Morphological and molecular identification of Sarcocystis arieticanis isolated from the cardiac muscles of domestic sheep and goats

Sarcocystis species are the most common intracellular protozoans and zoonotic parasites that infect the cardiac, striated, and non-striated muscles of omnivores, herbivores, carnivores, reptiles, fishes, and humans. This study aimed to detect and identify the existence of Sarcocystis species in the cardiac muscles of sheep and goats through a combination of morphological and molecular analysis. The morphological analysis relied on the cyst's wall structures obtained from the cardiac muscles of both hosts showed thin wall cysts with irregularly arranged hair-like protrusions. Furthermore, the molecular study based on the 18S rRNA genes found that the cysts were most closely related to S. arieticanis with 99.46% nucleotide homology. The total prevalence of sarcocystosis in sheep and goats via microscopical investigation was 98.70%, while it was 100% via molecular analysis. Sequencing and phylogenetic analysis illustrated that S. arieticanis has a strong phylogenetic correlation and regarded as a sibling species with a monophyletic cluster to S. tenella of sheep and S. capracanis of goats, in which canines are their definitive hosts. Due to the high frequency of sarcocysts infection and their impacts on the host's health status and economy in Iraq and in other countries, hygienic policies and preventative measures are essential for controlling the disease. To the author's knowledge, this is the first molecular and morphological study achieved to identify S. arieticanis in sheep and goats in Iraq.