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Ehrlichiosis, Monocytic 287

• Lymph node aspirates: cytologic evalua- ○ In acute infection, this results in rapid chronic disease. Clinical improvement is
tion rarely may demonstrate morulae in ○ In chronic infection, illness may not respond typically noted within 24-48 hours from
(24-48 hours) resolution of clinical signs.
VetBooks.ir • Advanced serologic testing: IFA tests for quickly, or damage may be irreparable (e.g., • Severe cases of CME with bleeding disorders Diseases and Disorders
lymphocytes.
the initiation of therapy.
have guarded prognosis, with up to a 25%
detecting serum antibodies to E. canis and
pancytopenia may not resolve).
E. chaffeensis
mortality.
○ A reciprocal titer ≥ 64 with clinical signs ○ Extended treatment (4 weeks) is recom- • Severely pancytopenic patients have poor
mended but may or may not eradicate
is recommended to confirm a diagnosis. the organism. prognosis, with mortality rates near 100%.
However, titers may initially be negative • Imidocarb dipropionate or enrofloxacin are
in acute cases. Therefore, a ≥ fourfold rise not effective. PEARLS & CONSIDERATIONS
between acute and convalescent titers (2-4 • Glucocorticoids can be used judiciously at
weeks apart) is ideal for serologic confir- antiinflammatory or immunosuppressive Comments
mation of acute infection. Titers are not dosages if a course of antimicrobial therapy • Animals that are febrile, lethargic, and
expected to rise during chronic infection. has failed to relieve immune-mediated thrombocytopenic should be tested for
• PCR analysis can detect and distinguish cytopenias, glomerulopathies, meningitis, vector-borne agents such as E. canis and E.
between E. canis and E. chaffeensis DNA in or arthropathies. chaffeensis.
blood. • E. canis infections in the United States are
○ PCR is much more sensitive than micro- Chronic Treatment often less virulent than infections in other
scopic evaluation for detecting organisms • Most chronic cases of CME respond to the parts of the world during the acute and
in acutely infected dogs. However, treatment regimen described above, but chronic phases of illness.
animals that are chronically infected or recovery from some manifestations of disease • Many animals that become infected do
are subclinical carriers may be seropositive (e.g., pancytopenia, glomerulonephritis) may not develop clinical signs or have transient
and PCR negative due to low numbers be slow or may not occur. clinical disease such that therapy is not initi-
of circulating organisms. • Animals that develop severe pancytopenia ated during the acute phase of infection.
○ A negative PCR result can never be used may require supportive care (e.g., blood These animals often progress to subclinically
to rule out ehrlichiosis. transfusions [p. 1169]). infected, chronic carriers. They will test posi-
○ No proven benefit of bone marrow tive on screening assays but appear clinically
TREATMENT stimulants (erythropoietin, granulocyte healthy.
colony-stimulating factor) • The two Ehrlichia spp that cause zoonotic
Treatment Overview • Animals with other complications may disease (E. chaffeensis and E. ewingii)
• In a patient with a positive Ehrlichia serologic require specific supportive care (e.g., severe are much more prevalent in the canine
result, a CBC, serum biochemistry profile, neutropenia can cause secondary bacterial population than is E. canis in areas of the
and urinalysis should be evaluated along with infection; glomerulonephritis can respond United States where the lone star tick is
physical exam findings. to standard therapy [p. 390]). found. In a large serosurvey in lone star-
○ In many dogs, the positive screening endemic areas, dogs were positive for E. canis
result (e.g., positive SNAP 4Dx Plus) is Drug Interactions (0.8%), E. chaffeensis (2.8%), and E. ewingii
an incidental finding (no clinical signs of Vomiting and drug-induced esophagitis are pos- (5.1%).
CME) and laboratory results are unre- sible with doxycycline. Risk reduced by giving
markable. Treatment in such cases may not it with meals and giving water after medicating Prevention
be necessary; the potential benefit must be • Regular use of acaricides for dogs, even
weighed against the risk of overtreatment Possible Complications using combinations of products for those
(test may be positive due to exposure but • Anemia (bleeding tendencies from severe with heavy tick exposure
not active disease). Whether treated or thrombocytopenia; bone marrow suppression) • Physical tick screening and removal imme-
not, seropositive dogs should be monitored • Thrombocytopenia (immune-mediated diately after activity in tick-bearing areas
annually (CBC, biochemistry profile, destruction of platelets, splenic sequestration
urinalysis), and any relevant abnormalities of platelets, bone marrow suppression) Technician Tips
would warrant treatment. • Severe neutropenia (bone marrow suppression • Medical hygiene precautions are impor-
○ A SNAP-positive animal with relevant or, less likely, immune-mediated destruction) tant; blood from acutely infected animals
clinical signs and laboratory abnormalities • Bone marrow aplasia is a severe life- has the potential to spread infection if
(e.g., thrombocytopenia, hyperglobulin- threatening complication of CME. inadvertently inoculated by contaminated
emia) compatible with CME should • Protein-losing glomerulonephropathy (limited needles.
receive a 4-week course of doxycycline number of dogs with CME) • Seropositive animals or animals previously
or minocycline. • Co-infections with other vector-borne agents infected with any tick-borne disease should
○ Due to genetic predisposition to CME, any can result in more severe clinical manifesta- not be used as blood donors.
German shepherd with a positive SNAP tions and/or poor response to antimicrobial • Gloves should be used when removing ticks
test result should be treated regardless of therapy. from dogs and cats.
laboratory findings.
○ Partial responders or animals that relapse Recommended Monitoring Client Education
after completion of doxycycline therapy • Periodic CBCs until cytopenias resolve • A positive blood test result may indicate a
should be tested for other vector-borne • Serum biochemical profiles to monitor disease risk for common-source exposure of other
agents, particularly Bartonella spp or progression by resolution of abnormalities dogs or of humans.
Babesia spp, which are poorly responsive • Urinalysis to monitor status of glomerular • Tick prevention is critical in subclinically
or nonresponsive to doxycycline. disease by presence/magnitude of proteinuria infected, seropositive animals.
○ Additional exposure to other tick-borne
Acute General Treatment PROGNOSIS & OUTCOME agents increases the likelihood for the
• Doxycycline or minocycline 5-10 mg/kg development of clinical manifestations.
PO q 12h × 28 days is the treatment of • The prognosis for complete recovery is good ○ Subclinically or clinically infected dogs
choice. for animals with acute infections or mild are potential reservoirs for ehrlichial

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