Ehrlichia (Anaplasmataceae) Flashcards
What agent causes ehrlichia?
Gram negative, obligate intracellular bacteria
- Ehrlichia canis (Canine monocytic ehrlichiosis)
- Ehrlichia chaffeensis (Canine monocytic ehrlichiosis)
- Ehrlichia ewingii (Canine granulocytic ehrlichiosis)
What type of cell(s) does ehrlichia infect?
Leukocytes and platelets
Where (geographically) is ehrlichia commonly seen?
Tropical areas (mostly in the south)
- “Tropical” transmits better than “temperate”
How do dogs get infected with ehrlichiosis?
Tick bites (transtadial, 3-host tick)
-
Ehrlichia canis (Canine monocytic)
- Rhipicephalus sanguineus/ Brown Dog Tick
-
Ehrlichia chaffeensis (Canine monocytic)
- Amblyomma/ Lone Star Tick
- Dermacentor variabilis/ American Dog Tick
-
Ehrlichia ewingii (Canine granulocytic)
- Amblyomma americanum/ Lone Star Tick
- TRANSMISSION FOR AT LEAST 150 DAYS
T or F. Ticks are the true reservoirs in ehrlichiosis.
False
- No transovarial transmission
- Need an infected dog
- Adult survives 2 years
What are the 3 phases and their clinical signs in canine monocytic ehrlichiosis (E. canis)?
-
Acute phase
- Non-specific signs (mild thrombocytopenia, anemia, and leukopenia)
- 2-3 weeks post infection
- Lasts 2-4 weeks
-
Subclinical phase
- No signs (mild thrombocytopenia)
- 40 days to several years
- Immunocompetent animals can eliminate the organism
-
Chronic phase
- Vague signs
- Organ failure
- Severe hematological changes
What are the clinical signs of acute or chronic phase ehrlichiosis (E. canis)?
-
Multisystemic
- Lethargy, weight loss, superficial bleeding, lymphadenomegaly, splenomegaly
-
Neuromuscular
- Meningitis, intracranial disease, poliomiositis, poliarthritis
-
Ocular
- Anterior uveitis, coriorretinitis
-
Others
- Renal failure, glomerulonephritis, myocarditis
What lab work changes can you see with ehrlichiosis (E. canis)?
CBC and proteinuria important
- Lymphocytosis (large granular) *- not many other ddx
- Thrombocytopenia, anemia, leukopenia
- Subclinical phase: thrombocytopenia
- Chronic phase: pancytopenia
-
Hyperglobulinemia
- Monoclonal or polyclonal (monoclonal gammopathy is usually multiple myeloma)
- Proteinuria
- Mast cell pleocytosis
How do you diagnose ehrlichiosis (E. canis)?
-
Signs & serology (exposure)
- Takes time to develop Abs and takes up to a year to clear
-
False negative:
- Test too soon (may take a month to seroconvert)
-
False positive:
- Cross reactivity (Abs to other ehrlichia)
- Previous exposure (Abs persist for > 1 year)
- If false positive, do PCR or just treat
-
Blood smear (morulae)
- High specificity, low sensitivity
-
PCR
- Ideal for confirmation
-
False negative
- On doxycycline (b/c out of circulation once treated)
How do you treat a dog with ehrlichiosis (E. canis)?
- Doxycycline
- Imidocarb
- Pro: injection and compliance
- For those that don’t get better (refractory)
- Coinfections with Babesia canis
- Parasympathetic stimulation (salivation, death)
- Dogs get better, but organism still in circulation
What do you tell the owner about the prognosis of their dog with ehrlichiosis (E. canis)?
Signs and thrombocytopenia improves in 48 hours (less effective in chronic phase)
How do you prevent a dog from getting ehrlichiosis (E. canis)?
- Absolute tick control
- Low dose tetracycline in endemic areas (in food)
Is canine monocytic ehrlichiosis (E. canis) zoonotic?
No (infection, yes)
What are the clinical signs in canine monocytic ehrlichiosis (E. chaffeensis)?
Milder disease than with E. canis
- Fever
- Anterior uveitis
- Lymphadenomegaly
- Vomiting
- Epistaxis
How do you diagnose a patient with suspected canine monocytic ehrlichiosis (E. chaffeensis)?
PCR (some cross reactivity with E. canis)
