Rickettsiae = obligate intracellular bacterial parasite
Incubation: 2-23 days
Carried by host anthropods
Widespread vasculitis and endothelial proliferation may affect any organ
Thrombotic occlusion may lead to gangrene
|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/
|Scrub typhus||Orientia tsutsugamushi||Harvest mites on humans or rodents||Most common is SE Asia||Signs include sudden deafness and lung signs|
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.
Doxycycline or chloramphenicol