NATURAL OCCURRENCE AND CHARACTERIZATION OF THE LYME-DISEASE SPIROCHETE, BORRELIA-BURGDORFERI, IN COTTON RATS (SIGMODON HISPIDUS) FROM GEORGIA AND FLORIDA

This is the first report of natural infection by Borrelia burgdorfei i n the cotton rat Sigmodon hispidus. Nine B. burgdorferi isolates were obtained from ear tissues, urinary bladders, or both, by culturing tis sues in BSKII medium. The rat from which the SI-3 isolate was cultured was from the same site (Sapelo Island, Georgia) as an infected cotton mouse Peromyscus gossypinus and Ixodes scapularis tick reported previ ously. The 8 B. burgdorferi isolates from rats in Florida included 1 ( AI-1) from Amelia Island, 1 (FD-1) from Paver-Dykes State Park, and 6 (MI-3 through MI-8) from Merritt Island. The distance between Sapelo I sland and Merritt Island is approximately 400 km. All B. burgdorferi i solates were characterized by indirect immunofluorescence using monocl onal antibodies to OspA (H3TS, H5332) and OspB (H5TS, H6831), polymera se chain reaction detection of specific B. burgdogferi B-31 DNA target sequences (ospA, fla, and a random chromosomal sequence), and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of spirochetal prot eins. The phenotypic and genotypic characteristics of the isolates are discussed, as well as the probable importance of the cotton rat as a reservoir for B. burgdorferi in the southern United States.