Clinical and Laboratory Characteristics of Human Granulocytic Ehrlichiosis

Human granulocytic ehrlichiosis is being increasingly recognized in Wisconsin and Minnesota. A more severe illness is associated with increased age, anemia, increased percentage of neutrophils and decreased percentage of lymphocytes in peripheral blood, and presence of morulae in neutrophils. The differential diagnosis for patients who develop an influenzalike illness following a tick bite should include HGE. Microscopic examination of the acute-phase blood smear to detect neutrophilic morulae is currently the quickest and most practical screening method for diagnosing HGE in the upper Midwest.