Prevalence, distribution and phylogenetic relationships of <i>Bartonella</i> in companion animals, wildlife and fleas from the Atlantic Forest ecoregion, Argentina

The aim of this study was to analyse the prevalence and distribution of Bartonella species in companion animals, wildlife and their associated fleas in different landscapes of the Atlantic Forest ecoregion of Argentina, and to analyse the phylogenetic relationships between the Bartonella species identified in this study in addition to those found in other regions available in GenBank. A total of 257 mammals, including rodents, opossums, dogs and cats, were examined to detect the presence of Bartonella in both fleas and host tissues. The study revealed the presence of Bartonella in rodent fleas (47.7%), opossum fleas (7.8%), rodent spleens (6.5%) and cat blood (10%). Analysis of 15 gltA gene fragments revealed the existence of at least three different genotypes and eight haplotypes. Genetic analysis has established a close association between Bartonella species from mammals and fleas in both the Atlantic Forest of Brazil and the Costanera Sur Reserve in Argentina. Bartonella henselae (Regnery et al.) Brenner et al. (Hyphomicrobiales: Bartonellaceae) was identified in three rodent species: Rattus rattus (L.; Muridae), Akodon montensis Thomas (Cricetidae) and Calomys tener Winge (Cricetidae). This marks the first report of B. henselae in R. rattus in Argentina, as well as the initial documentation of its association with A. montensis and C. tener. Additionally, Bartonella clarridgeiae Lawson and Collins (Hyphomicrobiales: Bartonellaceae) was identified in feline blood and in fleas from dogs and cats. These findings are particularly relevant in the context of areas undergoing deforestation, where interactions between wild and domestic hosts increase the risk of zoonotic disease transmission. A One Health approach is crucial to understand transmission dynamics and to address the challenges posed by fleas as infection amplifiers and spillover phenomena. These present significant challenges for public health and biodiversity conservation.