Clinical Background
Rickettsia typhi is the etiologic agent of both epidemic and endemic typhus.
Epidemiology
- Incidence - <100 cases annually in the U.S.
- Transmission - louse or flea-borne
Organism
- Gram-negative coccobacilli which are obligate intracellular organisms
- A characteristic feature of the Rickettsiae is that they multiply in an arthropod as part of their life cycle
- With typhus (Rickettsia prowazekii and Rickettsia typhi), the invertebrate hosts are both reservoirs and vectors
- Rickettsia are part of a family of organisms responsible for the following rickettsial diseases:
- Spotted fever and typhus (vector: tick, louse, flea or gamasid mite)
- Scrub typhus (vector: chigger)
- Ehrlichiosis (vector: tick)
- Neorickettsiosis
- Q-Fever
- Risk Factors
- Epidemic typhus (louse-borne) - common in poor hygienic areas (e.g. jails)
- Endemic murine typhus (flea-borne) - common in close-quartered poverty
- Recrudescent typhus (Brill-Zinsser disease) - previously acquired disease that results from immunosuppression or old age
Clinical Presentation
- The incubation period for most rickettsioses ranges from 3-14 days
- Most patients develop nonspecific symptoms and signs
- Onset of disease is sudden in about half of the cases
- Fever and headache are the most commonly reported symptoms, but chills, myalgias, arthralgias, malaise and anorexia also are noted
- Rash (maculopapular) is a hallmark of infection, but it usually follows systemic symptoms; its absence should not rule out a possible rickettsial etiology
- Pulmonary involvement is frequent in murine typhus
- Serious central nervous system impairment can also be seen with typhus
- Meningitis present as aseptic by CSF cell counts
Treatment
- Antibody treatment is curative
See Also
