Rickettsia prowazekii

Cell Wall: Gram Negative Shape: Rod
Life Cyle: Obligate Intracellular Parasite
  • R. prowazekii is spread by lice. Epidemic outbreaks occur in areas afflicted with war or in large refugee camps following a major disaster. Sporadic cases occur in areas with endemically-infected flying squirrels via louse or flea vectors. Inoculation occurs during scratching of skin contaminated by organisms which are shed in the feces of infected lice.
Clinical Consequences
  • Epidemic Typhus
    • Epidemic Typhus is characterized by the abrupt onset of severe headache, fever, and myalgias within a week after inoculation. A red macular and petechial rash begins on the upper trunk and spreads to cover the entire body whilst sparing the palms, soles, and face. In severe cases, extensive thrombosis in the fingers can lead to gangrenous necrosis of the digits. Confusion and somnolence are seen in a large number of patients. The disease often resolves within a few weeks, but is fatal in a significant minority of untreated patients. Notably, Rickettsia typhi and R. prowazekii are so serologically similar that infection with one provides immunity to the other.
  • Brill-Zinsser Disease
    • If Epidemic Typhus resolves without antibiotic treatment, the organism can enter a latent state and remain for years. Brill-Zinsser Disease represents a reactivation of R. prowzekii infection years after the initial infection. Clinical consequences are similar to that of Epidemic Typhus but are generally milder and skin rash is not evident. Diagnosis can be made by detection of an early rapid rise of anti-Rickettsial IgG rather than a delayed rise of anti-Rickettsial IgM which would occur during in initial infection.
  • Doxycycline or chloramphenicol