<i>Rickettsia parkeri:</i>A Newly Recognized Cause of Spotted Fever Rickettsiosis in the United States

TLDR

Ticks in the United States carry several spotted fever group Rickettsia, but only R. rickettsii has been definitively linked to human disease. The study aims to apply specific laboratory assays to patients with febrile, eschar‑associated illnesses after tick bites to uncover additional R. parkeri cases and other novel spotted fever rickettsioses.

Abstract

Ticks, including many that bite humans, are hosts to several obligate intracellular bacteria in the spotted fever group (SFG) of the genus Rickettsia. Only Rickettsia rickettsii, the agent of Rocky Mountain spotted fever, has been definitively associated with disease in humans in the United States. Herein we describe disease in a human caused by Rickettsia parkeri, an SFG rickettsia first identified >60 years ago in Gulf Coast ticks (Amblyomma maculatum) collected from the southern United States. Confirmation of the infection was accomplished using serological testing, immunohistochemical staining, cell culture isolation, and molecular methods. Application of specific laboratory assays to clinical specimens obtained from patients with febrile, eschar-associated illnesses following a tick bite may identify additional cases of R. parkeri rickettsiosis and possibly other novel SFG rickettsioses in the United States.