Submitted to: Journal of Wildlife Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/1994
Publication Date: N/A
Interpretive Summary: White-tailed deer can become infected with a microorganism called Anaplasma marginale when inoculated experimentally. The microorganism invades red blood cells and causes clinical disease in cattle. This microorganism is usually transmitted in nature by biting flies and/or ticks. Over the past several years, the white-tailed deer populations have increased dramatically in the southeastern United States. Cattle producers are thus concerned about the possible contribution of white-tailed deer in outbreaks of the disease in cattle. A study was designed in cooperation with the USDA-ARS and the Southeast Wildlife Cooperative to investigate the role of these deer in nature. Although deer were susceptible to experimental infection, there was no evidence of infection in 1,376 free-ranging deer, as assessed by the failure to detect antibodies specific for the microorganism in the blood of these animals. The samples were obtained from animals in 13 southeastern states and Puerto Rico. In addition, 31 samples from deer in a known cattle disease area were also negative. Since the deer that were experimentally inoculated developed very low levels of microorganisms, it is concluded that the level of infection in wild deer is too low for transmission by biting flies. As a consequence, even if deer were to occasionally become infected, they would not serve as a reservoir of infection to cattle. Cattle most likely serve as the actual reservoir.
Technical Abstract: The role of white-tailed deer in the epizootiology on anaplasmosis in the southeastern United States was examined through retrospective and prospective serosurveys and by experimental infection studies. No serum antibody reactive to Anaplasma marginale was detected with an indirect fluorescent antibody (IFA) assay from any of 1376 free-ranging deer samples sfrom 1968 through 1990 from 13 states and Puerto Rico. Thirty-one additional deer from three bovine anaplasmosis enzootic premises also were negative by IFA and Giemsa-stained blood films. Three captive deer given A. marginale intravenously developed antibodies 38 to 41 days post- inoculation (DPI) and remained seropositive for the duration of the study (161-287 DPI). At 42 DPI, rickettsemias of approximately 0.0001% infected erythrocytes were observed in all three deer using a DNA probe; low rickettsemias (maximum 0.01%) persisted through 56, 63 and 87 DPI, respectively. One deer had recrudescent infection from 126 to 146 DPI (maximum rickettsemia 0.001%). We believe that white-tailed deer in the southeastern United States, even though susceptible to A. marginale infection, are not exposed naturally, even and enzootic sites. Furthermore, white-tailed deer did not develop rickettsemias sufficient to support mechanical transmission by biting flies, which is believed to be the primary means of anaplasmosis in this region.