Contents
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
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
- Sepsis / shock
- Renal failure
- DIC
- Stroke
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
