ORIGINAL INVESTIGATION V. Fingerle á U. G. Munderloh á G. Liegl á B. Wilske Coexistence of ehrlichiae of the phagocytophila group with Borrelia burgdorferi in Ixodes ricinus from Southern Germany Received: 30 July 1999 Abstract Human granulocytic ehrlichiosis (HGE) is an emerging infectious disease recognized in the Western hemisphere. HGE is well known to occur in North America, but records from outside the United States are sparse. The great majority of data from Europe are re- stricted to seroprevalence studies and molecular bio- logical detection of granulocytic ehrlichiae (GE) in ticks and mammals, but include de®ned cases from Slovenia. They argue for the existence of this disease in many parts of Europe. In the present study, 510 Ixodes ricinus ticks collected in ®ve dierent regions of Southern Germany were investigated for the presence of GE and Borrelia burgdorferi sensu lato using polymerase chain reaction. In all, 8 (1.6%) of the 492 ticks that could be evaluated (193 females, 208 males, and 91 nymphs) contained GE and 178 (36.2%) B. burgdorferi s.l.. Four of these ticks were infected with both pathogens. Interestingly, all ehrlichia-infected ticks were adults and all were collected in the English Garden, a recreational park area located in the city of Munich. Sequencing of the 16S rDNA (bp 1±1101) of four of the GE showed 100% sequence identity to each other and greater than 99.9% identity with the published sequence of the HGE agent. The four GE diered in respect to other hitherto described GE by a nucleotide exchange at position 336. These results show that GE that are closely related to the HGE agent are present in Southern Germany, and that coinfection with B. burgdorferi is common in GE-infected ticks. However, in contrast to B. burgdorferi which is endemic everywhere in Southern Germany, the distribution of GE seems to be focal. Key words Human granulocytic ehrlichiosis á Granulocytic ehrlichiae á Ixodes ricinus á Borrelia burgdorferi á Southern Germany Introduction Ehrlichiae are obligate intracellular rickettsial pathogens that infect leukocytes or platelets of mammals [36]. Granulocytotropic ehrlichiae (GE) are well-recognized veterinary pathogens of horses, ruminants, dogs, and small mammals [6, 19±21, 37, 38, 40, 43] and have recently been identi®ed as the agents of human granulocytic ehrlichiosis (HGE), an emerging disease [2, 7]. Ehrlichia equi, E. phagocytophila and the HGE agent are genetically closely related if not identical organisms in the E. phagocytophila group [7, 39]. Seroepidemiological and molecular studies indicate that granulocytotropic ehrlichiae belonging to the E. phagocytophila group are widespread not only in the US but also in Europe [2, 5±8, 10, 12 14, 16±18, 26, 29± 31, 33, 34, 42]. However, in Europe, de®ned cases of HGE have only been reported from Slovenia [18, 30]. In the United States, Ixodes scapularis and I. paci®cus are the principal vectors of GE and other pathogens, especially Borrelia burgdorferi sensu lato (s.l.), the etio- logical agent of Lyme disease [23, 28, 32, 35, 40]. Simi- larly, I. ricinus has long been known to transmit E. phagocytophila, the cause of tick-borne fever, in Eu- rope as well as B. burgdorferi [8, 12, 29, 31, 33, 42, 46]. Southern Germany is a highly endemic region for Lyme borreliosis with tick infection rates up to 33% [11]. However, infection rates of ticks for GE are not known. Therefore, the aims of the present study were to deter- mine the prevalence and 16S rDNA nucleotide sequence of GE in I. ricinus from Southern Germany, and to determine coinfection with B. burgdorferi s.l. Med Microbiol Immunol (1999) 188: 145±149 Ó Springer-Verlag 1999 V. Fingerle á G. Liegl á B. Wilske (&) Max von Pettenkofer-Institut fuÈr Hygiene und Medizinische Mikrobiologie, Ludwig-Maximilians-UniversitaÈt MuÈnchen, Pettenkoferstrasse 9a, D-80336 MuÈnchen, Germany Tel.: +49-89-51605225, Fax: +49-89-51604757 V. Fingerle Institut fuÈr Mikrobiologie und Hygiene, Humboldt UniversitaÈt Berlin, Berlin, Germany U. G. Munderloh College of Agriculture, University of Minnesota, St. Paul, Minnesota, USA