Four-hundred seventy-five permanent residents of Wisconsin were tested for antibodies to the agent of human granulocytic ehrlichiosis (HGE) by indirect immunofluorescent antibody (IFA) testing with Ehrlichia equi as antigen marker. Each resident completed a standard survey questionnaire about outdoor activities, animal and tick exposure, and any febrile illness during the preceding 12 months. Seventy-one serum samples (14.9%) contained E. equi antibodies. The mean IFA titer for seropositive residents was 250 (range, 80- 10,240). Seropositive residents were older than seronegative ones (62 vs. 56 years; P = .019). None of the seropositive residents had a history suggestive of ehrlichiosis. There was no association between the IFA test outcome and specific demographic variables or history of tick bites. HGE appears to be a common subclinical or mild infection among residents in northwestern Wisconsin.
Bibliographical noteFunding Information:
Received 23 March 1998; revised 18 August 1998. Grant support: Duluth Clinic Education and Research Foundation (grant no. 050-9938-7203). Presented in part at the 37th International Congress on Antibiotic Agents and Chemotherapy, in Toronto (abstract K57). Reprints or correspondence: Dr. Johan S. Bakken, Department of Infectious Diseases, SMDC Health System, 400 East Third Street, Duluth, Minnesota 55805.