Rickettsia spp (9 species)

There are many pathogenic species of the genera Rickettsia.  This group of organisms contributes in many types of vector-borne diseases. There are two main groups of interest; the Spotted Fever Group (SFG) and the Typhus Group (TG) [1].

The most common species of Rickettsia are: R. rickettsii, R. akari, R. felis, R. prowazekii, R. typhi, R. conorri subsp. conorri, R. sibirica, R. africae, and R. parkeri [2].  The SFG consists of all that are listed here except R. prowazekii and R. typhi; these two make up the TG. There are many vectors for the many species of Rickettsia due to the large geographic distribution.   A few of the tick vectors are: Dermacentor andersoni, Rhipicepahlus sanguineus, Dermacentor nuttalli, Amblyomma maculatum [2, 5].  All of the SFG organisms share some clinical manifestations.  However, each species still contributes different symptoms.  Some of these manifestations are fever, eschar, rash, headache, myalgia, adenopathy and maculopapular rash.  The members of the TG are characterized by headache, chills, fever, prostration, confusion, rash, and photophobia [4].  The incubation period for the tick born Ricketssial diseases is about 4-10 days, after which the onset of the generalized symptoms begins.  More nonspecific, laboratory observed symptoms are leukopenia, anemia, thrombocytopenia, hyponatremia, hypoalbuminemia, and renal and hepatic abnormalities.  Because of the likeness between generalized symptoms in all forms of Ricketssial disease, laboratory diagnosis is pertinent to eliminating infection [2]

The most common method for detecting and diagnosing Rickettsia is serology. Unfortunately, the diversity within Rickettsia spp. contributes to the outcome of these analyses to be very unspecific and insensitive.  Culture methods are known to be more specific for detection of Rickettsia spp. but are difficult to maintain [2].  Molecular methods are sensitive and are capable of being specific to the species [5]. Spiro Stat Technologies, L.P. has a main testing panel that includes detection and identification of 9 specific species of Rickettsia. PCR or molecular methods for detection of Rickettsia are sensitive and can help diagnose early in infection [6].  

References:

  1. Philippe Parola, et al.  Tick- and flea-borne rickettsial emerging zoonoses.  Vet. Res. 2005.  36: 469-492. 
  2. Philippe Parola, et al.  Tick-Borne Rickettsioses around the World: Emerging Diseases Challenging Old Concepts.  Clin. Microbiol. Rev. Oct. 2005.  18(4): 719-756. 
  3. Abdu F. Azad and Charles B. Beard.  Rickettsial Pathogens and their Arthropod Vectors.  Emerging Infectious Diseases.  CDC Apr. 2008.  4(2): 179-186. 
  4. Jennifer Adjemian, Et Al.  Rickettsial (Spotted and Typhus Fevers) And Related Infections (Anaplasmosis And Ehrlichiosis).   Centers for Disease Control and Prevention.  Yellow Book July 2009. http://Wwwnc.Cdc.Gov/Travel/Yellowbook/2010/Chapter-5/Rickettsial-And-Related-Infections.Aspx.
  5. Isabel Jado, et al.  Molecular Method for Identification of Rickettsia Species in Clinical and Environmental Samples.  J. Clin. Microbiol. Dec. 2006.  44(12): 4572-4576. 
  6. Jianli Dong, et al.  Emerging Pathogens: Challenges and Successes of Molecular Diagnostics.  JMD, Vol. 10, No. 3, May 2008

Additional References:

  1. John Stenos, et al.  A Highly Sensitive and Specific Real-Time PCR Assay For the Detection of Spotted Fever and Typhus Group Rickettsiae.  Am. J. Trop. Med. Hyg.2005.  73(6): 1083-1085. 
  2. Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever, Ehrlichioses, and Anaplasmosis — United States.  WMMR.  CDC Mar. 2006.  55(4): 1-28. 
  3. Outbreak of Rickettsia typhi Infection --- Austin, Texas, 2008.  WMMR.  CDC Nov. 2009. 58(45): 1267-1270. 
  4.   Joseph J. Gillespie, et al.  Louse- and flea-borne rickettsioses: biological and genomic analyses.  Vet. Res. 2009.  40: 12-24. 
  5.   Carlos E. Pérez-Osorio, et al.  Rickettsia felis as Emergent Global Threat for Humans.  Emerging Infectious Diseases.  14(7): 1019-1023. 
  6.   Nelson Lee, et al.  Risk Factors Associated with Life-threatening Rickettsial Infections.  Am. J. Trop. Med. Hyg. 2008.  78(6): 973-978.
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Spiro Stat uses modern molecular diagnostic approaches that have been validated under stringent criteria. All laboratory testing is performed in our CAP accredited CLIA laboratory, Southwest Regional PCR.