Parasites of the genus Sarcocystis (Apicomplexa) are best known for their two-host lifecycle, which relies on prey–predator ecological relationships. All species produce sporocysts in the intestines of definitive hosts. However, while most Sarcocystis species form sarcocysts in the muscles of their intermediate hosts, some species develop them in the brains of intermediate hosts. In the present study, we aimed to evaluate the prevalence of Sarcocystis in the brains of small mammals from Lithuania and to perform a comprehensive analysis of their genetic variability.
In the period of 2021–2025, a total of 1528 small mammals (voles, mice, and shrews) belonging to 11 species were captured, and their brains were analysed for the presence of Sarcocystis cysts using microscopical and molecular techniques. The isolated parasites were genetically characterized using nuclear (18S rRNA, 28S rRNA, ITS1, ITS2), mitochondrial (cox1, cytb), and apicoplast (rpoB) markers.
Based on the light microscopy and DNA sequence analysis, Sarcocystis glareoli was identified in three rodent species (Apodemus flavicollis, Clethrionomys glareolus, and Microtus arvalis) and in a single eulipotyphlan species (Sorex araneus). By contrast to other Sarcocystis species, S. microti, known to form cysts in the brains of small mammals, was not observed. Statistically significantly, the highest prevalence of S. glareoli (11.5%) was established in Clethrionomys glareolus, while in other positive animals the infection rate did not exceed 2%. Some intraspecific genetic variability was observed in rRNA internal transcribed spacers ITS1 and ITS2. Phylogenetic analyses revealed that S. glareoli is closely related to S. jamaicensis, S. microti, and several undescribed Sarcocystis species using rodents as their intermediate hosts and raptors as their definitive hosts. The obtained results enhance the understanding of S. glareoli epidemiology, aid in its differentiation from related taxa, and advance phylogenetic insights into Sarcocystis species with small mammals as intermediate hosts.
