Page 1544 - Small Animal Internal Medicine, 6th Edition

1516 PART XIV Infectious Diseases

Babesia spp. infection by serology or PCR assays, and posi-
tive dogs should be excluded from the program (Wardrop
VetBooks.ir et al., 2016).
Babesia canis has been shown to be transmitted to 50% of
experimentally infected dogs by D. reticulatus after 8 hours
of feeding (Varloud et al., 2018). Thus acaricides that repel
or have a rapid kill time are indicated in endemic areas. In
one field study, an imidacloprid/flumethrin collar was 99.7%
against tick infestation, and had an efficacy of 91.6% for the
prevention of A. platys and 91.6% for B. vogeli (Dantas-
Torres et al., 2013).

CYTAUXZOONOSIS

Etiology and Epidemiology
Cytauxzoon felis is a protozoal disease of cats in the south- FIG 98.1
eastern, mid-Atlantic, and south-central United States that Cytauxzoon felis in the red blood cells of a cat. (Courtesy
is often fatal when clinical illness occurs unless appropriate Dr. Terry M. Curtis, Gainesville, FL.)
treatment is administered. Cytauxzoon spp. infection has
also been documented in a number of other countries
including Italy (Carli et al., 2012), France (Legroux et al., clinical findings. A primary differential diagnosis is hemo-
2017), Spain (Díaz-Regañón et al., 2017), and Portugal (Alho plasmosis. Ticks are rarely identified on affected cats.
et al., 2016). However, clinical illness has only occasionally
been detected in the cats infected in Europe suggesting it is Diagnosis
a different strain or variant of C. felis (Gallusová et al., 2016). Regenerative anemia, pancytopenia, and neutrophilic leu-
In contrast, isolates from domestic cats have been geneti- kocytosis are the most common hematologic findings;
cally similar between studies in the United States (Birken- thrombocytopenia occurs in some cats. Hemoglobinemia,
heuer et al., 2006b). Bobcats are usually subclinically affected hemoglobinuria, hyperbilirubinemia, and bilirubinuria are
and may therefore be the natural host of the organism. uncommon. Antemortem diagnosis is based on demonstra-
Recent genetic analysis performed on C. felis from bobcats tion of the erythrocytic phase on thin blood smears (Fig.
and pumas suggests multiple strains of the organism exist 98.1) stained with Wright or Giemsa stains (see Chapter
in wild felids (Shock et al., 2012). Domestic cats can be 91). Infected macrophages can be detected cytologically in
infected by different genotypes, alone or in combinations bone marrow, spleen, liver, or lymph node aspirates. The
(Cohn et al., 2011). The organism can be passed experimen- organism is easily identified on histopathologic evaluation of
tally from infected bobcats to domestic cats by Dermacentor most organs. Serologic testing is not commercially available.
variabilis (American dog tick) and Amblyomma americanum PCR can be used to amplify organism DNA from blood, and
(Lone Star tick), but based on geographical distribution of positive test results prove current infection.
infected cats, A. americanum is likely most important. Clini-
cal illness occurs after an incubation period of 5 to 20 days. Treatment
The majority of cases are diagnosed in April, May, and June Supportive care includes fluid therapy and blood transfusion
(Reichard et al., 2008). After infection, schizonts and mac- administered as indicated. Recently, a prospective study
roschizonts form in mononuclear phagocytes. The infected compared survival in cats treated with atovaquone at 15 mg/
macrophages line the lumen of veins throughout the body. kg PO q8h and azithromycin at 10 mg/kg PO q24h to cats
Merozoites released from the infected macrophages infect treated with imidocarb at 3.5 mg/kg IM (Cohn et al., 2011).
erythrocytes. Clinical disease results from obstruction of The survival rates for the atovaquone/azithromycin combi-
blood flow through tissues by the mononuclear infiltrates nation and imidocarb were 60% and 26%, respectively. Dim-
and from hemolytic anemia. Domestic cats occasionally inazene administered at 2 mg/kg IM twice, 7 days apart was
survive infection, suggesting that variants that are less viru- used in five cats that survived infection (Greene et al., 1999).
lent to cats also exist in the United States. Perinatal infec- However, some cases fail treatment with diminazene, and
tion did not occur from 2 queens to their 14 kittens (Lewis side-effects including monoparesis at the injection site, signs
et al., 2012). of nausea, and potential hepatotoxicity can occur (Lewis
et al., 2014).
Clinical Features
Most cases of cytauxzoonosis are in cats allowed to go out- Zoonotic Aspects and Prevention
doors. Fever, anorexia, dyspnea, depression, icterus, pale Cytauxzoon felis is not known to be zoonotic. The
mucous membranes, and death are the most common disease can only be prevented by avoiding exposure.