Disseminated sarcocystosis in a cat with lymphosarcoma.

Cysts of the protozoan Sarcocystis sp were found in skeletal and cardiac musculature in a 1.5-year-old cat with lymphosarcoma. The cat was FeLV-positive and had grossly visible neoplastic involvement of the spinal cord, mediastinum, bone marrow, and kidneys. Ultrastructural examination of the parasitic cyst wall suggested that the species in this case was different from that described in the only other reported case. It was hypothesized that immunosuppression from FeLV infection permitted an aberrant life cycle with encystment of Sarcocystis sp in this cat.