| Summary: | Despite increasing reports of tick-borne diseases in Africa, remarkably, reports of tick-borne relapsing fever (TBRF) in Nigeria are lacking. <i>Ornithodoros savignyi</i> from Nigeria have been reported with the relapsing fever <i>Candidatus</i> Borrelia kalaharica. Conversely, in Ethiopia, the agent of relapsing fever is the louse-borne relapsing fever (LBRF) spirochaete <i>Borrelia recurrentis</i> with no TBRF reported to occur. A total of 389 <i>Ornithodoros</i> ticks, Ethiopia (N = 312) and Nigeria (N = 77), were sampled, together with 350 cattle, and 200 goat sera were collected from Nigeria. Samples were screened for <i>Borrelia</i> spp. by RT-PCR. Reactive samples were confirmed, then sequenced using flagellin B, 16S rRNA, and 16S–23S intergenic spacer region. The prevalence of <i>Borrelia</i> spp. in livestock was 3.8% (21/550) and 14% (3/21) after final molecular confirmation. Of 312 ticks from Ethiopia, 3.5% (11/312) were positive for <i>Borrelia</i>, with 36% (4/11) by conventional PCR. Sequencing revealed that the borreliae in soft ticks was <i>C.</i> B. kalaharica, whilst that found in animals was <i>Borrelia theileri</i>. Soft ticks were confirmed by sequencing 7% (22/312) and 12% (9/77) of the Ethiopian and Nigerian ticks, respectively. Phylogenetic analysis revealed that these were <i>Ornithodoros savignyi</i>. This is the first evidence of <i>C</i>. B. kalaharica in Ethiopia and demonstrates the co-existence of TBRF in a country endemic to LBRF. Important, this might cause a diagnostic challenge given that LBRF is predominantly diagnosed by microscopy, which cannot differentiate these two spirochaetes. Furthermore, we report <i>B. theileri</i> in ruminants in Nigeria, which may also be of veterinary and economic importance.
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