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Borreliae Part 2: Borrelia Relapsing Fever Group and Unclassified Borrelia

Giusto Trevisan1, Marina Cinco2, Sara Trevisini3

  • 1DSM-Department of Medical Sciences, University of Trieste, 34149 Trieste, Italy.

Biology
|November 27, 2021
PubMed

Insights

Relapsing fever Borreliae are diverse, categorized by vectors like ticks and lice. These bacteria cause human relapsing fever, with evidence suggesting a common ancestor transmitted by hard-body ticks.

Area of Science:

  • Microbiology
  • Vector-borne diseases
  • Evolutionary biology

Background:

  • Relapsing fever Borreliae (RFG) are a heterogeneous group of bacteria.
  • They are classified into soft-tick-borne (STBRF), hard-tick-borne (HTBRF), louse-borne (LBRF), and avian relapsing fever groups.
  • STBRF Borreliae are further divided into Old World and New World strains.

Purpose of the Study:

  • To review the classification and characteristics of relapsing fever Borreliae.
  • To discuss the etiological agents of endemic and epidemic relapsing fever in humans.
  • To explore the evolutionary history and vector associations of RFG Borreliae.

Main Methods:

  • Literature review of existing studies on relapsing fever Borreliae.
  • Analysis of bacterial classification based on vectors and geographical distribution.
  • Examination of hypotheses regarding the evolutionary origins and vector switching of RFG Borreliae.

Main Results:

  • RFG Borreliae are transmitted by soft ticks (Ornithodoros spp.), hard ticks (Ixodes, Amblyomma, Dermacentor, Rhipicephalus spp.), and the human body louse (Pediculus humanus humanus).
  • All groups except avian relapsing fever Borreliae infect humans, causing significant spirochetemia and fever.
  • A hypothesis suggests a common ancestor transmitted by hard ticks, with subsequent vector shifts to soft ticks and lice.

Conclusions:

  • Relapsing fever Borreliae exhibit diverse vector associations and geographical distributions.
  • Understanding these classifications and evolutionary pathways is crucial for disease control.
  • New, unclassified Borreliae species relevant to relapsing fever are also identified.
Keywords:
BorreliaNew World strainsOld World strainsSpirochaetaavian relapsing feverhard-tick-borne relapsing feverlouse-borne relapsing feversoft-tick-borne relapsing feverunclassified Borreliae

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