Detection and Characterization of Babesia Species in Ixodes Ticks in Estonia Olga Katargina, 1,2 Julia Geller, 1,2 Veera Vasilenko, 1 Tatiana Kuznetsova, 1 Lilian Ja ¨ rveku ¨ lg, 2 Sirkka Vene, 3 A ˚ ke Lundkvist, 3 and Irina Golovljova 1,3 Abstract The presence of Babesia spp. was studied in 2603 Ixodes ricinus and Ixodes persulcatus ticks collected at seven sites in Estonia. By reverse line blot screening, Babesia spp. was detected in 36 (1.4%) ticks, among them 18 (0.7%) were further recognized by a Babesia microti probe, 3 (0.1%) by a Babesia divergens probe, and the other 15 (0.6%) were recognized only by the universal Babesia spp. ‘‘catch all’’ probe. Sequence analyses of 6 of these 15 samples revealed that all of them belonged to Babesia sp. EU1. B. microti was detected in both tick species I. ricinus and I. persulcatus at the seven sites, whereas B. divergens-like and Babesia sp. EU1 were found only in I. persulcatus and I. ricinus, respectively. Genetic characterization based on partial 18S rRNA showed that the Estonian sequences of B. microti, B. divergens-like, and Babesia sp. EU1 share a high rate of similarity and are closely related to sequences from other European countries, Siberia, and United States. The present study demonstrated for the first time the existence and distribution of Babesia spp. in I. persulcatus and I. ricinus ticks in Estonia. Key Words: Babesia divergens—Babesia microti—Babesia species—B. venatorum—Estonia—Ixodes persulcatus—Ixodes ricinus—Prevalence—Ticks. Introduction B abesia (Apicomplexa, Piroplasmida) are protozoan parasites transmitted by Ixodes ticks to mammals and infecting the host erythrocytes. Babesia microti and Babesia divergens are the main etiologic agents of human babesiosis in the United States and Europe, respectively (Telford et al. 1993, Brasseur and Gorenflot 1996). In Europe, *40 human cases in splenectomized or immunocompromised patients due to B. divergens and B. divergens-like infections have been reported (Vannier and Krause 2009) with up to 42% mor- tality rate (Gorenflot et al. 1998). Moreover, a new non-B. divergens species EU1 (proposed name Babesia venatorum) has been recently described as a human pathogen in Italy, Aus- tria, and Germany (Herwaldt et al. 2003, Ha ¨ selbarth et al. 2007) and also detected in ticks and roe deer (Telford and Goethert 2004, Duh et al. 2005, Casati et al. 2006, Bonnet et al. 2007). The first European human case caused by B. microti was reported in Germany (Hildebrandt et al. 2007) and a wide distribution of this pathogen in ticks and small mam- mals has been demonstrated in Europe (Duh et al. 2001, Skotarczak and Cichocka 2001, Foppa et al. 2002, Goether and Telford 2003, Kalman et al. 2003). In Estonia, no human cases due to Babesia infection have been registered. However, human cases have been reported in neighboring countries such as Sweden and Finland (Uhnoo et al. 1992, Haapasalo et al. 2010), and the circulation of Babesia in the tick popu- lation was reported in Lithuania and Norway (Radzijevskaja et al. 2008). Ticks from the genus Ixodes spp. are the main vectors in- volved in Babesia transmission. In Estonia, two tick species, I. ricinus and I. persulcatus, are prevalent and widely distrib- uted, whereas in other European countries, I. ricinus is the most representative tick and plays a central role in the transmission of Babesia spp. The distribution of I. persulcatus is restricted to southeastern Estonia, whereas I. ricinus circulates in the whole territory of Estonia (Golovljova et al. 2004). No studies concerning Babesia have been performed in Es- tonia. The present study was undertaken to investigate the prevalence of Babesia in ticks collected from different parts of Estonia and to characterize the pathogen by molecular methods. 1 Department of Virology, National Institute for Health Development, Tallinn, Estonia. 2 Tallinn University of Technology, Tallinn, Estonia. 3 Swedish Institute for Infectious Disease Control, Stockholm, Sweden. VECTOR-BORNE AND ZOONOTIC DISEASES Volume 00, Number 00, 2011 ª Mary Ann Liebert, Inc. DOI: 10.1089/vbz.2010.0199 1