C-Type Virus in Bone Marrow Cells of Cats With Myeloproliferative Disorders

Clinical and pathological descriptions of 5 cats with myeloproliferative disorders are presented. Electron microscopic studies compared the bone marrow of these 5 cats with 3 clinically normal cats. C-type virus particles, 110–120 mμ in diameter, were found in various types of bone marrow cells of the 5 cats with myeloproliferative disorders. Immature particles budded from the plasmalemma and cytoplasmic vacuolar membranes, whereas mature virions were seen in intercellular spaces and within cytoplasmic vacuoles. These virions were morphologically similar to those known as the causal factor of feline lymphosarcoma. C-type virus was not found in bone marrow cells of 3 clinically normal cats.