RESUMEN
The features of S. felis sarcocystosis in muscles of the domestic cats [Felis domesticus] were studied. A complete clinical history, post mortem, and histopathologic examinations were done for each cat. Multiple protozoan elliptical cysts were in the skeletal muscles, heart, and diaphragm muscles of 3/17 [17.6%] adult cats. Ultrastructural characteristics of the brady-zoites and cyst wall were consistent with those descried for S. felis in bobcat and domestic cat. Clinicopathological study in 3 cats showed hypertrophy cardiomyopathy and lymphosarcoma associated with S. felis. Tissue samples showed a spectrum of pathological changes such as multi-focal subacute myocarditis and multi-focal subarachnoid lymphocytic infiltration. DNA extracted from muscles diaphragm with cysts was tested by PCR and sequence analyses of ssurRNA gene. The phylogenetic reconstructions using neighbor-joining method showed that S. felis is closely related to S. neurona. The results were illustrated and photographed and peer discussed.