Detection of spotted fever group Rickettsia spp. from bird ticks in the U.K.

Migratory birds are known to play a role in the long‐distance transportation of microorganisms. To investigate whether this is true for rickettsial agents, we undertook a study to characterize tick infestation in populations of the migratory passerine bird Riparia riparia (Passeriformes: Hirundinidae), the sand martin. A total of 194 birds were sampled and ticks removed from infested birds. The ticks were identified as female Ixodes lividus (Acari: Ixodidae) using standard morphological and molecular techniques. Tick DNA was assayed to detect Rickettsia spp. using polymerase chain reaction and DNA was sequenced for species identification. A single Rickettsia spp. was detected in 100% of the ticks and was designated Rickettsia sp. IXLI1. Partial sequences of 17‐kDa and ompA genes showed greatest similarity to Rickettsia sp. TCM1, an aetiological agent of Japanese spotted fever‐like illness, previously described in Thailand. Phylogenetic analysis showed that Rickettsia sp. IXLI1 fitted neatly into a group containing strains Rickettsia japonica, Rickettsia sp. strain Davousti and Rickettsia heilongjiangensis. In conclusion, this research shows that U.K. migratory passerine birds host ticks infected with Rickettsia species and contribute to the geographic distribution of spotted fever rickettsial agents.     

Microorganisms in the ticks Amblyomma dissimile Koch 1844 and Amblyomma rotundatum Koch 1844 collected from snakes in Brazil

Knowledge about ticks (Acari) and screening of ticks parasitizing various hosts are necessary to understand the epidemiology of tick‐borne pathogens. The objective of this study was to investigate tick infestations on snakes (Reptilia: Squamata: Serpentes) arriving at the serpentarium at the Institute Vital Brazil, Rio de Janeiro. Some of the identified ticks were individually tested for the presence of bacteria of the genera Rickettsia (Rickettsiales: Rickettsiaceae), Borrelia (Spirochaetales: Spirochaetaceae), Coxiella (Legionellales: Coxiellaceae), Bartonella (Rhizobiales: Bartonellaceae), Ehrlichia (Rickettsiales: Anaplasmataceae), Anaplasma (Rickettsiales: Anaplasmataceae), and Apicomplexa protozoa of the genera Babesia (Piroplasmida: Babesiidae) and Hepatozoon (Eucoccidiorida: Hepatozoidae). A total of 115 hard ticks (Ixodida: Ixodidae) were collected from 17 host individuals obtained from four Brazilian states. Two species of tick were identified: Amblyomma dissimile Koch 1844 (four larvae, 16 nymphs, 40 adults), and Amblyomma rotundatum Koch 1844 (12 nymphs, 43 adults). Rickettsia bellii was found in A. rotundatum and A. dissimile ticks and Rickettsia sp. strain Colombianensi, Anaplasma‐like and Hepatozoon sp. in A. dissimile ticks. Among the tested ticks, no DNA of Borrelia, Bartonella, Coxiella or Babesia was found. The present findings extend the geographic range of Rickettsia sp. strain Colombianensi in Brazil and provide novel tick–host associations.     

Ticks Parasitizing Wild Birds in Portugal: Detection of Rickettsia aeschlimannii, R. helvetica and R. massiliae

From January 2002 to December 2004, 152 ticks were collected from 40 wild birds recovered in Santo André Natural Reserve and Monsanto Forestal Park, Portugal mainland. Five ticks species were identified from 22 species of birds, and new host record were provided for some species. In addition, 32 (21%) ticks were screened by PCR to detect infections with agents belonging to order Rickettsiales: Anaplasma phagocytophilum, Ehrlichia chaffeensis, and Rickettsia spp. PCR amplicons were obtained in 5 (15.6%) tick samples. Rickettsia DNA exhibiting gltA sequences similar to those of Rickettsia aeschilimannii, R. helvetica and R. massiliae were identified in Hyalomma marginatum, Ixodes ventalloi and in Rhipicephalus turanicus, respectively. This is the first report of rickettsiae infections in ticks collected from wild birds in Portugal. Giving the results presented above wild birds play an important role in the maintenance and dissemination of several tick species and associated rickettsiae.     

A prevalent alpha-proteobacterium Paracoccus sp. in a population of the Cayenne ticks (Amblyomma cajennense) from Rio de Janeiro,Brazil

As Rocky Mountain Spotted Fever is the most common tick-borne disease in South America, the presence of Rickettsia sp. in Amblyomma ticks is a possible indication of its endemicity in certain geographic regions. In the present work, bacterial DNA sequences related to Rickettsia amblyommii genes in A. dubitatum ticks, collected in the Brazilian state of Mato Grosso, were discovered. Simultaneously, Paracoccus sp. was detected in aproximately 77% of A. cajennense specimens collected in Rio de Janeiro, Brazil. This is the first report of Paracoccus sp. infection in a specific tick population, and raises the possibility of these bacteria being maintained and/or transmitted by ticks. Whether Paracoccus sp. represents another group of pathogenic Rhodobacteraceae or simply plays a role in A. cajennense physiology, is unknown. The data also demonstrate that the rickettsial 16S rRNA specific primers used forRickettsia spp. screening can also detect Paracoccus alpha-proteobacteria infection in biological samples. Hence, a PCR-RFLP strategy is presented to distinguish between these two groups of bacteria.     

Intracellular Symbionts and Other Bacteria Associated with Deer Ticks (Ixodes scapularis) from Nantucket and Wellfleet, Cape Cod, Massachusetts

The diversity of bacteria associated with the deer tick (Ixodes scapularis) was assessed using PCR amplification, cloning, and sequencing of 16S rRNA genes originating from seven ticks collected from Nantucket Island and Wellfleet, Cape Cod, Mass. The majority of sequences obtained originated from gram-negative proteobacteria. Four intracellular bacteria were detected including strains of Ehrlichia, Rickettsia, and Wolbachia and an organism related to intracellular insect symbionts from the Cytophaga-Flavobacterium-Bacteroides group. Several strains of members of the Sphingomonadaceae were also detected in all but one tick. The results provide a view of the diversity of bacteria associated with I. scapularis ticks in the field.     

Detection of a novel spotted fever group rickettsia in <Emphasis Type="Italic">Amblyomma parvum</Emphasis> ticks (Acari: Ixodidae) from Argentina

The present study evaluated the rickettsial infection in Amblyomma parvum ticks collected in Northwestern Córdoba Province, Argentina. Each tick was subjected to DNA extraction and tested by polymerase chain reaction (PCR) targeting fragments of the rickettsial genes gltA and ompB. Nine (69.2%) out of 13 adult ticks yielded expected PCR products for the two rickettsial genes. Products from the ompB PCR were sequenced, generating DNA sequences 100% identical for the nine PCR-positive ticks. Three of these ticks were tested in another battery of PCR targeting fragments of the rickettsial genes gltA, htrA, and ompA. Products from the gltA, htrA, and ompA PCRs were sequenced generating DNA sequences 100% identical for the three PCR-positive ticks. The rickettsia detected in the A. parvum ticks was designated as Rickettsia sp. strain Argentina. Phylogenetic analyses performed with partial sequences of the rickettsial genes gltA, htrA, ompB, and ompA showed that Rickettsia sp. strain Argentina belonged to the spotted fever group, being distinct from all known Rickettsia species and genotypes available in GenBank, representing possibly a new Rickettsia species. This was the first evidence of rickettsial infection in the tick A. parvum, and the third report of rickettsial infection among the Argentinean tick fauna. The role of Rickettsia sp. strain Argentina as a human pathogen is unknown. Further studies are needed to obtain tissue-cultured isolates of Rickettsia sp. strain Argentina, in order to better characterize it and to determine its taxonomic status as a new species.     

Rickettsial agents in Egyptian ticks collected from domestic animals

To assess the presence of rickettsial pathogens in ticks from Egypt, we collected ticks from domestic and peridomestic animals between June 2002 and July 2003. DNA extracts from 1019 ticks were tested, using PCR and sequencing, for Anaplasma spp., Bartonella spp., Coxiella burnetii, Ehrlichia spp., and Rickettsia spp. Ticks included: 29 Argas persicus, 10 Hyalomma anatolicum anatolicum, 55 Hyalomma anatolicum excavatum, 174 Hyalomma dromedarii, 2 Hyalomma impeltatum, 3 Hyalomma marginatum rufipes, 55 unidentified nymphal Hyalomma, 625 Rhipicephalus (Boophilus) annulatus, 49 Rhipicephalus sanguineus, and 17 Rhipicephalus turanicus. Ticks were collected predominantly (>80%) from buffalo, cattle, and camels, with smaller numbers from chicken and rabbit sheds, sheep, foxes, a domestic dog, a hedgehog, and a black rat. We detected Anaplasma marginale, Coxiella burnetii, Rickettsia aeschlimannii, and four novel genotypes similar to: “Anaplasma platys,” Ehrlichia canis, Ehrlichia spp. reported from Asian ticks, and a Rickettsiales endosymbiont of Ixodes ricinus.     

Highly Prevalent Coxiella sp. Bacterium in the Tick Vector Amblyomma americanum

Laboratory-reared and field-collected Amblyomma americanum ticks were hosts of a Coxiella sp. and a Rickettsia sp. While the Coxiella sp. was detected in 50 of 50 field-collected ticks, the Rickettsia sp. was absent from 32% of ticks. The Coxiella sp. showed evidence of a reduced genome and may be an obligate endosymbiont.     

Dissemination of Spotted Fever Rickettsia Agents in Europe by Migrating Birds

Migratory birds are known to play a role as long-distance vectors for many microorganisms. To investigate whether this is true of rickettsial agents as well, we characterized tick infestation and gathered ticks from 13,260 migratory passerine birds in Sweden. A total of 1127 Ixodes spp. ticks were removed from these birds and the extracted DNA from 957 of them was available for analyses. The DNA was assayed for detection of Rickettsia spp. using real-time PCR, followed by DNA sequencing for species identification. Rickettsia spp. organisms were detected in 108 (11.3%) of the ticks. Rickettsia helvetica, a spotted fever rickettsia associated with human infections, was predominant among the PCR-positive samples. In 9 (0.8%) of the ticks, the partial sequences of 17kDa and ompB genes showed the greatest similarity to Rickettsia monacensis, an etiologic agent of Mediterranean spotted fever-like illness, previously described in southern Europe as well as to the Rickettsia sp.IrITA3 strain. For 15 (1.4%) of the ticks, the 17kDa, ompB, gltA and ompA genes showed the greatest similarity to Rickettsia sp. strain Davousti, Rickettsia japonica and Rickettsia heilongjiangensis, all closely phylogenetically related, the former previously found in Amblyomma tholloni ticks in Africa and previously not detected in Ixodes spp. ticks. The infestation prevalence of ticks infected with rickettsial organisms was four times higher among ground foraging birds than among other bird species, but the two groups were equally competent in transmitting Rickettsia species. The birds did not seem to serve as reservoir hosts for Rickettsia spp., but in one case it seems likely that the bird was rickettsiemic and that the ticks had acquired the bacteria from the blood of the bird. In conclusion, migratory passerine birds host epidemiologically important vector ticks and Rickettsia species and contribute to the geographic distribution of spotted fever rickettsial agents and their diseases.     

Prevalence of tick-borne pathogens in ixodid ticks (Acari: Ixodidae) collected from European wild boar (<Emphasis Type="Italic">Sus scrofa</Emphasis>) and Iberian red deer (<Emphasis Type="Italic">Cervus elaphus hispanicus</Emphasis>) in central Spain

Emerging tick-borne diseases of humans and animals have occurred frequently during the past 30 years. These disease outbreaks appear to result from changes in the distribution of tick and vertebrate hosts, and the introduction of humans and domestic animals into tick–pathogen–wildlife cycles. Use of molecular technologies now available for identification of pathogens in ticks can provide valuable information that allows for risk analysis of emerging tick-borne diseases. In this study, the prevalence of selected pathogens in ticks collected in six locations in central Spain from the major wild ungulate species, European wild boar (Sus scrofa) and Iberian red deer (Cervus elaphus hispanicus), was determined by PCR. Tick species collected included Ixodes ricinus, Dermacentor marginatus, Rhipicephalus bursa and Hyalomma m. marginatum. Pathogens identified in ticks included piroplasmids, Anaplasma spp., Ehrlichia spp. and Rickettsia spp. Piroplasmids were identified in all tick species except I. ricinus. Ehrlichia spp. were detected in all tick species and collection locations, while Rickettsia spp., which proved to be R. slovaca and a recently identified Rickettsia sp. DnS28, were identified only in D. marginatus. A. marginale and A. phagocytophilum were detected in D. marginatus, R. bursa and Hy. m. marginatum. Concurrent infections of these pathogens were frequently observed in ticks. Notably, A. phagocytophilum, which is infective for a broad host range that includes humans and domestic and wild animals, was identified in ticks from all collection locations. The variety of ticks and tick-borne pathogens demonstrated in this study suggests a risk in central Spain for the emergence of tick-borne diseases in humans and domestic animals.     

Novel Genetic Variants of Anaplasma phagocytophilum, Anaplasma bovis, Anaplasma centrale, and a Novel Ehrlichia sp. in Wild Deer and Ticks on Two Major Islands in Japan

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.     

Genetic diversity of tick-borne pathogenes in Tomsk and environs

Two urban and two suburban biotopes of Tomsk were studied for tick-transmitted disease prevalence in ticks collected in the wild. Tick-borne encephalitis virus (TBEV), West Nile virus (WNV), Borrelia spp., Rickettsia spp., and Ehrlichia spp. were found in 6.5%, 2.2%, 8%, 2.5%, and 1.7% of tick specimens, respectively. Genetic markers of Powassan virus, Bartonella spp., and Babesia spp. were not found. Analysis of the genetic diversity of revealed pathogens demonstrated that TBEV strains belonged to the Siberian and Far-Eastern subtypes, and the Far-Eastern subtype of TBEV is most frequently found in urban biotopes (up to 43% of urban strains of TBEV). WNV strains belonged to the 1a genotype. Borrelia spp. was classified as B. garinii, Rickettsia spp. was classified as R. tarasevichiae and probably as a new Rickettsia raoultii subspecies, and Ehrlichia spp. was classified as E. muris. The coexistence of several pathogens was found in 5.7% of tick specimens, and TBEV + Borrelia spp. was the most frequent combination.     

Bacteria related to tick-borne pathogen assemblages in Ornithodoros cf. hasei (Acari: Argasidae) and blood of the wild mammal hosts in the Orinoquia region,Colombia

Interest in research on soft ticks has increased in recent decades, leading to valuable insight into their role as disease vectors. The use of metagenomics-based analyses have helped to elucidate ecological factors involved in pathogen, vector, and host dynamics. To understand the main bacterial assemblages present in Ornithodoros cf. hasei and its mammalian hosts, 84 ticks and 13 blood samples from bat hosts (Chiroptera) were selected, and the 16S rRNA gene V4 region was sequenced in five pools (each one related to each host-tick pairing). Bacterial taxonomic assignment analyses were performed by comparing operational taxonomic units (OTUs) shared between ticks and their host blood. This analysis showed the presence of Proteobacteria (38.8%), Enterobacteriaceae (25%), Firmicutes (12.3%), and Actinobacteria (10.9%) within blood samples, and Rickettsiaceae (39%), Firmicutes (25%), Actinobacteria (13.1%), and Proteobacteria (9%) within ticks. Species related to potentially pathogenic genera were detected in ticks, such as Borrelia sp., Bartonella tamiae, Ehrlichia sp. and Rickettsia-like endosymbiont, and the presence of these organisms was found in all analyzed bat species (Cynomops planirostris, Molossus pretiosus, Noctilio albiventris), and O. cf. hasei. About 41–48.6% of bacterial OTUs (genera and species) were shared between ticks and the blood of bat hosts. Targeted metagenomic screening techniques allowed the detection of tick-associated pathogens for O. cf. hasei and small mammals for the first time, enabling future research on many of these pathogens.

     

Molecular detection of Rickettsia aeschlimannii in Hyalomma spp. ticks from camels (Camelus dromedarius) in Nigeria,West Africa

Several species of the spotted fever group rickettsiae have been identified as emerging pathogens throughout the world, including in Africa. In this study, 197 Hyalomma ticks (Ixodida: Ixodidae) collected from 51 camels (Camelus dromedarius) in Kano, northern Nigeria, were screened by amplification and sequencing of the citrate synthase (gltA), outer membrane protein A (ompA) and 17‐kDa antigen gene fragments. Rickettsia sp. gltA fragments were detected in 43.3% (42/97) of the tick pools tested. Rickettsial ompA gene fragments (189 bp and 630 bp) were detected in 64.3% (n = 27) and 23.8% (n = 10) of the gltA‐positive tick pools by real‐time and conventional polymerase chain reaction (PCR), respectively. The amplicons were 99–100% identical to Rickettsia aeschlimannii TR/Orkun‐H and R. aeschlimannii strain EgyRickHimp‐El‐Arish in GenBank. Furthermore, 17‐kDa antigen gene fragments of 214 bp and 265 bp were detected in 59.5% (n = 25) and 38.1% (n = 16), respectively, of tick pools, and sequences were identical to one another and 99–100% identical to those of the R. aeschlimannii strain Ibadan A1 in GenBank. None of the Hyalomma impressum ticks collected were positive for Rickettsia sp. DNA. Rickettsia sp. gltA fragments (133 bp) were detected in 18.8% of camel blood samples, but all samples were negative for the other genes targeted. This is the first report to describe the molecular detection of R. aeschlimannii in Hyalomma spp. ticks from camels in Nigeria.     

The Microbiome of Ehrlichia-Infected and Uninfected Lone Star Ticks (Amblyomma americanum)

The Lone Star tick, Amblyomma americanum, transmits several bacterial pathogens including species of Anaplasma and Ehrlichia. Amblyomma americanum also hosts a number of non-pathogenic bacterial endosymbionts. Recent studies of other arthropod and insect vectors have documented that commensal microflora can influence transmission of vector-borne pathogens; however, little is known about tick microbiomes and their possible influence on tick-borne diseases. Our objective was to compare bacterial communities associated with A. americanum, comparing Anaplasma/Ehrlichia -infected and uninfected ticks. Field-collected questing specimens (n = 50) were used in the analyses, of which 17 were identified as Anaplasma/Ehrlichia infected based on PCR amplification and sequencing of groEL genes. Bacterial communities from each specimen were characterized using Illumina sequencing of 16S rRNA gene amplicon libraries. There was a broad range in diversity between samples, with inverse Simpson’s Diversity indices ranging from 1.28–89.5. There were no statistical differences in the overall microbial community structure between PCR diagnosed Anaplasma/Ehrlichia-positive and negative ticks, but there were differences based on collection method (P < 0.05), collection site (P < 0.05), and sex (P < 0.1) suggesting that environmental factors may structure A. americanum microbiomes. Interestingly, there was not always agreement between Illumina sequencing and PCR diagnostics: Ehrlichia was identified in 16S rRNA gene libraries from three PCR-negative specimens; conversely, Ehrlichia was not found in libraries of six PCR-positive ticks. Illumina sequencing also helped identify co-infections, for example, one specimen had both Ehrlichia and Anaplasma. Other taxa of interest in these specimens included Coxiella, Borrelia, and Rickettsia. Identification of bacterial community differences between specimens of a single tick species from a single geographical site indicates that intra-species differences in microbiomes were not due solely to pathogen presence/absence, but may be also driven by vector life history factors, including environment, life stage, population structure, and host choice.     

Infection by <Emphasis Type="Italic">Rickettsia bellii</Emphasis> and <Emphasis Type="Italic">Candidatus “Rickettsia amblyommii”</Emphasis> in <Emphasis Type="Italic">Amblyomma neumanni</Emphasis> Ticks from Argentina

The tick species, Amblyomma neumanni (Acari: Ixodidae) is the most frequent tick parasitizing humans in northwestern Argentina. The present study evaluated the rickettsial infection among 55 A. neumanni adult free-living ticks collected in Dean Funes, Córdoba Province. Ticks were individually processed by the hemolymph test with Gimenez staining, isolation of rickettsia in Vero cell culture by the shell vial technique, and polymerase chain reaction (PCR) targeting the citrate synthase rickettsial gene. Through the shell vial technique, rickettsiae were successfully isolated and established in Vero cell culture from two ticks (ticks 4 and 13), which previously showed to contain Rickettsia-like organisms by the hemolymph test. These two Rickettsia isolates were designated as An4 and An13. Molecular characterization (partial DNA sequences of two to three rickettsial genes were determined) of these two isolates and phylogenetic analyses identified them as Rickettsia bellii (isolate An4) and Candidatus “Rickettsia amblyommii” (isolate An13). After testing all A. neumanni ticks by PCR, the prevalence of Candidatus R. amblyommii and R. bellii was 23.6% (13/55) and 3.6% (2/55), respectively. These two rickettsiae have been considered of unknown pathogenicity and appropriate studies to test their pathogenicity to humans or animals need to be conducted. This is the first report of Rickettsia in ticks from Argentina, and also in the species A. neumanni. The results reinforce previous findings that R. bellii (and probably Candidatus R. amblyommii) are widespread among some Neotropical Amblyomma species, suggesting that these ticks gained these bacterial agents from a common ancestor and/or by recent horizontal transmission of rickettsiae between ticks.     

Borrelia, Coxiella, and Rickettsia in Carios capensis (Acari: Argasidae) from a brown pelican (Pelecanus occidentalis) rookery in South Carolina, USA

Argasid ticks are vectors of viral and bacterial agents of humans and animals. Carios capensis, a tick of seabirds, infests the nests of brown pelicans, Pelecanus occidentalis, and other ground nesting birds along the coast of South Carolina. This tick is associated with pelican nest abandonment and could pose a threat to humans visiting pelican rookeries if visitors are exposed to ticks harboring infectious agents. We collected ticks from a pelican rookery on Deveaux Bank, South Carolina and screened 64 individual ticks, six pools of larvae, and an egg mass for DNA from Bartonella, Borrelia, Coxiella, and Rickettsia by polymerase chain reaction amplification and sequencing. Ticks harbored DNA from “Borrelia lonestari”, a novel Coxiella sp., and three species of Rickettsia, including Rickettsia felis and two undescribed Rickettsia spp. DNA from the Coxiella and two undescribed Rickettsia were detected in unfed larvae that emerged in the laboratory, which implies these agents are transmitted vertically by female ticks. We partially characterize the novel Coxiella by molecular means.     

A Novel Rickettsia Species Detected in Vole Ticks (Ixodes angustus) from Western Canada

The genomic DNA of ixodid ticks from western Canada was tested by PCR for the presence of Rickettsia. No rickettsiae were detected in Ixodes sculptus, whereas 18% of the I. angustus and 42% of the Dermacentor andersoni organisms examined were PCR positive for Rickettsia. The rickettsiae from each tick species were characterized genetically using multiple genes. Rickettsiae within the D. andersoni organisms had sequences at four genes that matched those of R. peacockii. In contrast, the Rickettsia present within the larvae, nymphs, and adults of I. angustus had novel DNA sequences at four of the genes characterized compared to the sequences available from GenBank for all recognized species of Rickettsia and all other putative species within the genus. Phylogenetic analyses of the sequence data revealed that the rickettsiae in I. angustus do not belong to the spotted fever, transitional, or typhus groups of rickettsiae but are most closely related to “Candidatus Rickettsia kingi” and belong to a clade that also includes R. canadensis, “Candidatus Rickettsia tarasevichiae,” and “Candidatus Rickettsia monteiroi.”     

Detection of “<Emphasis Type="Italic">Candidatus</Emphasis> Rickettsia sp. strain Argentina”and <Emphasis Type="Italic">Rickettsia bellii</Emphasis> in <Emphasis Type="Italic">Amblyomma</Emphasis> ticks (Acari: Ixodidae) from Northern Argentina

Ixodid ticks were collected from vegetation and from humans, wild and domestic mammals in a rural area in the semi-arid Argentine Chaco in late spring 2006 to evaluate their potential role as vectors of Spotted Fever Group (SFG) rickettsiae. A total of 233 adult ticks, identified as Amblyomma parvum, Amblyomma tigrinum and Amblyomma pseudoconcolor, was examined for Rickettsia spp. We identified an SFG rickettsia of unknown pathogenicity, “Candidatus Rickettsia sp. strain Argentina”, in A. parvum and A. pseudoconcolor by PCR assays targeting gltA, ompA, ompB and 17-kDa outer membrane antigen rickettsial genes. Rickettsia bellii was detected in a host-seeking male of A. tigrinum. Amblyomma parvum is widespread in the study area and is a potential threat to human health.     

Isolation of Rickettsia rhipicephali and Rickettsia bellii from Haemaphysalis juxtakochi Ticks in the State of São Paulo, Brazil

In the present study, attempts to isolate Rickettsia in cell culture were performed individually in seven specimens of Haemaphysalis juxtakochi ticks collected in the state of São Paulo (southeastern Brazil). Rickettsia was successfully isolated by the shell vial technique and established in Vero cell culture from six ticks (six isolates). DNA extracted from infected cells of these isolates was tested by PCR and DNA sequencing, using genus-specific Rickettsia primers targeting the genes gltA, htrA, ompA, and ompB. After the generated sequences were compared with available sequences in GenBank, five out of the six isolates were identified as Rickettsia bellii (isolates HJ#1, HJ#2, HJ#3, HJ#4, and HJ#7). The sixth isolate (HJ#5) was closest to Rickettsia sp. strain R300, previously detected in H. juxtakochi in northern Brazil, and to Rickettsia rhipicephali, isolated from ticks in the United States. Following recent gene sequence-based criteria proposed for the identification of Rickettsia isolates, both isolate HJ#5 and strain R300 were identified as South American strains of R. rhipicephali, which was confirmed in this continent for the first time. Isolation of R. bellii from H. juxtakochi ticks, added to eight other tick species that have been reported to be infected with this bacterium in Brazil, indicates that R. bellii is indeed the most frequent Rickettsia species infecting ticks in Brazil. Currently, the role of both R. rhipicephali and R. bellii as human pathogens is regarded as unknown.