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1
Salomon, Jordan, Nadia Angelica Fernandez Santos, Italo B. Zecca, et al. "Brown Dog Tick (Rhipicephalus sanguineus Sensu Lato) Infection with Endosymbiont and Human Pathogenic Rickettsia Spp., in Northeastern México." International Journal of Environmental Research and Public Health 19, no. 10 (2022): 6249. http://dx.doi.org/10.3390/ijerph19106249.
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Of the documented tick-borne diseases infecting humans in México, Rocky Mountain spotted fever (RMSF), caused by the Gram-negative bacterium Rickettsia rickettsii, is responsible for most fatalities. Given recent evidence of brown dog tick, Rhipicephalus sanguineus s.l., as an emerging vector of human RMSF, we aimed to evaluate dogs and their ticks for rickettsiae infections as an initial step in assessing the establishment of this pathosystem in a poorly studied region of northeastern México while evaluating the use of dogs as sentinels for transmission/human disease risk. We sampled owned dogs living in six disadvantaged neighborhoods of Reynosa, northeastern México to collect whole blood and ticks. Of 168 dogs assessed, tick infestation prevalence was 53%, composed of exclusively Rh. sanguineus s. l. (n = 2170 ticks). Using PCR and sequencing, we identified an overall rickettsiae infection prevalence of 4.1% (n = 12/292) in ticks, in which eight dogs harbored at least one infected tick. Rickettsiae infections included Rickettsia amblyommatis and Rickettsia parkeri, both of which are emerging human pathogens, as well as Candidatus Rickettsia andeanae. This is the first documentation of pathogenic Rickettsia species in Rh. sanguineus s.l. collected from dogs from northeastern México. Domestic dog infestation with Rickettsia-infected ticks indicates ongoing transmission; thus, humans are at risk for exposure, and this underscores the importance of public and veterinary health surveillance for these pathogens.
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Sakamoto, Joyce M., and Abdu F. Azad. "Propagation of Arthropod-Borne Rickettsia spp. in Two Mosquito Cell Lines." Applied and Environmental Microbiology 73, no. 20 (2007): 6637–43. http://dx.doi.org/10.1128/aem.00923-07.
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ABSTRACT Rickettsiae are obligate intracellular alphaproteobacteria that include pathogenic species in the spotted fever, typhus, and transitional groups. The development of a standardized cell line in which diverse rickettsiae can be grown and compared would be highly advantageous to investigate the differences among and between pathogenic and nonpathogenic species of rickettsiae. Although several rickettsial species have been grown in tick cells, tick cells are more difficult to maintain and they grow more slowly than insect cells. Rickettsia-permissive arthropod cell lines that can be passaged rapidly are highly desirable for studies on arthropod-Rickettsia interactions. We used two cell lines (Aedes albopictus cell line Aa23 and Anopheles gambiae cell line Sua5B) that have not been used previously for the purpose of rickettsial propagation. We optimized the culture conditions to propagate one transitional-group rickettsial species (Rickettsia felis) and two spotted-fever-group rickettsial species (R. montanensis and R. peacockii) in each cell line. Both cell lines allowed the stable propagation of rickettsiae by weekly passaging regimens. Stable infections were confirmed by PCR, restriction digestion of rompA, sequencing, and the direct observation of bacteria by fluorescence in situ hybridization. These cell lines not only supported rickettsial growth but were also permissive toward the most fastidious species of the three, R. peacockii. The permissive nature of these cell lines suggests that they may potentially be used to isolate novel rickettsiae or other intracellular bacteria. Our results have important implications for the in vitro maintenance of uncultured rickettsiae, as well as providing insights into Rickettsia-arthropod interactions.
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Cente, Martin, Monika Danchenko, Ludovit Skultety, Peter Filipcik, and Zuzana Sekeyova. "Rickettsia Deregulates Genes Coding for the Neurotoxic Cell Response Pathways in Cerebrocortical Neurons In Vitro." Cells 12, no. 9 (2023): 1235. http://dx.doi.org/10.3390/cells12091235.
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Rickettsial infections of the central nervous system (CNS) are manifested by severe neurological symptoms and represent a serious life-threatening condition. Despite the considerable health danger, only a few studies have been conducted focusing on the pathogenesis induced by Rickettsia sp. in CNS. To investigate the signaling pathways associated with the neurotoxic effects of rickettsiae, we employed an experimental model of cerebrocortical neurons combined with molecular profiling and comprehensive bioinformatic analysis. The cytopathic effect induced by Rickettsia akari and Rickettsia slovaca was demonstrated by decreased neuronal viability, structural changes in cell morphology, and extensive fragmentation of neurites in vitro. Targeted profiling revealed the deregulation of genes involved in the neuroinflammatory and neurotoxic cell response pathways. Although quantitative analysis showed differences in gene expression response, functional annotation revealed that the biological processes are largely shared between both Rickettsia species. The identified enriched pathways are associated with cytokine signaling, chemotaxis of immune cells, responses to infectious agents, interactions between neurons, endothelial and glial cells, and regulation of neuronal apoptotic processes. The findings of our study provide new insight into the etiopathogenesis of CNS infection and further expand the understanding of molecular signaling associated with neuroinvasive Rickettsia species.
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Grindem, CB, EB Breitschwerdt, PC Perkins, LD Cullins, TJ Thomas, and BC Hegarty. "Platelet-associated immunoglobulin (antiplatelet antibody) in canine Rocky Mountain spotted fever and ehrlichiosis." Journal of the American Animal Hospital Association 35, no. 1 (1999): 56–61. http://dx.doi.org/10.5326/15473317-35-1-56.
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Antiplatelet antibodies were detected in the sera of dogs with naturally occurring and experimentally induced Rickettsia rickettsii and Ehrlichia canis infections. This is the first known report documenting elevated platelet-associated immunoglobulin (PAIg) titers in Rocky Mountain spotted fever (RMSF) infections. In the naturally occurring RMSF infections and ehrlichiosis, the antibodies persisted for weeks or months, even when the platelet counts had normalized. Results of this study indicate an immunological component for rickettsial thrombocytopenia. Therefore, current therapeutic recommendations, especially regarding avoiding the use of immunosuppressive drugs in patients with rickettsial diseases, need to be critically reviewed.
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Taraphdar, Debjani, Ranjana Hawaldar, and Sadhna Sodani. "A prospective study on Rickettsia infections in Central India." Indian Journal of Microbiology Research 11, no. 1 (2024): 34–37. http://dx.doi.org/10.18231/j.ijmr.2024.006.
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Rickettsial infections are under-reported in India. The actual disease burden has been underestimated as non-specific serological tests are mostly used to diagnose these infections. The aim of this study was the detection of Rickettsia infections in clinical specimens by Real-time Polymerase Chain Reaction.A study was established to analyse blood samples taken from pyrexia of unknown origin (PUO) or undifferentiated fever cases. A total of 69 such patients, were referred/walked-in to our diagnostic centre, Indore, India between October 2021 and May 2023. The blood samples were collected in EDTA lavender (purple) top tube.Of the tested samples, 14 patients (20.3%) were positive for Rickettsia infection.Gender wise distribution revealed higher incidence (57%) of Rickettsial infections in male patients. Children were majorly infected (50% of cases); multiple infection was also noted in them, though severity was not high. Severe clinical manifestation including hospitalization was also noted in some patients. Few reports are available from India on molecular diagnosis of Rickettsia infection. Early-stage molecular diagnosis will help to stave off and prevent serious complications.
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R, Archita. "Rocky mountain spotted fever- A case series." Panacea Journal of Medical Sciences 13, no. 1 (2023): 246–49. http://dx.doi.org/10.18231/j.pjms.2023.048.
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Rocky mountain spotted fever caused by Rickettsia rickettsii, is a life threatening tick transmitted infection, which is the most prevalent rickettiosis. It remains a diagnostic challenge because of its varied clinical presentation and the overlap of signs and symptoms with other diseases. Under diagnosed and misdiagnosed rickettsial infections are important public health problems. There is neither an effective vaccine nor an assay that is diagnostic during the early stages of the disease when treatment is most effective. Here, we report three cases with varied clinical manifestations.
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Walker, David H., Juan P. Olano, and Hui-Min Feng. "Critical Role of Cytotoxic T Lymphocytes in Immune Clearance of Rickettsial Infection." Infection and Immunity 69, no. 3 (2001): 1841–46. http://dx.doi.org/10.1128/iai.69.3.1841-1846.2001.
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ABSTRACT Cytotoxic T-lymphocyte (CTL) activity developed against the major infected target cells of rickettsial infections, endothelial cells and macrophages. Spleen cells from mice immune to Rickettsia conorii exerted specific major histocompatibility complex (MHC) class I-matched CTL activity against R. conorii-infected SVEC-10 endothelial cells, with peak activity on day 10. Similarly, spleen cells from Rickettsia australis-immune mice exerted specific CTL activity against an R. australis-infected macrophage-like cell line. Gamma interferon (IFN-γ) gene knockout mice were more than 100-fold more susceptible to R. australis infection than wild-type C57BL/6 mice. MHC class I gene knockout mice were the most susceptible, more than 50,000-fold more susceptible to a lethal outcome of R. australis infection than wild-type C57BL/6 mice. These results indicate that CTL activity was more critical to recovery from rickettsial infection than were the effects of IFN-γ. The observation that perforin gene knockout mice were more than 100-fold more susceptible than wild-type C57BL/6 mice indicates that perforin-mediated activity accounts for a large component, but not all, of the CTL-mediated antirickettsial effect. CTL activity was expressed by immune CD8 T lymphocytes. Adoptive transfer of immune CD8 T lymphocytes from IFN-γ gene knockout mice intoR. australis-infected IFN-γ gene knockout mice dramatically reduced the infectious rickettsial content in the organs, confirming that CD8 T lymphocytes provide immunity against rickettsiae besides that provided by the secretion of IFN-γ. CTLs appear to be crucial to recovery from rickettsial infection.
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Grassi, Laura, Maria Luisa Menandro, Rudi Cassini, et al. "High Prevalence of Tick-Borne Zoonotic Rickettsia slovaca in Ticks from Wild Boars, Northeastern Italy." Animals 12, no. 8 (2022): 967. http://dx.doi.org/10.3390/ani12080967.
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Tick-borne rickettsiae are emerging pathogens that are becoming widespread in Europe. Rickettsiae are endemic in Italy, but epidemiological data are currently scarce. This study aimed to improve our knowledge about rickettsial infections in tick and wild boar populations. Blood and ticks were collected from 102 wild boars in 2010 and 2018. Ticks were also collected from the vegetation in the area. All of the samples were examined using real-time PCR targeting the gltA gene to detect Rickettsia DNA. Positivity was confirmed by PCR amplifying the gltA and/or ompB genes. A total of 254 ticks and 89 blood samples were analyzed. Zoonotic rickettsiae were detected in the ticks but not in the blood samples. Rickettsia slovaca (R. slovaca) was the most prevalent in ticks and was found in 23.7% of Dermacentor marginatus (D. marginatus) and in 3.4% of Ixodes ricinus (I. ricinus). Other zoonotic species were identified, such as Rickettsia monacensis, which was detected in 12% of I. ricinus ticks, and Rickettsia helvetica which was found in 3.4% of questing I. ricinus ticks and in 1.1% of D. marginatus collected from wild boars. This study highlights a high prevalence of zoonotic rickettsiae, particularly that of R. slovaca, in northeastern Italy. As rickettsioses are underreported and underdiagnosed in human medicine, both clinicians and researchers should pay more attention to this topic.
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Dzul-Rosado, Karla R., Maria Fidelia Cardenas-Marrufo, Cesar Lugo-Caballero, Alberto Alvarez-Baeza, and Nina Mendez-Dominguez. "Clinical Manifestations in a Fatal Case of Probable Rickettsia and Leptospira Coinfection in Yucatan, Mexico." Pathogens 10, no. 8 (2021): 914. http://dx.doi.org/10.3390/pathogens10080914.
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Clinical or serological coinfections of Rickettsia and Leptospira are uncommon but should be included in differential diagnosis when poor sanitation and cohabitation with infected animals may converge. Rickettsial and leptospiral infections have been continuously increasing throughout the past decade in Yucatan, Mexico. Leptospirosis is a zoonotic disease caused by aerobic spirochetes, while rickettsiosis is an arthropod-borne disease. In 2020, 16% of all rickettsiosis cases and 10% of leptospirosis in the country originated in Yucatan. The objective of the present case report was to document an unusual case of probable coinfection with Rickettsia and Leptospira with emphasis on clinical manifestations and the epidemiological context that may orient future multidisciplinary measures. Here, we presented the case of a 12-year-old female whose mother had recently recovered from a rickettsial infection. The patient presented with fever and developed unspecific signs and symptoms of infection; however, her condition quickly deteriorated with gastrointestinal, hepatic, renal, and neurological dysfunction. After discounting rabies and identifying infection with Rickettsia and Leptospira, antibiotic treatment was indicated, but it was too late to prevent death. Simultaneous infections of Rickettsia and Leptospira may be considered in endemic regions when environmental, epidemiological, and clinical conditions converge.
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Ramírez, Carlos Víctor Hernández, and Dulce Carolina Sánchez García. "Rickettsiosis, Rocky Mountain Spotted Fever a current public health problem." Brazilian Journal of Animal and Environmental Research 8, no. 1 (2025): e77438. https://doi.org/10.34188/bjaerv8n1-081.
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Rickettsioses are a group of bacterial infections of zoonotic origin caused by intracellular bacteria of the genera Rickettsia and Orientia. These infections are transmitted to humans by arthropod vectors such as ticks, fleas, lice and mites. These illnes present clinically as acute febrile illnesses accompanied by symptoms such as headache, myalgia and general malaise, as well as skin manifestations that may include rash and scars and vary according to the species of rickettsia identified. From the point of view of public health and its impact on the population, the most important is Rocky Mountain spotted fever (RMSF), a serious infection caused by the bacteria, Rickettsia rickettsii, a pleomorphic, obligate intracellular coccobacillus, which was discovered in 1908 by Howard Ricketts who died of rickettsiosis in 1910 in Mexico, was first described in the Rocky Mountain region of the United States, and has been reported in Canada, Mexico, Costa Rica, Panama, Colombia, Brazil and Argentina. In Mexico, the most affected region is the north of the country, where the fatality rate reaches an average of 30%, mainly affecting the vulnerable population, including children and adults in conditions of poverty, overcrowding and unhealthy environments.
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Luedtke, Brandon E., Julie J. Shaffer, Estrella Monrroy, Corey W. Willicott, and Travis J. Bourret. "Molecular Detection of Spotted Fever Group Rickettsiae (Rickettsiales: Rickettsiaceae) in Dermacentor variabilis (Acari: Ixodidae) Collected Along the Platte River in South Central Nebraska." Journal of Medical Entomology 57, no. 2 (2019): 519–23. http://dx.doi.org/10.1093/jme/tjz167.
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Abstract Dermacentor variabilis is the predominant tick species in Nebraska and is presumed to be the primary vector of Rickettsia rickettsii associated with cases of Rocky Mountain spotted fever (RMSF). Interestingly, RMSF cases in Nebraska have increased on a year-to-year basis, yet the prevalence of R. rickettsii in D. variabilis ticks has not been established for Nebraska. Here we sought to set a baseline for the prevalence of R. rickettsii and other spotted fever group (SFG) rickettsiae harbored by D. variabilis ticks. Over a 3-yr period, D. variabilis were collected along the Platte River in south central Nebraska. Individual tick DNA was analyzed using endpoint PCR to identify ticks carrying SFG rickettsiae. In total, 927 D. variabilis were analyzed by PCR and 38 (4.1%) ticks tested positive for SFG rickettsiae. Presumptive positives were sequenced to identify the Rickettsia species, of which 29 (76%) were R. montanensis, 5 (13%) were R. amblyommatis, 4 (11%) were R. bellii, and R. rickettsii was not detected. These data indicate that R. rickettsii is likely at a low prevalence in south central Nebraska and spillover of R. amblyommatis into D. variabilis is likely occurring due to the invasive lone star tick (Amblyomma americanum). In addition, our data suggest that R. montanensis and R. amblyommatis could be associated with the increase in SFG rickettsiae infections in Nebraska. This information will be of value to clinicians and the general public for evaluating diagnosis of disease- and risk-associated environmental exposure, respectively.
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Narra, Hema P., Abha Sahni, David H. Walker, and Sanjeev K. Sahni. "Recent research milestones in the pathogenesis of human rickettsioses and opportunities ahead." Future Microbiology 15, no. 9 (2020): 753–65. http://dx.doi.org/10.2217/fmb-2019-0266.
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Infections caused by pathogenic Rickettsia species continue to scourge human health across the globe. From the point of entry at the site of transmission by arthropod vectors, hematogenous dissemination of rickettsiae occurs to diverse host tissues leading to ‘rickettsial vasculitis’ as the salient feature of pathogenesis. This perspective article accentuates recent breakthrough developments in the context of host–pathogen–vector interactions during rickettsial infections. The subtopics include potential exploitation of circulating macrophages for spread, identification of new entry mechanisms and regulators of actin-based motility, appreciation of metabolites acquired from and effectors delivered into the host, importance of the toxin–antitoxin module in host–cell interactions, effects of the vector microbiome on rickettsial transmission, and niche-specific riboregulation and adaptation. Further research on these aspects will advance our understanding of the biology of rickettsiae as intracellular pathogens and should enable design and development of new approaches to counter rickettsioses in humans and other hosts.
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O Chilongola, Jaffu, Elias J Sabuni, and Eliakimu Paul Kapyolo. "Prevalence of plasmodium, leptospira and rickettsia species in Northern Tanzania: a community based survey." African Health Sciences 20, no. 1 (2020): 199–207. http://dx.doi.org/10.4314/ahs.v20i1.25.
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Background: The overlap of symptoms, geographic and seasonal co-occurrence of Plasmodium, Leptospira and Rickettsia infections makes malaria diagnosis difficult, increasing the chances of misdiagnosis. The paucity of data on the prevalence Plasmodium, Leptospira and Rickettsia infections contributes to an overly diagnosis of malaria. We aimed to determine the prevalence and distribution of Plasmodium, Leptospira and Rickettsia infections in northern Tanzania.
 Methods: A community based, cross sectional survey was conducted in two sites in Northern Tanzania. PCR was used to detect Plasmodium, Leptospira and Rickettsia infections.
 Results: The prevalence of P. falciparum and Leptospira spp were 31/128 (24.2%) and 3/128 (2.3%), respectively. No Rickettsia infection was detected in any of the two sites. Taking study sites separately, Plasmodium infection was detected in 31/63(49.2%) of participants in Bondo while Leptospira infection was detected in 3/65(4.6%) of participants in Magugu. Plasmodium was not detected in Magugu while no Leptospira infections were detected in Bondo. Fever was significantly associated with Plasmodium infection (χ2= 12.44, p<0.001) and age (χ2=17.44, p=0.000).
 Conclusion: Results from this study indicate Plasmodium infection as the main cause of fever in the studied sites. While Plasmodium and Leptospira contribute to fevers, Rickettsia infection is an insignificant cause of fever in Northern Tanzania.
 Keywords: Neglected Infectious Diseases; Plasmodium; Leptospira; Rickettsia; co-occurrence; Tanzania.
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Van Kirk, Levi S., Stanley F. Hayes, and Robert A. Heinzen. "Ultrastructure of Rickettsia rickettsiiActin Tails and Localization of Cytoskeletal Proteins." Infection and Immunity 68, no. 8 (2000): 4706–13. http://dx.doi.org/10.1128/iai.68.8.4706-4713.2000.
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ABSTRACT Actin-based motility (ABM) is a mechanism for intercellular spread that is utilized by vaccinia virus and the invasive bacteria within the genera Rickettsia, Listeria, andShigella. Within the Rickettsia, ABM is confined to members of the spotted fever group (SFG), such asRickettsia rickettsii, the agent of Rocky Mountain spotted fever. Infection by each agent induces the polymerization of host cell actin to form the typical F (filamentous)-actin comet tail. Assembly of the actin tail propels the pathogen through the host cytosol and into cell membrane protrusions that can be engulfed by neighboring cells, initiating a new infectious cycle. Little is known about the structure and morphogenesis of the Rickettsia rickettsii actin tail relative to Shigellaand Listeria actin tails. In this study we examined the ultrastructure of the rickettsial actin tail by confocal, scanning electron, and transmission electron microscopy. Confocal microscopy of rhodamine phalloidin-stained infected Vero cells revealed the typhus group rickettsiae, Rickettsia prowazekii andRickettsia typhi, to have no actin tails and short (∼1- to 3-μm) straight or hooked actin tails, respectively. The SFG rickettsia, R. rickettsii, displayed long actin tails (>10 μm) that were frequently comprised of multiple, distinct actin bundles, wrapping around each other in a helical fashion. Transmission electron microscopy, in conjunction with myosin S1 subfragment decoration, revealed that the individual actin filaments of R. rickettsii tails are >1 μm long, arranged roughly parallel to one another, and oriented with the fast-growing barbed end towards the rickettsial pole. Scanning electron microscopy of intracellular rickettsiae demonstrated R. rickettsii to have polar associations of cytoskeletal material and R. prowazekii to be devoid of cytoskeletal interactions. By indirect immunofluorescence, both R. rickettsii and Listeria monocytogenesactin tails were shown to contain the cytoskeletal proteins vasodilator-stimulated phosphoprotein profilin, vinculin, and filamin. However, rickettsial tails lacked ezrin, paxillin, and tropomyosin, proteins that were associated with actin tails of cytosolic or protrusion-bound Listeria. The unique ultrastructural and compositional characteristics of the R. rickettsii actin tail suggest that rickettsial ABM is mechanistically different from previously described microbial ABM systems.
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Raoult, D., and V. Roux. "Rickettsioses as paradigms of new or emerging infectious diseases." Clinical Microbiology Reviews 10, no. 4 (1997): 694–719. http://dx.doi.org/10.1128/cmr.10.4.694.
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Rickettsioses are caused by species of Rickettsia, a genus comprising organisms characterized by their strictly intracellular location and their association with arthropods. Rickettsia species are difficult to cultivate in vitro and exhibit strong serological cross-reactions with each other. These technical difficulties long prohibited a detailed study of the rickettsiae, and it is only following the recent introduction of novel laboratory methods that progress in this field has been possible. In this review, we discuss the impact that these practical innovations have had on the study of rickettsiae. Prior to 1986, only eight rickettsioses were clinically recognized; however, in the last 10 years, an additional six have been discovered. We describe the different steps that resulted in the description of each new rickettsiosis and discuss the influence of factors as diverse as physicians' curiosity and the adoption of molecular biology-based identification in helping to recognize these new infections. We also assess the pathogenic potential of rickettsial strains that to date have been associated only with arthropods, and we discuss diseases of unknown etiology that may be rickettsioses.
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Tamekuni, Katia, Roberta dos Santos Toledo, Mauro de Freitas Silva Filho, et al. "Serosurvey of antibodies against spotted fever group Rickettsia spp. in horse farms in Northern Paraná, Brazil." Revista Brasileira de Parasitologia Veterinária 19, no. 4 (2010): 259–61. http://dx.doi.org/10.1590/s1984-29612010000400014.
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Brazilian spotted fever (BSF) is an emerging disease most likely caused by Rickettsia rickettsii. The objective of the present study was to estimate the seroprevalence of BSF rickettsia infections in equines from six horse farms located in Londrina County, Paraná, Southern Brazil. Six owners of horse farms situated in Cambé, Santa Fé, Guaraci and Londrina municipalities participated in the study. All farms were located in areas where BSF has not been reported. A total of 273 horses were sampled and their sera were tested by indirect Immunofluorescence assay (IFA) using R. rickettsii and R. parkeri antigens. Titers equal to and greater than 64 were considered positive. Of 273 sera tested, 15 (5.5%) reacted to R. rickettsii and 5 (1.8%) to R. parkeri. Five out of the six farms studied revealed seropositive animals and seropositivity rate ranged from 0 to 13%. The titers ranged from 64 to 512, and four samples had a titer of 512. Nine animals reacted to R. rickettsii with titers four-fold higher than those for R. parkeri. These results suggest that horses in Northern Paraná may have been exposed to rickettsiae identical or closely related to R. rickettsii.
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Anu, D., H. Sung-Hee, L. Sang-Eun, et al. "RECENT STUDIES OF TICK-BORNE INFECTIONS IN MONGOLIA." Acta Biomedica Scientifica 3, no. 4 (2018): 152–54. http://dx.doi.org/10.29413/abs.2018-3.4.23.
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We have aimed to detect both Rickettsiae species and Babesia microti in adult ticks of Dermacentor nutalli in Tuv province; and looked for only Rickettsiae species in Ixodes persulcatus in Selenge province. Using the PCR and DNA sequencing techniques, we amplified and sequenced the 16S rRNA, gltA, rOmpA genes of Rickettsia and 18S rRNA gene of B. microti and Rickettsia species were identified. Infection rate for Rickettsiae spp. was 82.7 % (115/139 samples) by 16S rRNA sequencing results and among them the highest prevalence rate was that for R. raoultii strain – 71.4 % (80/111 samples) by gltA gene sequencing and 100 % (81/81 samples) by rOmpA gene sequencing. Canditatus Rickettsia tarasevichiae strain was detected in 27.9 % (31/11 samples) by gltA gene sequencing. Infection rate for Rickettsiae spp. in D. nutalli ticks was 84.3 % (81/96 samples) and R. raoultii strain comprised 96.2–98.7 % among them. Adult ticks of I. persulcatus were infected with Rickettsiae spp. with 78 % and 93.75 % of them were R. raoultii strain. Seventeen out of 97 ticks (17.5 %) were found to be infected with B. microti. Nucleotide DNA sequencing of partial 18S rRNA and gltA genes supported the PCR results. We have identified that the same species of ticks commonly distributed in Mongolia have been infected with R. sibirica, R. raoultii and B. microti. It might be the strength of our study as B. microti have not been detected in D. nuttalli ticks yet. We are considering to detect the tick-borne infections in humans.
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Clifton, Dawn R., Elena Rydkina, Robert S. Freeman та Sanjeev K. Sahni. "NF-κB Activation during Rickettsia rickettsii Infection of Endothelial Cells Involves the Activation of Catalytic IκB Kinases IKKα and IKKβ and Phosphorylation-Proteolysis of the Inhibitor Protein IκBα". Infection and Immunity 73, № 1 (2005): 155–65. http://dx.doi.org/10.1128/iai.73.1.155-165.2005.
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ABSTRACT Rocky Mountain spotted fever, a systemic tick-borne illness caused by the obligate intracellular bacterium Rickettsia rickettsii, is associated with widespread infection of the vascular endothelium. R. rickettsii infection induces a biphasic pattern of the nuclear factor-κB (NF-κB) activation in cultured human endothelial cells (ECs), characterized by an early transient phase at 3 h and a late sustained phase evident at 18 to 24 h. To elucidate the underlying mechanisms, we investigated the expression of NF-κB subunits, p65 and p50, and IκB proteins, IκBα and IκBβ. The transcript and protein levels of p50, p65, and IκBβ remained relatively unchanged during the course of infection, but Ser-32 phosphorylation of IκBα at 3 h was significantly increased over the basal level in uninfected cells concomitant with a significant increase in the expression of IκBα mRNA. The level of IκBα mRNA gradually returned toward baseline, whereas that of total IκBα protein remained lower than the corresponding controls. The activities of IKKα and IKKβ, the catalytic subunits of IκB kinase (IKK) complex, as measured by in vitro kinase assays with immunoprecipitates from uninfected and R. rickettsii-infected ECs, revealed significant increases at 2 h after infection. The activation of IKK and early phase of NF-κB response were inhibited by heat treatment and completely abolished by formalin fixation of rickettsiae. The IKK inhibitors parthenolide and aspirin blocked the activities of infection-induced IKKα and IKKβ, leading to attenuation of nuclear translocation of NF-κB. Also, increased activity of IKKα was evident later during the infection, coinciding with the late phase of NF-κB activation. Thus, activation of catalytic components of the IKK complex represents an important upstream signaling event in the pathway for R. rickettsii-induced NF-κB activation. Since NF-κB is a critical regulator of inflammatory genes and prevents host cell death during infection via antiapoptotic functions, selective inhibition of IKK may provide a potential target for enhanced clearance of rickettsiae and an effective strategy to reduce inflammatory damage to the host during rickettsial infections.
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Londoño, Andrés F., Jennifer M. Farner, Marlon Dillon, et al. "Benidipine impairs innate immunity converting sublethal to lethal infections in a murine model of spotted fever rickettsiosis." PLOS Neglected Tropical Diseases 18, no. 2 (2024): e0011993. http://dx.doi.org/10.1371/journal.pntd.0011993.
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Spotted fever group rickettsiae are tick-borne obligate intracellular bacteria that infect microvascular endothelial cells. Humans and mammalian infection results in endothelial cell barrier dysfunction and increased vascular permeability. We previously demonstrated that treatment of Rickettsia parkeri-infected cells with the calcium channel blocker benidipine significantly delayed vascular barrier permeability. Thus, we hypothesized that benidipine, known to be safe and effective for other clinical processes, could reduce rickettsia-induced vascular permeability in vivo in an animal model of spotted fever rickettsiosis. Based on liver, lung and brain vascular FITC-dextran extravasation studies, benidipine did not reliably impact vascular permeability. However, it precipitated a deleterious effect on responses to control sublethal R. parkeri infection. Animals treated with benidipine alone had no clinical signs or changes in histopathology and splenic immune cell distributions. Benidipine-treated infected animals had marked increases in tissue and blood bacterial loads, more extensive inflammatory histopathologic injury, and changes in splenic architecture and immune cell distributions potentially reflecting diminished Ca2+ signaling, reduced innate immune cell activation, and loss of rickettsial propagation control. Impaired T cell activation by R. parkeri antigen in the presence of benidipine was confirmed in vitro with the use of NKT cell hybridomas. The unexpected findings stand in stark contrast to recent discussions of the benefits of calcium channel blockers for viral infections and chronic infectious or inflammatory diseases. A role for calcium channel blockers in exacerbation of human rickettsiosis and acute inflammatory infections should be evaluated by a retrospective review of patient’s outcomes and medications.
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Venzal, José M., Agustín Estrada-Peña, Aránzazu Portillo, et al. "Rickettsia parkeri: a Rickettsial pathogen transmitted by ticks in endemic areas for spotted fever rickettsiosis in southern Uruguay." Revista do Instituto de Medicina Tropical de São Paulo 54, no. 3 (2012): 131–34. http://dx.doi.org/10.1590/s0036-46652012000300003.
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At first Rickettsia conorii was implicated as the causative agent of spotted fever in Uruguay diagnosed by serological assays. Later Rickettsia parkeri was detected in human-biting Amblyomma triste ticks using molecular tests. The natural vector of R. conorii, Rhipicephalus sanguineus, has not been studied for the presence of rickettsial organisms in Uruguay. To address this question, 180 R. sanguineus from dogs and 245 A. triste from vegetation (flagging) collected in three endemic localities were screened for spotted fever group (SFG) rickettsiosis in southern Uruguay. Tick extracted DNA pools were subjected to PCR using primers which amplify a fragment of the rickettsial gltA gene. Positive tick DNA pools with these primers were subjected to a second PCR round with primers targeting a fragment of the ompA gene, which is only present in SFG rickettsiae. No rickettsial DNA was detected in R. sanguineus. However, DNA pools of A. triste were found to be positive for a rickettsial organism in two of the three localities, with prevalences of 11.8% to 37.5% positive pools. DNA sequences generated from these PCR-positive ticks corresponded to R. parkeri. These findings, joint with the aggressiveness shown by A. triste towards humans, support previous data on the involvement of A. triste as vector of human infections caused by R. parkeri in Uruguay.
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Abeyagunawardena, I. A., K. K. S. N. Sirisena, B. H. N. R. Vitharana, P. Thuvarakan, and R. M. S. H. Karunatilake. "Severe bilateral retinal vasculitis as a delayed manifestation of rickettsial infection." Asian Journal of Internal Medicine 3, no. 2 (2024): 104–7. http://dx.doi.org/10.4038/ajim.v3i2.167.
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Ophthalmic manifestations of rickettsial infections are reported as mostly asymptomatic and self-limiting. A 27-year-old woman, 29 weeks pregnant, recently treated for rickettsial infection, presented ten days following discharge with visual blurring and was diagnosed to have severe bilateral retinal vasculitis. Rickettsial antibody testing (indirect immunofluorescence assay) revealed Rickettsia conorii IgG titer >1:128. Antinuclear antibody, retroviral, syphilis and toxoplasmosis screens were negative. Bilateral intra-vitreous triamcinolone, azithromycin and prednisolone were administered. However, despite some improvement, a residual visual deficit remained. This case report highlights the possibility of debilitating visual loss following rickettsial infections, need for ophthalmic screening at diagnosis and prompt treatment initiation.
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Pascucci, Ilaria, Marco Di Domenico, Valentina Curini, et al. "Diversity of Rickettsia in Ticks Collected in Abruzzi and Molise Regions (Central Italy)." Microorganisms 7, no. 12 (2019): 696. http://dx.doi.org/10.3390/microorganisms7120696.
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Rickettsiae have worldwide occurrence and rickettsiosis are widely recognized as emerging infections in several parts of the world. For decades, it was thought that a single pathogenic tick-borne spotted fever group (SFG), Rickettsia, occurred in each continent. Nowadays, thanks to molecular biology, new species of Rickettsia responsible for disease in humans are continuously identified worldwide. In a framework of diagnostic activities of the Istituto Zooprofilattico Sperimentale dell’Abruzzo e del Molise “G. Gaporale” and considering some reports of suspected human clinical cases of rickettsiosis, a survey on ticks collected form animals and humans was carried out with the aim to identify the Rickettsia species circulating in Abruzzi and Molise regions. A total of 603 ticks, previously identified at species level by morphology, pooled into 178 tick samples, were tested by pan-Rickettsia RealTime PCR. DNA from specimens positive for Rickettsia spp. was then sequenced in order to identify the Rickettsia species involved. The highest infection rate was detected in Dermacentor marginatus followed by Ixodes ricinus. The selected targets for this purpose were OmpA and gltA. Rickettsia slovaca, Rickettsia monacensis, Rickettsia massiliae, Rickettsia conorii, Rickettsia aeschlimannii, Rickettsia helvetica, Rickettsia raoultii, and Rickettsia felis – like organisms were identified in this study. These are the first data available in the literature for the circulation of SFG Rickettsia species in the selected geographical area. Results made evidence of high rate of infection in ticks. All Rickettsia species detected have been previously involved in human infection. The diversity of Rickettsia detected, and tick species collected reflects the biodiversity in term of wildlife and environment of the area. An association between Rickettsia species, ticks, and the relationships with vertebrate host species are discussed. Due to the peculiar eco-biology of each Rickettsia species, the use of diagnostic tools able to identify Rickettsia at the species level is thus recommended in order to assess the risk for humans and to elucidate more precise etiological diagnosis in clinical cases.
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Breitschwerdt, Edward B., Barbara C. Hegarty, Michael G. Davidson, and Nancy S. Szabados. "Evaluation of the pathogenic potential of Rickettsia canada and Rickettsia prowazekii organisms in dogs." Journal of the American Veterinary Medical Association 207, no. 1 (1995): 58–63. http://dx.doi.org/10.2460/javma.1995.207.01.58.
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Summary An unusual pattern of seroreactivity to antigens of rickettsial organisms (Rickettsia rickettsii, R rhipicephali, R montana, and R bellii), particularly to R bellii antigen, was detected in 3 dogs during a 2-month period. Thus, studies were initiated to clarify the pathogenic potential of the more distantly related rickettsial organisms (R canada and R prowazekii) in dogs. Because R bellii are nonpathogenic rickettsiae that share numerous common properties with spotted fever-group and typhus-group rickettsiae, and because closely related pathogenic relatives of R bellii have not been identified, we examined the pathogenic potential of these typhus-group rickettsiae by testing stored serum samples, by attempting rickettsial isolation from febrile dogs, and by experimentally inoculating dogs with R canada and R prowazekii. Evaluation of results of a serosurvey of acute and convalescent serum samples from 80 dogs in which Rocky Mountain spotted fever had been considered as a differential diagnosis, but seroconversion to R rickettsii had not been documented, identified 1 dog with a fourfold increase in antibody titer to R rhipicephali and 3 dogs with fourfold increases in antibody titer to 1 or more antigens of typhus-group rickettsial organisms. A study of 15 dogs that were febrile during summer months failed to identify serologic or tissue culture evidence of typhus-group rickettsial infection or typhus-group rickettsemia, but did result in isolation of R rickettsii and Ehrlichia canis, respectively, from 1 dog each. In our final study, after experimentally inoculating 6 dogs with R canada and R prowazekii, all dogs seroconverted to the respective rickettsiae, but rickettsemia or clinical and hematologic evidence of disease was not observed. Collectively, our results did not provide convincing evidence to support a pathogenic role for R canada and R prowazekii organisms in dogs. Our findings supported the conclusion that an unidentified microorganism, which results in production of antibodies against R bellii and antigens of typhus-group rickettsial organisms, contributed to an unexplained febrile illness of dogs in the southeastern United States. In an effort to identify dogs in which serologic evidence supports this conclusion, we recommend the use of selected spotted fever-group, typhus-group, and R bellii antigens for serodiagnostic purposes. We also recommend that diagnosticians attempt tissue culturing to isolate organisms when a rickettsial agent is suspected.
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Ammerman, Nicole C., M. Sayeedur Rahman, and Abdu F. Azad. "Characterization of Sec-Translocon-Dependent Extracytoplasmic Proteins of Rickettsia typhi." Journal of Bacteriology 190, no. 18 (2008): 6234–42. http://dx.doi.org/10.1128/jb.00794-08.
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ABSTRACT As obligate intracellular, vector-borne bacteria, rickettsiae must adapt to both mammalian and arthropod host cell environments. Deciphering the molecular mechanisms of the interactions between rickettsiae and their host cells has largely been hindered by the genetic intractability of these organisms; however, research in other gram-negative pathogens has demonstrated that many bacterial determinants of attachment, entry, and pathogenesis are extracytoplasmic proteins. The annotations of several rickettsial genomes indicate the presence of homologs of the Sec translocon, the major route for bacterial protein secretion from the cytoplasm. For Rickettsia typhi, the etiologic agent of murine typhus, homologs of the Sec-translocon-associated proteins LepB, SecA, and LspA have been functionally characterized; therefore, the R. typhi Sec apparatus represents a mechanism for the secretion of rickettsial proteins, including virulence factors, into the extracytoplasmic environment. Our objective was to characterize such Sec-dependent R. typhi proteins in the context of a mammalian host cell infection. By using the web-based programs LipoP, SignalP, and Phobius, a total of 191 R. typhi proteins were predicted to contain signal peptides targeting them to the Sec translocon. Of these putative signal peptides, 102 were tested in an Escherichia coli-based alkaline phosphatase (PhoA) gene fusion system. Eighty-four of these candidates exhibited signal peptide activity in E. coli, and transcriptional analysis indicated that at least 54 of the R. typhi extracytoplasmic proteins undergo active gene expression during infections of HeLa cells. This work highlights a number of interesting proteins possibly involved in rickettsial growth and virulence in mammalian cells.
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De Vito, Andrea, Nicholas Geremia, Maria Sabrina Mameli, et al. "EPIDEMIOLOGY, CLINICAL ASPECTES,LABORATORY DIAGNOSIS AND TREATMENT OF RICKESIAL DISEASES IN THE MEDITERRANEAN AREA DURIN COVID-19 PANDEMIC:A REVIEW OF THE LITERATURE." Mediterranean Journal of Hematology and Infectious Diseases 12, no. 1 (2020): e2020056. http://dx.doi.org/10.4084/mjhid.2020.056.
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The purpose of the present review is to give an update regarding the classification, the epidemiology, the clinical manifestation, the diagnoses, and the treatment of the Rickettsiae species present in the Mediterranean area.
 We performed a comprehensive search, through electronic databases (Pubmed – MEDLINE) and search engines (Google Scholar), of peer-reviewed publications (articles, reviews, and books).
 The availability of new diagnostic tools, including Polymerase Chain Reaction and nucleotide sequencing has significantly modified the classification of intracellular bacteria, including the order Rickettsiales with more and more new Rickettsia species recognized as human pathogens. Furthermore, emerging Rickettsia species have been found in several countries and are often associated with unique clinical pictures that may challenge the physician in the early detection of the diseases.
 Rickettsial infections include a wide spectrum of clinical presentations ranging from a benign to a potentially life treating disease that requires prompt recognition and proper management. Recently, due to the spread of SARS-CoV-2 infection, the differential diagnosis with COVID-19 is of crucial importance. The correct understanding of the clinical features, diagnostic tools, and proper treatment can assist clinicians in the management of Rickettsioses in the Mediterranean area.
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Feng, Hui-Min, Ted Whitworth, Juan P. Olano, Vsevolod L. Popov, and David H. Walker. "Fc-Dependent Polyclonal Antibodies and Antibodies to Outer Membrane Proteins A and B, but Not to Lipopolysaccharide, Protect SCID Mice against Fatal Rickettsia conorii Infection." Infection and Immunity 72, no. 4 (2004): 2222–28. http://dx.doi.org/10.1128/iai.72.4.2222-2228.2004.
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ABSTRACT An emphasis on cellular immunity against Rickettsia has led to neglect of analysis of the role of antibody. The availability of an excellent mouse model of spotted fever rickettsiosis enabled investigation of a potential role of antibody in immunity to Rickettsia conorii. C3H severe combined immunodeficiency (SCID) mice were passively transfused with monoclonal antibodies against rickettsial outer membrane protein A (OmpA), OmpB, or lipopolysaccharide (LPS), polyclonal anti-R. conorii serum, Fab fragments of polyclonal antiserum, or no antibodies and then challenged 48 h later with 10 50% lethal doses (LD50) of R. conorii. All mice that received monoclonal antibodies against OmpA and two of four mice that received monoclonal antibodies against OmpB or polyclonal antisera were completely protected, but the recipients of anti-LPS antibodies or the Fab fragments were not protected. Polyclonal antibody treatment of C3H SCID mice that had been infected with 10 LD50 of R. conorii 4 or 5 days earlier prolonged the life of the infected mice from 10.4 to 22.5 days and resulted in decreased levels of infectious rickettsiae in the spleen and liver 24 and 48 h later. Treatment with protective antibodies resulted in the development of large aggregates of R. conorii antigens in splenic macrophages and intraphagolysosomal rickettsial death and digestion. The kinetics of development of antibodies to R. conorii determined by immunoblotting revealed antibodies to LPS on day 6 and antibodies to OmpA and OmpB on day 12, when recovery from the infection had already occurred. Antibodies to particular epitopes of OmpA and OmpB may protect against reinfection, but they may not play a key role in immunity against primary infection. Antibodies might be useful for treating infections with antibiotic-resistant organisms, and some B-cell epitopes should be included in a subunit vaccine.
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Piotrowski, Mariusz, and Anna Rymaszewska. "Expansion of Tick-Borne Rickettsioses in the World." Microorganisms 8, no. 12 (2020): 1906. http://dx.doi.org/10.3390/microorganisms8121906.
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Tick-borne rickettsioses are caused by obligate intracellular bacteria belonging to the spotted fever group of the genus Rickettsia. These infections are among the oldest known diseases transmitted by vectors. In the last three decades there has been a rapid increase in the recognition of this disease complex. This unusual expansion of information was mainly caused by the development of molecular diagnostic techniques that have facilitated the identification of new and previously recognized rickettsiae. A lot of currently known bacteria of the genus Rickettsia have been considered nonpathogenic for years, and moreover, many new species have been identified with unknown pathogenicity. The genus Rickettsia is distributed all over the world. Many Rickettsia species are present on several continents. The geographical distribution of rickettsiae is related to their vectors. New cases of rickettsioses and new locations, where the presence of these bacteria is recognized, are still being identified. The variety and rapid evolution of the distribution and density of ticks and diseases which they transmit shows us the scale of the problem. This review article presents a comparison of the current understanding of the geographic distribution of pathogenic Rickettsia species to that of the beginning of the century.
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Toan, Van Trinh, Viet Vo Cuong, Van Nguyen Dat, et al. "Detection of Rickettsia species in rodents collected in the Northern provinces of Vietnam, 2020–2022." Problems of Particularly Dangerous Infections, no. 1 (April 4, 2024): 162–67. http://dx.doi.org/10.21055/0370-1069-2024-1-162-167.
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Rickettsiae, which are obligate intracellular bacterial parasites, have a life cycle commonly associated with arthropod vectors and animal hosts. Rodents are recognized as their natural reservoir hosts and play a role in transmitting the bacteria to humans through arthropod vectors. The true extent of rickettsial infections in Vietnam remains underestimated due to a limited understanding of the disease’s epidemiology, resulting in a significant public health burden.The aim of this investigation was to assess the prevalence of Rickettsia in wild-living rodents in Dien Bien, Son La, and Phu Tho provinces of Northern Vietnam between 2020 and 2022.Materials and methods. A total of 396 wild-living rodents were collected from the Northern provinces of Vietnam during 2020–2022. Real-time polymerase chain reaction (PCR) was employed to detect the percentage of Rickettsia-positive specimens. Subsequently, the ompB and 17kDa genes were extracted, amplified, and sequenced from the Rickettsia-positive rodents.Results and discussion. Among the 396 rodents examined, the majority were Rattus norvegicus (56.1%), followed by R. tanezumi (37.4%), R. nitidus (2.5%), and R. germaini (1.8%). R. korodentsensis and R. argentiverter constituted the remaining rodents, accounting for 2.2% of the total. The real-time PCR analysis revealed that 27 blood samples out of the 396 rodent samples collected, tested positive for Rickettsia (6.81%). R. germaini was shown to have the highest positive rate 1/8 (12.5%), followed by R. nitidus 1/10 (10.0%), R. tanezumi 14/149 (9.5%), and R. norvegicus 11/222 (4.9%). No other tick-borne pathogens were detected in any of the provinces. Sequencing of the positive samples as regards the ompB and 17kDa genes revealed the closest relation to R. felis. These findings highlight the potentially high risk of R. felis infection in humans and animals within the studied areas.
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Sawant, Dr Surbhi D., Dr Abhijit Shinde, Dr Suresh Waydande, Prof Dr Sunil Natha Mhaske, and Dr. Sushrut Kumar. "Purpura Fulminans Secondary to Indian Tick Typhus of Spotted Fever Group of Rickettsial Infections: A Case Report." VIMS Health Science Journal 9, no. 5 (2023): 110–13. http://dx.doi.org/10.46858/vimshsj/9404.
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Rickettsia is a group of vector-borne organisms that beget acute febrile illnesses throughout the world. While the clinical presentation of rickettsial infection is analogous, the causative species and epidemiology can vary depending upon the region. Purpura fulminans (PF) is a rare pattern of intravascular thrombosis and haemorrhagic infarction of the skin that is fleetly progressive and is accompanied by vascular collapse and disseminated intravascular coagulation. We report a case of 11 month old male child presented with high grade fever and necrotic skin lesion over lower limbs. The child was diagnosed with acute contagious PF secondary to Indian tick typhus of spotted fever group of rickettsial infections. Underdiagnosed and misdiagnosed rickettsial infections are an important public health problem leading to an increased morbidity and mortality in cases with PF.
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YEŞİL, Edanur, Berfin ÖZGÖKÇE ÖZMEN, Mehtap AKÇA, Özlem KAYABEY, and Necdet KUYUCU. "A clinical case series of Rickettsia spp. from southern Türkiye." Cukurova Medical Journal 48, no. 4 (2023): 1439–42. http://dx.doi.org/10.17826/cumj.1345813.
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Rickettsial infections should be considered in the presence of a maculopapular rash, especially in the endemic area with a history of tick bite. In this study, Rickettsia spp. infections of three cases will be mentioned. Three cases with positive Rickettsia spp immunofluorescent antibody serology were included in the study. Case-1 was a 17-year-old male patient, who had a history of tick bite one week before the admission was admitted with chest pain. He had tachycardia and a "tache noir" rash with a necrotic center in the area of the tick bite. Laboratory parameters showed lymphopenia, cardiac enzymes elevation. The patient’s serelogy of Rickettsia conorii IgM was 1/192 titer positive and IgG was negative. He hospitalized as acute Mediterranean Spotted Fever myocarditis. He recovered with doxycycline treatment. Case-2 was a nine-month-old girl presented with fever, rash and lymphadenomegaly on left axilla two weeks after the tick bite of her left arm. The rash was localized to the arm. R. slovaca and R. aeschlimannii serologies were detected 1/40 titer positive. After ciprofloxacin treatment her symptoms had dissapeared. Case-3 was a seven-year-old girl presented with fever reaching 39ºC for five days, myalgia and rash all over her body. She had scratched the tick from the scalp five days before the admission. Rickettsia conorii IgM serology was 1/768, IgG was 1/640 titer positive. She recovered after doxycycline treatment. Rickettsia spp. infections can lead to infections like myocarditis or the spotted fever group Rickettsiosis diseases. Complications can be prevented with early diagnosis and treatment.
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Shih, Chien-Ming, Pei-Wen Yang, and Li-Lian Chao. "Molecular Detection and Genetic Identification of Rickettsia Infection in Ixodes granulatus Ticks, an Incriminated Vector for Geographical Transmission in Taiwan." Microorganisms 9, no. 6 (2021): 1309. http://dx.doi.org/10.3390/microorganisms9061309.
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Tick-borne Rickettsia pathogens have become an emerging source of zoonotic infections and have a major impact on human health worldwide. In this study, the prevalence and genetic identity of Rickettsia infections in Ixodes granulatus ticks was firstly determined in Kinmen Island of Taiwan. A total of 247 I. granulatus ticks were examined for Rickettsia infection by nested-PCR assay targeting the citrate synthase (gltA) gene of Rickettsia. The Rickettsia infection was detected with a general infection rate of 4.86%, and was detected in nymph, male and female stages with an infection rate of 3.81%, 0% and 6.84%, respectively. Phylogenetic relationships were analyzed by comparing the gltA sequences obtained from four Taiwan strains and 19 other strains representing 13 genospecies of Rickettsia. Phylogenetic analyses reveal that all Taiwan strains were genetically affiliated to the genospecies of spotted fever (R. parkeri) and transitional (R. felis) groups of Rickettsia. Our findings reveal the first detection of R. parkeri-like and R. felis in I. granulatus ticks from Kinmen Island. As a tourist island between Taiwan and mainland China, these results demonstrate the epidemiological significance of diverse Rickettsia species existed in I. granulatus ticks and highlight the potential threat of geographical transmission among humans in the Taiwan area.
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Nováková, Mária, Bronislava Víchová, and Michal Baláž. "Monitoring Rickettsia spp. v podhorskej oblasti Slovenska." Zdravotnícke štúdie 14, no. 2 (2022): 41–44. http://dx.doi.org/10.54937/zs.2022.14.2.41-44.
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Objectives: Ticks, as a vector of various infections occur every year in Liptov, a popular tourist location in Slovakia, and their occurrence generally has an increasing trend. As up to now several rickettsiae from the spotted fever group were confirmed in tick vectors from different areas of Slovakia. Therefore, identification of previously unknown areas with endemic occurrence of Rickettsia spp. is of great importance. Material and methods: Questing ixodid ticks, small mammals, birds and wild boars from recreational areas of Liptov valley in northern Slovakia were tested for the presence of Rickettsia spp. and obtained sequences were further analyzed. Results: Overall, 8 out of 55 ixodid ticks (14.5%) tested positive for Rickettsia helvetica and one male tick (1.8%) was infected with Rickettsia monacensis. The identification of this species was based on the sequencing of 23S-5S internal transcribed spacer (ITS), gltA and ompA genes. Rickettsia spp. was detected in 7 rodents (5.8%) and 5 wild boars (5.9%) originated from Liptov valley, using gltA gene primer set. Conclusion: Our results confirm the presence of spotted fever group rickettsiae in tick vectors and hosts from northern part of Slovakia. Moreover, the evidence of the presence of Rickettsia spp. in vectors and in reservoirs indicate the circulation of the pathogen in nature and the need to monitor the situation in this popular location in Slovakia.
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Vilibic-Cavlek, Tatjana, Natasa Janev-Holcer, Maja Bogdanic, et al. "Current Status of Vector-Borne Diseases in Croatia: Challenges and Future Prospects." Life 13, no. 9 (2023): 1856. http://dx.doi.org/10.3390/life13091856.
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Different vector-borne pathogens are present or have (re-)emerged in Croatia. Flaviviruses tick-borne encephalitis (TBEV), West Nile (WNV), and Usutu (USUV) are widely distributed in continental regions, while Toscana virus (TOSV) and sandfly fever viruses are detected at the Croatian littoral. Recently, sporadic clinical cases of Tahyna orthobunyavirus (TAHV) and Bhanja bandavirus infection and seropositive individuals have been reported in continental Croatia. Acute infections and serologic evidence of WNV, TBEV, USUV, and TAHV were also confirmed in sentinel animals and vectors. Autochthonous dengue was reported in 2010 at the Croatian littoral. Lyme borreliosis is the most widely distributed vector-borne bacterial infection. The incidence is very high in northwestern and eastern regions, which correlates with numerous records of Ixodes ricinus ticks. Acute human Anaplasma phagocytophilum infections are reported sporadically, but there are many records of serologic evidence of anaplasmosis in animals. Mediterranean spotted fever (Rickettsia conorii) and murine typhus (Rickettsia typhi) are the main rickettsial infections in Croatia. Human leishmaniasis is notified sporadically, while serologic evidence of leishmaniasis was found in 11.4% of the Croatian population. After the official eradication of malaria in 1964, only imported cases were reported in Croatia. Since vector-borne diseases show a growing trend, continuous monitoring of vectors is required to protect the population from these infections.
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Ghavami, Mohammad Bagher, Zohreh Alibabaei, Mohammad Reza Jamavar, and Behrooz Taghiloo. "Emergent spotted fever group Rickettsiae infections among hard ticks in Islamic Republic of Iran." Eastern Mediterranean Health Journal 30, no. 2 (2024): 145–55. http://dx.doi.org/10.26719/emhj.24.030.
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Background: Tick-borne rickettsioses have become a health concern worldwide following the increasing incidence in recent decades. However, there is limited information about these diseases in Islamic Republic of Iran. Aim: This cross-sectional study was conducted to estimate the Rickettsia infection among ixodid ticks collected from cattle, sheep and goats in Islamic Republic of Iran. Methods: The DNA of ixodid ticks collected from cattle, sheep and goats in 54 villages of Zanjan Province, Islamic Republic of Iran, were collected and analysed using a spectrophotometer. Rickettsial-positive samples were screened by targeting the htrA gene and fragments of gltA gene were analysed. The variables were analysed using descriptive statistics and the χ2 test was used to compare the variables. Results: A total of 528 ticks were tested. Overall, Rickettsia infection rate was 6.44%. Nine of the 12 tick species were infected. Rickettsial positive rates in Hyalomma marginatum and Dermacentor marginatus were 21.33% and 12.77%, respectively. R. aeschlimannii, the predominant rickettsia, was detected only in Hy. marginatum. R. raoultii, R. sibirica and R. slovaca comprised about half of the positive ticks and were recovered from more than one tick species. Conclusion: Considering the discovery of infected ticks in the Islamic Republic of Iran, there is a need to establish a tick control programme in the country, paying attention to populations at high-risk.
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Jordan, Jeffrey M., Michael E. Woods, Juan Olano, and David H. Walker. "The Absence of Toll-Like Receptor 4 Signaling in C3H/HeJ Mice Predisposes Them to Overwhelming Rickettsial Infection and Decreased Protective Th1 Responses." Infection and Immunity 76, no. 8 (2008): 3717–24. http://dx.doi.org/10.1128/iai.00311-08.
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ABSTRACT The importance of toll-like receptor 4 (TLR4) in immunity to rickettsiae remains elusive. To investigate the role of TLR4 in protection against rickettsioses, we utilized C3H/HeJ mice, which are naturally defective in TLR4 signaling, and compared the responses of C3H/HeN and C3H/HeJ mice following intravenous inoculation with Rickettsia conorii. Mice genetically defective in TLR4 signaling developed overwhelming, fatal rickettsial infections when given an inoculum that was nonfatal for TLR4-competent mice. In addition, mice lacking the ability to signal through TLR4 had significantly greater rickettsial burdens in vivo. Moreover, we observed greater concentrations of the cytokines interleukin 6 (IL-6), tumor necrosis factor alpha, IL-12p40, IL-12p70, and IL-17 in the sera of mice with intact TLR4 function as well as significantly greater quantities of activated CD4+ and CD8+ T lymphocytes. Additionally, we also observed that Th17 cells were present only in TLR4-competent mice, suggesting an important role for TLR4 ligation in the activation of this subset. In agreement with these data, we also observed significantly greater percentages of immunosuppressive regulatory T cells in the spleen during infection in TLR4-defective mice. Together, these data demonstrate that, while rickettsiae do not contain endotoxic lipopolysaccharide, they nevertheless initiate TLR4-specific immune responses, and these responses are important in protection.
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Zhu, Wen-Jie, Run-Ze Ye, Di Tian, et al. "The first direct detection of spotted fever group Rickettsia spp. diversity in ticks from Ningxia, northwestern China." PLOS Neglected Tropical Diseases 19, no. 1 (2025): e0012729. https://doi.org/10.1371/journal.pntd.0012729.
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Background Tick-borne infectious diseases caused by the spotted fever group Rickettsia (SFGR) have continuously emerging, with many previously unidentified SFGR species reported. The prevalence of SFGRs in northwestern China remains unclear. This study aimed to examine the prevalence of SFGRs and Anaplasma species by analyzing tick samples collected from the Ningxia region. Methods During 2022–2023, ticks were collected from Ningxia, northwestern China, and screened using PCR to amplify target genes (16S rRNA, gltA, ompA and groEL). The amplicons were confirmed by Sanger sequencing. Single-gene sequences and concatenated sequences were used to infer phylogenetic relationships for identifying Rickettsia species. Results Out of the 425 DNA samples, a total of 210 samples tested positive for SFGRs in ticks from Ningxia, China, with a relatively high positive rate of 49.4% (210/425). Eight spotted fever group rickettsiae and one Anaplasma species were identified and characterized, including Rickettsia raoultii (102, 24.0%), R. aeschlimannii (65, 15.3%), R. sibirica (12, 2.8%), R. slovaca (4, 0.9%), R. heilongjiangensis (1, 0.2%), Cadidatus Rickettsia hongyuanensis (4, 0.9%), Ca. R. jingxinensis (11, 2.6%), Ca. R. vulgarisii (11, 2.6%) and Anaplasma ovis (98, 23.1%). The positive rate of bacterial species ranged from 0.2% to 24.0%. Interestingly, one novel Rickettsia species, provisionally named “Candidatus Rickettsia vulgarisii”, was detected in Argas ticks from Zhongwei city, which suggests the possibility of local transmission to other areas through birds. Genetic and phylogenetic analysis based on the 16S rRNA, gltA, ompA, and 17kDa genes indicated that it was divergent from all known SFG Rickettsia species but mostly related to R. vini. Different SFGR species were associated with specific tick species or genera. In addition, Anaplasma ovis was detected in two Dermacentor species, and co-infection with SFGRs was observed in 14.6% (62/425) of samples. Conclusions This study describes the prevalence and diversity of SFGRs in ticks from Ningxia for the first time by direct detection, reveals that Rickettsia diversity related to tick species. This data suggests that surveillance for tick-borne SFGR infections among human populations should be enhanced in this region, and further investigations on their pathogenicity to humans and domestic animals are still needed.
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Feng, Hui-Min, and David H. Walker. "Mechanisms of Intracellular Killing of Rickettsia conorii in Infected Human Endothelial Cells, Hepatocytes, and Macrophages." Infection and Immunity 68, no. 12 (2000): 6729–36. http://dx.doi.org/10.1128/iai.68.12.6729-6736.2000.
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ABSTRACT The mechanism of killing of obligately intracellularRickettsia conorii within human target cells, mainly endothelium and, to a lesser extent, macrophages and hepatocytes, has not been determined. It has been a controversial issue as to whether or not human cells produce nitric oxide. AKN-1 cells (human hepatocytes) stimulated by gamma interferon, tumor necrosis factor alpha, interleukin 1β, and RANTES (regulated by activation, normal T-cell-expressed and -secreted chemokine) killed intracellular rickettsiae by a nitric oxide-dependent mechanism. Human umbilical vein endothelial cells (HUVECs), when stimulated with the same concentrations of cytokines and RANTES, differed in their capacity to kill rickettsiae by a nitric oxide-dependent mechanism and in the quantity of nitric oxide synthesized. Hydrogen peroxide-dependent intracellular killing of R. conorii was demonstrated in HUVECs, THP-1 cells (human macrophages), and human peripheral blood monocytes activated with the cytokines. Rickettsial killing in the human macrophage cell line was also mediated by a limitation of the availability of tryptophan in association with the expression of the tryptophan-degrading enzyme indoleamine-2,3-dioxygenase. The rates of survival of all of the cell types investigated under the conditions of activation and infection in these experiments indicated that death of the host cells was not the explanation for the control of rickettsial infection. This finding represents the first demonstration that activated human hepatocytes and, in some cases, endothelium can kill intracellular pathogens via nitric oxide and that RANTES plays a role in immunity to rickettsiae. Human cells are capable of controlling rickettsial infections intracellularly, the most relevant location in these infections, by one or a combination of three mechanisms involving nitric oxide synthesis, hydrogen peroxide production, and tryptophan degradation.
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Kordick, S. K., E. B. Breitschwerdt, B. C. Hegarty, et al. "Coinfection with Multiple Tick-Borne Pathogens in a Walker Hound Kennel in North Carolina." Journal of Clinical Microbiology 37, no. 8 (1999): 2631–38. http://dx.doi.org/10.1128/jcm.37.8.2631-2638.1999.
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Both dogs and humans can be coinfected with variousEhrlichia, Bartonella, Rickettsia, and Babesia species. We investigated a kennel of sick Walker Hounds and their owners in southeastern North Carolina for evidence of tick-borne infections and associated risk factors. A high degree of coinfection was documented in the dog population. Of the 27 dogs, 26 were seroreactive to an Ehrlichia sp., 16 toBabesia canis, and 25 to Bartonella vinsonii, and 22 seroconverted to Rickettsia rickettsii antigens. According to PCR results, 15 dogs were infected with Ehrlichia canis, 9 with Ehrlichia chaffeensis, 8 withEhrlichia ewingii, 3 with Ehrlichia equi, 9 with Ehrlichia platys, 20 with a Rickettsiaspecies, 16 with a Bartonella species, and 7 with B. canis. The detection of DNA from any Ehrlichiaspecies was associated with clinical illness and with concurrentB. canis infection (by PCR). Both E. canis and an uncharacterized Rickettsia species appeared to result in chronic or recurrent infection. Death in the dog population was associated with living in a dirt lot rather than the concrete kennel. Of 23 people on whom serologic testing was conducted, eight were seroreactive to Bartonella henselae, one to E. chaffeensis, and one to R. rickettsii antigen; however, none had clinical or hematologic abnormalities consistent with illness caused by these organisms. We conclude that kennel dogs with heavy tick exposure can be infected at a high rate with multiple, potentially zoonotic, tick-borne pathogens. In addition, our findings further illustrate the utility of PCR for documenting coinfection with tick-transmitted pathogens.
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Michalski, Mirosław M., Katarzyna Kubiak, Magdalena Szczotko, and Małgorzata Dmitryjuk. "Tick-Borne Pathogens in Ticks Collected from Wild Ungulates in North-Eastern Poland." Pathogens 10, no. 5 (2021): 587. http://dx.doi.org/10.3390/pathogens10050587.
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This study was carried out in north-eastern Poland during two hunting seasons between 2018 and 2020. Ticks (Ixodes ricinus and Dermacentor reticulatus) were removed from wild cervids and boars and examined for the presence of Borrelia spirochetes and Rickettsiales members: Rickettsia spp. and Anaplasma phagocytophilum. The present study contributes to the knowledge of even-toed ungulates, which are an important reservoir of the above-mentioned pathogens and a potential source of infections for humans through ticks as vectors. Almost 40% of the collected ticks (191 out of 484) were infected with the following pathogens: 3.3% with Borrelia spp., 19.2% with A. phagocytophilum and 26.9% with Rickettsia spp. Only the ticks collected from cervids carried Borrelia. Typing of the species DNA confirmed the presence of B. afzelii, B. garinii, B. lusitaniae and B. miyamotoi. An analysis of Rickettsia spp. sequences using the GenBank data revealed the presence of R. helvetica, R. raoultii and R. monacensis. Monoinfections (79.1%) dominated over co-infections (20.9%). Among co-infections, the most frequent was A. phagocytophilum/Rickettsia spp. (70%), however co-infections, including B. afzelii/A. phagocytophilum, B. afzelii/Rickettsia spp., B. miyamotoi/A. phagocytophilum and B. afzelii/B. garinii/B. lusitaniae, were also noted. Significant differences were observed in the affinity of some pathogens to their vectors. Thus, Borrelia spp. and A. phagocytophilum were more frequently detected in I. ricinus (5.3% and 23.1%) than in D. reticulatus (1.2% and 15.3%). Infection frequency with Rickettsia spp. was similar (approximately 25–29%) in both tick species. The prevalence of A. phagocytophilum and Rickettsia spp. in ticks removed from cervids was 19.8% and 27.1%, and in ticks from wild boars it was 13.3% and 24.4%, respectively.
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Baldridge, Gerald D., Nicole Y. Burkhardt, Jason A. Simser, Timothy J. Kurtti, and Ulrike G. Munderloh. "Sequence and Expression Analysis of the ompA Gene of Rickettsia peacockii, an Endosymbiont of the Rocky Mountain Wood Tick, Dermacentor andersoni." Applied and Environmental Microbiology 70, no. 11 (2004): 6628–36. http://dx.doi.org/10.1128/aem.70.11.6628-6636.2004.
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ABSTRACT The transmission dynamics of Rocky Mountain spotted fever in Montana appears to be regulated by Rickettsia peacockii, a tick symbiotic rickettsia that interferes with transmission of virulent Rickettsia rickettsii. To elucidate the molecular relationships between the two rickettsiae and glean information on how to possibly exploit this interference phenomenon, we studied a major rickettsial outer membrane protein gene, ompA, presumed to be involved in infection and pathogenesis of spotted fever group rickettsiae (SFGR) but which is not expressed in the symbiont. Based on PCR amplification and DNA sequence analysis of the SFGR ompA gene, we demonstrate that R. peacockii is the most closely related of all known SFGR to R. rickettsii. We show that R. peacockii, originally described as East Side agent in Dermacentor andersoni ticks from the east side of the Bitterroot Valley in Montana, is still present in that tick population as well as in D. andersoni ticks collected at two widely separated locations in Colorado. The ompA genes of R. peacockii from these locations share three identical premature stop codons and a weakened ribosome binding site consensus sequence relative to ompA of R. rickettsii. The R. peacockii ompA promoter closely resembles that of R. rickettsii and is functional based on reverse transcription-PCR results. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting showed that OmpA translation products were not detected in cultured tick cells infected with R. peacockii. Double immunolabeling studies revealed actin tail structures in tick cells infected with R. rickettsii strain Hlp#2 but not in cells infected with R. peacockii.
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Kim, Chul-Min, Ying-Hua Yi, Do-Hyeon Yu, et al. "Tick-Borne Rickettsial Pathogens in Ticks and Small Mammals in Korea." Applied and Environmental Microbiology 72, no. 9 (2006): 5766–76. http://dx.doi.org/10.1128/aem.00431-06.
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ABSTRACT In order to investigate the prevalence of tick-borne infectious agents among ticks, ticks comprising five species from two genera (Hemaphysalis spp. and Ixodes spp.) were screened using molecular techniques. Ticks (3,135) were collected from small wild-caught mammals or by dragging/flagging in the Republic of Korea (ROK) and were pooled into a total of 1,638 samples (1 to 27 ticks per pool). From the 1,638 tick samples, species-specific fragments of Anaplasma phagocytophilum (1 sample), Anaplasma platys (52 samples), Ehrlichia chaffeensis (29 samples), Ehrlichia ewingii (2 samples), Ehrlichia canis (18 samples), and Rickettsia rickettsii (28 samples) were amplified by PCR assay. Twenty-one pooled and individual tick samples had mixed infections of two (15 samples) or three (6 samples) pathogens. In addition, 424 spleen samples from small captured mammals (389 rodents, 33 insectivores, and 2 weasels) were screened for selected zoonotic pathogens. Species-specific DNA fragments of A. phagocytophilum (110 samples), A. platys (68 samples), E. chaffeensis (8 samples), E. ewingii (26 samples), E. canis (51 samples), and Rickettsia sp. (22 samples) were amplified by PCR assay. One hundred thirty small mammals had single infections, while 4, 14, and 21 striped field mice (Apodemus agrarius) had mixed infections of four, three, and two pathogens, respectively. Phylogenetic analysis based on nucleotide sequence comparison also revealed that Korean strains of E. chaffeensis clustered closely with those from China and the United States, while the Rickettsia (rOmpA) sequences clustered within a clade together with a Chinese strain. These results suggest that these agents should be considered in differential diagnosis while examining cases of acute febrile illnesses in humans as well as animals in the ROK.
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Pacheco, Filipe Corrêa, Jonas Moraes Filho, Vlamir José Rocha, et al. "Anti-Rickettsia rickettsii antibodies in capybaras (Hydrochoerus hydrochaeris Linnaeus, 1766) from an agricultural landscape in Araras, São Paulo, Brazil." Semina: Ciências Agrárias 38, no. 4Supl1 (2017): 2543. http://dx.doi.org/10.5433/1679-0359.2017v38n4supl1p2543.
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Spotted fever is a typically endemic infectious disease caused by rickettsiae from the spotted fever group, of which Rickettsia rickettsii is the main etiologic agent. It presents high mortality rates in Brazil, with transmission to humans or animals through the bite of infected ticks. The capybara (Hydrochoerus hydrochaeris) is an important reservoir for Rickettsia spp.; these bacteria can circulate in an infected animal presenting only fever as a clinical sign of the disease, as demonstrated by experimental infection. Considering the high zoonotic potential and the damage caused to human, animal, and environmental health, this study searched for anti-Rickettsia rickettsii antibodies in capybaras from an agricultural landscape in the city of Araras, State of São Paulo, Brazil. The indirect immunofluorescence (IFA) technique was used to detect anti-R. rickettsii antibodies. From the 28 serum samples tested using IFA, 18 (64.28%) were considered reactive, with antibody titers ranging from 256 to 2048. Seven (38.88%) samples presented titers of 256, three (16.67%) with titers of 512, five (27.78%) with titers of 1024, and three (16.67%) with titers of 2048. However, it was not possible to significantly associate gender to these serologic results. These results demonstrate that at some point during their lives, the studied capybaras were exposed to the etiologic agent, but it is impossible to know when this occurred. Further studies need to be performed to clarify which serological titers ensure an infection in capybaras, based on clinical and laboratory assessment of rickettsemia, and to establish the relationship between titers and the chronicity of disease. This is necessary owing to the possibility of cross-reactions with other rickettsiae species of the same subgroup, leading to the need for molecular tests to confirm diagnosis.
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Pacheco, Filipe Corrêa, Jonas Moraes Filho, Vlamir José Rocha, et al. "Anti-Rickettsia rickettsii antibodies in capybaras (Hydrochoerus hydrochaeris Linnaeus, 1766) from an agricultural landscape in Araras, São Paulo, Brazil." Semina: Ciências Agrárias 38, no. 4Supl1 (2017): 2543. http://dx.doi.org/10.5433/1679-0359.2017v38n4suplp2543.
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Spotted fever is a typically endemic infectious disease caused by rickettsiae from the spotted fever group, of which Rickettsia rickettsii is the main etiologic agent. It presents high mortality rates in Brazil, with transmission to humans or animals through the bite of infected ticks. The capybara (Hydrochoerus hydrochaeris) is an important reservoir for Rickettsia spp.; these bacteria can circulate in an infected animal presenting only fever as a clinical sign of the disease, as demonstrated by experimental infection. Considering the high zoonotic potential and the damage caused to human, animal, and environmental health, this study searched for anti-Rickettsia rickettsii antibodies in capybaras from an agricultural landscape in the city of Araras, State of São Paulo, Brazil. The indirect immunofluorescence (IFA) technique was used to detect anti-R. rickettsii antibodies. From the 28 serum samples tested using IFA, 18 (64.28%) were considered reactive, with antibody titers ranging from 256 to 2048. Seven (38.88%) samples presented titers of 256, three (16.67%) with titers of 512, five (27.78%) with titers of 1024, and three (16.67%) with titers of 2048. However, it was not possible to significantly associate gender to these serologic results. These results demonstrate that at some point during their lives, the studied capybaras were exposed to the etiologic agent, but it is impossible to know when this occurred. Further studies need to be performed to clarify which serological titers ensure an infection in capybaras, based on clinical and laboratory assessment of rickettsemia, and to establish the relationship between titers and the chronicity of disease. This is necessary owing to the possibility of cross-reactions with other rickettsiae species of the same subgroup, leading to the need for molecular tests to confirm diagnosis.
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Breitschwerdt, E. B., M. G. Papich, B. C. Hegarty, B. Gilger, S. I. Hancock, and M. G. Davidson. "Efficacy of Doxycycline, Azithromycin, or Trovafloxacin for Treatment of Experimental Rocky Mountain Spotted Fever in Dogs." Antimicrobial Agents and Chemotherapy 43, no. 4 (1999): 813–21. http://dx.doi.org/10.1128/aac.43.4.813.
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ABSTRACT Dogs were experimentally inoculated with Rickettsia rickettsii (canine origin) in order to compare the efficacies of azithromycin and trovafloxacin to that of the current antibiotic standard, doxycycline, for the treatment of Rocky Mountain spotted fever. Clinicopathologic parameters, isolation of rickettsiae in tissue culture, and PCR amplification of rickettsial DNA were used to evaluate the response to therapy or duration of illness (untreated infection control group) in the four groups. Concentrations of the three antibiotics in plasma and blood cells were measured by high-performance liquid chromatography. Doxycycline and trovafloxacin treatments resulted in more-rapid defervescence, whereas all three antibiotics caused rapid improvement in attitudinal scores, blood platelet numbers, and the albumin/total-protein ratio. Based upon detection of retinal vascular lesions by fluorescein angiography, trovafloxacin and doxycycline substantially decreased rickettsia-induced vascular injury to the eye, whereas the number of ocular lesions in the azithromycin group did not differ from that in the infection control group. As assessed by tissue culture isolation, doxycycline resulted in the earliest apparent clearance of viable circulating rickettsiae; however, rickettsial DNA could still be detected in the blood of some dogs from all four groups on day 21 postinfection, despite our inability to isolate viable rickettsiae at that point. As administered in this study, trovafloxacin was as efficacious as doxycycline but azithromycin proved less efficacious, possibly due to the short duration of administration.
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Silva, Kamila Alves, Vanesa Borges do Prado, Rafael Rodrigues Silva, et al. "A Mini-Review of Diagnostic Methods for the Antigen and Antibody Detection of Rocky Mountain and Brazilian Spotted Fever." Biomedicines 12, no. 7 (2024): 1501. http://dx.doi.org/10.3390/biomedicines12071501.
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Rocky Mountain or Brazilian spotted fever, caused by Rickettsia rickettsii, is a fulminant, seasonal, and neglected disease that occurs in focal points of North America and South America. Its rapid detection is essential for the better prognosis and survival rate of infected individuals. However, disease diagnosis still faces challenges as the accuracy of many of the available laboratory tests fluctuates. This review aimed to analyze methods for antibody or antigen detection, their gaps, and their evolution over time. A search was conducted to find all studies in the Pubmed database that described the antibody or antigen detection of R. rickettsii infections. Initially, a total of 403 articles were screened. Of these articles, only 17 fulfilled the pre-established inclusion criteria and were selected. Among the different methods applied, the IFA technique was the one most frequently found in the studies. However, it presented varied results such as a low specificity when using the indirect method. Other techniques, such as ELISA and immunohistochemistry, were also found, although in smaller numbers and with their own limitations. Although some studies showed promising results, there is a pressing need to find new techniques to develop a rapid and effective diagnosis of R. rickettssi infection.
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Panferova, Yu A., M. A. Suvorova, A. O. Shapar, and N. K. Tokarevich. "BACTERIAL AND VIRAL PATHOGENS IN IXODES SP. TICKS IN ST. PETERSBURG AND LENINGRAD DISTRICT." Russian Journal of Infection and Immunity 8, no. 2 (2018): 219–22. http://dx.doi.org/10.15789/2220-7619-2018-2-219-222.
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Tick-borne infections are the most common group of zooanthroponotic diseases in the Northern Hemisphere. For the Baltic Sea region and Fennoscandia, the dominant infectious pathologies transmitted by ticks are tick-borne borreliosis and tick- borne encephalitis. The presence of vast forested areas, actively visited by people in St. Petersburg and the Leningrad region, contributes to a rather high level of encroachment on the flares and intelligence of the borreliosis and tick-borne encephalitis among the population of these regions. The relatively dangerous pathogens that can be transmitted with the tick bite are also of particular danger: Anaplasma sp., Ehrlichia sp., Coxiella burnetii, Rickettsia sp. In this work, detection was performed using molecular genetic methods of TBE virus, B. burgdorferi sensu lato and Rickettsia sp. in engorged ticksple, as well as questing ticks collected from vegetation. The established levels of infection of TBE on infected ticks, levels of infection by pathogenic Borrelia of questing and engorgeded ticks were approximately equal. Rickettsia was not found in the ticks. The conducted analysis of the pathogens prevalence in comparison with the data of russian and foreign authors. Monitoring the prevalence of tick-borne pathogens is an important issue in the prevention of tick- borne infections in the North-Western Russia.
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Giulieri, Stefano, Katia Jaton, Alain Cometta, Laurence T. Trellu, and Gilbert Greub. "Development of a duplex real-time PCR for the detection of Rickettsia spp. and typhus group rickettsia in clinical samples." Fems Immunology and Medical Microbiology 64, no. 1 (2011): 92–97. https://doi.org/10.1111/j.1574-695X.2011.00910.x.
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Molecular diagnosis using real-time polymerase chain reaction (PCR) may allow earlier diagnosis of rickettsiosis. We developed a duplex real-time PCR that amplifies (1) DNA of any rickettsial species and (2) DNA of both typhus group rickettsia, that is, Rickettsia prowazekii and Rickettsia typhi. Primers and probes were selected to amplify a segment of the 16S rRNA gene of Rickettsia spp. for the pan-rickettsial PCR and the citrate synthase gene (gltA) for the typhus group rickettsia PCR. Analytical sensitivity was 10 copies of control plasmid DNA per reaction. No cross-amplification was observed when testing human DNA and 22 pathogens or skin commensals. Real-time PCR was applied to 16 clinical samples. Rickettsial DNA was detected in the skin biopsies of three patients. In one patient with severe murine typhus, the typhus group PCR was positive in a skin biopsy from a petechial lesion and seroconversion was later documented. The two other patients with negative typhus group PCR suffered from Mediterranean and African spotted fever, respectively; in both cases, skin biopsy was performed on the eschar. Our duplex real-time PCR showed a good analytical sensitivity and specificity, allowing early diagnosis of rickettsiosis among three patients, and recognition of typhus in one of them.
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Liu, Ya-Ting, Yi-Fei Wang, Ming-Zhu Zhang, et al. "High Diversity and Prevalence of Rickettsial Agents in Rhipicephalus microplus Ticks from Livestock in Karst Landscapes of Southwest China." Microorganisms 13, no. 4 (2025): 765. https://doi.org/10.3390/microorganisms13040765.
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Ticks and tick-borne pathogens pose a significant threat to human and animal health, yet the diversity and prevalence of tick-borne microorganisms in karst regions remains inadequately explored. In October 2023, a total of 274 Rhipicephalus microplus ticks were collected from livestock in Guizhou Province, which boasts the largest karst area in China. Pathogen identification was subsequently performed using PCR amplification, Sanger sequencing, and phylogenetic analysis. High microbial diversity was noted, with five bacterial species from the order Rickettsiales detected, including those from the genera Rickettsia (family Rickettsiaceae), Anaplasma, and Ehrlichia (family Anaplasmataceae). The overall prevalence of infection with at least one pathogen was remarkably high at 94.5%. The highest positive rate was observed for Candidatus Rickettsia jingxinensis at 90.9%. A novel Ehrlichia species, provisionally designated as Candidatus Ehrlichia carsus, was identified with a positive rate of 16.8%. In addition, Anaplasma marginale, Ehrlchia minasensis and Ehrlichia canis were detected in 15.3%, 4.7% and 1.5%, respectively. The co-infections involving two or three rickettsial species were observed in 34.3% ticks. These findings highlight the high diversity and prevalence of tick-borne rickettsial agents in the karst area, underscoring the need for enhanced surveillance and effective tick control to mitigate disease risks to both humans and livestock.
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Mendes, Juliana Cristina Rebonato, Louise Bach Kmetiuk, Camila Marinelli Martins, et al. "Serosurvey of Rickettsia spp. in cats from a Brazilian spotted fever-endemic area." Revista Brasileira de Parasitologia Veterinária 28, no. 4 (2019): 713–21. http://dx.doi.org/10.1590/s1984-29612019092.
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Abstract Rickettsia spp. bacteria are responsible for tick-borne diseases worldwide, mostly maintained by rickettsial amplifiers capybaras in Brazilian endemic areas. The campus of the University of São Paulo, in southeastern Brazil, is an area endemic for Brazilian spotted fever (BSF), with high density of capybaras and Amblyomma spp., along with confirmed human cases. Besides capybaras, the university has also an in-campus high population of sheltered and free-roaming cats. Accordingly, the aim of this study was to determine the prevalence and characteristics associated with Rickettsia rickettsii, Rickettsia parkeri and Rickettsia felis exposure among cats in a BSF-endemic area. Out of 51 cats sampled, 23/35 shelter (65.7%) and 5/16 free-roaming (31.2%) were positive (titers ≥ 64) for at least one Rickettsia species. Ticks species were present in 3/16 free-roaming cats (18.8%), consisting of Amblyomma spp., nymphs of Amblyomma sculptum and adult Rhipicephalus sanguineus sensu lato. Despite sharing the capybaras environment, the seropositivity among the free-roaming and shelter cats was lower than owned cats in other endemic areas. Whether equally or less exposed to rickettsial infection, compared with owned cats in endemic areas, free-roaming and shelter cats may be used as environmental sentinels for human exposure to rickettsiae in such areas.
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Schjørring, Susanne, Martin Tugwell Jepsen, Camilla Adler Sørensen, et al. "Laboratory Diagnostics of Rickettsia Infections in Denmark 2008–2015." Biology 9, no. 6 (2020): 133. http://dx.doi.org/10.3390/biology9060133.
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Rickettsiosis is a vector-borne disease caused by bacterial species in the genus Rickettsia. Ticks in Scandinavia are reported to be infected with Rickettsia, yet only a few Scandinavian human cases are described, and rickettsiosis is poorly understood. The aim of this study was to determine the prevalence of rickettsiosis in Denmark based on laboratory findings. We found that in the Danish individuals who tested positive for Rickettsia by serology, the majority (86%; 484/561) of the infections belonged to the spotted fever group. In contrast, we could confirm 13 of 41 (32%) PCR-positive individuals by sequencing and identified all of these as R. africae, indicating infections after travel exposure. These 13 samples were collected from wound/skin material. In Denmark, approximately 85 individuals test positive for Rickettsia spp. annually, giving an estimated 26% (561/2147) annual prevalence among those suspected of rickettsiosis after tick bites. However, without clinical data and a history of travel exposure, a true estimation of rickettsiosis acquired endemically by tick bites cannot be made. Therefore, we recommend that both clinical data and specific travel exposure be included in a surveillance system of Rickettsia infections.