The aim of this study was to describe the state of infection of roe deer (Capreolus capreolus) and red deer (Cervus elaphus) by Bartonella sp. in North-Western Poland through PCR detection of Bartonella 16S-23S rRNA ITS region in isolates of animal tissues, and also to describe the genetic diversity of detected Bartonella species based on molecular analysis of ITS. The multiple alignment analysis of ITS sequences was carried out, and homology matrices and phylogenetic trees were constructed. The DNA of Bartonella sp. was detected in tissues of 45.6% (36/79) C. capreolus and of 50% (15/30) C. elaphus. Products of two different sizes were detected: 317 bp, characteristic for B. schoenbuchensis, and 198 bp, characteristic for B. bovis. The obtained results suggest that roe and red deer are potential reservoirs of Bartonella sp. Most of the analysed ITS sequences was not specific for one host species. In constructed phylogenetic trees, sequences obtained from roe and red deer clustered together. These results suggest a lack of host specificity of most detected B. schoenbuchensis and B. bovis intraspecies strains
