Rickettsia prowazekii

• Cause of epidemic typhus

Background

Microbiology

• One of the Rickettsiae

Life Cycle

• Adult louse becomes infected when feeding on a rickettsemic patient
• The louse poops on another person
• The person scratches their skin or touches their mucous membrane, innoculating themselves with louse feces

Epidemiology

• Carried by the human body louse, Pediculus humanus corporis
• Outbreaks are associated with poverty, refugee camps, jails, and cold climate
• The only non-human reservoir is the flying squirrel (Glaucomys volans) in the US
• Previously-infected patients may still have latent infection

Clinical Presentation

• Incubation 1 to 2 weeks
• High fever, severe headache, myalgia, non-producive cough, delirium
• Dull, red rash starting on the trunk and spreading peripherally
  • Spares palms and soles
  • Rash not always present
• Delirium, hemorrhagic rash
• In its severe form, can progress to pulmonary edema, encephalitis, shock, and death

Brill-Zinsser disease (BZD)

• Reactivation or recrudescence of dormant typhus years after the initial infection
• Often in the context of malnutrition, chronic illness, and poor hygeine
• Rash may be evanescent or absent, and resolves faster

Diagnosis

• Four-fold rise in indirect immunofluorescence assay for IgG
• PCR may be useful during acute illness

Management

• Need to treat even without confirmed diagnosis
• Doxycycline 100 mg po bid for 7 to 10 days, until afebrile for 24 to 48 hours
• Chloramphenicol is the alternative
• Wash clothing to prevent outbreaks