Literatura académica sobre el tema "Rickettsia infections"
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Artículos de revistas sobre el tema "Rickettsia infections"
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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.
Tesis sobre el tema "Rickettsia infections"
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Angerami, Rodrigo Nogueira. "Febre maculosa brasileira no estado de São Paulo = aspectos clínicos e epidemiológicos." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/310588.
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Orientadores: Luiz Jacintho da Silva, Raquel Silveira Bello Stucchi<br>Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas<br>Made available in DSpace on 2018-08-18T15:04:22Z (GMT). No. of bitstreams: 1
Angerami_RodrigoNogueira_D.pdf: 7670692 bytes, checksum: f6634d52b90eaf383ed11a180b9179aa (MD5)
Previous issue date: 2011<br>Resumo: Causada pela bactéria Rickettsia rickettsii e transmitida pelos carrapatos Amblyomma cajennense e Amblyomma aureolatum, a febre maculosa brasileira (FMB), após décadas de aparente silêncio epidemiológico, desde sua reemergência nos anos 80, vem figurando como importante problema de saúde pública no estado de São Paulo, sobretudo, em decorrência da aparente expansão das áreas de transmissão e da elevada letalidade a ela associada. O objetivo principal do presente estudo foi descrever características clínicas e epidemiológicas da FMB a partir da análise retrospectiva de casos confirmados da doença em áreas endêmicas no estado de São Paulo. Foi observado que manifestações inespecíficas como febre, cefaléia, mialgia e exantema, foram os sinais clínicos mais freqüentes e precoces. Embora variáveis, elevadas frequências de fenômenos hemorrágicos (22,9%-77,6%), icterícia (16,7%-52%), alterações neurológicas (27,2%-51,7%) e insuficiência respiratória (17,5%-62%) foram observadas. A taxa de letalidade média no estado de São Paulo no período de 2003 a 2008 foi de 29,6%(21,9%-40%). Trombocitopenia e elevação de transaminases hepáticas foram as alterações laboratoriais mais frequentes, ocorrendo em até 100% dos casos. Na faixa etária pediátrica, a FMB também se apresentou como doença severa, associando-se, embora em menor freqüência, às complicações acima mencionadas e à elevada letalidade (28,4%). Entretanto, em estudo comparativo entre o perfil clínico da FMB nos estados de São Paulo e Santa Catarina, observou-se no estado do Sul uma doença com evolução benigna, pequena frequência de sinais de gravidade e ausência de óbitos. Entre pacientes com FMB, as síndromes febris hemorrágica, icterohemorrágica e exantemática foram as mais comumente observadas (37,1%, 33,9%, 11,3%, respectivamente). Dentre os principais diagnósticos diferenciais da FMB, leptospirose, dengue e doença meningocócica foram as mais prevalentes (28,5%, 17,2%, 5,4%, respectivamente). Em 31% dos casos descartados para FMB não foi possível a identificação do diagnóstico etiológico. A doença foi mais incidente no gênero masculino e entre indivíduos da faixa etária de 20 a 49 anos. Em áreas em que o A. cajennense é o principal vetor foi possível observar maior incidência da doença entre o período de Junho a Setembro. Surtos de FMB se associaram a elevadas taxas de letalidade e a diferentes determinantes ecoepidemiológicos. Atividades de lazer e ocupacionais em áreas de mata, pastagem, próximas a coleções hídricas e/ou com presença de animais (cavalos, capivaras e, eventualmente, cães) foram consideradas importantes exposições de risco para infecção. O presente estudo permitiu observar que a infecção pela R. rickettsii no estado de São Paulo se associa à elevada morbimortalidade, sendo, aparentemente, mais severa que a febre das Montanhas Rochosas nos Estados Unidos. Exantema, icterícia e hemorragias são importantes marcadores clínicos que devem ser considerados na suspeição da doença e seus diagnósticos diferencias. O conhecimento das características epidemiológicas e dos fatores de risco para infecção deve fundamentar as ações de prevenção e controle da FMB. A maior severidade da infecção pela R. rickettsii no estado de São Paulo, a ocorrência de casos atípicos em Santa Catarina e a ausência de elucidação diagnóstica em casos descartados para FMB sugerem que cepas de R. rickettsii com distintos padrões de virulência, bem como outras espécies de riquétsias e, eventualmente, outros microorganismos transmitidos por carrapatos devam estar ocorrendo no Brasil<br>Abstract: Brazilian spotted fever (BSF) is caused by Rickettsia rickettsii and transmited by Amblyomma cajennense and Amblyomma aureolatum ticks. After decades of an apparent epidemiological silence, BSF reemerged as an important public health problem in São Paulo State in the 1980's, mostly because the possible expansion of its transmission areas and the high BSF related fatality-rate. The main objective of the present study was to describe clinical and epidemiological features of BSF through a retrospective analysis of BSF confirmed cases in endemic areas. Non-specific clinical signs like fever, myalgia, headache, and exanthema were the earliest and most frequent clinical signs. A high frequency of hemorrhagic manifestations (22.9%-77.6%), icterus (16.7%-52%), neurological signs (27.2%-51.7%), and respiratory distress (17.5%-62%) was also observed. Case-fatality ratio in São Paulo State between 2003 and 2008 was 29.6% (21.9%-40%). Thrombocytopenia and elevated liver enzymes were the most frequent laboratorial abnormalities, reaching 100% in some groups. In the pediatric age-group, BSF also presented as a severe disease with a slightly lower rate of clinical complications, but a similar high lethality rate (28.4%). Interestingly, when we compared the clinical profile of BSF cases between São Paulo state and Santa Catarina state, located in the southernmost part of Brazil, a milder disease, with a lower frequency of clinical signs of severity and no fatalities was observed in the latter. The most frequent clinical syndromes occurring in BSF patients were hemorrhagic, ictero-hemorrhagic, and exanthematic acute febrile syndromes (37.1%, 33.9% and 11.3% respectively). The most important differential diagnosis to BSF was leptospirosis, dengue fever, and meningococcal disease (28.5%, 17.2%, and 5.4%, respectively). In 31% of non-confirmed BSF cases, no etiological diagnosis was defined. A higher incidence of BSF was observed in males and in the 20-49 years age-group. In areas where A. cajennense is recognized as the most important vector, a higher BSF incidence was observed from June to September. Clusters of BSF were associated to elevated fatality rates and a wide number of ecoepidemiological determinants. Recreational and occupational activities in rural, periurban, and waterside areas, with presence of animals (mostly horses and capybaras, and eventually dogs) were considered the most important exposure risk factors to infection. The present study suggests a more severe pattern of R. rickettsii in São Paulo state when compared with Rocky Mountain spotted fever in United States. Exanthema, icterus, and hemorrhage are important clinical markers of BSF and should be considered in the suspicion of this disease and as a differential diagnosis. Knowledge of clinical, epidemiological, and risk factors for infection should be used to structure and improve the measures for control and prevention of BSF. Together, the higher severity of R. rickettsii infection in São Paulo state, the occurrence of atypical cases in Santa Catarina, and the unknown etiological diagnosis of a high percentage of post-tick exposure febrile patients suggest that more virulent R. rickettsii strains, other Rickttsiae species and, eventually, other tick-borne diseases could be occurring in Brazil<br>Doutorado<br>Clinica Medica<br>Doutor em Clínica Médica
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Lindblom, Anders. "Spotted Fever Rickettsioses in Sweden : Aspects of Epidemiology, Clinical Manifestations and Co-infections." Doctoral thesis, Uppsala universitet, Klinisk mikrobiologi och infektionsmedicin, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-302137.
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The spotted fever group rickettsiae are emerging diseases. They cause damage in their hosts by invading the endothelium in small to medium-sized blood vessels, which results in vasculitis that can cause clinical manifestations from most organs. The present thesis describes the prevalence of Rickettsia helvetica in ticks, the incidence of rickettsial infection based on seroreactivity and seroconversion in humans and their symptoms, from different parts of Sweden and the Åland Islands in Finland. This was accomplished through serological analysis of both retrospective and prospective serum samples from confirmed and suspected tick-bitten individuals compared to individuals with no knowledge of tick exposure (blood donors). We found a comparable seroprevalence to Rickettsia spp. in different geographical areas where ticks are present; it was also comparable to the seroprevalence of Borrelia spp. Seroprevalence was also more common, as suspected, in the tick-exposed group compared to blood donors. In comparison with co-infections with other tick-borne infections (Anaplasma spp. and Borrelia spp.), we could conclude that co-infections do exist and that, based on clinical findings, it is difficult to distinguish which microorganism causes certain clinical manifestations. For reliable conclusions regarding the causative microorganism, the diagnosis should basically rely on diagnostic tests. In comparison with Borrelia spp., seroconversion to Rickettisa spp. was more common in the areas we investigated, indicating that rickettsiosis is a common tick-borne infection in Sweden and most likely underdiagnosed. When investigating patients with meningitis, we found R. felis in cerebrospinal fluid from two patients with subacute meningitis. This was the first report in which R. felis was found and diagnosed in patients in Sweden. The patients recovered without sequelae and without causal treatment. To provide guidelines on when to treat Rickettisa spp. infections, more investigations are needed. The present thesis shows that Rickettsia spp. are common in ticks and do infect humans. Rickettsial infection should be considered in both non-specific or specific symptoms after a tick bite. It was also shown in the thesis that flea-borne rickettsiosis (R. felis) occurs in Sweden and may cause invasive infections
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Dong, Xin. "Comparative genomics of rickettsia species." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM5054/document.
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Le genre Rickettsia, sont des petites bactéries Gram-négatives et symbiotes intracellulaires obligatoires des eucaryotes. Les Rickettsia sont surtout connus pour leur pathogénicité et pour provoquer des maladies graves chez l'homme et les autres animaux. À ce jour, 26 espèces valides de Rickettsies ont été identifiées dans le monde entier, dont 20 sont des agents pathogènes éprouvées. Toutes les espèces de Rickettsies validées sont associées à des arthropodes. Les phylogénies basées sur divers marqueurs moléculaires ont présenté des topologies discordantes, avec seulement R. bellii et R. canadensis qui ne sont classées ni parmi la fièvre boutonneuse groupe rickettsies, ni parmi le typhus groupe rickettsies. En utilisant les méthodes avancées de séquençage de génomes entiers, nous avons obtenu et analysé quatre séquences génomiques de Rickettsies : R. helvetica, R. honei, R. australis et R. japonica. Via la phylogénomique qui constitue une nouvelle stratégie permettant de mieux comprendre leur évolution, l'on remarque que ces micro-organismes ont subi une évolution génomique réduite au cours de spécialisation en intracellulaire. Plusieurs caractéristiques évolutives, comme le réarrangement des gènes, la réduction génomique, le transfert horizontal de gènes et l'acquisition d'ADN égoïste, ont formé les génomes Rickettsia d'aujourd'hui. Ces processus peuvent jouer un rôle important pour équilibrer la taille du génome afin de l'adapter au mode de vie intracellulaire. En outre, la pathogénicité des rickettsies peut être associée à la réduction génomique<br>The Rickettsia genus is composed of small, Gram-negative, bacteria that are obligate intracellular eukaryotic symbionts. Members of the genus Rickettsia are best known for infecting and causing severe diseases in humans and other animals. To date, 26 valid Rickettsia species have been identified worldwide, including 20 that are proven pathogens. All validated Rickettsia species are associated to arthropods that act as vectors and/or reservoirs. The phylogenies based on various molecular markers have resulted in discrepant topologies, with R. bellii and R. canadensis being classified neither among spotted fever nor typhus group rickettsiae. In this thesis, using the advanced whole genomic sequencing methods, we have and analyzed the genomic sequences from four Rickettsia species, including R. helvetica, R. honei, R. australis and R. japonica. Phylogenomics constitute a new strategy to better understand their evolution. These microorganisms underwent a reductive genomic evolution during their specialization to their intracellular lifestyle. Several evolutive characteristics, such as gene rearrangement, reduction, horizontal gene transfer and aquisition of selfish DNA, have shaped Rickettsia genomes. These processes may play an important role in free-living bacteria for balancing the size of genome in order to adapt the intracellular life style. In addition, in contrast with the concept of bacteria becoming pathogens by acquisition of virulence factors, rickettsial pathogenecity may be linked to genomic reduction of metabolism and regulation pathways
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Wallménius, Katarina. "Studies of Spotted Fever Rickettsia - Distribution, Detection, Diagnosis and Clinical Context : With a Focus on Vectors and Patients in Sweden." Doctoral thesis, Uppsala universitet, Institutionen för medicinska vetenskaper, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-280667.
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The spotted fever rickettsia, Rickettsia helvetica, is an endemic tick-borne bacteria in Sweden. It causes infections in humans, manifested as aneruptive fever, headache, arthralgia and myalgia, and sometimes an inoculation eschar or a rash. There have also been two known cases of human infections with R. felis in Sweden. The present thesis starts by investigating dispersal of ticks and Rickettsia spp. by migrating birds flying from Africa to Europe. Almost 15,000 birds were searched and 734 ticks collected, mainly of the species Hyalomma marginatum complex. Almost half (48%) of the ticks were infected with Rickettsia spp., 96% of which was R. aeschlimannii, the remaining R. africae and undefined species. The next study focused on questing ticks over a large area in Sweden and determining the prevalence of Rickettsia spp., Anaplasma spp. and Coxiella burnetii. Rickettsia spp. was found in 9.5-9.6% of the ticks and A. phagocytophilum in 0.7%; no C. burnetii was found. The last three papers in the thesis focused on the clinical presentation of rickettsiosis, the symptoms associated with the infection in general and particularly in patients with neurological complications. A tick-exposed population in Sweden was investigated to gain a better understanding of symptoms due to rickettsioses, also in relation to co-infections with other tick-borne bacteria. Based on symptoms, it was not possible to distinguish what pathogen caused the infections. Most patients had erythema migrans, some had serological reactions to Rickettsia spp., Borrelia spp. or co-infections by Rickettsia spp., Borrelia spp. and/or Anaplasma spp. In the fourth and fifth papers, we found associations between antibodies against Rickettsia spp. and sudden deafness (in 10-24% of patients) and facial nerve paralysis (in 8.3-25% of patients). In three patients R. felis was detected in the cerebrospinal fluids. Briefly, the thesis helps to clarify our knowledge about tick dispersal, shows a narrower prevalence estimate of Rickettsia spp. in Swedish ticks, and illuminates symptoms of rickettsioses and co-infections with other tick-borne infections. It also shows that presence of erythema migrans may be explained by more than Lyme disease and indicates a possible association between rickettsiosis and sudden deafness and facial nerve paralysis.
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Bechah, Yassina. "Typhus épidémique : mise au point d'un modèle murin." Aix-Marseille 2, 2007. http://www.theses.fr/2007AIX20672.
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Le typhus épidémique, une maladie infectieuse ré-émergente due à Rickettsia prowazekii, est transmis à l'homme par le pou de corps humain. L’infection peut demeurer sous forme latente chez l’homme pendant des années. Sa réactivation, à la suite d’un stress par exemple, déclenche une forme modérée de typhus épidémique, la maladie de Brill-Zinsser, qui peut être source de nouvelles épidémies en présence de poux. R. Prowazekii, un agent potentiel de bioterrorisme, est une bactérie intracellulaire qui infecte l'endothélium vasculaire, ce qui conduit à une vascularite et des lésions inflammatoires constituées d'infiltrats de leucocytes mononucléés. La pathogénèse de l'infection à R. Prowazekii est mal connue, en partie par manque de modèles animaux adéquats. L'objectif de ma thèse a été de mettre au point un modèle murin d’infection à R. Prowazekii et d'étudier certains aspects de la physiopathologie de cette infection. J’ai montré que l’infection des souris dépend de leur fond génétique. Les souris BALB/c miment par bien des aspects l’infection humaine: sont ainsi trouvés, chez les souris infectées, des pneumonies avec consolidation des alvéoles, des hémorragies au niveau pulmonaire et cérébral, de multiples granulomes hépatiques. L’infection des souris BALB/c est associée à une réponse inflammatoire au sein des tissus atteints, comme l’illustre l’augmentation de l'expression de cytokines inflammatoires telles que l’IFN-γ, le TNF et RANTES. J’ai également réussi à réactiver l'infection à R. Prowazekii chez les souris BALB/c soumises à une corticothérapie, ce qui conforte notre modèle expérimental de typhus épidémique et offre, de surcroît, le premier modèle de maladie de Brill-Zinsser. J’ai enfin posé quelques jalons dans l’étude de la pathogénèse de l’infection à R. Prowazekii. L’infection des cellules endothéliales par des bactéries virulentes augmente la migration transendothéliale des leucocytes, alors que les bactéries atténuées n'ont pas d'effet. Ce phénomène de migration transendotheliale implique la production de cytokines inflammatoires par les cellules endothéliales infectées, ce qui rend inflammatoires les leucocytes ayant transmigré. Le profil inflammatoire induit par R. Prowazekii participe probablement aux lésions caractéristiques du typhus épidémique.
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Dearth, Stephanie M. "Detection and quantification of Rickettsia amblyommii, Ehrlichia chaffeensis, and Borrelia lonestari in adult Amblyomma americanum ticks from southern Indiana." Virtual Press, 2007. http://liblink.bsu.edu/uhtbin/catkey/1380098.
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Amblyomma americanum is a hard tick species found in southern Indiana. Once a notorious pest to humans and livestock, A. americanum has now taken on a role as vector to pathogenic organisms. This study aimed to detect and quantify three microbes in A. americanum: Rickettsia amblyommii, Ehrlichia chaffeensis, and Borrelia lonestari. A primary objective of this study was to determine microbial interaction within a single A. americanum tick through quantification of each microbe within a co-infected tick. A second objective was to determine the density of R. amblyommii within the salivary glands of A. americanum ticks. Infection rates were 44%, 1%, and 0% for R. amblyommii, E. chaffeensis, and B. lonestari respectively. This study found no co-infected ticks, therefore no microbial interaction was determined. This study also found multiple drawbacks with utilizing quantitative real-time PCR to determine the density of R. amblyommii within the salivary glands of A. americanum ticks.<br>Department of Biology
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Jönsson, Johanna. "Identification of the tick-borne pathogens Anaplasma phagocytophilum, Neoehrlichia mikurensis and Rickettsia in Swedish ticks : Investigation of transovarial transmission and co-infection." Thesis, Linnéuniversitetet, Institutionen för kemi och biomedicin (KOB), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-53366.
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Globally, vector borne diseases cause more than a million deaths each year and more than a billion infections in humans. Ticks are of big medicinal importance since they can transmit pathogens that can cause serious infections. Some recently discovered pathogens that can cause infections in humans are Anaplasma phagocytophilum (A. phagocytophilum) that can cause human granulocytic anaplasmosis (HGA) and Candidatus Neoehrlichia mikurensis (N. mikurensis) that can cause Neoehrlichiosis. It is still widely unknown how prevalent these pathogens are, if ticks can be infected with both of these pathogens and if these pathogens can be transovarially transmitted from adult female to egg and larvae. This study aims to screen for these pathogens in collected ticks from southern Sweden and to detect eventual co-infections and transovarial transmission. A real-time qPCR assay targeting the 16S rRNA gene of N. mikurensis and other Anaplasmataceae was applied on 1356 Ixodes ricinus (I. ricinus) ticks collected from 5 sites in southern Sweden. Positive samples were subjected to Sanger sequencing. A. phagocytophilum occurred in 4.64 % of the ticks, N. mikurensis occurred in 1.33 % of the ticks and also Rickettsia was found to occur in 6.27 % of the ticks. No co-infection was detected. Some samples of tick larvae showed positive results after qPCR, indicating transovarial transmission, but none of the sequences were readable.
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Hebert, Kathryn S. "Investigation of Anaplasma phagocytophilum and Anaplasma marginale adhesin-host cell interactions." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4130.
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Anaplasma phagocytophilum and A. marginale are the etiologic agents of bovine anaplasmosis and human granulocytic anaplasmosis, respectively. As obligate intracellular pathogens, binding and entry of host cells is a prerequisite for survival. The molecular events associated with these processes are poorly understood. Identifying the adhesins mediating binding, delineating their key functional domains, and determining the molecular determinants to which they bind not only benefits better understanding of Anaplasma spp. pathobiology, but could also benefit the development of novel approaches for protecting against infection. We previously demonstrated that A. phagocytophilum outer membrane protein A (ApOmpA) is critical for bacterial binding and entry host through recognition of α2,3-sialic acid and α1,3-fucose of its receptors, including 6-sulfo-sLex. In this study, we determined that two amino acids, G61 and K64, within its binding domain (ApOmpA59-74), are essential for ApOmpA function. We also confirmed the ability of ApOmpA to act as an adhesin and invasin as it conferred adhesiveness and invasiveness to inert beads. We next extended our studies to A. marginale as it also expresses OmpA (AmOmpA) and its role in infection has not been studied. Molecular models of ApOmpA and AmOmpA were nearly identical, especially in the ApOmpA binding domain and its counterpart in AmOmpA. Antisera raised against AmOmpA or its putative binding domain inhibit A. marginale infection. AmOmpA G55 and K58 are contributory and K59 is essential for AmOmpA to bind to host cells. AmOmpA binding is dependent on α2,3-sialic acid and α1,3-fucose. Coating inert beads with AmOmpA conferred the ability to bind to and be taken up by host cells, confirming that it acts as an adhesin and invasin. 6-sulfo-sLex is dispensable for AmOmpA binding and A. marginale infection. ApOmpA works cooperatively with Asp14 (14-kDa A. phagocytophilum surface protein) to promote optimal infection of host cells. We found that Asp14 is conserved across A. phagocytophilum strains and in A. marginale and confirmed the ability of Asp14 to act as an adhesin and invasin as it conferred adhesiveness and invasiveness to inert beads. Collectively, this work advances our understanding of A. phagocytophilum and A. marginale adhesion and invasion of host cells.
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Vellaiswamy, Manohari. "Characterization of mechanisms involved in rickettsia pathogenicity." Phd thesis, Université de la Méditerranée - Aix-Marseille II, 2011. http://tel.archives-ouvertes.fr/tel-00640585.
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Les rickettsies sont de petites bactéries à Gram-négatif associées à différentes espèces d'arthropodes. Leur nature intracellulaire stricte a longtemps été un obstacle à la compréhension des mécanismes moléculaires responsables de leur pathogénicité qui restent mal connus. L'adhésion bactérienne, qui est une étape clef de l'invasion des tissus de l'hôte, met en jeu les protéines rOmpA et rOmpB (rickettsial outer membrane proteins), identifiées depuis longtemps comme des antigènes de surface majeurs des rickettsies. L'objectif de cette thèse a été de caractériser une autre adhésine potentielle de Rickettsia prowazekii récemment identifiée, soit Adr2. La stratégie mise en œuvre a été basée sur la production d'anticorps monoclonaux spécifiques de cette protéine, dont une forme recombinante a été exprimée. Cet outil a permis, non seulement de localiser Adr2 à la surface des rickettsies, mais aussi d'apporter la preuve de son rôle dans le phénomène invasif puisque les anticorps anti-Adr2 diminuent significativement la cytotoxicité des rickettsies sur les cellules épithéliales. Un autre aspect de la pathogénicité que nous avons abordé concerne la mobilité des rickettsies du groupe boutonneux, fonction attribuée à la protéine RickA lorsque ce travail a été initié. La résolution des images obtenues par immunofluorescence, ou par microscopie électronique après marquage immunogold, montrent que l'expression de RickA est non-polarisée et répartie sur la surface entière de Rickettsia conorii. Enfin, plusieurs protéines recombinantes ont été utilisées dans des tests de screening sérologiques avec des sérums de patients infectés par diverses rickettsies, avec des résultats encourageants. L'ensemble de ces résultats contribue à une meilleure connaissance de la pathogénicité des bactéries du genre Rickettsia.
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Dieme, Constentin. "Etude des relations entre arthropodes et rickettsia felis." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM5042/document.
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La lutte anti-vectorielle est l’un des volets le plus important de l’entomologie médicale et nécessite une identification précise des vecteurs. Cette dernière décennie, la technique du MALDI-TOF MS a prouvé son potentiel comme outil rapide et efficace pour l'identification des arthropodes hématophages adultes. Dès lorsNous nous sommes intéressés à la mise au point d’un protocole d’identification des stades aquatiques de moustique par MALDI-TOF MS d’une part. D’autre part la détection d’un pathogène dans un arthropode n’implique pas forcement sa capacité à transmettre. L’incrimination d’un arthropode comme vecteur respecte certaines règles allant de la suspicion à la démonstration de sa compétence vectorielle au laboratoire. Afin de mieux comprendre l’épidémiologie de R. felis nous avons d’abord participé à une investigation conduite à l’Ile de la Réunion, en testant des puces, les seuls vecteurs biologiques connus jusqu’à présent. Ensuite Nous avons démontré le rôle potentiel des moustiques en particulier d’Anopheles gambiae à transmettre Rickettsia felis. Enfin nous avons utilisé le MALDI-TOF MS pour la détermination du statut infectieux d’Anopheles gambiae à R. felis. Nous proposons également un cycle probable de transmission de R. felis à l’homme incluant les psoques et les moustiques<br>Vector control is one of the most important aspects of medical entomology and requires accurate identification of vectors. Within the past decade, the MALDI-TOF MS technique has proven its potential as a fast and effective tool for identification of adult blood-sucking arthropods. From then on we were interested in the development of an identification protocol of aquatic stages of mosquitoes by MALDI-TOF MS. On the other hand, the detection of a pathogen in an arthropod does not necessarily mean its ability to transmit. Incrimination of an arthropod as vector follows certain rules ranging from suspicion to demonstrate its vector competence in the laboratory. To better understand the epidemiology of R. felis we first participated in an investigation conducted in Reunion, testing fleas, the only biological vectors known to date. We demonstrated the potential role of the mosquito particularly Anopheles gambiae, in the transmission of R. felis. Finally, we used the MALDI-TOF MS for the determination of the Anopheles gambiae infection status to R. felis. We also offer a probable transmission cycle of R. felis to man including psocids and mosquitoes
Libros sobre el tema "Rickettsia infections"
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Tarasevich, Irina Vladimirovna. Astrakhanskai͡a︡ pi͡a︡tnistai͡a︡ likhoradka. "Medit͡s︡ina", 2002.
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E, Hechemy Karim, and New York Academy of Sciences, eds. Century of rickettsiology: Emerging, reemerging rickettsioses, molecular diagnostics, and emerging veterinary rickettsioses. Blackwell Pub. on behalf of the New York Academy of Sciences, 2006.
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J, Schmidt Nathalie, and Emmons Richard W, eds. Diagnostic procedures for viral, rickettsial, and chlamydial infections. 6th ed. American Public Health Association, 1989.
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Burt, Anderson, Friedman Herman 1931-, and Bendinelli Mauro, eds. Rickettsial infection and immunity. Plenum Press, 1997.
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Ming, Tan, Guy Palmer, and Abdu F. Azad. Intracellular pathogens II: Rickettsiales. ASM Press, 2012.
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Anderson, Burt, Herman Friedman, and Mauro Bendinelli, eds. Rickettsial Infection and Immunity. Kluwer Academic Publishers, 2002. http://dx.doi.org/10.1007/b111094.
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E, Hechemy Karim, and American Society for Rickettsiology and Rickettsial Diseases. Meeting, eds. Rickettsiology: Current issues and perspectives. New York Academy of Sciences, 1990.
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J, Schmidt Nathalie, and Emmons Richard W, eds. Diagnostic procedures for viral, rickettsial, and chlamydial infections. 7th ed. American Public Health Association, 1995.
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Evermann, James F. Laboratory diagnosis of zoonotic infections: Viral, rickettsial, and parasitic agents obtained from food animals and wildlife. Edited by Garcia Lynne Shore, Stone Diana M, and Inzana Thomas J. American Society for Microbiology, 1999.
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Fletcher, Tom, and Nick Beeching. Rickettsial infection. Edited by Patrick Davey and David Sprigings. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780199568741.003.0314.
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Rickettsial infections are caused by a variety of obligate intracellular, Gram-negative bacteria from the genera Rickettsia, Orientia, Ehrlichia, and Anaplasma. Rickettsia is further subdivided into the spotted fever group and the typhus group. Bartonella and Coxiella burnetii bacteria are similar to rickettsiae and cause similar diseases. The range of recognized spotted fever group infections is rapidly expanding, complementing long-recognized examples such as Rocky Mountain spotted fever (Rickettsia rickettsii) in the US, and Australian tick typhus (Rickettsia australis), as well as those in southern Europe and Africa. Animals are the predominant reservoir of infection, and transmission to people is usually through ticks, mites, fleas, or lice, during blood-feeding or from scarification of faeces deposited on the skin. This chapter focuses on the two of the most relevant infections encountered in UK practice: African tick typhus, and Q fever.
Capítulos de libros sobre el tema "Rickettsia infections"
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Kolo, Agatha. "Tick-borne rickettsioses in Africa." In Climate, ticks and disease. CABI, 2021. http://dx.doi.org/10.1079/9781789249637.0072.
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Abstract This expert opinion focuses on the impact of global warming and climate change on the incidence, prevalence and distribution of rickettsial infections in Africa, with emphasis on Rickettsia africae, R. conorii, R. aeschlimannii, R. sibirica subsp. mongolotimonae and other tick-borne rickettsiae.
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Isaäcson, M., and M. J. Hale. "Infections Caused by Rickettsiae and Rickettsia-Like Organisms, and Bartonellosis." In Tropical Pathology. Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-57863-2_8.
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Khayat, Abeer, and Mobeen H. Rathore. "Rickettsia rickettsii." In The Neurological Manifestations of Pediatric Infectious Diseases and Immunodeficiency Syndromes. Humana Press, 2008. http://dx.doi.org/10.1007/978-1-59745-391-2_26.
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Stovall, Stephanie H., and Richard F. Jacobs. "Rickettsial Infections." In Textbook of Clinical Pediatrics. Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-02202-9_89.
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Stadler, Rudolf. "Rickettsial Infections." In Braun-Falco’s Dermatology. Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-540-29316-3_16.
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Lydyard, Peter M., Michael F. Cole, John Holton, et al. "Rickettsia spp." In Case Studies in Infectious Disease, 2nd ed. CRC Press, 2023. http://dx.doi.org/10.1201/9781003155447-30.
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Dong, Fei, Jiaying Tang, and Pingfeng Dai. "Intracranial Rickettsial Infection." In Radiology of Infectious and Inflammatory Diseases - Volume 1. Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-0039-8_16.
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Grossman, Marc E., Lindy P. Fox, Carrie Kovarik, and Misha Rosenbach. "Rickettsiae." In Cutaneous Manifestations of Infection in the Immunocompromised Host. Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-1578-8_7.
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Hussein, Mansour F. "Rickettsial Diseases." In Infectious Diseases of Dromedary Camels. Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-79389-0_29.
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Del Brutto, Oscar H. "Rickettsial and Parasitic Infections." In International Neurology. Wiley-Blackwell, 2010. http://dx.doi.org/10.1002/9781444317008.ch82.
Texto completoActas de conferencias sobre el tema "Rickettsia infections"
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Luraschi-Monjagatta, CARMEN, and Linda Snyder. "A Case Of Rickettsia Rickettsii Infection And ARDS In Arizona." In American Thoracic Society 2011 International Conference, May 13-18, 2011 • Denver Colorado. American Thoracic Society, 2011. http://dx.doi.org/10.1164/ajrccm-conference.2011.183.1_meetingabstracts.a6453.
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Zhang, Wenli, and Adarsh Radadia. "Point-of-Care Microelectronic Diagnostics for Early Phase Rickettsial Infections." In 2016 32nd Southern Biomedical Engineering Conference (SBEC). IEEE, 2016. http://dx.doi.org/10.1109/sbec.2016.102.
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Huang, Lisa Ting, Victoria Wong Murray, and Judith Anne Lightfood. "Rocky Mountain High Titer: An Unusual Delay In Surgical Clearance." In 28th Annual Rowan-Virtua Research Day. Rowan University Libraries, 2024. http://dx.doi.org/10.31986/issn.2689-0690_rdw.stratford_research_day.77_2024.
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Rocky Mountain Spotted Fever, carried by a variety of ticks, is classically caused by Ricksettsia rickettsii, but may be clinically indistinguishable from other bacteria in the same family. A 47 year old female presented in December for presurgical clearance due to fever, petechial rash on the thighs and trunk, and ecchymoses on the forearms, gluteal region, and toes; additional symptoms included arthralgia in bilateral lower limbs. Bacterial infection was suspected and empirical doxycycline was initiated pending specific PCR testing. Patient adherence was unclear at the followup visit, so IV ceftriaxone was initiated and repeated immunoglobulin testing was ordered to follow her course. Her symptoms waxed and waned over the next several weeks, but ultimately improved and resolved over the next two months, at which point she was successfully cleared for surgery. This case was unusual as she presented in December but disease prevalence typically wanes by August. She was evaluated by rheumatology and dermatology for arthralgia and rash prior to presentation to infectious disease service, but prior treatment was unsuccessful; a missed opportunity to prevent delay in surgery and potential sequelae of long-term infectious vasculitis. As changes in climate increase host range for the variety of vectors, geographic range and temporal duration is also expected to increase, and so it should be considered in the differential more frequently.
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Widiastuti, Dyah, Nova Pramestuti, Siwi Pramatama Mars Wijayanti, and Jastal. "Detection of Rickettsial Infection Among Febrile Patients in Semarang City." In 5th Universitas Ahmad Dahlan Public Health Conference (UPHEC 2019). Atlantis Press, 2020. http://dx.doi.org/10.2991/ahsr.k.200311.004.
Texto completoInformes sobre el tema "Rickettsia infections"
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Hunter, Martha S., and Einat Zchori-Fein. Rickettsia in the whitefly Bemisia tabaci: Phenotypic variants and fitness effects. United States Department of Agriculture, 2014. http://dx.doi.org/10.32747/2014.7594394.bard.
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The sweet potato whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae) is a major pest of vegetables, field crops, and ornamentals worldwide. This species harbors a diverse assembly of facultative, “secondary” bacterial symbionts, the roles of which are largely unknown. We documented a spectacular sweep of one of these, Rickettsia, in the Southwestern United States in the B biotype (=MEAM1) of B. tabaci, from 1% to 97% over 6 years, as well as a dramatic fitness benefit associated with it in Arizona but not in Israel. Because it is critical to understand the circumstances in which a symbiont invasion can cause such a large change in pest life history, the following objectives were set: 1) Determine the frequency of Rickettsia in B. tabaci in cotton across the United States and Israel. 2) Characterize Rickettsia and B. tabaci genotypes in order to test the hypothesis that genetic variation in either partner is responsible for differences in phenotypes seen in the two countries. 3) Determine the comparative fitness effects of Rickettsia phenotypes in B. tabaci in Israel and the United States. For Obj. 1, a survey of B. tabaci B samples revealed the distribution of Rickettsia across the cotton-growing regions of 13 sites from Israel and 22 sites from the USA. Across the USA, Rickettsia frequencies were heterogeneous among regions, but were generally at frequencies higher than 75% and close to fixation in some areas, whereas in Israel the infection rates were lower and declining. The distinct outcomes of Rickettsia infection in these two countries conform to previouslyreported phenotypic differences. Intermediate frequencies in some areas in both countries may indicate a cost to infection in certain environments or that the frequencies are in flux. This suggests underlying geographic differences in the interactions between bacterial symbionts and the pest. Obj. 2, Sequences of several Rickettsia genes in both locations, including a hypervariableintergenic spacer gene, suggested that the Rickettsia genotype is identical in both countries. Experiments in the US showed that differences in whitefly nuclear genotype had a strong influence on Rickettsia phenotype. Obj. 3. Experiments designed to test for possible horizontal transmission of Rickettsia, showed that these bacteria are transferred from B. tabaci to a plant, moved inside the phloem, and could be acquired by other whiteflies. Plants can serve as a reservoir for horizontal transmission of Rickettsia, a mechanism that may explain the occurrence of phylogenetically-similarsymbionts among unrelated phytophagous insect species. This plant-mediated transmission route may also exist in other insect-symbiont systems, and since symbionts may play a critical role in the ecology and evolution of their hosts, serve as an immediate and powerful tool for accelerated evolution. However, no such horizontal transmission of Rickettsia could be detected in the USA, underlining the difference between the interaction in both countries, or between B. tabaci and the banded wing whitefly on cotton in the USA (Trialeurodes sp. nr. abutiloneus) and the omnivorous bug Nesidiocoristenuis. Additionally, a series of experiments excluded the possibility that Rickettsia is frequently transmitted between B. tabaci and its parasitoid wasps Eretmocerusmundus and Encarsiapergandiella. Lastly, ecological studies on Rickettsia effects on free flight of whiteflies showed no significant influence of symbiont infection on flight. In contrast, a field study of the effects of Rickettsia on whitefly performance on caged cotton in the USA showed strong fitness benefits of infection, and rapid increases in Rickettsia frequency in competition population cages. This result confirmed the benefits to whiteflies of Rickettsia infection in a field setting.
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Zchori-Fein, Einat, Judith K. Brown, and Nurit Katzir. Biocomplexity and Selective modulation of whitefly symbiotic composition. United States Department of Agriculture, 2006. http://dx.doi.org/10.32747/2006.7591733.bard.
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Whiteflies are sap-sucking insects that harbor obligatory symbiotic bacteria to fulfill their dietary needs, as well as a facultative microbial community with diverse bacterial species. The sweetpotato whitefly Bemisia tabaci (Gennadius) is a severe agricultural pest in many parts of the world. This speciesconsists of several biotypes that have been distinguished largely on the basis of biochemical or molecular diagnostics, but whose biological significance is still unclear. The original objectives of the project were (i) to identify the specific complement of prokaryotic endosymbionts associated with select, well-studied, biologically and phylogeographically representative biotypes of B. tabaci, and (ii) to attempt to 'cure’ select biotypes of certain symbionts to permit assessment of the affect of curing on whitefly fitness, gene flow, host plant preference, and virus transmission competency.To identify the diversity of bacterial community associated with a suite of phylogeographically-diverseB. tabaci, a total of 107 populations were screened using general Bacteria primers for the 16S rRNA encoding gene in a PCR. Sequence comparisons with the available databases revealed the presence of bacteria classified in the: Proteobacteria (66%), Firmicutes (25.70%), Actinobacteria (3.7%), Chlamydiae (2.75%) and Bacteroidetes (<1%). Among previously identified bacteria, such as the primary symbiont Portiera aleyrodidarum, and the secondary symbionts Hamiltonella, Cardinium and Wolbachia, a Rickettsia sp. was detected for the first time in this insect family. The distribution, transmission, and localization of the Rickettsia were studied using PCR and fluorescence in situ hybridization (FISH). Rickettsia was found in all 20 Israeli B. tabaci populations screened as well as some populations screened in the Arizona laboratory, but not in all individuals within each population. FISH analysis of B. tabaci eggs, nymphs and adults, revealed a unique concentration of Rickettsia around the gut and follicle cells as well as its random distribution in the haemolymph, but absence from the primary symbiont housing cells, the bacteriocytes. Rickettsia vertical transmission on the one hand and its partial within-population infection on the other suggest a phenotype that is advantageous under certain conditions but may be deleterious enough to prevent fixation under others.To test for the possible involvement of Wolbachia and Cardiniumin the reproductive isolation of different B. tabacibiotypes, reciprocal crosses were preformed among populations of the Cardinium-infected, Wolbachia-infected and uninfected populations. The crosses results demonstrated that phylogeographically divergent B. tabaci are reproductively competent and that cytoplasmic incompatibility inducer-bacteria (Wolbachia and Cardinium) both interfered with, and/or rescued CI induced by one another, effectively facilitating bidirectional female offspring production in the latter scenario.This knowledge has implications to multitrophic interactions, gene flow, speciation, fitness, natural enemy interactions, and possibly, host preference and virus transmission. Although extensive and creative attempts undertaken in both laboratories to cure whiteflies of non-primary symbionts have failed, our finding of naturally uninfected individuals have permitted the establishment of Rickettsia-, Wolbachia- and Cardinium-freeB. tabaci lines, which are been employed to address various biological questions, including determining the role of these bacteria in whitefly host biology.