Detection and genetic diversity of Bartonella species in small mammals from the central region of the Qinghai-Tibetan Plateau, China

In this study, we aimed to investigate the prevalence and molecular characteristics of Bartonella infections in small mammals from the central region of the Qinghai-Tibetan Plateau. Toward this, small mammals were captured using snap traps in Yushu City and Nangqian County, West China, and the spleen tissue was used for Bartonella culture. The suspected positive colonies were evaluated using polymerase chain reaction (PCR) amplification and by sequencing the citrate synthase (gltA) gene. We discovered that 31 out of the 103 small mammals tested positive for Bartonella, with an infection rate of 30.10%. Sex differences between the mammals did not result in a significant difference in infection rate (chi(2) = 0.018, P = 0.892). However, there was a significant difference in infection rates in different small mammals (Fisher's exact probability method, P = 0.017) and habitats (chi(2) = 7.157, P = 0.028). Additionally, 31 Bartonella strains belonging to three species were identified, including B. grahamii (25), B. japonica (4) and B. heixiaziensis (2), among which B. grahamii was the dominant epidemic strain (accounting for 80.65%). Phylogenetic analyses showed that most of the B. grahamii isolates identified in this study may be closely related to the strains isolated from Japan and China. Genetic diversity analyses revealed that B. grahamii strains had high genetic diversity, which showed a certain host and geographical specificity. The results of Tajima's test suggested that the B. grahamii followed the progressions simulated by a neutral evolutionary model in the process of evolution. Overall, a high prevalence and genetic diversity of Bartonella infection were observed in small mammals in the central region of the Qinghai-Tibetan Plateau. B. grahamii as the dominant epidemic strain may cause diseases in humans, and the corresponding prevention and control measures should be taken into consideration in this area.