Cytology and histopathology remain the only commercially available tests for diagnosing C. felis infection. Serologic and molecular tests have been described but have only been available for research.12,73 The tissue phase of the infection can often be diagnosed by identifying schizont-infected macrophages in cytologic preparations
of tissues such as the lymph nodes, liver, or spleen (Figure 2). These infected macrophages will occasionally be seen in the feathered edge of stained thin blood smears. The erythrocytic
phase is characterized by the classic signet-ring-shaped piroplasms within red blood cells (Figure 3). The intracellular piroplasms can be differentiated from hematotropic Mycoplasma species, which have an epicellular location. Keep in mind that the erythrocytic phase is not always present or detected at
the time of presentation. So in endemic regions, perform a cytologic examination of the lymph nodes, liver, or spleen in cats
that are presented with acute febrile illness, especially when it is accompanied by icterus or cytopenias.
Figure 2. Schizont-laden macrophages occluding a splenic arteriole in a cat with cytauxzoonosis (hematoxylin-eosin; 200X).
Treatment and prevention
No treatments have demonstrated consistent efficacy against C. felis infection or consistent decreases in morbidity and mortality. Most clinicians agree that aggressive supportive care with
anticoagulants such as heparin and intravenous fluid therapy is the standard of care for cats with or suspected of having
cytauxzoonosis.70 The use of antiprotozoal drugs is somewhat controversial. There are a few reports of using imidocarb dipropionate or diminazene
aceturate to treat C. felis infection, but the effect of these treatments on survival is not clear.12,74 Some naturally infected cats that survived infection were treated with imidocarb, but at least as many cats that survived
either were not treated with imidocarb or received no treatment at all.12 If you institute treatment with imidocarb, pretreat with atropine to minimize cholinergic side effects. The dose of imidocarb
used in cats (2 mg/kg intramuscularly once) is lower than that used in dogs.74
Figure 3. Feline red blood cells infected with Cytauxzoon felis (Wright's-Giemsa; 750X).
Because no consistently effective treatment for C. felis infection is available, disease prevention is of the utmost importance. Tick transmission appears to be the primary route
of transmission, so avoiding exposure to ticks and promptly removing ticks are likely to be important to prevent transmission.
Ideally, cats should be housed indoors, especially during the spring and summer when ticks are most active.
Bartonella species are fastidious facultative intracellular gram-negative bacteria. Many Bartonella species have been demonstrated to be transmitted by insect vectors.75,76 The first Bartonella species was isolated in 1909 and was determined to be the agent of human disease in South America.77
Bartonella species are responsible for many diseases in both immunocompetent and immunocompromised people, including Oroya fever, trench
fever, cat-scratch disease, bacillary angiomatosis, and bacillary peliosis.
Most Bartonella species have been identified in the past 10 years.76 One characteristic of Bartonella species infections is their ability to cause persistent infections in their mammalian hosts that can last for years. Canine
Bartonella species infection was first described 1995.14 Since that time, five species of Bartonella have been identified in dogs: Bartonella vinsonii subsp berkhoffi, Bartonella clarridgeiae, Bartonella washoensis, Bartonella henselae, and Bartonella elizabethae.78-82