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Rickettsiales are obligate intracellular bacteria that need vertebrates and arthropods to maintain their life cycles. Some species of the genera Anaplasma, Ehrlichia, and Rickettsia are transmitted by ticks to both animals and humans and can cause mild to severe and even fatal cases. In the Americas, there is substantial data on rickettsial agents, encompassing both clinical cases and the detection of these agents in ticks, but in Ecuador, the information about them remains poorly understood. Therefore, the objective of this study was to detect molecularly rickettsial agents in Amblyomma maculatum ticks in both parasitic and free-living phases collected from domestic animals and pasture in five localities across three coastal provinces of Ecuador. Rickettsia parkeri, Candidatus Rickettsia andeanae, and Ehrlichia sp. were recorded in A. maculatum for the first time in Ecuador. These records were made in a region where antibodies to the Spotted Fever Rickettsia Group were detected in humans. Additional studies are needed to characterize Ehrlichia sp. at a specific level. Furthermore, recognizing the specific Rickettsiales species circulating in the ticks and the hosts within a region is crucial for assessing potential contact risks., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

The aim of this work was to report the detection of a putative novel Ehrlichia strain associated with the tick Amblyomma triste . Free-living adult ticks determined as A. triste were collected by drag-sampling in Argentina and Uruguay. Molecular detection of Ehrlichia agents was performed targeting three different loci: 16S rRNA gene, dsb gene and a fragment of groESL heat shock operon. In total, 164 adults of A. triste (38 from INTA E.E.A Delta del Paraná in Argentina and 126 from Toledo Chico in Uruguay) were analyzed. One tick (0.6%) collected in INTA E.E.A. Delta del Paraná (Argentina) was positive. The phylogenetic analyses show that the Ehrlichia strain found in this study (named Ehrlichia sp. strain Delta) represents an independent lineage within the genus Ehrlichia , close to E. chaffeensis and E. muris . This is also the first report of an Ehrlichia agent infecting the tick A. triste . The medical and veterinary significance of Ehrlichia sp. strain Delta remains to be demonstrated. However, it is important to mention that adults of A. triste are aggressive to humans and domestic mammals. Therefore, the potential role of A. triste in the transmission of Ehrlichia agents to humans or domestic animals across its distributional range should be highlighted, even more considering that Ehrlichia sp. strain Delta is phylogenetically related to the zoonotic E. chaffeensis , which is recognized as pathogenic to both humans and animals.