Expanding Recognition of<i>Rickettsia parkeri</i>Rickettsiosis in Southern Arizona, 2016–2017

Yaglom, Hayley; Casal, Mariana; Carson, Sharon; O’Grady, Catherine; Dominguez, Victor; Singleton, Joseph; Chung, Ida H.; Lodge, Heidi; Paddock, Christopher D.

doi:10.1089/vbz.2019.2491

Cited by 15 publications

(14 citation statements)

References 16 publications

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“…There have been confirmed human cases of R. parkeri rickettsiosis reported from Brazil, Colombia, Argentina, Uruguay, and the United States ( 5 – 12 , 14 , 49 ). In the United States, cases have been reported from 11 states: Arizona, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, South Carolina, Texas, and Virginia ( 10 , 11 , 14 ). However, these states represent a small segment of the total distribution of A. maculatum in the country.…”

Section: Discussionmentioning

confidence: 93%

“…Other symptoms in humans are less specific but often include a combination of fever, headache, malaise, and myalgia ( 3 , 4 ). Since the initial case, more than 50 cases of R. parkeri rickettsiosis have been identified, all limited to the Americas ( 5 – 14 ).…”

Section: Introductionmentioning

confidence: 99%

“…The primary vectors of R. parkeri in North America are the ixodid ticks Amblyomma maculatum Koch sensu stricto (s. s.) in the eastern and Gulf Coast regions of the United States and A. maculatum sensu lato (s. l.) in southern Arizona ( 10 – 12 , 14 , 15 ). Recent field studies further identified R. parkeri sensu stricto (s. s.) in A. maculatum s. l. ticks in West Texas ( 16 ) and New Mexico ( 17 ), as well as in the northern state of Sonora ( 18 ) and the southeastern state of Tabasco, Mexico ( 19 ).…”

Section: Introductionmentioning

confidence: 99%

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Phylogenetic Differentiation of Rickettsia parkeri Reveals Broad Dispersal and Distinct Clustering within North American Strains

et al. 2021

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Section: Discussionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Phylogenetic Differentiation of Rickettsia parkeri Reveals Broad Dispersal and Distinct Clustering within North American Strains

et al. 2021

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“…3,[6][7][8] Since then, additional cases of R. parkeri rickettsiosis have been reported in many southeastern and southwestern regions of the United States. [9][10][11] In addition to the primary vector, A. maculatum, R. parkeri has also been found in different species of ticks, including Amblyomma americanum, [12][13][14] Amblyomma triste, 15 and Ixodes scapularis. 14,16 R. amblyommatis, formerly named Rickettsia amblyommii and 'Candidatus Rickettsia amblyommii', has been detected in A. americanum throughout the United States.…”

Section: Introductionmentioning

confidence: 99%

Association between Growth Rate and Pathogenicity of Spotted Fever Group Rickettsia

Bourchookarn¹,

Paddock²,

Macaluso³

et al. 2022

J. Pure Appl. Microbiol.

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Rickettsia parkeri and Rickettsia amblyommatis are spotted fever group Rickettsia (SFGR) associated with Amblyomma ticks. R. parkeri is a recognized human pathogen that causes an eschar-associated febrile illness, while R. amblyommatis has not been confirmed as a causative agent of human disease. We hypothesized that the rate of replication is one of the factors contributing to rickettsial pathogenicity. In this study, growth and infectivity of R. parkeri and R. amblyommatis in mammalian (Vero E6) and tick-derived (ISE6) cell lines were assessed and compared over a 96-hour time course of infection using quantitative real-time polymerase chain reaction and microscopy. The pathogenic R. parkeri displayed a significantly higher level of infection in both Vero E6 and ISE6 cells than R. amblyommatis at 72 hours post-inoculation (hpi). Distinct growth profiles between rickettsial species with known and uncertain pathogenicity were identified. R. parkeri burdens were significantly greater than those of R. amblyommatis from 24 to 96 hpi. The relative fold changes of load were significantly higher in the pathogenic agent than in R. amblyommatis from 48 hpi onward and reached the maximum fold increase of ~2002- and ~296-fold in Vero E6 cells and ~1363- and ~161-fold in ISE6 cells, respectively, at 96 hpi. The results from the present study demonstrate that growth rate is associated with the pathogenicity of rickettsiae. Understanding SFGR growth characteristics in mammalian and tick cells will provide insight into rickettsial biology and pathogenesis.

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“…Rickettsia parkeri is an emerging pathogenic SFGR species and agent of SFR; it is primarily transmitted via Amblyomma maculatum (Gulf Coast tick) in the southern USA [4]. A closely related tick species in the A. maculatum group, Amblyomma triste, was also recently identified as the vector for R. parkeri in SFR cases from Arizona [5]. In 2010, Rickettsia 364D became the third known tick-borne pathogenic SFGR species in the US; it is transmitted to humans through Dermacentor occidentalis along the West Coast [6].…”

Section: Introductionmentioning

confidence: 99%

Beyond the IFA: Revisiting the ELISA as a More Sensitive, Objective, and Quantitative Evaluation of Spotted Fever Group Rickettsia Exposure

et al. 2021

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Based on limited serological studies, at least 10% of the US population has been exposed to spotted fever group Rickettsia (SFGR) species. The immunofluorescence antibody assay (IFA) has been the gold standard for the serodiagnosis of rickettsial infections such as spotted fever rickettsiosis (SFR). However, the IFA is semi-quantitative and subjective, requiring a high level of expertise to interpret it correctly. Here, we developed an enzyme-linked immunosorbent assay (ELISA) for the serodiagnosis of Rickettsia parkeri infection in the guinea pig. Our ELISA is an objective, quantitative, and high-throughput assay that shows greater sensitivity and resolution in observed titers than the IFA. We methodically optimized relevant parameters in sequence for optimal signal-to-noise ratio and low coefficient of variation% values. We used a guinea pig model as it is a part of our overall research efforts to understand the immunological and clinical response to SFGR species after tick transmission. Guinea pigs are a useful model to study SFR and show clinical signs of SFR, such as fever and eschars. We anticipate that this assay will be easily adapted to other hosts, including humans and other SFGR species.

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Expanding Recognition ofRickettsia parkeriRickettsiosis in Southern Arizona, 2016–2017

Cited by 15 publications

References 16 publications

Phylogenetic Differentiation of Rickettsia parkeri Reveals Broad Dispersal and Distinct Clustering within North American Strains

Phylogenetic Differentiation of Rickettsia parkeri Reveals Broad Dispersal and Distinct Clustering within North American Strains

Association between Growth Rate and Pathogenicity of Spotted Fever Group Rickettsia

Beyond the IFA: Revisiting the ELISA as a More Sensitive, Objective, and Quantitative Evaluation of Spotted Fever Group Rickettsia Exposure

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