HUMAN GRANULOCYTIC EHRLICHIOSIS IN SOUTHERN GERMANY - INCREASED SEROPREVALENCE IN HIGH-RISK GROUPS

To date, human granulocytic ehrlichiosis (HGE), the causative agent of which is likely transmitted by ticks in the Ixodes ricinus-Ixodes per sulcatus complex, has not been diagnosed,vith certainty in patients ou tside the United States. The presence of a closely related vector tick , I. ricinus, as well as the occurrence of similar Ehrlichia spp, of v eterinary importance, suggests that this disease is likely to be prese nt in Europe, The aim of the present study was to compare the prevalen ce of antibodies against the HGE agent in sera collected from patients in groups at high risk for exposure to I. ricinus with that of a cont rol population, Risk groups consisted of 150 forestry workers and 105 patients with an established diagnosis of Lyme disease, The control gr oup was 103 healthy blood donors without a history of tick bites. We u sed a patient isolate of the HGE agent from Minnesota (J. L. Goodman, C. Nelson, B. Vitale, J. E. Madigan, J. S. Dumler, T. J. Kurtti, and U . G. Munderloh, N. Engl. J. Med. 334:209-215, 1996) propagated in HLBO cells as the source of antigen for a specific immunofluorescence assa y (IFA). Elevated IFA titers (greater than or equal to 1:80) were pres ent in 21 of 150 (14%) serum samples from forestry workers and in 12 o f 105 (11.4%) serum samples from Lyme disease patients, but in only 2 of 103 (1.9%) serum samples from blood donors (P less than or equal to 0.01 for either of the at-risk groups versus blood donors), The resul ts of this study suggest that the HGE agent or a closely related organ ism exists In southern Germany and that seroconversion to it is common among groups exposed to Ixodes ticks. Final proof that HGE occurs in Germany will require the isolation of the causative agent from patient s, HGE should be considered in the differential diagnosis of febrile i llnesses in individuals exposed to Ixodes ticks in Europe as well as i n North America.