 tick isolate from Shandong Peninsula, where all patients exhibited severe clinical manifestations, were grouped as one clan based on the phylogenetic analyses, while 2 other human isolates were clustered in a second clan. 43.5% of H. longicornis were infected with A. phagocytophilum.The present study is the first to obtain clinical isolates of A. phagocytophilum in China. The diversity of the ank A genes of Chinese isolates will help us to further discern the relationship between the variations in the ank A genes and the severity of the disease's clinical manifestations in China.
Dermacentor albipictus (Packard) is a North American tick that feeds on cervids and livestock. It is a suspected vector of anaplasmosis in cattle, but its microbial flora and vector potential remain underevaluated. We screened D. albipictus ticks collected from Minnesota white-tailed deer (Odocoileus virginianus) for bacteria of the genera Anaplasma, Ehrlichia, Francisella, and Rickettsia using polymerase chain reaction (PCR) gene amplification and sequence analyses. We detected Anaplasma phagocytophilum and Francisella-like endosymbionts (FLEs) in nymphal and adult ticks of both sexes at 45 and 94% prevalences, respectively. The A. phagocytophilum and FLEs were transovarially transmitted to F1 larvae by individual ticks at efficiencies of 10–40 and 95–100%, respectively. The FLEs were transovarially transmitted to F2 larvae obtained as progeny of adults from F1 larval ticks reared to maturity on a calf, but A. phagocytophilum were not. Based on PCR and tissue culture inoculation assays, A. phagocytophilum and FLEs were not transmitted to the calf. The amplified FLE 16S rRNA gene sequences were identical to that of an FLE detected in a D. albipictus from Texas, whereas those of the A. phagocytophilum were nearly identical to those of probable human-nonpathogenic A. phagocytophilum WI-1 and WI-2 variants detected in white-tailed deer from central Wisconsin. However, the D. albipictus A. phagocytophilum sequences differed from that of the nonpathogenic A. phagocytophilum variant-1 associated with Ixodes scapularis ticks and white-tailed deer as well as that of the human-pathogenic A. phagocytophilum ha variant associated with I. scapularis and the white-footed mouse, Peromyscus leucopus. The transovarial transmission of A. phagocytophilum variants in Dermacentor ticks suggests that maintenance of A. phagocytophilum in nature may not be solely dependent on horizontal transmission.
Ixodid tick; Anaplasma; Francisella-like; transovarial transmission
A broad-range 16S rRNA gene PCR assay followed by partial sequencing of the 16S rRNA gene was used for the detection of members of the family Anaplasmataceae in ticks in North Africa. A total of 418 questing Ixodes ricinus ticks collected in Tunisia and Morocco, as well as 188 Rhipicephalus ticks from dogs and 52 Hyalomma ticks from bovines in Tunisia, were included in this study. Of 324 adult I. ricinus ticks, 16.3% were positive for Ehrlichia spp., whereas only 3.4 and 2.8% of nymphs and larvae, respectively, were positive. A large heterogeneity was observed in the nucleotide sequences. Partial sequences identical to that of the agent of human granulocytic ehrlichiosis (HGE) were detected in I. ricinus and Hyalomma detritum, whereas partial sequences identical to that of Anaplasma platys were detected in Rhipicephalus sanguineus. However, variants of Anaplasma, provisionally designated Anaplasma-like, were predominant in the I. ricinus tick population in Maghreb. Otherwise, two variants of the genus Ehrlichia were detected in I. ricinus and H. detritum. Surprisingly, a variant of Wolbachia pipientis was evidenced from I. ricinus in Morocco. These results emphasized the potential risk of tick bites for human and animal populations in North Africa.
Human granulocytic ehrlichiosis (HGE) is a potentially fatal, tick-borne disease caused by a bacterium related or identical to Ehrlichia phagocytophila. To identify and characterize E. phagocytophila group-specific protein antigen genes, we prepared and screened HGE agent and Ehrlichia equi genomic DNA expression libraries using polyclonal equine E. equi antibodies. Two clones, one each from HGE agent and E. equi, that were recognized specifically by antibodies to the E. phagocytophila group ehrlichiae had complete open reading frames of 3,693 and 3,615 nucleotides, respectively. The two clones were 96.6% identical and predicted a protein with at least 11 tandemly repeated ankyrin motifs. Thus, the gene was named ank (for ankyrin). When the encoded protein, named AnkA, was expressed in Escherichia coli, it was recognized by antibodies from rabbits and mice immunized with the HGE agent, sera from humans convalescent from HGE, and sera from horses convalescent from HGE and E. equi infection. Monospecific AnkA antibodies reacted with proteins in HGE agent immunoblots, and AnkA monoclonal antibodies detected cytoplasmic antigen in E. phagocytophila group bacteria and also detected antigen associated with chromatin in infected but not uninfected HL-60 cell cultures. These results suggest that this Ehrlichia protein may influence host cell gene expression.