Cytauxzoonosis

Anisa D. Dunham, AS, RVT Lynn F. Guptill, DVM, PhD, DACVIM (Small Animal)

BASIC INFORMATION • Parasites may also be found in aspirates of lymph nodes Description (glands), spleen, liver, or bone marrow. Cytauxzoonosis is a tick-borne blood disease of cats that occurs • Polymerase chain reaction tests are used to detect parasite DNA in central, south central, and southeastern states in the United in blood or tissues of ill cats and can be performed at some spe- States. It is also found in many locations worldwide. Infection cialized laboratories. However, results may not be reported for of domestic cats often results in a rapidly progressive, fatal dis- several days. ease. Bobcats are believed to be the reservoir host for the para- Other tests may be recommended to rule out other diseases that site. Affected bobcats may have long-term, usually asymptomatic cause similar signs. Such tests include chest and abdominal x-rays, infections. an abdominal ultrasound, and tests for other parasites. A necropsy Causes (similar to an autopsy in people) can confirm the diagnosis after Cytauxzoon felis , a protozoan (one-celled) parasite, causes cytaux- death of the animal. zoonosis. Ticks transmit the infection in nature. Cats usually become ill 2-3 weeks after exposure to infected ticks. Most infec- TREATMENT AND FOLLOW-UP tions are seen between March and September. Treatment Options Clinical Signs Treatment is often unsuccessful. Domestic cats appear to be highly Affected cats initially have nonspecific signs, such as decreased susceptible to this organism. Drugs used for treatment include a appetite and lethargy. A rapid course of severe illness and death combination of atovaquone and azithromycin (currently believed follows, usually in fewer than 5 days. Difficulty breathing, dark most effective) or imidocarb (alone). Supportive care is of utmost urine, dehydration, anemia, jaundice (yellow color to the skin and importance. Intravenous fluids, treatment for bleeding disorders, membranes of the eyes and mouth), and fever may occur. Low and blood transfusions are often necessary. body temperature and coma may develop shortly before death. Follow-up Care Diagnostic Tests If the cat survives, blood smears are usually monitored regu- Diagnosis is complicated by the fact that infected cats deteriorate larly to check for the parasite. Other tests may also be repeated so rapidly and may die before any testing can be performed. Early to monitor response to treatment. A program of strict tick control in the clinical course, diagnosis can be made by utilizing labora- and keeping cats indoors may help prevent cytauxzoonosis. Most tory tests, such as the following: cases of cytauxzoonosis have involved cats that roamed freely in • A complete blood cell count usually shows anemia. A very low wooded, tick-infested areas. The disease appears to be increasing white blood cell count, a low platelet count, or both occur later in incidence in many areas of the southeastern United States where in the course of the disease. bobcat populations have rebounded in recent years. • A blood biochemistry profile shows high total bilirubin, and Prognosis a urinalysis shows bilirubin in the urine, both of which are Prognosis is poor in most cases. Recently, an increasing number of related to the jaundice produced by the disease. cats have survived natural infections, perhaps due to early recogni- • Definitive diagnosis can be made by finding the parasite in red tion and treatment of the disease. In many cases; however, the death blood cells on blood smears. rate is high even with treatment using the most effective drugs.