ABSTRACT.- Background: Ixodes fuscipes is a tick species found in the Southern Cone of America and the only member of the Ixodes ricinus complex present in Uruguay. Members of this complex are particularly recognized as vectors of diseases affecting human health, such as babesiosis, caused by parasites of the genus Babesia (Apicomplexa: Piroplasmida). However, even though potential hosts of I. fuscipes in Uruguay (rodents, birds, and artiodactyls) are known carriers of Babesia species, the potential role of I. fuscipes as a vector of piroplasmids has not been studied. Methods: In this study, questing I. fuscipes ticks were collected from five locations in Uruguay, and the presence of piroplasmid DNA was assessed using polymerase chain reaction (PCR) to amplify fragments of the small subunit ribosomal RNA (18S rRNA) and cytochrome c oxidase subunit 1 (COI) genes. Results: A total of 953 ticks (larvae, nymphs, and adults) were collected; 14 samples (two larval pools and 12 nymphs) tested positive. Genetic analyses using 18S rDNA and COI sequences revealed the presence of undescribed Babesia lineages, belonging to the Babesia odocoilei clade and others to the Babesia microti sensu stricto clade. Conclusions: This work represents the first association of Babesia spp. with I. fuscipes and highlights the importance of this type of study to detect and mitigate the emergence of diseases associated with these arthropods. © The Author(s) 2025.
