Rickettsiae

• Typhus groups

  1. Epidemic typhus ( Brill Zinsser disease )
  2. Endemic typhus ( Murine typhus )
  3. Scrub typhus ( Tsutsugamushi fever )
• Epidemic typhus is due to Rickettsia prowazekii and louse act as vector
• Rickettsia typhi causes Endemic typhus and it's vector is flea
• Orientia tsutsugamushi causes Scrub typhus and it's vector is mite
• Spotted fever group

  1. Rockey mountain spotted fever
  2. Rickettsial pox
• Tick carries Rickettsia rickettsii and causes rockey mountain spotted fever
• Mite carries Rickettsia akari and causes Rickettsial pox
• Coxiella burnetii causes Q fever and it's vector is tick
• Rickettsia isn't true bacteria
• Rickettsiae are lower protists
• Rickettsiae are sensitive to antibacterial drugs
• Rickettsia contains DNA, RNA and mucopeptide
• Unlike bacteria, it cannot breakdown glucose
• Unlike bacteria, rickettsiae are obligate intracellular parasites
• Rickettsia is gram negative
• Stain blue in Giesma stain
• Cannot grow on bacteriological culture media
• Can grow in intact animals, Yolk sac of chick embryo and tissue
• Multiply by binary fission
• Scrub typhus resembles epidemic typhus
• Eschar indicates the location of the mite bite in scrub typhus
• Isolation of Rickettsiae is technically difficult
• Indirect immunofluorescence and enzyme immunoassays are most widely used serological tests
• Polymerase chain reaction PCR is used for diagnosis
• Mites transmit the infection transovarially