see also:

• clinically important bacteria
• Lyme disease
• tick-borne relapsing fever

• caused by Borrelia recurrentis which evolved to spread via the human louse rather than ticks as is the case with other Borrelia sp. presumably in response to higher density living of the Neolithic period
• evolved from the tick-borne cousin, Borrelia duttonii, about 6,000 to 4,000 years ago ¹⁾
• no non-human, animal reservoir exists
• 1st given the name of “relapsing fever” after an outbreak in Edinburgh in the 1840s - but this could have been a tick-borne relapsing fever
• in 1907, Frederick Percival Mackie discovered that human body louse can transmit Borrelia recurrentis, which causes relapsing fever as well
• not to be confused with tick-borne relapsing fever or Lyme disease both of which are caused by other Borrelia species

• occurs in epidemics amid poor living conditions, famine, and war in the developing world
• it is prevalent in Ethiopia and Sudan.

• spread via human body louse (which can also spread Rickettsia prowazekii and Bartonella quintana)
• humans become infected when it contacts their mucous membranes after they have crushed the infected body louse or scratch the area where the louse has been feeding

• incubation period of 5-15 days
• generally have a pattern of 3-4 cycles of fevers over several weeks
• initial cycle starts as a sudden fever, chills, headaches, muscle or joint aches, and nausea which lasts for 2-9 days
• severe cases may develop jaundice (icterus), severe mental state changes, bleeding, prolonged QTc

• blood smear or PCR

• mortality rate is 1% with treatment and 30–70% without treatment

• 1-2 week course of antibiotics - usually a tetracycline
• 50% develop Jarisch–Herxheimer reaction with tachycardia and hypotension which appears to be related to TNFa