SEROLOGIC EVIDENCE OF A NATURAL INFECTION OF WHITE-TAILED DEER WITH THE AGENT OF HUMAN GRANULOCYTIC EHRLICHIOSIS IN WISCONSIN AND MARYLAND

White-tailed deer participate in the maintenance of the Ixodes tick li fe cycle and are reservoirs for some tick-borne infectious agents. Dee r may be useful sentinels for tick-transmitted agents, such as ehrlich iae, In order to determine whether white-tailed deer are markers of na tural transmission or are reservoirs for the human granulocytic ehrlic hiosis (HGE) agent, we performed indirect immunofluorescent-antibody ( IFA) tests and immunoblotting with the HGE agent and Ehrlichia chaffee nsis on sera from 43 and 294 deer captured in northwest Wisconsin duri ng 1994 and 1995, respectively, and 12 deer from southern Maryland. Ac cording to IFA testing, 47% of 1994 Wisconsin sera, 60% of 1995 Wiscon sin sera, and 25% of Maryland sera contained HGE agent antibodies. All IFA-positive deer sera tested reacted with the 44-kDa band which is u nique to the Ehrlichia phagocytophila group. Serologic reactions to E. chaffeensis were detected by IFA testing in 15 of 337 (4%) Wisconsin deer and in 10 of 12 (83%) Maryland deer, while 60 and 80% of E. chaff eensis IFA-positive Wisconsin and Maryland deer sera, respectively, re acted with the E. chaffeensis 28- to 29-kDa antigens by immunoblotting . A total of 4% of deer from Wisconsin and 25% of deer from Maryland w ere found by IFA testing to have antibodies to both the HGE agent and E. chaffeensis; 75% of these were confirmed to contain E. chaffeensis antibodies by immunoblotting. These results suggest that white-tailed deer in diverse geographical regions of the United States are naturall y infected with the HGE agent, E. chaffeensis, or both and that these animals, and potentially humans, are exposed to infected ticks at a hi gh frequency in nature.