Page 1503 - Small Animal Internal Medicine, 6th Edition

CHAPTER 95 Polysystemic Rickettsial Diseases 1475

TABLE 95.3
VetBooks.ir Clinicopathologic Abnormalities Associated With
Ehrlichia canis Infection in Dogs
STAGE OF
INFECTION ABNORMALITIES
Acute Thrombocytopenia
Leukopenia followed by neutrophilic
leukocytosis and monocytosis
Morulae
Low-grade, nonregenerative anemia
unless hemorrhage has occurred
Variable Ehrlichia titer
PCR-positive
Subclinical Hyperglobulinemia
Thrombocytopenia FIG 95.5
Neutropenia Lymph node cytology from a dog with chronic Ehrlichia
Lymphocytosis canis infection.
Monocytosis
Positive Ehrlichia titer
PCR-positive of neutropenia, thrombocytopenia, and anemia can occur.
Chronic Monocytosis Changes in bone marrow cell lines associated with ehrlichi-
Lymphocytosis osis vary from hypercellular (acute phase) to hypocellular
Thrombocytopenia (chronic phase). Bone marrow plasmacytosis is common
Nonregenerative anemia
Hyperglobulinemia in dogs with subclinical and chronic ehrlichiosis, and the
Hypocellular bone marrow disease can be confused with multiple myeloma, particularly
Bone marrow/spleen plasmacytosis in dogs with monoclonal gammopathies. However, dogs
Hypoalbuminemia with ehrlichiosis are typically normocalcemic and do not
Proteinuria have lytic bone lesions.
Polyclonal or immunoglobulin G Hypoalbuminemia in the acute phase is probably caused
monoclonal gammopathy by third spacing of albumin in tissues because of vasculitis
Cerebrospinal fluid mononuclear cell or due to the acute phase response (i.e., albumin is a negative
pleocytosis acute phase protein [APP]), whereas in the chronic-phase
Nonseptic, suppurative polyarthritis disease it is caused by glomerular loss from immune complex
Rare azotemia deposition or chronic immunostimulation (i.e., monoclonal
Increased alanine aminotransferase and or polyclonal gammopathy). Prerenal azotemia can occur
alkaline phosphatase activities
Positive Ehrlichia titer with acute or chronic disease; renal azotemia develops in
Variable PCR positive some dogs with severe glomerulonephritis from chronic
ehrlichiosis. The combination of hyperglobulinemia and
PCR, Polymerase chain reaction. hypoalbuminemia is consistent with subclinical or chronic
ehrlichiosis. Polyclonal gammopathies are most common,
but monoclonal (e.g., immunoglobulin G) gammopathies
granules (i.e., large granular lymphocytes). Ehrlichia canis can also occur. Serum cardiac troponin I concentration is
infection results in changes in lymphocyte subsets in dogs, increased in dogs with ehrlichiosis compared with healthy
sometimes mimicking chronic lymphocytic leukemia (i.e., controls, but concentrations did not correlate to clinical
clonal proliferation); further data are needed to determine outcome (Koutinas et al., 2012). The positive APP C-reactive
the clinical significance of these findings (Villaescusa et al., protein (CRP), serum amyloid A (SAA), and haptoglobin
2012). Regenerative anemia is from blood loss (acute and (Hp) and the negative APP albumin concentrations were
chronic phases); normocytic, normochromic nonregenera- measured in 27 dogs with nonmyelosuppressive chronic
tive anemia is from bone marrow suppression or anemia monocytropic ehrlichiosis, 29 dogs with myelosuppressive
of chronic disease (chronic phase). Thrombocytopenia can chronic monocytropic ehrlichiosis, and 7 healthy dogs. The
occur with either acute or chronic ehrlichiosis but is gener- APP levels correlated to type of clinical syndrome but not to
ally more severe in the chronic phase disease. Thrombocyto- clinical outcome (Mylonakis et al., 2011a).
pathies from hyperglobulinemia potentiate bleeding in some Aspirates of enlarged lymph nodes and spleen reveal reac-
dogs with chronic ehrlichiosis. Chronic ehrlichiosis is clas- tive lymphoreticular and plasma cell hyperplasia (Fig. 95.5).
sically associated with pancytopenia, but any combination In one study, plasma cells were more commonly detected in