Ectoparasite-borne <i>Bartonella</i> and <i>Rickettsia</i> in Chilean populations of <i>Rattus rattus</i> : prevalence, genetic diversity and environmental associations

<i>Rattus rattus</i> is a known reservoir of zoonotic pathogens, including <i>Bartonella</i> and <i>Rickettsia</i>, transmitted by ectoparasites such as fleas, mites, lice and ticks. The circulation of <i>Bartonella</i> and <i>Rickettsia</i> in these vectors in Chile remains poorly characterized. To evaluate the association between ectoparasite abundance, prevalence and diversity (including lice, fleas, mites and ticks) and the presence of <i>Bartonella</i> and <i>Rickettsia</i> within ectoparasites collected from <i>R. rattus</i> across different anthropogenic gradients in Chile, a total of 1,339 ectoparasites were collected from 411 <i>R. rattus</i> individuals across 27 localities. Ectoparasites were identified morphologically, and molecular detection of bacteria was performed using conventional and qPCR, targeting multiple genetic markers. Haplotype diversity and phylogenetic relationships were assessed. <i>Bartonella</i> and <i>Rickettsia</i> DNA were detected in fleas, ticks, mites and lice of <i>R. rattus</i>, with prevalence values reported separately for pooled and individually analysed ectoparasites. <i>Bartonella tribocorum, B. rochalimae</i> and <i>B. mastomydis</i> were identified. <i>Rickettsia felis</i> was confirmed in multiple ectoparasite groups. High haplotype diversity was observed in <i>Bartonella</i> but not in <i>Rickettsia</i>. Urbanization and tick prevalence were negatively associated with <i>Bartonella</i> occurrence; flea and tick prevalences were negatively associated with <i>Rickettsia. Rattus rattus</i> and their ectoparasites harbour a diverse range of potentially zoonotic <i>Bartonella</i> and <i>Rickettsia</i> species. These findings highlight the need for integrated surveillance and vector control strategies, especially in areas with variable human-wildlife interaction.