Typhus fever
Introduction.
There are 3 clinical forms of typhus fever: epidemic, endemic,
and scrub typhus; none are to be confused with typoid fever (Salmonella). Epidemic
typhus fever is caused by the highly infectious Rickettsia prowazekii and is
common in Africa and South America. Epidemic typhus fever has a human reservoir
and is transmitted by the human body louse. Endemic typhus,
present on most continents but less so in the US, is caused by R.
typhi is a zoonotic disease (rodent reservoir) transmitted by
fleas, and scrub typhus (Orientia tsutsugamushi) is a zoonosis
carried in and transmitted by mites. It is most common in Asia and
Australia.
Summary
Epidemic typhus
- Cause: Rickettsia prowazekii
- Microscopy: Gram-negative bacilli; tiny; intracellular
- Transmission: Human-to-human via body lice
- Symptoms: fever, chills, headache, myalgia, rash in <40%
- Complications: myocarditis, CNS dysfunction, high mortality if
untreated
- Pathogenesis: Intracellular replication in vascular endothelium
- Treatment: tetracycline, chloramphenicol
Endemic typhus
- Cause: Rickettsia typhi
- Microscopy: Gram-negative bacilli; tiny; intracellular
- Transmission: Zoonotic (rodents) via fleas
- Symptoms: fever, headache, myalgia, cough, rash in > 55%
- Pathogenesis: Intracellular replication in vascular endothelium
- Treatment: tetracycline, chloramphenicol, doxycycline
Scrub typhus
- Cause: Orientia tsutsugamushi
- Microscopy: Gram-negative bacilli; tiny; intracellular
- Transmission: Zoonotic (mites)
- Symptoms: fever, severe headache, myalgia, rash in < 50%
- Complications: spleen enlargement, CNS complications, heart failure
- Pathogenesis: Intracellular replication in vascular endothelium
- Treatment: tetracycline, chloramphenicol, doxycycline