VECTOR-BORNE AND ZOONOTIC DISEASES Volume 7, Number 4, 2007 © Mary Ann Liebert, Inc. DOI: 10.1089/vbz.2007.0143 Brucellosis of the Common Vole (Microtus arvalis) Z. HUBÁLEK, 1 H.C. SCHOLZ, 2 I. SEDLÁC ˇ EK, 3 F. MELZER, 4 Y.O. SANOGO, 1 and J. NESVADBOVÁ 1 ABSTRACT A systemic disease occurred in a wild population of the common vole Microtus arvalis in South Moravia (Czech Republic) during the years 1999–2003. Acute infections were characterized by edema of extremities, occasionally with colliquating abscesses, arthritis, lymphadenitis, perforations of the skin resulting from colliquated abscesses, orchitis, and peritoneal granulomas. From the clinical samples, small Gram-negative coccobacilli were isolated and identified as Ochrobactrum intermedium by API 20NE and colistin sensitivity profiles. However, subsequent rrs (16S rRNA) and recA (recombinase A) gene sequencing analysis of two isolates (CCM 4915  CAPM 6434; CCM 4916  CAPM 6435) identified them as Brucella sp. with sequence identities of 100% to other Brucella spp. Analy- sis of the omp2a/b genes confirmed the two isolates as Brucella. In AMOS polymerase chain reaction (PCR), a 2000-bp fragment was generated that was not seen in other brucellae. Experimental infection of outbred ICR mice with these isolates resulted in a mortality rate of 50%. Based on the results of the molecular investigations and the mortality observed in experimentally infected mice we conclude that the epizootic was caused by Brucella sp. and not by Ochrobactrum intermedium. The study demonstrates the limitations of commercial biochemical test systems in accurately differentiating among Ochrobactrum and Brucella. 679 INTRODUCTION T HE COMMON VOLE Microtus arvalis (Pallas) is a widely distributed rodent species in Eurasia, encountered from the European At- lantic coast to Central Siberia (Mitchell-Jones et al. 1999, Haynes et al. 2003). Primarily found in open habitats such as meadow, heath, and fallowland, the species has become abundant in agricultural fields (Mackin-Rogalska 1981, Zejda and Nesvadbová 2000, Jacob 2003). Be- sides its role as an agricultural pest, M. arvalis is the well-known host or reservoir of some human pathogens, e.g., Leptospira interrogans serovar Grippotyphosa, Francisella tularensis, and Babesia microti. The common vole population has been sub- jected to a longitudinal zoological investigation in a study area in South Moravia (Czech Re- public) since 1996. The study has involved cap- turing, marking, and recapture of the animals, with the aim of studying the population fluc- tuation (Zejda and Nesvadbová 2000, Jánová et al. 2003). In the late summer and autumn of 1999, an epizootic of unknown etiology occur- red in the common vole, with a marked impact on its population in the area, although sporadic cases had already been observed in 1998. This study describes the clinical presentation, the isolation of the causative agent, and its pheno- typical and subsequent molecular characteri- zation. 1 Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, Brno, Czech Republic 2 Bundeswehr Institute of Microbiology, D-80937 Munich, Germany 3 Czech Collection of Microorganisms, Masaryk University, Brno, Czech Republic 4 Friedrich Loeffler Institute of Bacterial Infections and Zoonoses, German Reference Center for Brucellosis, Jena, Germany.