Page 827 - Cote clinical veterinary advisor dogs and cats 4th

394 Granulocytic Anaplasmosis and Ehrlichiosis

• Most infected animals remain well but seen in granulocyte cytoplasm in some with doxycycline. To avoid these side effects,
can develop a chronic carrier state (either cases, depending on stage of infection and oral doxycycline should be given with meals.
VetBooks.ir • The reason that some animals develop clinical Advanced or Confirmatory Testing Possible Complications
the microscopist’s skill.
pathogen).
disease is uncertain and may depend on the
Co-infections with other tick-borne/vector-
immune status of the animal and complicat-
clinical manifestations and/or poor response
ing co-infections with other vector-borne • Microscopic analysis: buffy coat smears borne agents can result in more severe
prepared from peripheral blood can enhance
agents. the probability of identifying morulae in to antimicrobial therapy.
• A. phagocytophilum is transmitted by the deer circulating granulocytes.
tick (Ixodes scapularis, Ixodes pacificus, Ixodes • Serologic testing Recommended Monitoring
ricinus), and E. ewingii is transmitted by the ○ Negative serology result can occur in acute • Clinical response to treatment
lone star tick (Amblyomma americanum). infection because antibody production • To confirm infection if initially serology
• After inoculation, the organism invades takes time. negative, perform convalescent titers in
granulocytes and multiplies in membrane- ○ Positive antibody test result does not prove ≈3 weeks.
bound vacuoles, forming morulae that disease causation and must be interpreted
contain several individual bacteria. in light of other clinical findings. PROGNOSIS & OUTCOME
• Organisms are found in circulating granu- ○ The in-clinic ELISA, SNAP 4Dx Plus, can
locytes, granulocytes in synovial fluid, and detect antibodies to E. ewingii, Ehrlichia The prognosis for recovery from acute A.
in various tissues, including liver and canis, E. chaffeensis, A. phagocytophilum, phagocytophilum or E. ewingii infection is
spleen. and Anaplasma platys. excellent, but the organism may not be cleared
○ IFA tests run by diagnostic laboratories entirely.
DIAGNOSIS detect antibodies in patient serum and
provide a numeric titer. Ideally, serologic PEARLS & CONSIDERATIONS
Diagnostic Overview confirmation is based on a ≥ fourfold rise
The diagnosis is suspected in any dog with in titer between acute and convalescent Comments
a febrile lameness (or other findings listed serum samples taken 2-4 weeks apart, • In endemic areas, veterinarians often treat
above) that lives in or has recently traveled to although a single titer ≥ 64 in an animal based on clinical presentation (polyar-
an endemic area. Confirmation of infection with suggestive clinical signs is strongly thropathy, fever, thrombocytopenia) with
requires finding morulae in granulocytic cells, supportive. or without laboratory confirmation.
serologic evidence of infection, or polymerase • PCR analysis (anticoagulated blood, • Although illness due to these infections
chain reaction (PCR) analysis. synovial fluid) performed at commercial is remarkably similar and appearance of
labs can detect and distinguish between A. morulae is identical, there is only minor
Differential Diagnosis phagocytophilum and E. ewingii. overlap in the geographic area where these
• Because many tick-borne/vector-borne ○ PCR is much more sensitive in detecting infections are recognized.
agents can result in similar clinical find- organisms than microscopic evaluation. • A positive Anaplasma serologic test on the
ings, ticks can be simultaneously infected ○ Those chronically infected or subclinical SNAP 4Dx Plus in an area where E. ewingii
with multiple agents, and pets often have carriers may be seropositive and PCR infection is more likely than A. phagocyto-
multiple ectoparasites simultaneously, other negative due to the low numbers of philum may be due to A. platys. A. platys
tick-borne disease should be considered in circulating organisms. causes cyclic canine thrombocytopenia, but
the differential diagnosis, including but not ○ Even a single dose of appropriate antibiotic in the United States, clinical bleeding from
limited to other Ehrlichia spp, Anaplasma can result in a negative PCR test. the infection rarely occurs.
spp, Bartonella spp, and Rickettsia spp. • Most animals that become inoculated with
• Other causes of polyarthritis (pp. 803 TREATMENT either agent do not develop clinical signs
and 1270) or have clinical disease that is transient and
Treatment Overview self-limited. These animals often have positive
Initial Database Doxycycline is the treatment of choice and results on screening assays such as SNAP
• CBC often results in rapid (24-48 hours) resolu- 4Dx Plus but are clinically healthy.
○ Thrombocytopenia is the most common tion of clinical signs. Prolonged treatment is • Repeat infection/illness has not been known
abnormality (up to 90% of ill animals). usually prescribed to attempt to eradicate the to occur with either of these agents.
○ Mild anemia possible, particularly in dogs infection, but the efficacy of this treatment
with evidence of hemorrhage regimen for eliminating the organism has been Prevention
○ Initial, transient neutropenia; then normal questioned. Tick control: routine use of ascaricides and
neutrophil count or neutrophilia careful examination of the skin and haircoat
○ Morulae may or may not be identified in Acute and Chronic Treatment after any activity that carries the risk of tick
neutrophils. • Doxycycline or minocycline 5-10 mg/kg PO exposure
○ Lymphocyte counts vary; a reactive q 12h for 28 days
lymphocyte population is common. • Nonsteroidal antiinflammatory drugs or Technician Tips
• Serum biochemical profile: nonspecific antiinflammatory doses of glucocorticoids • It is best to use a smaller-gauge needle and
findings; increases in liver enzyme (alanine can be used judiciously in the initial period an easily compressible vein (cephalic or
aminotransferase, alkaline phosphatase) to relieve clinical signs of joint disease. saphenous, not jugular) and apply prolonged
activities may occur. Transient hypoalbu- • Animals with an incomplete response or pressure after venipuncture in animals with
minemia possible in dogs with acute A. relapse should be tested for other vector- severe thrombocytopenia.
phagocytophilum infection. borne agents, particularly those that respond • Blood from acutely infected animals has the
• Radiographs of affected joints: soft-tissue poorly to doxycycline (e.g., Bartonella spp). potential to spread infection if inadvertently
swelling from nonerosive polyarthritis inoculated into another animal or person by
• Arthrocentesis (p. 1059): with polyarthri- Drug Interactions contaminated needles.
tis, the synovial fluid contains increased Some dogs are sensitive to the gastrointestinal • Seropositive animals or animals previously
numbers of neutrophils. Morulae can be side effects (nausea and vomiting) associated infected with either of these agents, or any

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