Rickettsia parkeri rickettsiosis and its clinical distinction from Rocky Mountain spotted fever.
BACKGROUND
Rickettsia parkeri rickettsiosis, a recently identified spotted fever transmitted by the Gulf Coast tick (Amblyomma maculatum), was first described in 2004. We summarize the clinical and epidemiological features of 12 patients in the United States with confirmed or probable disease attributable to R. parkeri and comment on distinctions between R. parkeri rickettsiosis and other United States rickettsioses.


METHODS
Clinical specimens from patients in the United States who reside within the range of A. maculatum for whom an eschar or vesicular rash was described were evaluated by > or =1 laboratory assays at the Centers for Disease Control and Prevention (Atlanta, GA) to identify probable or confirmed infection with R. parkeri.


RESULTS
During 1998-2007, clinical samples from 12 patients with illnesses epidemiologically and clinically compatible with R. parkeri rickettsiosis were submitted for diagnostic evaluation. Using indirect immunofluorescence antibody assays, immunohistochemistry, polymerase chain reaction assays, and cell culture isolation, we identified 6 confirmed and 6 probable cases of infection with R. parkeri. The aggregate clinical characteristics of these patients revealed a disease similar to but less severe than classically described Rocky Mountain spotted fever.


CONCLUSIONS
Closer attention to the distinct clinical features of the various spotted fever syndromes that exist in the United States and other countries of the Western hemisphere, coupled with more frequent use of specific confirmatory assays, may unveil several unique diseases that have been identified collectively as Rocky Mountain spotted fever during the past century. Accurate assessments of these distinct infections will ultimately provide a more valid description of the currently recognized distribution, incidence, and case-fatality rate of Rocky Mountain spotted fever.
Paddock
Christopher D
CD
Infectious Diseases Pathology Branch, Mailstop G-32, Centers for Disease Control and Prevention, 1600 Clifton Rd., Atlanta, GA 30333, USA. CPaddock@cdc.gov
Finley
Richard W
RW
Wright
Cynthia S
CS
Robinson
Howard N
HN
Schrodt
Barbara J
BJ
Lane
Carole C
CC
Ekenna
Okechukwu
O
Blass
Mitchell A
MA
Tamminga
Cynthia L
CL
Ohl
Christopher A
CA
McLellan
Susan L F
SL
Goddard
Jerome
J
Holman
Robert C
RC
Openshaw
John J
JJ
Sumner
John W
JW
Zaki
Sherif R
SR
Eremeeva
Marina E
ME
D000328:Adult; D000368:Aged; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D001096:Arachnid Vectors / Q000382:microbiology; D004269:DNA, Bacterial / Q000235:genetics; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D026863:Ixodidae / Q000382:microbiology; D008297:Male; D008875:Middle Aged; D012281:Rickettsia / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification / Q000472:pathogenicity; D012282:Rickettsia Infections / Q000175:diagnosis* / Q000382:microbiology / Q000635:transmission; D012373:Rocky Mountain Spotted Fever / Q000175:diagnosis*; D014481:United States
D000907:Antibodies, Bacterial; D004269:DNA, Bacterial