Identification of a novel strain of Borrelia hermsii in a previously undescribed northern California focus.

An epizootiologic investigation testing for the presence of tick-borne relapsing fever spirochetes in rodent and tick hosts was conducted at Eagle Lake in Lassen County, California. Six of 211 O. hermsii ticks and none of 180 rodents were polymerase chain reaction (PCR)-positive for Borrelia spirochetes. Sequencing of the PCR-amplified flagellin gene fragment suggests that the spirochetes from Eagle Lake represent a previously undescribed strain of Borrelia hermsii.