"Candidatus Borrelia kalaharica" Detected from a Febrile Traveller Returning to Germany from Vacation in Southern Africa

Abstract

A 26 year-old female patient presented to the Tropical Medicine outpatient unit of the Ludwig Maximilians-University in Munich with febrile illness after returning from Southern Africa, where she contracted a bite by a large mite-like arthropod, most likely a soft-tick. Spirochetes were detected in Giemsa stained blood smears and treatment was started with doxycycline for suspected tick-borne relapsing fever. The patient eventually recovered after developing a slight Jarisch-Herxheimer reaction during therapy. PCR reactions performed from EDTA-blood revealed a 16S rRNA sequence with 99.4% similarity to both, Borrelia duttonii, and B. parkeri. Further sequences obtained from the flagellin gene (flaB) demonstrated genetic distances of 0.066 and 0.097 to B. parkeri and B. duttonii, respectively. Fragments of the uvrA gene revealed genetic distance of 0.086 to B. hermsii in genetic analysis and only distant relations with classic Old World relapsing fever species. This revealed the presence of a novel species of tick-borne relapsing fever spirochetes that we propose to name "Candidatus Borrelia kalaharica", as it was contracted from an arthropod bite in the Kalahari Desert belonging to both, Botswana and Namibia, a region where to our knowledge no relapsing fever has been described so far. Interestingly, the novel species shows more homology to New World relapsing fever Borrelia such as B. parkeri or B. hermsii than to known Old World species such as B. duttonii or B. crocidurae.

Fig 1. Microphotograph of a thick blood smear of the patient at the time of admission.

The image shows spirochetes together with leucocytes. Striking is the relative short length of the bacterial cells (10μm) and the relative small number of turns. This morphology was observed in all intact bacteria in the slide. Pictures were taken with a 100x oil immersion objective and a T2 DSLR photo adapter.

Fig 2

Molecular phylogenetic analysis using the maximum likelihood method based on partial sequences of (A) 16S rRNA (473 bp), (B) flaB (694 bp) and (C) uvrA (900 bp). The taxa labels show the NCBI accession number, Borrelia species, and strain information (if available). The strain investigated in this study (indicated by a black dot)–although acquired in Africa–clusters more closely to New World RF species in flaB (B) and uvrA (C) phylogenies. The trees with the highest log likelihood are shown. The percentage of trees in which the associated taxa clustered together is shown next to the branches. Scale bar: substitutions per site. RF = relapsing fever; LB = Lyme borreliosis