Rickettsia akari

From IDWiki
Rickettsia akari


  • Causes rickettsialpox


  • Disease caused by Rickettsia akari, an intracellular Gram-negative bacterium
  • Unlike most rickettsiae, it has a plasmid


  • Transmitted by the house mouse mite (Liponyssoides sanguineus)
    • Rodents are the reservoir
  • Most cases are in New York, but it is found worldwide
  • Most likely rickettsiosis to be found in Ontario
  • Homelessness and IV drug use are risk factors

Clinical Manifestations

  • Incubation period of 7 to 14 days
  • Present with fever, vesicular rash, and eschar
    • Headache also common
  • The eschar is painless, and appears as a papule about a week after innoculation, followed by vesicle that dries and leaves a brown or black eschar
  • The rash is vesicular, but may be papulovesicular or any other type of rash
    • Lesions leaves black crust and heal without scarring
    • Spares palms and soles
    • Resolves in two to three weeks
  • May find leukocytosis


  • Detection of a four-fold rise in convalescent titres by complement fixation or indirect fluorescent antibodies


  • Usually self-limited, resolving in 7 to 10 days, though antibiotics help
  • Doxycycline 100 mg po bid for 2 to 5 days and 48 h after fever resolves