The prevalence and genetic diversity of Bartonella species in wild rodents from South Korea

Bartonella species, which are globally distributed gram-negative facultative intracellular bacteria, can infect a diverse range of hosts. Rodents are crucial for the maintenance and dissemination of Bartonella spp., several of which are pathogenic to humans. Although Bartonella infections have been studied in various animals, Bartonella genetic diversity in wild rodents and their fleas has not been investigated. This study examined Bartonella prevalence and genetic diversity in wild rodents and fleas from South Korea in 2023-2024. Bartonella was predominantly detected in the rodent species, Apodemus agrarius. A total of 278 rodent blood and spleen samples, along with 22 pools derived from 33 fleas, were analyzed for the presence of Bartonella DNA. Quantitative real-time PCR (qPCR), targeting the small stable RNA A gene, identified Bartonella spp. in 133 rodents (47.84%) and 11 flea pools (50%). Phylogenetic analysis was conducted using partial sequences of the Bartonella citrate synthase gene and the 16S-23S rRNA internal transcribed spacer region. Sequencing and phylogenetic analysis using the maximum likelihood method identified eight Bartonella spp. in these rodents, including Bartonella grahamii and Bartonella elizabethae, which are pathogenic to humans. Bartonella taylorii was the species most frequently detected in the rodents. Half of the flea pools analyzed using qPCR were positive for Bartonella spp. Bartonella grahamii and taylorii were identified as the dominant species in fleas. These findings suggest that in South Korea, wild rodents serve as natural reservoirs for a diverse range of Bartonella spp., with fleas enhancing the risk of zoonotic disease transmission to humans, necessitating caution to prevent infection. This study outlines a potential vector-host relationship concerning Bartonella spp. transmission and persistence in South Korea.