Population Structure of East African Relapsing Fever Borrelia spp.

摘要

Differentiation of endemic East African tick-borne re-lapsing fever Borrelia duttonii spirochetes from epidemic louse-borne relapsing fever (LBRF) B. recurrentis spiro-chetes into different species has been questioned. We as-sessed a noncoding intragenic spacer (IGS) region to com-pare genotypes found in clinical samples from relapsing fever patients. Although IGS typing was highly discrimina-tory and resolved 4 East African tick-borne relapsing fever groups from a disease-endemic region in Tanzania, 2 IGS clades were found among LBRF patients in Ethiopia. The 2 IGS sequence types for B. recurrentis overlapped with 2 of the 4 groups found among B. duttonii. All cultivable isolates of B. duttonii fell into a single IGS cluster, which suggests their analysis might introduce selective bias. We provide further support that B. recurrentis is a subset of B. duttonii and represents an ecotype rather than a species. These ob-servations have disease control implications and suggest LBRF Borrelia spp. could reemerge from its tick-borne res-ervoirs in which vectors coexist