Rickettsiales in South America: A Systematic Review of Their Molecular Detection and Distribution in Arthropods and Vertebrates

ABSTRACT Bacteria of the order Rickettsiales comprise a diverse group of obligate intracellular microorganisms that are globally distributed and highly prevalent in tropical and subtropical regions. In South America, these bacteria have been associated with arthropod vectors, such as ticks, fleas, mites, lice, and certain dipterans, as well as with a wide range of vertebrate hosts. Despite their relevance to human and animal health, many Rickettsiales species remain underestimated or are not included in official epidemiological surveillance systems, limiting their timely diagnosis and effective control. Given this context, the objective of this study was to conduct a systematic review, following the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) guidelines, on the distribution of Rickettsiales in South America based on molecular reports, addressing their detection in arthropods and vertebrates (including humans). A total of 646 articles meeting the inclusion criteria were analyzed, from which 43 Rickettsiales species were identified, spanning seven genera, including Candidatus taxa. The results demonstrate the molecular detection of Rickettsiales in 58 species of the order Ixodida, mainly of the genus Amblyomma , as well as in seven other arthropod orders. In vertebrates, infections were detected in 160 species of vertebrates, notably 53 species of birds and 107 species of mammals (including humans). The presence of 11 species of Rickettsiales in humans, including emerging forms, such as Candidatus Anaplasma sparouinense . These findings significantly expand knowledge about the diversity and distribution of Rickettsiales in South America and highlight the need to strengthen integrated approaches to research and public health, especially in regions of high biodiversity.