Identification and distribution of nine tick-borne spotted fever group Rickettsiae in the Country of Georgia

Rickettsial pathogens cause diseases that vary in severity and clinical presentation. Rickettsia species transmitted by ticks are mostly classified within the spotted fever group of rickettsiae (SFGR) and are often associated with febrile diseases. Preliminary studies have detected three human-pathogenic SFGR from ticks in Georgia: Rickettsia aeschlimannii, Rickettsia raoultii, and Rickettsia slovaca. To more broadly assess the presence of tick-borne rickettsiae from Georgia we examined 1594 ticks, representing 18 species from five genera (Ixodes, Hyalomma, Haemaphysalis, Dermacentor, and Rhipicephalus), collected from eight regions of Georgia. A total of 498 tick DNA samples extracted from single ticks or pooled ticks were assessed by molecular methods. Genus-specific Rick17b and species-specific qPCR assays were used to identify six rickettsiae: R. aeschlimannii, R. raoultii, R. slovaca, Rickettsia conorii subsp. conorii, Rickettsia massiliae, and Rickettsia monacensis. Tick samples that were positive for Rickettsia, but not identified by the species-specific assays, were further evaluated by multi-locus sequence typing (MLST) using sequences of four protein-coding genes (gltA, ompA,ompB, sca4). Three additional Rickettsia species were identified by MLST: Candidatus Rickettsia barbariae, Rickettsia helvetica, and Rickettsia hoogstraalii. Overall, nine species of Rickettsia (six human pathogens and three species with unknown pathogenicity) were detected from 12 tick species of five different genera. A distribution map for the tick-borne rickettsiae revealed six newly identified endemic regions in Georgia.     

黑龙江立克次体的免疫印迹分析

本文应用蛋白免疫印迹试验对黑龙江立克次体５４与３６株，国内分离株ＪＨ－７４、Ｈｕ－８４株及国际标准株西柏利亚２４６株，康氏Ｓｉｍｋｏ株，小蛛Ｋａｐｌａｎ株等斑点热群立克次体作抗原多肽分析。图谱表明，黑龙江立克次体５４与３６株两者完全一致，具有两条分子量为２１５ＫＤ、６６ＫＤ的主要抗原多肽带，和其它立克次体有明显区别，说明在抗原结构上的特异性。ＪＨ－７４、Ｈｕ－８４与西伯利亚２４６三者相同，同属一个     

内蒙呼盟地区斑点热立克次体分离与血清学鉴定

本文报告自我国内蒙呼盟地区分离的一株立克次体,经动物试验和初步血清学鉴定,证明属于斑点热群立克次体。以分离株的小鼠抗血清与自WHO引进的五种斑点热立克次体及国内三个地方株应用微量间接免疫荧光交互试验[3,4]作了分型鉴定,结果表明呼盟株与斑点热群中立氏立克次体、北亚立克次体,派氏立克次体。康氏立克次体、小蛛立克次体及立克次体黑龙江株的抗原结构不同,存在明显差异,但与国内过去分离的虎林株[1]、精河株[2]相同,可能是斑点热群中一个新种的成员。     

Two novel Rickettsia species of soft ticks in North Africa: ‘Candidatus Rickettsia africaseptentrionalis’ and ‘Candidatus Rickettsia mauretanica’

Rickettsia are obligate intracellular bacteria often reported from hard ticks but more rarely from soft ticks. In this study, we detected in Northern Africa two putatively novel Rickettsia species in soft tick species of the Ornithodoros erraticus complex: Ornithodoros occidentalis from Morocco, Ornithodoros erraticus from Algeria and Ornithodoros normandi from Tunisia. We characterized these two novel Rickettsia species on the basis of comparative DNA sequence analyses and phylogenetics of four genes (gltA, 16S rRNA, coxA and ompB). These Rickettsia, provisionally named ‘Candidatus Rickettsia africaseptentrionalis’ and ‘Candidatus Rickettsia mauretanica’, differed in nucleotide sequence from those of other Rickettsia species by 0.38–21.43 % depending on the gene examined. Phylogenetics further showed that the two novel Rickettsia species are closely related to each other and represent sister taxa to R. hoogstraalii, R. felis and R. asembonensis within the transitional Rickettsia group. While Ornithodoros host species of ‘Candidatus Rickettsia africaseptentrionalis’ and ‘Candidatus Rickettsia mauretanica’ are among the most common soft ticks to bite humans, their pathogenicity remains to be investigated.     

Spotted fever group rickettsiae in ticks, Germany

To explore increased risk for human Rickettsia spp. infection in Germany, we investigated recreational areas and renatured brown coal surface-mining sites (also used for recreation) for the presence of spotted fever group rickettsiae in ticks. R. raoultii (56.7%), R. slovaca (13.3%), and R. helvetica (>13.4%) were detected in the respective tick species.     

Rhipicephalus ticks infected with Rickettsia and Coxiella in Southern Switzerland (Canton Ticino).

Ticks of the Rhipicephalus sanguineus species complex may be vector of various pathogens including Rickettsia conorii (the etiological agent of the Mediterranean spotted fever) and Coxiella burnetii (cause of the Query (Q) fever). R. sanguineus ticks have been imported in several parts of central and northern Europe, especially in environments such as kennels and houses providing the appropriate microclimatic conditions and the blood source necessary for their survival. Since 1940 these ticks have occasionally been recorded in Switzerland. In Ticino (the southern part of Switzerland), they have been reported since 1980 and their probable establishment in this area has been suggested in the '90s. By means of PCR and direct sequencing, we tested the identity of these ticks (using 12S rDNA gene) and the occurrence of Rickettsia spp. (using 16S rDNA, gltA and OmpA genes) as well as Coxiella sp. (using 16S rDNA). The results indicated that in Ticino, two different tick species coexist, i.e. R. sanguineus sensu stricto and Rhipicephalus turanicus. A few individuals of R. sanguineus sensu stricto are infected with Rickettsia massiliae/Bar29, which are strains of unknown pathogenicity. Coxiella sp., an endosymbiont of Rhipicephalus ticks, has also been identified in both tick species. Due to climatic changes towards global warming, imported tick species may therefore adapt to new area and might be considered as epidemiological markers for a number of infectious agents transmitted by them.     

Spotted fever group rickettsiae in ticks, Morocco

A total of 370 ticks, encompassing 7 species from 4 genera, were collected during 2002-2006 from domestic animals and vegetation in the Taza region of northeastern Morocco. Rickettsial DNA was identified in 101 ticks (27%) by sequencing PCR products of fragments of the citrate synthase and outer membrane protein genes of Rickettsia spp. Seven rickettsiae of the spotted fever group were identified, including 4 pathogens: R. aeschlimannii in Hyalomma marginatum marginatum, R. massiliae in Rhipicephalus sanguineus, R. slovaca in Dermacentor marginatus, and R. monacensis in Ixodes ricinus. Two suspected pathogens were also detected (R. raoultii in D. marginatus and R. helvetica in I. ricinus). An incompletely described Rickettsia sp. was detected in Haemaphysalis spp. ticks.     

Antigenic relationships between the typhus and spotted fever groups of rickettsiae.

Paired sera from cases of epidemic typhus in Ethiopia and from probable cases of Rocky Mountain spotted fever (RMSF) in the United States were examined by microagglutination (MA) and microimmunofluorescence (micro-IF) tests for antibodies against Rickettsia prowazekii, Rickettsia typhi, Rickettsia canada, Rickettsia rickettsii, Rickettsia conorii and Ricksettsia akari. IgG and IgM antibodies against the various rickettsiae were titrated with specific fluorescein-conjugated anti-IgG and anti-IgM sera. Purified, particulate rickettsial antigens were employed in all tests. A majority of patients acutely ill with epidemic typhus produced both IgG and IgM antibodies against R. prowazekii, R. typhi and R. canada. Concurrently they produced IgG (but seldom IgM) antibodies against members of the spotted fever group. In contrast, patients ill with probably spotted fever, while producing IgG and IgM antibodies against R. rickettsii, R. conorii and R. akari, also produced both IgG and IgM antibodies with about equal frequency against members of the typhus group. It was concluded that a relatively broad antigenic relationship exists between rickettsiae of the typhus and spotted fever groups.     

Tick-borne rickettsioses in Europe

Rickettsioses are caused by obligate intracellular bacteria within the genus Rickettsia, mainly transmitted by arthropods. Until recently, Mediterranean spotted fever (MSF) caused by Rickettsia conorii was considered the only tick-borne rickettsiosis in Europe. However, ‘new’ TBR have been described in Europe during last years. For instance, other subspecies such as R. conorii caspia and R. conorii israelensis have been involved in MSF. Dermacentor-borne necrosis erythema and lymphadenopathy/tick-borne lymphadenopathy (DEBONEL/TIBOLA) cases caused by Rickettsia slovaca, Rickettsia raoultii, and Rickettsia rioja been described in several countries where Dermacentor marginatus ticks (the mainly implicated vector) are present. Rickettsia helvetica has also been involved as a human pathogen in cases of fever with and without rash and in patients with meningitis and carditis. Other TBR such as lymphangitis-associated rickettsioses (LAR), caused by Rickettsia sibirica mongolitimonae, have been diagnosed in different European countries (France, Spain, Portugal and Greece). Rickettsia massiliae is considered an etiological agent of MSF-like illness in the Mediterranean basin. Furthermore, Rickettsia monacensis that is distributed all along Europe has been isolated from patients with MSF-like illness in Spain. Although Rickettsia aeschlimannii has been associated with MSF-like in Africa and is distributed in the Mediterranean area, no autochthonous human cases have been reported for Europe. Other Rickettsia species detected in ticks and unrelated to human disease (Candidatus Rickettsia kotlanii, Candidatus Rickettsia barbariae, Candidatus Rickettsia vini) could be potentially involved in the next years. Climate changes, among other factors, may contribute to the emergence of other rickettsioses or change their distribution. Lastly, African tick-bite fever (ATBF), caused by Rickettsia africae, is frequently diagnosed in Europe in patients returning from endemic areas.     

Role of birds in dispersal of etiologic agents of tick-borne zoonoses, Spain, 2009

We amplified gene sequences from Anaplasma phagocytophilum, Borrelia garinii, B. valaisiana, B. turdi, Rickettsia monacensis, R. helvetica, R. sibirica sibirica, and Rickettsia spp. (including Candidatus Rickettsia vini) in ticks removed from birds in Spain. The findings support the role of passerine birds as possible dispersers of these tick-borne pathogens.     

海南岛斑点热疫源地的调查研究

本文报告在海南岛发现了斑点热疫源地，其人群北亚斑点热抗体的阳性率３８．３％，鼠类抗体阳性率５３．０％。从７种鼠检出抗体，其中优势种黄毛鼠（Ｒａｔｔｕｓｌｏｓｅａ）、黄胸鼠（Ｒ．ｆｌａｖｉｐｅｃｔｕｓ）和海南屋顶鼠（Ｒ．ｒａｔｔｕｓｈａｉｎａｎｉｃｕｓ）阳性率＞５０．０％，应用ＰＣＲ技术从该３种鼠检出斑点热群立克次体特异ＤＮＡ。小兽类寄生蜱３种、革螨５种，优势种分别为粒形硬蜱（Ｉｘｏｄｅｓｇｒａｎｕｌａｔｕｓ）和毒棘厉螨（Ｌａｅｌａｐｓｅｃｈｉｄｎｉｎｕｓ）；牛羊寄生蜱为微小牛蜱（Ｂｏｏｐｈｉｌｕｓｍｉｃｒｏｐｌｕｓ）。从粒形硬蜱和微小牛蜱检出斑点热群立克次体特异ＤＮＡ。     

Occurrence and clinical manifestations of tick-borne rickettsioses in Western Siberia: First Russian cases of Rickettsia aeschlimannii and Rickettsia slovaca infections

Rickettsia sibirica subsp. sibirica is a main agent of tick-borne rickettsioses in Western Siberia, Russia. Recently, the first cases of Rickettsia raoultii infection in patients hospitalized in Novosibirsk Province were described. The aim of this study was to establish the etiologic agents of tick-borne rickettsioses in Western Siberia during three epidemiological seasons.Clinical samples from 1008 patients hospitalized after tick bites in April–September 2017–2019 were examined by nested PCR for the presence of Rickettsia spp. All positive specimens were genetically characterized by sequencing of the gltA gene; some specimens were also genotyped based on the 16S rRNA, ompA, and ompB genes. Rickettsia spp. DNA was detected in clinical samples from 56 (5.6%) patients. Five Rickettsia species were identified: R. sibirica (n = 28), R. raoultii (n = 15), Rickettsia aeschlimannii (n = 3), “Candidatus Rickettsia tarasevichiae” (n = 2), and Rickettsia slovaca (n = 1). In addition, new unclassified Rickettsia genovariants were found in specimens from seven patients. Patients with R. raoultii infection presented rash, eschar, and high serum aminotransferase levels less frequently compared to patients with R. sibirica infections, but more frequently showed neurological symptoms. Among other patients, only persons with an R. aeschlimannii infection had rash and/or eschar, which are typical for tick-borne rickettsioses. The current study showed that R. raoultii is a common agent of tick-borne rickettsioses in Novosibirsk Province. DNA from R. aeschlimannii and R. slovaca was found in clinical samples of patients in the Russian Federation for the first time.     

Rickettsia and Anaplasma species in Dermacentor andersoni ticks from Washington

Dermacentor andersoni, the Rocky Mountain wood tick, occurs predominantly in the northwestern United States and southwestern Canada. There are relatively few contemporary data to evaluate the occurrence of Rickettsia and Anaplasma species in D. andersoni in western North America, and even less information about these associations in the state of Washington, where this tick species is widely distributed and often bites humans. We used PCR assays to detect DNA of Rickettsia and Anaplasmataceae bacteria in 203 adult D. andersoni ticks collected from 17 sites in 9 counties of Washington between May 2012 and May 2015. Of these, 56 (27.6 %) were infected with a Rickettsia species and 3 (5.4 %) with a member of the Anaplasmataceae family. Rickettsia peacockii, R. bellii and R. rhipicephali were found in 17.7 %, 4.9 %, and 4.4 % of the Rickettsia positive ticks, respectively. Coinfections of R. bellii with R. peacockii or R. rhipicephali were identified in 6 ticks. Of the Anaplasmataceae-positive ticks, one was identified as being infected with Anaplasma phagocytophilum AP-Variant 1. No ticks were infected with a recognized human or animal pathogen, including R. rickettsii, A. phagocytophilum-ha, A. bovis, or A. marginale.     

Detection of Rickettsia tamurae-like and other spotted fever group rickettsiae in ticks (Acari: Ixodidae) associated with wild birds in the Western Amazon,Brazil

Ticks are vectors for several pathogens, including bacteria belonging to the Rickettsia genus, such as Rickettsia rickettsii and Rickettsia parkeri, the causative agents of spotted fever. The aim of the present study was to investigate the tick species richness and rickettsial agents associated with wild birds captured in the Humaita Forest Reserve, Acre, in the Western Amazon region. Wild birds were captured with ornithological nets for visual inspection with the purpose of collecting ticks, which were identified through morphological analyses and molecular tests for several genes (12S rDNA, 16S rDNA, gltA, ompA, and sca4). A total of 607 wild birds were captured, 12% of which were parasitized by 268 ticks of the Amblyomma genus, with new host-parasite associations reported for Amblyomma calcaratum, Amblyomma geayi, Amblyomma longirostre, Amblyomma naponense, Amblyomma nodosum, and Amblyomma varium. Of the total ticks collected, 113 were tested for the presence of rickettsial DNA fragments, with 19 testing positive for R. parkeri in A. geayi, Rickettsia tamurae-like in Amblyomma sp., and Rickettsia amblyommatis in A. geayi, A. longirostre, and Amblyomma sp. We detected R. tamurae-like in Amblyomma larvae for the first time in the Western Brazilian Amazon biome, and registered spotted fever group rickettsiae, although the relevance of the detected species in a public health context should be further explored in South America, as well as new host-parasite interactions in this underexplored region.     

Genetic characterization of Candidatus Rickettsia vini,a new rickettsia amplified in ticks from La Rioja,Spain

A total of 222 ticks removed from birds in La Rioja (Spain) were screened for spotted fever group rickettsia species using ompA PCR assays. Rickettsia monacensis (n = 1) and R. sibirica (n = 1) were detected. Apart from that, 27 out of 29 Ixodes spp. DNA extracts that tested positive for ompA did not match with any validated spotted fever group rickettsia. Multilocus sequence typing for 16S rRNA, gltA, ompB, sca4, and 17-kDa antigen genes was performed, and R. heilongjiangensis was found to be the nearest validly published spotted fever group rickettsia. Based on genetic criteria agreed by experts, this genotype can be classified as a new Candidatus Rickettsia sp. and was named Candidatus Rickettsia vini.     

Rickettsia felis infection, Tunisia

We report, for the first time, serologic evidence of Rickettsia felis and R. aeschlimannii infections acquired in Tunisia from 1998 to 2003. We found that most patients with antibodies against both R. conorii and R. typhi had serologic evidence of R. felis infection.     

Rickettsia raoultii-like Bacteria in Dermacentor spp. Ticks, Tibet, China

TO THE EDITOR: Rickettsia raoultii is an obligate intracellular gram-negative bacterium belonging to the spotted fever group (SFG) of the genus Rickettsia. Genotypes RpA4, DnS14, and DnS28, originally isolated from ticks from Russia in 1999 (1), were designated as Rickettsia raoultii sp. nov. on the basis of phylogenetic analysis (2). R. raoultii has been found mainly in Dermacentor spp. ticks in several countries in Europe (3). It was detected in a Dermacentor marginatus tick from the scalp of a patient with tick-borne lymphadenitis in France (2), which suggests that it might be a zoonotic pathogen. We determined the prevalence of R. raoultii-like bacteria in Dermacentor spp. in highland regions in Tibet.     

河南省信阳地区鼠类感染立克次体的调查

目的了解河南省信阳疫区鼠类中恙虫病东方体、斑点热及斑疹伤寒立克次体感染状况。方法采用巢式-聚合酶链反应(nested-PCR),对信阳市淮滨县捕获的家鼠肝、脾、肾、血液标本进行扩增恙虫病东方体、斑点热群及斑疹伤寒群立克次体热休克蛋白(groEL)基因并测序分析。采用间接免疫荧光方法(IFA)对家鼠血清标本进行斑疹伤寒病原体、恙虫病东方体特异抗体检测。结果共捕获鼠62只,其中内脏标本中检出恙虫病东方体10份(16．13％),斑疹伤寒立克次体5份(8．06％),斑点热群立克次体4份(6．45％);血液标本中检出恙虫病东方体5份(8．06％),斑疹伤寒群立克次体4份(6．45％),斑点热群立克次体1份(1．61％)。有5份标本同时检出恙虫病和斑疹伤寒,复合感染率为8．06％。在鼠内脏标本中检测到2株蚤传斑点热病原体R．felis。用IFA检测26份鼠血清抗体,3份恙虫病阳性(11．5％)。结论信阳地区啮齿动物宿主鼠类标本中检测出恙虫病东方体、斑点热群和斑疹伤寒群立克次体,存在复合带菌状况,鼠血清恙虫病东方体特异抗体流行率较高。     

“Candidatus Rickettsia uralica” and “Candidatus Rickettsia thierseensis” are genetic variants of one species

The spotted fever group is the largest group in the Rickettsia genus, and new candidate species of this group are found throughout the world. "Candidatus Rickettsia thierseensis" was observed in a single Ixodes ricinus in Austria in 2020. However, sequences of five genes (total length: 5305 bp) of the "Candidatus R. thierseensis" were nearly identical to those available for "Candidatus Rickettsia uralica" identified in Ixodes trianguliceps and small mammals in Russia in 2015. To confirm the identity of these species, appropriate fragments of seven genetic loci from four isolates of "Candidatus R. uralica" were sequenced and compared with the "Candidatus R. thierseensis" sequences. Additionally, the groEL gene fragment was first sequenced for "Candidatus R. uralica". In this analysis, "Candidatus R. uralica" and "Candidatus R. thierseensis" demonstrated 100% identity in the 23S-5S IGS region (354 bp) and in fragments of the 16S rRNA (991 bp), gltA (1119 bp), and htrA (463 bp) genes, differing by only one substitution in each of the ompA (3696 bp), ompB (4871 bp), and sca4 (2971 bp) gene fragments. Thus, "Candidatus R. uralica" and "Candidatus R. thierseensis" are likely the same species based on comparative sequence analysis.