First report of natural Besnoitia akodoni infection in synanthropic (Muridae) and wild (Cricetidae) rodents from Argentina.

Besnoitia spp. are cyst-forming Apicomplexa parasites within the Sarcocystidae family. The objective of this study was to identify Besnoitia spp. in synanthropic (Muridae) and wild (Cricetidae) rodents from Argentina. Samples were collected from different organs and tissues of 356 rodents and examined by histopathological methods. Besnoitia cysts were detected by histopathology in 2 % (7/356) of the animals (i.e., two Mus musculus, two Necromys spp., two Oxymycterus rufus, and one Akodon azarae). The morphological diagnosis was molecularly confirmed by PCR and bidirectional sequencing of the ITS1 marker and flanking regions. The complete ITS1 region was identical in all seven samples, exhibiting 100 % identity with Besnoitia akodoni (AY545987). In addition, further characterization of the isolates targeting 18S rRNA and CoxI gene fragments was performed. Five identical 18S rRNA consensus sequences were amplified, which matched 100 % with Besnoitia sp. from Abrothrix hirta (Chile; OR052141) and B. jellisoni (AF291426) sequences. Besides, three CoxI consensus sequences were obtained from three different rodent species. These were identical among them and showed 92.88-92.93 % similarity to sequences from Besnoitia besnoiti uncharacterized protein (XM_029362743, among others). This is the first study to identify B. akodoni in naturally infected murid (Mus musculus) and cricetid (Necromys spp., Oxymycterus rufus, and A. azarae) rodents from Argentina, using both histopathological and molecular assessment. Further research is necessary to elucidate the significance of this parasite in rural ecosystems in our country.