Zoonotic Surveillance of Bartonella spp.: Exploring the Public Health Risks in Human Settlements

Urban rodents are reservoirs of zoonotic pathogens, including Bartonella spp., which are transmitted by ectoparasites such as fleas. Zoonotic diseases caused by Bartonella often go undocumented due to confusing or subtle clinical symptoms, lack of awareness and poor diagnosis. This study aimed to assess the prevalence and diversity of Bartonella spp. by screening free-ranging rodents and their ectoparasites in the unique ecological settings of Alipore Railway Station, Kolkata, India. The station's high passenger traffic and proximity to food stalls create favourable conditions for rodents and fleas to thrive, increasing the risk of zoonotic transmission.

Rodents and fleas were identified by morphological features and DNA sequencing. Detection of Bartonella was carried out by DNA sequencing of citrate synthase (gltA) gene. Phylogenetic relationships among the obtained sequences were inferred through phylogenetic tree and haplotype network analyses. Q-PCR testing from human samples from the surrounding area was performed to confirm the zoonotic transfer potential.

Of 60 rodents, identified as Bandicota indica 28 (46.7%) and Bandicota bengalensis 32 (53.3%), and 110 fleas ( Xenopsylla cheopis ) were collected. The prevalence of Bartonella infection varied across three different hosts, that is, 32/60 rodents (53.33%), 87/110 fleas (79.1%) and 4/25 human (16%). Phylogenetic analysis revealed four distinct Bartonella lineages comprising 11 novel haplotypes (H1-H11), with haplotype H4 shared between rodents, fleas and humans, indicating active and cross species transmission of Bartonella spp. Haplotype H10, identified as B. rochalimae , was a phylogenetically diverged lineage exclusively found in fleas, suggesting a potentially novel lineage.

The results highlight the significant public health risks posed by Bartonella spp. in densely populated urban areas, particularly in environments like railway stations where human-rodent interactions are frequent. This study underscores the necessity of integrated pest management and surveillance strategies, using molecular tools such as Q-PCR, to mitigate the risk of zoonotic disease transmission in urban settings.