Molecular and morphological characterization of Sarcocystis infections in muscles of red foxes (Vulpes vulpes) from Pennsylvania, USA

Sarcocystis infections are common in many species of herbivores and carnivores, but there is no report of Sarcocystis infections in red fox ( Vulpes vulpes ) from the USA. Here, we identified muscular infections in 10 (47.6%) of 21 red foxes from Pennsylvania. By a combination of different methods (light microscopy, electron microscopy, and molecular) we identified more than two Sarcocystis species. By light microscopy, sarcocysts had three types of sarcocyst walls (thin without any protrusions, thick with finger like protrusions, and thick without visible protrusions). By transmission electron microscopy, one sarcocyst resembled Sarcocystis neurona . By molecular characterization using 18S ribosomal RNA ( 18S rRNA), mitochondrial cytochrome c oxidase subunit 1 ( cox1 ), the internal transcribed spacer 1 (ITS1) surface antigen (SAG2) and protein markers such as GAPDH1, ROP21, and TUBA1, two Sarcocystis species were identified: S. neurona and S. caninum . Results indicate that the red fox is an intermediate host for S. neurona, a species causing fatal illness in horses and many other hosts in North America. Another species identified was S. caninum, which causes fatal illness in dogs.