K9 Ehrlichiosis Flashcards
Overview
Tick transmitted, intracytoplasmic Intracytoplasmic stage --> morula Species divided into 3 genera based on 16S rRNA sequences Used to be based on cell type infect --some infect multiple cell types
Ehrlichia canis
World-wide
Vertebrate hosts: canids but also cats
–similar syndromes but not well characterized
Endemic in German Shepards from Vietnam
E. Canis epizootiology - vector
Rhipicephalus sanguineus = brown dog tick
E. Canis epizootiology
Geographic range depends on tick
Ticks infected when feed on dogs during first 5-10d of acute IFX
–chronically infected dogs NOT source of IFX
Transtadial IFX occurs
No transovarial –> tick not true reservoir
E. Canis - when/how infectious?
Adult ticks live 570d Infectious for 5mo --Overwinter in ticks Both M and F infectious Concurrent IFX occur: Babesia, Hepatozaoon, RBC mycoplasmas
E. Canis Pathogenesis
Incubation 8-20d Development of 3 phases of dz: --acute (most cases) --subclinical --chronic (few reach true chronic stage)
E canis Acute Phase (2-4wks)
Invade mononuclear cells --> division VASCULITIS (endothelial damage) in multiple organs --Spleen, LN, liver --> organomegaly Parasite enters sub-endothelial tissues Varying degrees of IFM THROMBOCYTOPENIA mainly from vasculitis --exacerbated by anti-platelet AB Most dogs survive to enter subclin phase
E canis Subclinical Phase (mo-yrs)
ANTIGENIC PERSISTENCE
Thrombocytopenia, leukopenia +/- CS
AB Titers rise 7-21d
HYPERGLOBULINEMIA begins to develop
Phase can last 6-9 wks –> even into years
Most will eliminate organism during this phase
E canis Chronic Phase - Mo
Develops in dogs that don't eliminate organism Severity of clinical dz based on: --Strain --Age --Breed --Presence of other dz
CS of E canis Chronic Phase
PANCYTOPENIA
–thrombocytopenia
–Erythroid hypoplasia w/ plasma cell cytosine
Dogs remain immune to re-IFX if retain organism –> successful tx will allow re-IFX
Death DT hemorrhage, secondary IFX
CS E canis - systemic illness
Fever, depression +/- bleeding
Less common:
–Splenomegaly
–Lymphadenopathy
CS E canis - acute dz
May find ticks!
CS E canis - Ocular
Uveitis
Chorioetinitis
Retinal Hemorrhages
Papillodema
Other CS of E canis
Neuromuscular --Meningitis, sz, stupor, ataxia Polyarthritis --E. Ewingii, N. Risticii Chronic Stage --Severe WL --Dz as a consequence of pancytopenia
Dx E canis - CBC
Suspect based on hx, PE and LD Non regen anemia Thrombocytopenia Leukopenia Granular lymphocytosis Pancytopenia in chronic disease Morula --> BM or buffy coat
Dx E canis Chemistry Panel
Hyperproteinemia --HYPERGLOBULINEMIA (usually multiclonal vs multiple myelomas which are monoclonal) --Hypoalbuminemia Increased ALT CSF = increased protein/lymphocytes
Dx E canis - serology
IFA: pos test usually 1:80 or greater
Most labs measure IgG
–most positive by 1wk PI
Paired titers as a single titer can reflect past IFX
Titer progressively decreases over 6-9mo after tx