Morphological and molecular identification of Sarcocystis arctica sarcocysts in three red foxes (Vulpes vulpes) from the Czech Republic.

Muscular sarcocystosis by Sarcocystis arctica was found for the first time in the Czech Republic, in different muscles of red fox (Vulpes vulpes). Cysts were slim, elongated, thread-like, whitish, 1-7mm long, and 206-270μm wide; bradyzoites were 7.9×2.7μm in unstained wet mounts and 9.2×2.9μm in cyst Giemsa-stained smears. The cyst wall was thin, with short villi-like protrusions, and no host response was observed in the histological sections. Examination of the distribution and intensity of sarcocysts in 17 different muscle groups revealed that the highest intensity was in the cranial tibial muscle (>15 cysts in compressoria), followed by the diaphragm, forearm, and other groups (with intensities of 3-15 cysts in compressoria). Sarcocysts were detected in 3 out of 86 foxes. Genetic characterization at 18S rRNA, 28S rRNA, ITS1 and cox1, consistently showed that the species was identical with S. arctica. Interestingly, this protozoan was also detected as a co-infection in 3 foxes with the nematode Trichinella spp. for the first time.