Page 1506 - Small Animal Internal Medicine, 6th Edition

1478 PART XIV Infectious Diseases

pale mucous membranes were other reported physical 2 mL of a liquid (Bennett et al., 2010). Optimal treatment
examination abnormalities. Concurrent diseases are rarely duration is unknown, but 28 days is generally recommended
VetBooks.ir reported but have included hemoplasmas (previously Hae- provided there is resolution of clinical and laboratory abnor-
malities. For cats with treatment failure or those intolerant
mobartonella felis), Cryptococcus neoformans, feline leuke-
mia virus and feline immunodeficiency virus infections, and
(5 mg/kg IM or SC twice, 14 days apart). Salivation and pain
lymphoma. of doxycycline, imidocarb diproprionate can be given safely
at the injection site are the common adverse effects, and
Diagnosis imidocarb efficacy is in question for the treatment of canine
Anemia is common and usually nonregenerative. Leukope- monocytotropic ehrlichiosis (Eddlestone et al., 2007).
nia; leukocytosis characterized by neutrophilia, lymphocyto-
sis, and monocytosis; and intermittent thrombocytopenia Zoonotic Aspects and Prevention
have been reported in some cats. Bone marrow evaluation of Although cats and human beings can both be infected by E.
cats with cytopenias has revealed primarily hypoplasia of the canis and E. chaffeensis, direct transmission is not known to
affected cell line. However, one cat had bone marrow cyto- occur. Care should be taken when removing ticks, and
logic characteristics consistent with myeloid leukemia (Bre- arthropod control should be maintained at all time for cats,
itschwerdt et al., 2002). Hyperglobulinemia was reported in particularly if allowed outdoors.
multiple cats; protein electrophoresis usually reveals a poly-
clonal gammopathy. An epidemiologic link has been made
between the presence of Ehrlichia spp. antibodies in serum CANINE GRANULOCYTOTROPIC
and monoclonal gammopathy (Stubbs et al., 2000). On the EHRLICHIOSIS
basis of the cases reported to date, ehrlichiosis should be
considered on the list of differential diagnoses for cats with Etiology and Epidemiology
unexplained leukocytosis (primarily lymphocytosis), cyto- Ehrlichia ewingii forms morulae in neutrophils and eosino-
penias, and hyperglobulinemia. Biochemical abnormalities phils, and has been detected in dogs and human beings that
were infrequently reported in cats with suspected monocy- reside in the central region, as well as the Southern and
totropic ehrlichiosis and were nonspecific. The three cats Southeastern United States. In one seroprevalence study of
with E. canis–like DNA in the blood also had antinuclear dogs in North America and the Caribbean, positive dogs
antibodies, similar to results reported for infected dogs (Bre- were most common in Oklahoma (14.3%) and North Caro-
itschwerdt et al., 2002). lina (10.3%) (Qurollo et al., 2014). Ehrlichia ewingii has been
Some cats with suspected clinical ehrlichiosis seroreacted detected most commonly in A. americanum (Wright et al.,
to E. canis or N. risticii morulae in indirect fluorescent anti- 2014), and deer are reservoirs (Yabsley et al., 2002). In one
body assays. Antibodies that seroreact to more than one study of dogs naturally exposed to ticks in Oklahoma, all 10
Ehrlichia spp. are sometimes detected in cat sera. Some cats dogs became positive for E. ewingii DNA, but clinical abnor-
with E. canis–like DNA in blood were seronegative (Bre- malities were not detected (Starkey et al., 2014). The incuba-
itschwerdt et al., 2002), so suspect cases should be screened tion period after tick exposure is approximately 13 days.
concurrently by PCR assays. Information concerning accu- Pathogenesis of disease is unknown but is likely to be similar
racy of results from commercial kits optimized for the detec- to other Ehrlichia spp. In general, clinical signs of E. ewingii
tion of E. canis antibodies in canine serum when used with infection are less severe than those of E. canis. Concurrent
feline serum is not currently available. Positive serologic disease or infections may play a role in the pathogenesis of
test results occur in both healthy and clinically ill cats, so E. ewingii infection.
a diagnosis of clinical ehrlichiosis should not be based on
serologic test results alone. A tentative diagnosis of clinical Clinical Features
feline ehrlichiosis can be based on the combination of posi- Nonspecific signs of E. ewingii infection include fever, leth-
tive serologic test results or PCR assay results, clinical signs argy, anorexia, depression, and signs consistent with polyar-
of disease consistent with Ehrlichia infection, exclusion of thritis, such as stiffness. Other clinical signs include vomiting,
other causes of the disease syndrome, and response to anti- diarrhea, and peripheral edema and neurologic signs such as
Ehrlichia drugs. ataxia, paresis, and vestibular disease. Clinical signs can be
mild, self-limited, or inapparent (Goodman et al., 2003).
Treatment Similar to R. rickettsii, acute disease seems to be most
Clinical improvement after therapy with tetracycline, doxy- common, so E. ewingii infection should be highest on the list
cycline, or imidocarb dipropionate was reported for most of differential diagnoses from the spring through autumn
cats. However, for some cats a positive response to therapy when A. americanum is most active.
was a criterion for the diagnosis of ehrlichiosis. As for dogs,
administration of doxycycline at 5 mg/kg, PO, q12h or Diagnosis
10 mg/kg, PO, q24h should be effective. Doxycycline has Suppurative polyarthritis is most common. Other clini-
been associated with esophageal strictures and so should be copathologic findings typically associated with acute E.
formulated into a liquid for use in cats or followed by at least canis infection (see Table 95.3), such as mild to moderate