AN ASSESSMENT OF THE ROLE OF WHITE-TAILED DEER IN THE EPIZOOTIOLOGY OF ANAPLASMOSIS IN THE SOUTHEASTERN UNITED-STATES

The role of white-tailed deer (Odocoileus virginianus) in the epizooti ology of anaplasmosis in the southeastern United States was examined t hrough retrospective and prospective serosurveys and by experimental i nfection studies. No serum antibody reactive to Anaplasma marginale wa s detected with an indirect fluorescent antibody (IFA) assay from any of 1,376 free-ranging deer sampled from 1968 through 1990 from 13 stat es and Puerto Rico. Thirty-one additional deer from three bovine anapl asmosis enzootic premises also were negative by IFA and Giemsa-stained blood films. Three captive deer given A. marginale intravenously deve loped antibodies 38 to 41 days post-inoculation (DPI) and remained ser opositive for the duration of the study (161 to 287 DPI). At 42 DPI, r ickettsemias of approximately 0.0001% infected erythrocytes were obser ved in all three deer using a DNA probe; low rickettsemias (maximum 0. 01%) persisted through 56, 63, and 87 DPI, respectively. One deer had a recrudescent infection from 126 to 146 DPI (maximum rickettsemia 0.0 01%). We believe that white-tailed deer in the southeastern United Sta tes, even though susceptible to A. marginale infection, are not expose d naturally, even at enzootic sites. Furthermore, white-tailed deer di d not develop rickettsemias sufficient to support mechanical transmiss ion by biting flies, which is believed to be the primary means of anap lasmosis transmission in this region.