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First Confirmed Case of Feline Cytauxzoonosis at ADDL

First Confirmed Case of Feline Cytauxzoonosis at ADDL

Macrophages laden with C. felis schizonts are present in vessel lumens of a section of liver (left) and lung (right) from a 6-year-old DSH cat that died from this infection.

The first cat in Ohio to be confirmed with a fatal infection of Cytauxzoon felis was diagnosed in June, 2018 at the ADDL. Necropsy of a 6-year-old, female, Domestic Short Haired cat from Scioto County showed gross lesions that included moderate dehydration, pale yellow mucus membranes and subcutaneous tissues (jaundice), splenomegaly, hydrothorax, pulmonary congestion and edema, hepatopathy evidenced by red mottled areas in the parenchyma, and dark yellow urine. The cat was 1 of 3 affected cats in a household of six that died suddenly with signs of anemia, high fever, lethargy, kidney disease and liver disease. All 3 affected felines were covered in ticks.


Histopathology of the lung showed multiple pulmonary vessels and septal capillaries filled with numerous macrophages laden with schizonts that had numerous 1-2-micron diameter, round to oval, basophilic organisms (merozoites). Hepatic vessels have myriad schizont-laden macrophages with smaller numbers in the sinusoids. Low numbers of macrophages containing similar schizonts were found in the kidney. Spleen tissue was forwarded to the North Carolina State University College of Veterinary Medicine Vector Borne Diagnostic Laboratory, which detected nucleic acid of Cytauxzoon by PCR testing.


Cytauxzoon felis is a protozoan hemoparasite in the family of Theileriidae, that causes severe clinical disease and high mortality in domestic and exotic cats in the south central and southeastern United States. The disease has erythocytic and tissue macrophage stages of infection. The natural reservoir is the North American bobcat (Lynx fufus) where the Cytauxzooninfection is usually subclinical. The infection is transferred from wild bobcats to domesticated cats by tick vectors (Dermacentor variabilis and Amblyomma americanum). Pet owners are reminded to check their pets often for ticks and to develop a tick bite prevention program for their pets in consultation with their veterinarian.


Dr. Craig Sarver, MS, DVM, Pathologist, and Dr. Jeff Hayes, MS, DVM, Pathology Section Head