Isolation of Rickettsia parkeri and Identification of a Novel Spotted Fever Group Rickettsia sp. from Gulf Coast Ticks (Amblyomma maculatum) in the United States

Authors

• Christopher D. Paddock, Centers for Disease Control and Prevention
• Pierre-Edouard Fournier, Université de la Méditerranee
• John W. Sumner, Centers for Disease Control and Prevention
• Jerome Goddard, Mississippi State University
• Yasmin Elshenawy, Centers for Disease Control and Prevention
• Maureen G. Metcalfe, Centers for Disease Control and Prevention
• Amanda D. Loftis, Ross University
• Andrea Varela-Stokes, Mississippi State University

ORCID

Goddard: https://orcid.org/0000-0002-2617-7141

MSU Affiliation

College of Agriculture and Life Sciences; Department of Entomology and Plant Pathology; College of Veterinary Medicine; Department of Basic Sciences

Creation Date

2026-07-30

Abstract

Until recently, Amblyomma maculatum (the Gulf Coast tick) had garnered little attention compared to other species of human-biting ticks in the United States. A. maculatum is now recognized as the principal vector of Rickettsia parkeri, a pathogenic spotted fever group rickettsia (SFGR) that causes an escharassociated illness in humans that resembles Rocky Mountain spotted fever. A novel SFGR, distinct from other recognized Rickettsia spp., has also been detected recently in A. maculatum specimens collected in several regions of the southeastern United States. In this study, 198 questing adult Gulf Coast ticks were collected at 4 locations in Florida and Mississippi; 28% of these ticks were infected with R. parkeri, and 2% of these were infected with a novel SFGR. Seventeen isolates of R. parkeri from individual specimens of A. maculatum were cultivated in Vero E6 cells; however, all attempts to isolate the novel SFGR were unsuccessful. Partial genetic characterization of the novel SFGR revealed identity with several recently described, incompletely characterized, and noncultivated SFGR, including "Candidatus Rickettsia andeanae" and Rickettsia sp. Argentina detected in several species of Neotropical ticks from Argentina and Peru. These findings suggest that each of these "novel" rickettsiae represent the same species. This study considerably expanded the number of low-passage, A. maculatum -derived isolates of R. parkeri and characterized a second, sympatric Rickettsia sp. found in Gulf Coast ticks. Copyright © 2010, American Society for Microbiology. All Rights Reserved.

Publication Date

5-1-2010

Publication Title

Applied and Environmental Microbiology

Publisher

American Society for Microbiology

First Page

2689

Last Page

2696

Rights

© 2010 American Society for Microbiology

Recommended Citation

Paddock, C. D., Fournier, P.-E., Sumner, J. W., Goddard, J., Elshenawy, Y., Metcalfe, M. G., Loftis, A. D., & Varela-Stokes, A. (2010). Isolation of Rickettsia parkeri and Identification of a Novel Spotted Fever Group Rickettsia sp. From Gulf Coast Ticks (Amblyomma maculatum) in the United States. Applied and Environmental Microbiology, 76(9), 2689–2696. https://doi.org/10.1128/AEM.02737-09