There are two types: Endemic (tick-borne) and Epidemic (louse-borne).
Rickettsia typhi infection; rat fleas (Xenopsylla cheopis) defaecate, human autoinnoculates by scratching. Humans are incidental hosts.
Similar disease inn southern Texas (Rickettsia felis). Vector is cat and opossum fleas (Ctenocephalides felis)
Incubation period of 1–2/52. Chills, fevers. Day 4: Macular rash → maculopapular (→ petechial rarely).
Chest signs are prominent. Hacking, non-productive cough; CXR shows interstitial pneumonia, pulmonary oedema, pulmonary effusions. May necessitate intubation and ventilation. Mortality is 1%.
Thrombocytopaenia, hyponatraemia, hypoalbuminaemia, mildly elevated liver enzymes, uraemia.
Treat with doxycycline for 7–15/7.
Rickettsia prowazekii infection; human louse vector (Pediculus humanus corporis). Louse defaecates, human autoinnoculates by scratching.
Incubation 1/52. Abrupt onset, severe headache, high fever (38.8 – 40.0°C). On day 5, widespread macular rash sparing palms, soles, face → maculopapular → petechial → confluent (→ skin necrosis rarely).
CNS signs are prominent: photophobia, conjunctival injection, eye pain. Mortality untreated is 40% (renal failure, multivisceral failure).
Brill-Zinsser disease is recrudescent epidemic typhus.
Treat with doxycycline until patient afrebrile for 24h.