Numerous species of Sarcocystis have been reported from wild ruminants but none has been
named from the Rocky Mountain goat (Oreamnos americanus). Mature sarcocysts were found in frozen
muscle samples of three of seven mountain goats from Alaska, USA. Two morphological types of
sarcocysts were found; one had Sarcocystis cornagliai-like sarcocysts, previously named from the Alpine
ibex (Capra ibex) from Europe. Two other goats were infected with a new species, Sarcocystis oreamni.
Sarcocystis oreamni sarcocysts were microscopic with 2 μm-thick sarcocyst wall. By transmission
electron microscopy, the sarcocyst wall had 1.7 μm-thick with unusual molar tooth-like villar protusions
(vp), type 29. The vp had electron dense core and two disc-shaped plaques at the tip with fine
microtubules. Bradyzoites were 8.6-9.1 μm long. Single nucleotide polymorphism (SNP) identified in
18S rRNA, and 28S rRNA loci of rDNA regions that suggested S. oreamni molecularly apart from related
species. The phylogenetic analysis based on 18S rRNA, and 28S rRNA sequences suggested S. oreamni is
related with Sarcocystis species that employ members of Canidae family as their definitive host.