louse-borne relapsing fever

Introduction

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

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

¹⁾