What you should know about... Cytauxzoonosis - Veterinary Medicine
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What you should know about... Cytauxzoonosis
A new treatment regimen shows promise in managing cats with this serious, often fatal infection.


Q: How do we diagnose this infection in domestic cats?

1. Signet-ring shaped Cytauxzoon felis. (Courtesy of Dr. Marlyn Whitney, University of Missouri Veterinary Medical Diagnostic Laboratory.)
A: Microscopic examination of a peripheral blood smear will reveal signet-ring-shaped piroplasms in the red blood cells (Figure 1) of most acutely infected cats, but since illness can occur before the red blood cell stage of infection, negative smears should be re-evaluated the next day. Alternatively, schizont-distended mononuclear cells accompany clinical illness (Figures 2A & 2B). These large cells are commonly found on aspirates of lymph nodes or spleen and are occasionally observed on blood smears. The infection can also be confirmed by polymerase chain reaction testing.

Q: What is the latest on how we should treat cytauxzoonosis in domestic cats?

2A & 2B. Schizont-laden macrophage (2A 100X; 2B 1000X). (Courtesy of Dr. Marlyn Whitney, University of Missouri Veterinary Medical Diagnostic Laboratory.)
A: In a recent study, the combination of an antimalarial drug, atovaquone, and the antibiotic azithromycin was demonstrated to result in improved survival of acutely ill cats compared with cats treated with the antiprotozoal drug imidocarb dipropionate.2 All cats also received supportive care including fluid therapy and blood transfusions when required. While only 26% of the imidocarb-treated cats survived, 60% of those treated with the combination drug therapy lived. However, the antimalarial drug is expensive and not readily available from nearby pharmacies.

Q: How do we prevent cytauxzoonosis in domestic cats?

A: Since the infection is transmitted only by ticks, tick prevention is key. Because there are no acaricides that can prevent tick bites perfectly, in endemic regions the most effective prevention is to apply products such as fipronyl and to keep cats indoors to minimize exposure.

Leah A. Cohn, DVM, PhD, DACVIM
Department of Veterinary Medicine and Surgery
College of Veterinary Medicine
University of Missouri
Columbia, MO 65211


1. Haber MD, Tucker MD, Marr HS, et al. The detection of Cytauxzoon felis in apparently healthy free-roaming cats in the USA. Vet Parasitol 2007;146(3-4):316-320.

2. Cohn LA, Birkenheuer AJ, Brunker JD et al. Improved survival of cats with acute cytauxzoonosis treated with atovaquone and azithromycin as compared to imidocarb dipropionate. J Vet Intern Med 2011;25(1):55-60.


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