Cytauxzoonosis in cats: eight cases (1985-1992)

Cytauxzoonosis is a rapidly and highly fatal disease in cats that is caused by the protozoan Cytauxzoon felis, which may be transmitted by Ixodid ticks (Dermacentor variabilis) from parasitemic bobcats (Lynx rufus). During an 8-year period, cytauxzoonosis was diagnosed in 8 cats, 7 cats within 14 months. Risk factors for these cats were warm weather, access to a wooded environment, and exposure to ticks. The most consistent clinical signs were acute lethargy, anorexia, decreased response to external stimuli (depression), icterus, dehydration, and capillary refill time > 2 seconds. Pertinent clinicopathologic findings were normocytic normochromic anemia, leukopenia, and thrombocytopenia; high serum concentrations of total bilirubin and glucose, low serum concentrations of albumin and potassium, high serum alanine transaminase activity; and, bilirubinuria. Confirmation of cytauxzoonosis was made by cytologic or histologic identification of the C felis organism. Splenic, lymph node, and bone marrow aspirates can provide an antemortem diagnosis when the number of parasitized erythrocytes is low on blood smears. Supportive treatment of 6 cats was temporarily palliative in some, but all 8 cats either died (3) or were euthanatized (5) when they became moribund. Survival time from observed onset of illness to death was < 5 days. Necropsy of 4 cats revealed predominately pulmonary involvement with venous congestion. Histologic examination revealed venous occlusion by parasitized mononuclear phagocytes in all tissue specimens, but only minimal inflammatory infiltrates.