Serological and clinical evidence for human granulocytic ehrlichiosis in north-eastern Switzerland

Background: Tick-borne human granulocytic ehrlichiosis (HGE) has not been diagnosed in Switzerland, although the HGE agent has been identified in ticks and animal reservoirs and human infections have been suspected on the basis of serological surveys. Methods: We retrospectively tested sera of 48 persons with antibodies to B. burgdorferi and/or tick-borne encephalitis virus for the presence of antibodies to E. phagocytophila (a surrogate marker of the agent of HGE), and reviewed their charts with regard to clinical manifestations possibly associated with a tick-borne infection. We then prospectively examined EDTA blood of 80 patients who presented with fever 7 to 21 days after a tick bite for the presence of the HGE agent (using nested PCR and microscopic examination of blood smears) and anti-E. phagocytophila antibodies. We also collected clinical data. Results: The retrospective study revealed 12 persons (25%) with anti-E. phagocytophila antibody titers greater than or equal to1:80, suggesting coinfection with HGE and either Lyme Borrelia or tick-borne encephalitis virus. Among these, 7 patients presented with clinical manifestations compatible with HGE disease. The prospective investigation identified 8 patients (10%) with anti-E. phagocytophila antibody titers greater than or equal to1:80, and 7 of these presented with signs and symptoms suggesting HGE. The HGE agent, however, was detected neither by PCR nor by microscopic examination. Conclusions: Serological and clinical data suggest die occurrence of an HGE-like agent as well as of coinfections with HGE and B. burgdorferi or tick-borne encephalitis virus in Switzerland. However, the HGE agent was not identified in persons living in Switzerland.