Rickettsia parkeri Rickettsiosis--Georgia, 2012-2014.
R. parkeri, recently recognized as a pathogen of humans, is transmitted by Amblyomma maculatum (Gulf Coast) ticks (Figure). The disease in humans is most commonly characterized by a necrotic, ulcerated, or scabbed lesion at the tick bite site, known as an inoculation eschar (Figure), which is generally followed by the patient experiencing some combination of fever, headache, malaise, and a sparse maculopapular or vesiculopustular rash (7). The first confirmed human infection with R. parkeri was described in 2004; through June 2016, a total of 39 cases, predominantly from the southeastern United States, have been documented in the scientific literature or confirmed by laboratory assays at CDC (2,3). The incidence of R. parkeri rickettsiosis in the United States is unknown. Serological assays currently used to diagnose spotted fever group rickettsial infections lack species-specificity, and there is considerable cross-reactivity among pathogens. It is likely that some, or possibly many, of the approximately 13,500 noncharacterized cases of spotted fever group rickettsioses reported in the United States during 2008--2012 were caused by R. parkeri (4).
The identification of five cases of R. parkeri rickettsiosis from one medical practice during a 3-year interval suggests that this disease is underrecognized in Georgia. During 2012-2014, a total of 335 cases of spotted fever group rickettsiosis were reported in Georgia, including 38 from the health district where the urgent care practice is located.* Four cases of R. parkeri rickettsiosis recently were diagnosed by one clinician in southern Mississippi (5), indicating that the disease might be more common throughout the range of A. maculatum than currently realized.
The recognized range of A. maculatum has increased considerably during the past 70 years and now includes most states in the southeastern United States (7). Clinicians should suspect R. parkeri rickettsiosis in patients who have febrile illnesses after being bitten by a tick, particularly in patients with an eschar at the bite site. Eschar biopsy samples are the most versatile diagnostic specimen and can be tested by IHC stains, qPCR assays, or cell culture isolation techniques; alternatively, a sterile swab of the eschar can be tested using qPCR and is less invasive than a biopsy (6). These tests are not widely available but can be performed at CDC and some academic hospitals (3). Because different spotted fever rickettsioses vary greatly in severity, species-specific diagnoses provide more accurate determinations of hospitalization and case-fatality rates associated with each disease. Doxycycline is the recommended treatment for all patients with a tickborne rickettsial infection, including R. parkeri rickettsiosis (3). Infection with R. parkeri rickettsiosis and other tickborne rickettsial diseases can be minimized by avoiding contact with ticks and by promptly removing attached or crawling ticks after exposures to tick-infested habitats. Persons should use Environmental Protection Agency-approved repellent products and check themselves, their children, and their pets after spending time in tick-infested habitats (3).
(1.) Paddock CD, Finley RW, Wright CS, et al. Rickettsia parkeri rickettsiosis and its clinical distinction from Rocky Mountain spotted fever. Clin Infect Dis 2008;47:1188-96. http://dx.doi.org/10.1086/592254
(2.) Paddock CD, Goddard J. The evolving medical and veterinary importance of the Gulf Coast tick (Acari: Ixodidae). J Med Entomol 2015;52:230-52. http://dx.doi.org/10.1093/jme/tju022
(3.) Biggs HM, Behravesch CB, Bradley KK, et al. Diagnosis and management of tickborne rickettsial diseases: Rocky Mountain spotted fever and other spotted fever group rickettsioses, ehrlichioses, and anaplasmosis--United States. MMWR Recomm Rep 2016(No. RR-2).
(4.) Drexler NA, Dahlgren FS, Heitman KN, Massung RF, Paddock CD, Behravesh CB. National surveillance of spotted fever group rickettsioses in the United States, 2008-2012. Am J Trap Med Hyg 2016;94:26-34. http://dx.doi.org/10.4269/ajtmh.15-0472
(5.) Ekenna O, Paddock CD, Goddard J. Gulf coast tick rash illness in Mississippi caused by Rickettsia parkeri. J Miss State Med Assoc 2014;55:216-9.
(6.) Myers T, Lalani T, Dent M, et al. Detecting Rickettsia parkeri infection from eschar swab specimens. Emerg Infect Dis 2013;19:778-80. http://dx.doi.org/10.3201/eid1905.120622
Anne Straily, DVM [1,2]; Amanda Feldpausch, MPH ; Carl Ulbrich, DO ; Kiersten Schell ; Shannon Casillas, MPH ; Sherif R. Zaki, MD, PHD ; Amy M. Denison, PhD ; Marah Condit, MS ; Julie Gabel, DVM ; Christopher D. Paddock, MD 
 Epidemic Intelligence Service, CDC;  Rickettsial Zoonoses Branch, Division of Vector-Borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, CDC;  Georgia Department of Public Health;  Summit Urgent Care Clinic, Newnan, Georgia;  Infectious Diseases Pathology Branch, Division of Vector-Borne Diseases, CDC.
Corresponding author: Anne Straily, email@example.com, 404-718-1422.
* Data from the State Electronic Notifiable Disease Surveillance System, Georgia Department of Public Health Epidemiology Section (https://dph.georgia.gov/epidemiology).
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|Title Annotation:||Notes from the Field|
|Author:||Straily, Anne; Feldpausch, Amanda; Ulbrich, Carl; Schell, Kiersten; Casillas, Shannon; Zaki, Sherif|
|Publication:||Morbidity and Mortality Weekly Report|
|Date:||Jul 22, 2016|
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