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Organism

Rickettsiae = obligate intracellular bacterial parasite

Incubation: 2-23 days

Transmission

Carried by host anthropods

Pathogenesis

Widespread vasculitis and endothelial proliferation may affect any organ

Thrombotic occlusion may lead to gangrene

Clinical features

Typhus clinical features

Rickettsial rash

Rickettsial rash

Types

Type Bacteria Vector Epidemiology  Notes
Epidemic typhus R. prowazekii Lice on humans often causes epidemics following wars and natural disasters i.e. Caused hundreds of deaths in Nazi concentration camps  

 

this is usually the condition meant when just talking about “typhus”

 

Rash begins in trunkal region, the spreads to peripheries.

Murine / endemic typhus R.typhi Fleas on rats More prevalent in warm coastal regions most commonly, southern California, Texas and Hawaii.  

Generally causes flu-like symptoms(often confused with flu)

Rocky mountain spotted typhus R.rickettsii Tick-borne Endemic in rocky mountains and SE USA Rash begins peripherally as macules and then becomes petechial/

Haemorrhagic.

Scrub typhus Orientia tsutsugamushi Harvest mites on humans or rodents Most common is SE Asia Signs include sudden deafness and lung signs

Complications

Diagnosis

Should be considered in all travellers form endemic areas with apparent septicaemia but negative blood cultures

  • Rise in antibody titre in paired sera is diagnostic
  • Skin biopsy may be diagnostic in rocky mountain spotted fever.

Treatment

Doxycycline or chloramphenicol

Prevention

Vaccine available

References

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