Geographic variation in the distribution of hard tick relapsing fever spirochete (Borrelia miyamotoi) (Spirochaetales: Spirochaetaceae) genotypes in host-seeking Ixodes scapularis (Acari: Ixodidae) nymphs and adults in the eastern United States.

Borrelia miyamotoi Fukunaga (Spirochaetales: Spirochaetaceae), the etiological agent of hard tick relapsing fever, has been detected at low prevalence in Ixodes spp. (Acari: Ixodidae) ticks from the Northern Hemisphere. Genetically distinct populations of B. miyamotoi have been described across continents and among Ixodes tick species distributed within continents. Within the eastern United States, a previous study identified two B. miyamotoi genotypes infecting Ixodes scapularis Say (Acari: Ixodidae). Here, we expand upon that work by developing a new multiplex PCR amplicon sequencing assay to differentiate B. miyamotoi genotypes (Am-East-1 and Am-East-2), and we use the new assay to differentiate genotypes in an expanded sample of 186 B. miyamotoi ticks collected from 17 eastern states. All 80 infections derived from the Northeast (Delaware, Massachusetts, Maryland, Maine, New Hampshire, and Vermont) or northern states in the Southeast region (North Carolina and Virginia) were identified as Am-East-1. Among the 106 B. miyamotoi infections identified in I. scapularis from the Ohio Valley (Illinois, Indiana, Kentucky, Ohio, and West Virginia), Upper Midwest (Michigan, Minnesota, and Wisconsin), or Northern Rocky Mountains and Plains (Nebraska) regions, 10 (9.4%) were characterized as Am-East-1 and 96 (90.6%) were characterized as Am-East-2. We also identified a new B. miyamotoi genotype (Am-IxKi1) in a single I. keiransi Beati, Nava, Venzal, & Guglielmone (Acari: Ixodidae) collected from Virginia.