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Christopher D Paddock - One of the best experts on this subject based on the ideXlab platform.
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Rickettsia parkeri (Rickettsiales: Rickettsiaceae) in the Sky Islands of West Texas.
Journal of medical entomology, 2020Co-Authors: Christopher D Paddock, Sandor E. Karpathy, Joy A. Hecht, Amy N Green, Kenneth A. Waldrup, Pete D. Teel, Tammi L. JohnsonAbstract:Rickettsia parkeri, a tick-borne pathogen distributed throughout several countries of the Americas, causes a mild to moderately severe, eschar-associated spotted fever rickettsiosis. Although most U.S. cases of R. parkeri rickettsiosis are reported from southeastern states, some have been reported recently from remote regions of southern Arizona. These cases are linked to R. parkeri-infected ticks of the Amblyomma maculatum (Acari: Ixodidae) group found in several isolated mountain ranges of southern Arizona and New Mexico, referred to as ‘sky islands'. Archival records also document ticks of the A. maculatum group collected from domestic and wild animals in West Texas. We surveyed sites in two sky island chains of Jeff Davis and Brewster counties to document the off-host occurrence of these ticks and identify the presence of R. parkeri in the Trans-Pecos region of Texas. During August 2019, 43 adult A. maculatum group ticks were flagged from vegetation or removed from a road-killed, female mule deer. Of 39 samples evaluated by PCR, eight contained a partial sca0 sequence with complete identity to R. parkeri and two with complete identity to ‘Candidatus Rickettsia andeanae’, a species of undetermined pathogenicity. Four isolates of R. parkeri were obtained using cell culture. Persons at risk for R. parkeri rickettsiosis include those who work or recreate in these mountains, such as hikers, backpackers, research scientists, foresters, and border enforcement personnel. Additional investigations are needed to define the distribution of these medically important arthropods in other parts of the southwestern United States and northern Mexico.
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expanding recognition of Rickettsia parkeri rickettsiosis in southern arizona 2016 2017
Vector-borne and Zoonotic Diseases, 2020Co-Authors: Hayley Yaglom, Mariana Casal, Sharon Carson, Victor Dominguez, Joseph Singleton, Ida Chung, Heidi Lodge, Catherine Ogrady, Christopher D PaddockAbstract:Rickettsia parkeri rickettsiosis is an emerging, tick-borne disease in the United States (US), transmitted by the bite of Amblyomma maculatum group ticks. Clinical manifestations include fever, hea...
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Expanding Recognition of Rickettsia parkeri Rickettsiosis in Southern Arizona, 2016–2017
Vector borne and zoonotic diseases (Larchmont N.Y.), 2019Co-Authors: Hayley Yaglom, Mariana Casal, Sharon Carson, Catherine L. O'grady, Victor Dominguez, Joseph Singleton, Ida Chung, Heidi Lodge, Christopher D PaddockAbstract:Rickettsia parkeri rickettsiosis is an emerging, tick-borne disease in the United States (US), transmitted by the bite of Amblyomma maculatum group ticks. Clinical manifestations include fever, hea...
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Rickettsia parkeri and "Candidatus Rickettsia andeanae" in Amblyomma maculatum (Acari: Ixodidae) collected from the Atlanta metropolitan area, Georgia, United States.
Ticks and tick-borne diseases, 2019Co-Authors: Michelle E. J. Allerdice, Joy A. Hecht, Sandor E. Karpathy, R. Ryan Lash, Christopher D PaddockAbstract:Rickettsia parkeri is a recently recognized human pathogen transmitted in the southeastern United States by Amblyomma maculatum, the Gulf Coast tick. Since R. parkeri was conclusively identified as a human pathogen in 2004, over 40 cases of R. parkeri rickettsiosis have been identified in the United States, most of which occur in the southeastern states. During 2012-2014, five of these cases were identified by a single urgent care practice in Coweta County, a Georgia county within the Atlanta metropolitan area. To investigate the occurrence of R. parkeri-infected A. maculatum in the Atlanta metropolitan area, ticks were collected from 6 counties around the city of Atlanta and evaluated for infection with a Rickettsia species. A total of 263 questing adult A. maculatum were collected during 2015 and 2016. Of these, 93 (35%) were PCR-positive for DNA of R. parkeri and an additional 46 (17%) were PCR-positive for DNA of "Candidatus Rickettsia andeanae," a spotted fever group Rickettsia species of unknown pathogenicity. No co-infections of these two Rickettsiae were detected; however four of the six counties sampled showed presence of both Rickettsial organisms. The high frequency of R. parkeri in these tick populations indicates a potential risk for those living, working, or recreating in A. maculatum-infested habitats within these six counties in the Atlanta metropolitan area.
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Rickettsia parkeri and Candidatus Rickettsia andeanae in Tick of the Amblyomma maculatum Group, Mexico.
Emerging infectious diseases, 2019Co-Authors: Jesús Delgado-de La Mora, Christopher D Paddock, Sokani Sánchez-montes, Carmen Guzmán-cornejo, Pablo Colunga-salas, Jesus D Licona-enriquez, David Delgado-de La Mora, Lorenza Beati, Maria L. Zambrano, Sandor E. KarpathyAbstract:We report Rickettsia parkeri and Candidatus Rickettsia andeanae in ticks of the Amblyomma maculatum group collected from dogs in Sonora, Mexico. Molecular characterization of these bacteria was accomplished by DNA amplification and sequence analysis of portions of the Rickettsial genes gltA, htrA, ompA, and ompB.
Marcelo B. Labruna - One of the best experts on this subject based on the ideXlab platform.
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Implications of domestic dogs in the epidemiology of Rickettsia parkeri strain Atlantic rainforest and Rangelia vitalii in Southeastern Brazil.
Revista brasileira de parasitologia veterinaria = Brazilian journal of veterinary parasitology : Orgao Oficial do Colegio Brasileiro de Parasitologia , 2020Co-Authors: Gislene Fatima Da Silva Rocha Fournier, Marcelo B. Labruna, Jonas Moraes-filho, Adriano Pinter, Thiago F. Martins, Sebastián Muñoz-leal, Marcos Gomes Lopes, Luciana Colácio, Cayo Rodrigo Santos Môra, Ricardo Augusto DiasAbstract:This study aimed to evaluate the occurrence of diseases transmitted by Amblyomma ovale in 61 dogs monitored for three years through collections of ticks and blood, interviews, telemetry and camera traps in three areas of Serra do Mar State Park, Brazil. Blood samples were used to investigate infection by Rangelia vitalii by real-time TaqMan PCR and Rickettsia parkeri by IIFA. The collected ticks were submitted to conventional PCR to investigate the presence of R. parkeri . These data were compared with the monitoring results and interviews with the owners. Dogs considered as companion presented a risk of infection by R. parkeri strain Mata Atlantica 5.4 times higher than those not considered as companion (p = 0.009). Dogs that had at least one A. ovale collected during the campaigns had a 10 times higher risk of infection by R. parkeri strain Mata Atlantica than those who did not (p = 0.009). One dog positive for R. vitalii by real-time TaqMan PCR was parasitized by A. ovale frequently during monitoring. Sequenced ompaA - positive DNA samples had 100% identity of R. parkeri strain Mata Atlantica clone As106. From the findings, it is urgent to control domestic dogs around rainforests to reduce zoonoses transmission.
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A human case of spotted fever caused by Rickettsia parkeri strain Atlantic rainforest and its association to the tick Amblyomma ovale
Parasites & Vectors, 2019Co-Authors: Anaiá Paixão Sevá, Adriano Pinter, Sebastián Muñoz-leal, Thiago Fernandes Martins, Ana Carla Rodrigues, Hermes R. Luz, Rodrigo N. Angerami, Marcelo B. LabrunaAbstract:Background Rickettsia parkeri strain Atlantic rainforest has emerged in Brazil during the last 10 years, with three laboratory-confirmed human cases. While these cases were epidemiologically associated with the tick Amblyomma ovale , in none of them the tick specimens that bit the patients could be identified. Results We report a clinical case of spotted fever rickettsiosis that was acquired in an Atlantic forest area in Bahia state, northeast Brazil. The case was determined to be caused by R. parkeri strain Atlantic rainforest, based on molecular analysis of the crust removed from the tick bite site (inoculation eschar) of the patients’ skin. DNA extracted from the crust yielded partial sequences of three Rickettsial genes ( gltA , ompA and ompB ), which were 99–100% identical to R. parkeri strain Atlantic rainforest. The tick specimen that was attached to patient skin was identified as a female of A. ovale. Conclusions We report the fourth confirmed case of spotted fever rickettsiosis caused by R. parkeri strain Atlantic rainforest, providing to our knowledge for the first time, direct evidence of R. parkeri strain Atlantic rainforest transmission by A. ovale .
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A human case of spotted fever caused by Rickettsia parkeri strain Atlantic rainforest and its association to the tick Amblyomma ovale.
Parasites & vectors, 2019Co-Authors: Anaiá Paixão Sevá, Adriano Pinter, Thiago F. Martins, Sebastián Muñoz-leal, Ana Carla Rodrigues, Hermes R. Luz, Rodrigo N. Angerami, Marcelo B. LabrunaAbstract:Rickettsia parkeri strain Atlantic rainforest has emerged in Brazil during the last 10 years, with three laboratory-confirmed human cases. While these cases were epidemiologically associated with the tick Amblyomma ovale, in none of them the tick specimens that bit the patients could be identified. We report a clinical case of spotted fever rickettsiosis that was acquired in an Atlantic forest area in Bahia state, northeast Brazil. The case was determined to be caused by R. parkeri strain Atlantic rainforest, based on molecular analysis of the crust removed from the tick bite site (inoculation eschar) of the patients’ skin. DNA extracted from the crust yielded partial sequences of three Rickettsial genes (gltA, ompA and ompB), which were 99–100% identical to R. parkeri strain Atlantic rainforest. The tick specimen that was attached to patient skin was identified as a female of A. ovale. We report the fourth confirmed case of spotted fever rickettsiosis caused by R. parkeri strain Atlantic rainforest, providing to our knowledge for the first time, direct evidence of R. parkeri strain Atlantic rainforest transmission by A. ovale.
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febre maculosa por Rickettsia parkeri no brasil condutas de vigilância epidemiologica diagnostico e tratamento
Journal of Health & Biological Sciences, 2018Co-Authors: Alvaro A Faccinimartinez, Stefan Vilges De Oliveira, Crispim Cerutti, Marcelo B. LabrunaAbstract:Introducao : A febre maculosa (FM) e uma doenca infecciosa, aguda, transmitida por carrapatos, e de gravidade variavel. No Brasil, recentemente, tem sido descrita uma nova FM causada por Rickettsia parkeri, cujo perfil clinico, epidemiologico e laboratorial e diferente do perfil da FM causada por Rickettsia rickettsii. Metodologia : trata-se de uma revisao narrativa cujo objetivo e caracterizar a febre maculosa causada por Rickettsia parkeri no Brasil, discutindo as condutas de vigilância epidemiologica, diagnostico e tratamento. Resultados : A febre maculosa por Rickettsia parkeri no Brasil e produzida, principalmente, pela R. parkeri cepa Mata Atlântica, presente no bioma Mata Atlântica das regioes Sul, Sudeste e Nordeste, onde o carrapato Amblyomma ovale figura como o principal vetor da doenca. A suspeicao clinica e epidemiologica deve considerar os pacientes que apresentam doenca febril e presenca da escara de inoculacao, associadas a visita em area de mata e ou contatos com carrapatos. A coleta de material biologico (que inclua a escara de inoculacao) deve ser realizada, oportunamente, para a caracterizacao do agente etiologico. O tratamento com antibioticoterapia deve ser iniciado ja no inicio dos sintomas, e todos os casos devem ser notificados ao Ministerio da Saude e investigados imediatamente. A caracterizacao do ambiente de infeccao e importante para melhor compreensao da ecoepidemiologia da doenca e desencadeamento de medidas de prevencao e controle. Conclusao : Estabelecemos um protocolo para os profissionais de saude com as condutas de vigilância epidemiologica, diagnostico e tratamento para febre maculosa causada por Rickettsia parkeri no Brasil.
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Phylogenetic evidence for the existence of multiple strains of Rickettsia parkeri in the New World
Applied and environmental microbiology, 2018Co-Authors: Fernanda A. Nieri-bastos, Christopher D Paddock, Arlei Marcili, Rita De Sousa, Marcelo B. LabrunaAbstract:The bacterium Rickettsia parkeri has been reported to infect ticks of the "Amblyomma maculatum species complex" in the New World, where it causes spotted fever illness in humans. In South America, three additional Rickettsial strains, namely, Atlantic rainforest, NOD, and Parvitarsum, have been isolated from the ticks Amblyomma ovale, Amblyomma nodosum, and Amblyomma parvitarsum, respectively. These three strains are phylogenetically closely related to R. parkeri, Rickettsia africae, and Rickettsia sibirica Herein, we performed a robust phylogenetic analysis encompassing 5 genes (gltA, ompA, virB4, dnaA, and dnaK) and 3 intergenic spacers (mppE-pur, rrl-rrf-ITS, and rpmE-tRNAfMet) from 41 Rickettsial isolates, including different isolates of R. parkeri, R. africae, R. sibirica, Rickettsia conorii, and strains Atlantic rainforest, NOD, and Parvitarsum. In our phylogenetic analyses, all New World isolates grouped in a major clade distinct from the Old World Rickettsia species (R. conorii, R. sibirica, and R. africae). This New World clade was subdivided into the following 4 clades: the R. parkerisensu stricto clade, comprising the type strain Maculatum 20 and all other isolates of R. parkeri from North and South America, associated with ticks of the A. maculatum species complex; the strain NOD clade, comprising two South American isolates from A. nodosum ticks; the Parvitarsum clade, comprising two South American isolates from A. parvitarsum ticks; and the strain Atlantic rainforest clade, comprising six South American isolates from the A. ovale species complex (A. ovale or Amblyomma aureolatum). Under such evidences, we propose that strains Atlantic rainforest, NOD, and Parvitarsum are South American strains of R. parkeriIMPORTANCE Since the description of Rickettsia parkeri infecting ticks of the "Amblyomma maculatum species complex" and humans in the New World, three novel phylogenetic close-related Rickettsial isolates were reported in South America. Herein, we provide genetic evidence that these novel isolates, namely, strains Atlantic rainforest, NOD, and Parvitarsum, are South American strains of R. parkeri. Interestingly, each of these R. parkeri strains seems to be primarily associated with a tick species group, namely, R. parkerisensu stricto with the "Amblyomma maculatum species group," R. parkeri strain NOD with Amblyomma nodosum, R. parkeri strain Parvitarsum with Amblyomma parvitarsum, and R. parkeri strain Atlantic rainforest with the "Amblyomma ovale species group." Such Rickettsial strain-tick species specificity suggests a coevolution of each tick-strain association. Finally, because R. parkerisensu stricto and R. parkeri strain Atlantic rainforest are human pathogens, the potential of R. parkeri strains NOD and Parvitarsum to be human pathogens cannot be discarded.
Matthew D. Welch - One of the best experts on this subject based on the ideXlab platform.
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Rickettsia parkeri Sca2 promotes dissemination in an intradermal infection mouse model
2020Co-Authors: Thomas P. Burke, Cuong J. Tran, Patrik Engström, Dustin R. Glasner, Diego A. Espinosa, Eva Harris, Matthew D. WelchAbstract:Abstract Arthropod-borne pathogens cause severe human and animal diseases worldwide; however, current animal models are often inadequate in recapitulating key features of infection. Here, we report an intradermal infection model for Rickettsia parkeri, which causes eschar-associated spotted fever rickettsiosis in humans. We show that infection of mice lacking both interferon receptors (Ifnar−/−Ifngr−/−) with R. parkeri causes skin lesion formation similar to human eschars and disseminated disease with as few as 10 bacteria. Using this model, we found that the actin-based motility protein Sca2 is dispensable for R. parkeri survival in organs but is required for R. parkeri dissemination from the skin to peripheral tissues and for causing lethal disease. We also found that immunizing mice with sca2 and ompB mutant R. parkeri protects against subsequent rechallenge with wild-type bacteria. This study characterizes a mouse model that mimics aspects of human Rickettsial disease and reveals a pathogenic role for the R. parkeri actin-based motility protein Sca2 in dissemination.
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A Metabolic Dependency for Host Isoprenoids in the Obligate Intracellular Pathogen Rickettsia parkeri Underlies a Sensitivity to the Statin Class of Host-Targeted Therapeutics.
mSphere, 2019Co-Authors: Vida Ahyong, Thomas P. Burke, Charles A. Berdan, Daniel K. Nomura, Matthew D. WelchAbstract:Gram-negative bacteria in the order Rickettsiales have an obligate intracellular growth requirement, and some species cause human diseases such as typhus and spotted fever. The bacteria have evolved a dependence on essential nutrients and metabolites from the host cell as a consequence of extensive genome reduction. However, it remains largely unknown which nutrients they acquire and whether their metabolic dependency can be exploited therapeutically. Here, we describe a genetic rewiring of bacterial isoprenoid biosynthetic pathways in the Rickettsiales that has resulted from reductive genome evolution. Furthermore, we investigated whether the spotted fever group Rickettsia species Rickettsia parkeri scavenges isoprenoid precursors directly from the host. Using targeted mass spectrometry, we found that infection caused decreases in host isoprenoid products and concomitant increases in bacterial isoprenoid metabolites. Additionally, we report that treatment of infected cells with statins, which inhibit host isoprenoid synthesis, prohibited bacterial growth. We show that growth inhibition correlates with changes in bacterial size and shape that mimic those caused by antibiotics that inhibit peptidoglycan biosynthesis, suggesting that statins lead to an inhibition of cell wall synthesis. Altogether, our results describe a potential Achilles' heel of obligate intracellular pathogens that can potentially be exploited with host-targeted therapeutics that interfere with metabolic pathways required for bacterial growth.IMPORTANCE Obligate intracellular pathogens, which include viruses as well as certain bacteria and eukaryotes, are a subset of infectious microbes that are metabolically dependent on and unable to grow outside an infected host cell because they have lost or lack essential biosynthetic pathways. In this study, we describe a metabolic dependency of the bacterial pathogen Rickettsia parkeri on host isoprenoid molecules that are used in the biosynthesis of downstream products, including cholesterol, steroid hormones, and heme. Bacteria make products from isoprenoids, such as an essential lipid carrier for making the bacterial cell wall. We show that bacterial metabolic dependency can represent a potential Achilles' heel and that inhibiting host isoprenoid biosynthesis with the FDA-approved statin class of drugs inhibits bacterial growth by interfering with the integrity of the cell wall. This work supports the potential to treat infections by obligate intracellular pathogens through inhibition of host biosynthetic pathways that are susceptible to parasitism.
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A metabolic dependency for host isoprenoids in the obligate intracellular pathogen Rickettsia parkeri underlies a sensitivity for the statin class of host-targeted therapeutics
2019Co-Authors: Vida Ahyong, Charles A. Berdan, Daniel K. Nomura, Matthew D. WelchAbstract:Abstract Gram-negative bacteria in the order Rickettsiales are obligate intracellular parasites that cause human diseases such typhus and spotted fever. They have evolved a dependence on essential nutrients and metabolites from the host cell as a consequence of extensive genome streamlining. However, it remains largely unknown which nutrients they require and whether their metabolic dependency can be exploited therapeutically. Here, we describe a genetic rewiring of bacterial isoprenoid biosynthetic pathways in the Rickettsiales that has resulted from reductive genome evolution. We further investigated whether the spotted fever group Rickettsia species Rickettsia parkeri scavenges isoprenoid precursors directly from the host. Using targeted mass spectrometry in uninfected and infected cells, we found decreases in host isoprenoid products and concomitant increases in bacterial isoprenoid metabolites. Additionally, we report that bacterial growth is prohibited by inhibition of the host isoprenoid pathway with the statins class of drugs. We show that growth inhibition correlates with changes in bacterial size and shape that mimic those caused by antibiotics that inhibit peptidoglycan biosynthesis, suggesting statins inhibit cell wall synthesis. Altogether, our results describe an Achilles’ heel of obligate intracellular pathogens that can be exploited with host-targeted therapeutics that interfere with metabolic pathways required for bacterial growth. Importance Obligate intracellular parasites, which include viruses as well as certain bacteria and eukaryotes, extract essential nutrients and metabolites from their host cell. As a result, these pathogens have often lost essential biosynthetic pathways and are metabolically dependent on the host. In this study, we describe a metabolic dependency of the bacterial pathogen Rickettsia parkeri on host isoprenoid molecules that are used in the biosynthesis of downstream products including cholesterol, steroid hormones, and heme. Bacteria make products from isoprenoids such as an essential lipid carrier for making the bacterial cell wall. We show that bacterial metabolic dependency can represent an Achilles’ heel, and that inhibiting host isoprenoid biosynthesis with the FDA-approved statin class of drugs inhibits bacterial growth by interfering with the integrity of the cell wall. This work highlights a potential to treat infections by obligate intracellular pathogens through inhibition of host biosynthetic pathways that are susceptible to parasitism.
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A streamlined method for transposon mutagenesis of Rickettsia parkeri yields numerous mutations that impact infection.
PloS one, 2018Co-Authors: Rebecca L. Lamason, Natasha M. Kafai, Matthew D. WelchAbstract:The Rickettsiae are obligate intracellular alphaproteobacteria that exhibit a complex infectious life cycle in both arthropod and mammalian hosts. As obligate intracellular bacteria, Rickettsiae are highly adapted to living inside a variety of host cells, including vascular endothelial cells during mammalian infection. Although it is assumed that the Rickettsiae produce numerous virulence factors that usurp or disrupt various host cell pathways, they have been challenging to genetically manipulate to identify the key bacterial factors that contribute to infection. Motivated to overcome this challenge, we sought to expand the repertoire of available Rickettsial loss-of-function mutants, using an improved mariner-based transposon mutagenesis scheme. Here, we present the isolation of over 100 transposon mutants in the spotted fever group species Rickettsia parkeri. Transposon insertions disrupted genes whose products are implicated in a variety of pathways, including bacterial replication and metabolism, the type IV secretion system, factors with previously established roles in host cell interactions and pathogenesis, or are of unknown function. Given the need to identify critical virulence factors, forward genetic screens such as this will provide an excellent platform to more directly investigate Rickettsial biology and pathogenesis.
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Role of Sca2 and RickA in the Dissemination of Rickettsia parkeri in Amblyomma maculatum.
Infection and immunity, 2018Co-Authors: Emma K. Harris, Matthew D. Welch, Krit Jirakanwisal, Victoria I. Verhoeve, Chanida Fongsaran, Chanakan Suwanbongkot, Kevin R MacalusoAbstract:ABSTRACT The Gram-negative obligate intracellular bacterium Rickettsia parkeri is an emerging tick-borne human pathogen. Recently, R. parkeri Sca2 and RickA have been implicated in adherence and actin-based motility in vertebrate host cell infection models; however, the Rickettsia-derived factors essential to tick infection are unknown. Using R. parkeri mutants lacking functional Sca2 or RickA to compare actin polymerization, replication, and cell-to-cell spread in vitro, similar phenotypes in tick and mammalian cells were observed. Specifically, actin polymerization in cultured tick cells is controlled by the two separate proteins in a time-dependent manner. To assess the role of Sca2 and RickA in dissemination in the tick host, Rickettsia-free Amblyomma maculatum, the natural vector of R. parkeri, was exposed to wild-type, R. parkeri rickA::tn, or R. parkeri sca2::tn bacteria, and individual tick tissues, including salivary glands, midguts, ovaries, and hemolymph, were analyzed at 12 h and after continued bloodmeal acquisition for 3 or 7 days postexposure. Initially, ticks exposed to wild-type R. parkeri had the highest Rickettsial load across all organs; however, Rickettsial loads decreased and wild-type Rickettsiae were cleared from the ovaries at 7 days postexposure. In contrast, ticks exposed to R. parkeririckA::tn or R. parkerisca2::tn had comparatively lower Rickettsial loads, but bacteria persisted in all organs for 7 days. These data suggest that while RickA and Sca2 function in actin polymerization in tick cells, the absence of these proteins did not change dissemination patterns within the tick vector.
Wayne L. Hynes - One of the best experts on this subject based on the ideXlab platform.
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Survey of Rickettsia parkeri and Amblyomma maculatum associated with small mammals in southeastern Virginia.
Ticks and tick-borne diseases, 2020Co-Authors: Alexandra N. Cumbie, Robyn M. Nadolny, Wayne L. Hynes, Christina Espada, Robert K. Rose, Raymond D. Dueser, Holly GaffAbstract:Abstract Small mammals are often parasitized by the immature stages of hard-bodied ticks (family Ixodidae) and may serve as reservoir hosts of tick-borne pathogens. Amblyomma maculatum, the Gulf Coast tick, is the primary vector of Rickettsia parkeri, the causative agent of R. parkeri rickettsiosis. This hard-bodied tick species is expanding its historical range from the Gulf Coast of the U.S. up the Mid-Atlantic coast. In Mid-Atlantic states, such as Virginia, R. parkeri prevalence is higher in these ticks than those found in its historical range. This high prevalence may be explained in part by small mammal populations. In this study, small mammals were trapped and checked for the presence of immature A. maculatum. The ticks as well as tissue samples from these mammals were tested for the presence of R. parkeri. This study found six rodent species acting as hosts to immature A. maculatum and three species that may play a role in the enzootic cycle of R. parkeri in Virginia.
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Rickettsia parkeri infections diagnosed by eschar biopsy, Virginia, USA.
Infection, 2018Co-Authors: Pamela Kelman, Wayne L. Hynes, Chelsea Wright Thompson, Christian Bergman, Cameron Lenahan, Joel S. Brenner, Michelle G. Brenner, Demetria Borges, Benjamin M. Goodman, Michael FilakAbstract:Infection with Rickettsia parkeri is an emerging tick-borne illness, often accompanied by fever and an eschar at the site of tick attachment. We present three cases of R. parkeri in Virginia residents. Case 1 presented initially afebrile, failed to seroconvert to Rickettsial antigens, and was diagnosed by DNA testing of the eschar. Case 2 presented febrile with eschar, no serologies were performed, and was diagnosed by DNA testing of the eschar. Case 3 presented febrile with eschar, serologies were negative for Rickettsial antigens, and was diagnosed by DNA testing of the eschar. DNA testing of eschars represents an under-utilized diagnostic test and may aid in cases where the diagnosis is not made clinically.
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Rickettsia parkeri in Gulf Coast Ticks, Southeastern
2016Co-Authors: Chelsea L. Wright, Allen L. Richards, Ju Jiang, Robyn M. Nadolny, Daniel E. Sonenshine, Holly D. Gaff, Wayne L. HynesAbstract:We report evidence that Amblyomma maculatum tick populations are well established in southeastern Virginia. We found that 43.1 % of the adult Gulf Coast ticks collected in the summer of 2010 carried Rickettsia parkeri, suggesting that persons living in or visiting southeastern Virginia are at risk for infection with this pathogen. Rickettsia parkeri is an obligate intracellular bacterium belonging to the spotted fever group of Rickettsiae; this organism has recently been found to be pathogenic to humans (1). Infection with R. parkeri can be considered an emerging infectious disease, referred to as R. parkeri rickettsiosis, American Boutonneuse fever, and Tidewater spotted fever. Two confi rmed cases of R. parkeri infections, including the index case in 2002, occurred in southeastern Virginia (1–3). Since then, 20 R. parkeri infections have been reported, mainly from the southern United States (2). In the United States, Amblyomma maculatum (family Ixodidae) ticks, commonly referred to as Gulf Coast ticks, are the only known natural vector of R. parkeri. A. maculatum ticks have been reported fro
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Rickettsia parkeri transmission to amblyomma americanum by cofeeding with amblyomma maculatum acari ixodidae and potential for spillover
Journal of Medical Entomology, 2015Co-Authors: Chelsea L. Wright, Daniel E. Sonenshine, Holly Gaff, Wayne L. HynesAbstract:Amblyomma americanum (L.) is a human-biting ixodid tick distributed throughout much of the southeastern United States. Rickettsia parkeri is a member of the spotted fever group Rickettsiae and causes a febrile illness in humans commonly referred to as "Tidewater spotted fever" or "R. parkeri rickettsiosis." Although the Gulf Coast tick, Amblyomma maculatum Koch, is the primary vector of R. parkeri, a small proportion of A. americanum have also been shown to harbor R. parkeri. The purpose of this investigation was to determine whether R. parkeri is spilling over into A. americanum in eastern Virginia and also to determine through laboratory experiments, whether A. americanum can acquire R. parkeri by cofeeding alongside infected ticks. Of 317 wild-caught, flat adult A. americanum tested from 29 counties and independent cities in coastal Virginia, a single female A. americanum was positive for R. parkeri, suggesting that R. parkeri is spilling over into this species, but at very low rates (<1.0%). Laboratory studies using guinea pigs indicated that nymphal A. americanum were able to acquire R. parkeri while feeding alongside infected A. maculatum and then transstadially maintain the infection. Nymphal A. americanum infected with Rickettsia amblyommii, however, were less likely to acquire R. parkeri, suggesting that infection with R. amblyommii may prevent R. parkeri from establishing infection in A. americanum.
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Rickettsia parkeri Transmission to Amblyomma americanum by Cofeeding with Amblyomma maculatum (Acari: Ixodidae) and Potential for Spillover
Journal of medical entomology, 2015Co-Authors: Chelsea L. Wright, Daniel E. Sonenshine, Holly Gaff, Wayne L. HynesAbstract:Amblyomma americanum (L.) is a human-biting ixodid tick distributed throughout much of the southeastern United States. Rickettsia parkeri is a member of the spotted fever group Rickettsiae and causes a febrile illness in humans commonly referred to as "Tidewater spotted fever" or "R. parkeri rickettsiosis." Although the Gulf Coast tick, Amblyomma maculatum Koch, is the primary vector of R. parkeri, a small proportion of A. americanum have also been shown to harbor R. parkeri. The purpose of this investigation was to determine whether R. parkeri is spilling over into A. americanum in eastern Virginia and also to determine through laboratory experiments, whether A. americanum can acquire R. parkeri by cofeeding alongside infected ticks. Of 317 wild-caught, flat adult A. americanum tested from 29 counties and independent cities in coastal Virginia, a single female A. americanum was positive for R. parkeri, suggesting that R. parkeri is spilling over into this species, but at very low rates (
Amy M. Denison - One of the best experts on this subject based on the ideXlab platform.
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Detection of Rickettsia rickettsii, Rickettsia parkeri, and Rickettsia akari in Skin Biopsy Specimens Using a Multiplex Real-time Polymerase Chain
2016Co-Authors: Reaction Assay, William L. Nicholson, Amy M. Denison, Bijal D. Amin, Christopher D PaddockAbstract:Background. Rickettsia rickettsii, Rickettsia parkeri, and Rickettsia akari are the most common causes of spotted fever group rickettsioses indigenous to the United States. Infected patients characteristically present with a maculo-papular rash, often accompanied by an inoculation eschar. Skin biopsy specimens are often obtained from these lesions for diagnostic evaluation. However, a species-specific diagnosis is achieved infrequently from pathologic specimens because immunohistochemical stains do not differentiate among the causative agents of spotted fever group Rickettsiae, and existing polymerase chain reaction (PCR) assays generally target large gene segments that may be difficult or impossible to obtain from formalin-fixed tissues. Methods. This work describes the development and evaluation of a multiplex real-time PCR assay for the de-tection of these 3 Rickettsia species from formalin-fixed, paraffin-embedded (FFPE) skin biopsy specimens. Results. The multiplex PCR assay was specific at discriminating each species from FFPE controls of unrelated bacterial, viral, protozoan, and fungal pathogens that cause skin lesions, as well as other closely related spotted fever group Rickettsia species. Conclusions. This multiplex real-time PCR demonstrates greater sensitivity than nested PCR assays in FFPE tissues and provides an effective method to specifically identify cases of Rocky Mountain spotted fever, Rickettsialpox, and R. parkeri rickettsiosis by using skin biopsy specimens
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Notes from the Field: Rickettsia parkeri Rickettsiosis - Georgia, 2012-2014.
MMWR. Morbidity and mortality weekly report, 2016Co-Authors: Anne Straily, Marah E. Condit, Amy M. Denison, Sherif R. Zaki, Amanda Feldpausch, Carl Ulbrich, Kiersten Schell, Shannon Casillas, Julie Gabel, Christopher D PaddockAbstract:During 2012-2014, five cases of Rickettsia parkeri rickettsiosis were identified by a single urgent care practice in Georgia, located approximately 40 miles southwest of Atlanta. Symptom onset occurred during June-October, and all patients had a known tick bite. Patients ranged in age from 27 to 72 years (median = 53 years), and all were male. The most commonly reported initial signs were erythema (n = 3) and swelling (n = 2) at the site of the bite. Two patients reported fever and a third patient reported a rash and lymphadenopathy without fever. Other symptoms included myalgia (n = 3), chills (n = 3), fatigue (n = 2), arthralgia (n = 2), and headache (n = 2). Eschar biopsy specimens were collected from each patient using a 4-mm or 5-mm punch and placed in 10% neutral buffered formalin or sterile saline. These specimens were tested by immunohistochemical (IHC) stains, quantitative polymerase chain reaction (qPCR) assays, or cell culture isolation to determine if there was evidence of infection with a Rickettsia species (1). IHC evidence of spotted fever group Rickettsiae was found in the eschar biopsy specimens in all five cases. In four cases, the biopsy specimens were also positive for R. parkeri by qPCR. The fifth case (specimen positive only by IHC testing) was considered a probable R. parkeri case based on clinical signs and symptoms. R. parkeri was grown in cell culture from one specimen from which isolation was attempted. All patients were treated with oral doxycycline (100 mg twice daily) for a minimum of 10 days, and all recovered.
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Rickettsia parkeri Rickettsiosis, Arizona, USA.
Emerging infectious diseases, 2016Co-Authors: Kristen Herrick, Hayley Yaglom, Joseph Singleton, Sandra A. Pena, Brent J. Layton, Amanda Moors, Amanda D. Loftis, Marah E. Condit, Cecilia Y. Kato, Amy M. DenisonAbstract:In the United States, all previously reported cases of Rickettsia parkeri rickettsiosis have been linked to transmission by the Gulf Coast tick (Amblyomma maculatum). Here we describe 1 confirmed and 1 probable case of R. parkeri rickettsiosis acquired in a mountainous region of southern Arizona, well beyond the recognized geographic range of A. maculatum ticks. The likely vector for these 2 infections was identified as the Amblyomma triste tick, a Neotropical species only recently recognized in the United States. Identification of R. parkeri rickettsiosis in southern Arizona demonstrates a need for local ecologic and epidemiologic assessments to better understand geographic distribution and define public health risk. Education and outreach aimed at persons recreating or working in this region of southern Arizona would improve awareness and promote prevention of tickborne rickettsioses.
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High prevalence of "Candidatus Rickettsia andeanae" and apparent exclusion of Rickettsia parkeri in adult Amblyomma maculatum (Acari: Ixodidae) from Kansas and Oklahoma.
Ticks and tick-borne diseases, 2015Co-Authors: Christopher D Paddock, Amy M. Denison, Bruce H. Noden, Joy A. Hecht, R. Ryan Lash, Michael W. Dryden, Sarah S. Abdelghani, Anna E. Evans, Aubree R. Kelly, Sandor E. KarpathyAbstract:Amblyomma maculatum (the Gulf Coast tick), an aggressive, human-biting, Nearctic and Neotropical tick, is the principal vector of Rickettsia parkeri in the United States. This pathogenic spotted fever group Rickettsia species has been identified in 8–52% of questing adult Gulf Coast ticks in the southeastern United States. To our knowledge, R. parkeri has not been reported previously from adult specimens of A. maculatum collected in Kansas or Oklahoma. A total of 216 adult A. maculatum ticks were collected from 18 counties in Kansas and Oklahoma during 2011–2014 and evaluated by molecular methods for evidence of infection with R. parkeri. No infections with this agent were identified; however, 47% of 94 ticks collected from Kansas and 73% of 122 ticks from Oklahoma were infected with “Candidatus Rickettsia andeanae” a spotted fever group Rickettsia species of undetermined pathogenicity. These preliminary data suggest that “Ca. R. andeanae” is well-adapted to survival in populations of A. maculatum in Kansas and Oklahoma, and that its ubiquity in Gulf Coast ticks in these states may effectively exclude R. parkeri from their shared arthropod host, which could diminish markedly or preclude entirely the occurrence of R. parkeri rickettsiosis in this region of the United States.
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Rickettsia parkeri rickettsiosis in different ecological regions of Argentina and its association with Amblyomma tigrinum as a potential vector.
The American journal of tropical medicine and hygiene, 2014Co-Authors: Yamila Romer, Joseph Singleton, Cecilia Y. Kato, Amy M. Denison, Santiago Nava, Francisco Govedic, Gabriel L. Cicuttin, Aubree J. Kelly, Christopher D PaddockAbstract:Rickettsia parkeri, a newly recognized tick-borne pathogen of humans in the Americas, is a confirmed cause of spotted fever group rickettsiosis in Argentina. Until recently, almost all cases of R. parkeri rickettsiosis in Argentina have originated from the Parana River Delta, where entomological surveys have identified populations of R. parkeri-infected Amblyomma triste ticks. In this report, we describe confirmed cases of R. parkeri rickettsiosis from Cordoba and La Rioja provinces, which are located several hundred kilometers inland, and in a more arid ecological region, where A. triste ticks do not occur. Additionally, we identified questing A. tigrinum ticks naturally infected with R. parkeri in Cordoba province. These data provide evidence that another human-biting tick species serves as a potential vector of R. parkeri in Argentina and possibly, other countries of South America.
