Occurrence and preliminary molecular characterization of Sarcocystis spp. in wild Korean roe deer from Jeju Island, Korea

Sarcocystis spp. are common protozoan parasites infecting a wide range of intermediate hosts, including wild cervids. In this study, we investigated the occurrence and molecular characteristics of Sarcocystis infection in wild Korean roe deer (Capreolus pygargus tianschanicus) from Jeju Island, Korea. Sarcocysts were identified in the heart and skeletal muscle of 18 out of 40 examined animals (45.0%) based on histopathological examination. The cysts were oval to spherical in shape, measuring 42.41-340.29 μm in length and 31.62-129.76 μm in width, and were not associated with significant inflammatory responses. Molecular analysis targeting the 18S rRNA gene yielded 2 representative sequences, which showed 99.82% identity and high similarity to Sarcocystis linearis, as well as closely related species including S. taeniata and S. grueneri. Phylogenetic analysis placed these sequences within a clade of ungulate-associated Sarcocystis spp., although species-level resolution was not achieved due to the conserved nature of the marker. These findings provide baseline data on Sarcocystis infection in wild roe deer from Jeju Island and highlight the limitations of 18S rRNA-based identification for closely related Sarcocystis species.