Cytauxzoonosis: A Tick-Transmitted Cat Parasite
Veterinary & Aquatic Services Department, Drs. Foster & Smith

What is cytauxzoonosis?

Cytauxzoon felis is a one-celled parasite that infects cats, causing the disease cytauxzoonosis. In the grand scheme of things, C. felis is a newly recognized parasite. It was first reported to cause disease in 1976. Since then, it has been reported from throughout the Southeast and into the Midwest United States.

How is cytauxzoonosis spread?

The life cycle has not been fully researched, but the parasite is spread by ticks. Bobcats appear to be the natural host, and usually have only mild symptoms when infected. Domestic cats are thought to be accidental hosts, i.e., not the usual host.

What are the symptoms of cytauxzoonosis?

Infected cats show signs 1 to 3 weeks after being bitten by an infected tick. Cats become extremely ill when infected, and C. felis affects many organ systems. It infects blood cells, and cells of the liver, lungs, spleen, and lymph nodes. The signs of disease include sudden listlessness, loss of appetite, anemia, difficulty breathing, high fever, and jaundice. It is commonly fatal, and the cat often dies in less than 14 days from the time the symptoms start.

How is cytauxzoonosis diagnosed?

The diagnosis of cytauxzoonosis is based on the history, results of the physical examination, and seeing the organism in blood cells examined microscopically. A polymerase chain reaction (PCR) blood test is also being used.

Can cytauxzoonosis be treated?

Until recently, there has been no known effective treatment; diminazene aceturate and imidocarb dipropionate have successfully treated a small number of cats. The combination of atovaquone and azithromycin has showed better promise. Intravenous fluids and other supportive care are also necessary. It is possible that a cat who recovers from the disease may become a carrier.

How can cytauxzoonosis be prevented?

Because there is no cure, tick prevention is extremely important. EPA-licensed products which contain the ingredients pyrethrin, etofenprox, selamectin, or fipronil are good choices, when used according to the manufacturer's directions. You may also want to keep your cat indoors during the tick season. For more information, see Tick Control.

References and Further Reading

Birkenheuer, AJ; Cohn, LA; Levy, MG; et al. Atovaquone and azithromycin for the treatment of Cytauxzoon felis. Abstract #13. Presented at the ACVIM Forum. San Antonio, TX; June 4-7, 2008.

Bondy, PJ; Cohn, LA; Kerl, ME. Feline cytauxzoonosis. Compendium Continuing Education for Veterinarians 2005;January:69-75.

Cohn, LA; Birkenheuer, JD; et al. Efficacy of atovaquone and azithromycin or imidocarb propionate in cats with acute cytauxzoonosis. Journal of Veterinary Internal Medicine 2011;25:55-60.

Yin, S. Rapid diagnosis needed for cytauxzoonosis. Veterinary Forum 2007;July:56-57.

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