A case report of Sarcocystis sp. isolated from a tumor-like tissue mass on the back of a 6-year-old ewe in Isfahan, Iran

Summary Sarcocystosis is a zoonotic disease in sheep caused by an intracellular parasite belongs to the phylum Apicomplexa, order Eucoccidioria, and Sarcocystidae family. In the parasite life cycle, there is a need for an intermediate host and a definite host. Some species of Sarcocystis can cause disease and consequently cause weight loss, anorexia, fever, anemia, muscle weakness, decreased milk production, abortion, and sometimes death in intermediate hosts such as cattle, goats, and sheep. Cysts of Sarcocystis spp. are found nearly always in skeletal, striated muscles, particularly in the diaphragm, heart, liver, lungs, and esophageal.  A six-years-old native ewe was referred to the veterinary clinic in Najafabad, Isfahan province, Iran with major clinical signs of nasal discharge, enlarged superficial lymph nodes, anorexia, and a round tumor-like mass on the back. After tissue processing and hematoxylin and eosin staining, different sizes of Sarcocystis spp. (with 3.03 ± 0.44 µm in length) each surrounded by a thin layer of muscle fibers and contained banana-shape bradyzoites were seen in the subcutaneous muscle fibers. Hemorrhage and infiltration of inflammatory cells, mainly, neutrophils were also seen in the dermis.