The enlarging spectrum of tick-borne spirochetoses: R. R. Parker Memorial Address.

The author reviews his changing interest in tick-borne spirochetoses during his career (1951-1985) as a medical entomologist at the U.S. Public Health Service's Rocky Mountain Laboratory. The discoveries of relapsing fevers in the western United States in the 1930s and 1940s led to well-supported epidemiologic research, including studies on the relationships between vectors and spirochetes. When tick-borne relapsing fever in the United States was shown to be a relatively rare and readily treatable disease, financial support was withdrawn, and ongoing research was limited or terminated. Interest in relapsing fever spirochetes, particularly the relation to the relapse phenomenon in animal hosts, resurfaced in the 1960s and 1970s with the introduction of immunofluorescence assays and with the development of Kelly's medium for continuous cultivation of certain spirochetes. This interest increased significantly in 1981 when the author discovered a tick-borne spirochete to be the causative agent of Lyme disease and of several clinically related disorders in Europe. The discovery of this agent, now known as Borrelia burgdorferi, has led not only to intensive clinical, epidemiologic, and ecologic investigations in the United States and abroad but also to the identification of molecular and immunochemical techniques necessary for the study of the complex biology of tick-borne spirochetes. Reference is also made to a new species of Borrelia that may be the etiologic agent of epizootic bovine abortion in the western United States.