Tick-borne Pathogens in Northwestern California, USA

In northwestern California, USA, the western blacklegged tick, Ixodes pacificus, is a known vector of Borrelia burgdorferi, the spirochete that causes Lyme disease.B. miyamotoi, which is more closely related to spirochetes that cause relapsing fever, has also been detected in 2 locations in California (1,2) and has recently been implicated as a human pathogen in the northeastern United States (3,4).Other studies may have unintentionally included B. miyamotoi infections among measures of B. burgdorferi if the diagnostics were for spirochetes (e.g., direct fluorescent antibody tests or dark-field microscopy) or genetically targeted for Borrelia spp.(5).To investigate Borrelia spp.ecology in California, we collected adult I. pacificus ticks by dragging a 1-m 2 white flannel blanket along vegetation and/or leaf litter in 12 recreational