Relapse phenomena in rats infected with single spirochetes (Borrelia recurrentis var. turicatae

Antigenic variation by the spirochete is generally believed to be responsible for the relapse phenomena in spirochetal relapsing fever. Schuhardt (1942) has reviewed the literature prior to 1942 on this subject, and little if any evidence has been presented subsequently to alter or extend this concept. Among the unanswered questions in spirochetal relapse phenomena are: (a) the antigenic variation capacity of a single spirochete, and (b) the capacity of an antigenic variety to recur in a series of relapses in a given animal. Although Cunningham, Theodore, and Fraser (1934) believe that antigenic varieties do not recur, other workers are not convinced that this possibility has been ruled out. Consequently we undertook a study of single spirochete infections in white rats in an effort to answer these two and possibly other questions related to the relapse phenomenon in spirochetal relapsing fever. METHODS A modification of the method developed by Hansen (1926), for the isolation of single fungus spores, was used for isolating single spirochetes for inoculatio