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SA Infectious Diseases > K9 Ehrlichiosis > Flashcards

K9 Ehrlichiosis Flashcards

1
Q

Overview

A 
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
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2
Q

Ehrlichia canis

A

World-wide
Vertebrate hosts: canids but also cats
–similar syndromes but not well characterized
Endemic in German Shepards from Vietnam

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3
Q

E. Canis epizootiology - vector

A

Rhipicephalus sanguineus = brown dog tick

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4
Q

E. Canis epizootiology

A

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

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5
Q

E. Canis - when/how infectious?

A 
Adult ticks live 570d
Infectious for 5mo 
--Overwinter in ticks 
Both M and F infectious 
Concurrent IFX occur: Babesia, Hepatozaoon, RBC mycoplasmas
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6
Q

E. Canis Pathogenesis

A 
Incubation 8-20d
Development of 3 phases of dz:
--acute (most cases)
--subclinical 
--chronic (few reach true chronic stage)
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7
Q

E canis Acute Phase (2-4wks)

A 
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
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8
Q

E canis Subclinical Phase (mo-yrs)

A

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

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9
Q

E canis Chronic Phase - Mo

A 
Develops in dogs that don't eliminate organism 
Severity of clinical dz based on:
--Strain
--Age 
--Breed 
--Presence of other dz
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10
Q

CS of E canis Chronic Phase

A

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

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11
Q

CS E canis - systemic illness

A

Fever, depression +/- bleeding
Less common:
–Splenomegaly
–Lymphadenopathy

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12
Q

CS E canis - acute dz

A

May find ticks!

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13
Q

CS E canis - Ocular

A

Uveitis
Chorioetinitis
Retinal Hemorrhages
Papillodema

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14
Q

Other CS of E canis

A 
Neuromuscular 
--Meningitis, sz, stupor, ataxia 
Polyarthritis 
--E. Ewingii, N. Risticii 
Chronic Stage 
--Severe WL 
--Dz as a consequence of pancytopenia
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15
Q

Dx E canis - CBC

A 
Suspect based on hx, PE and LD 
Non regen anemia 
Thrombocytopenia 
Leukopenia 
Granular lymphocytosis 
Pancytopenia in chronic disease 
Morula --> BM or buffy coat
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16
Q

Dx E canis Chemistry Panel

A 
Hyperproteinemia 
--HYPERGLOBULINEMIA (usually multiclonal vs multiple myelomas which are monoclonal)
--Hypoalbuminemia 
Increased ALT
CSF = increased protein/lymphocytes
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17
Q

Dx E canis - serology

A

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

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18
Q

Challenges with E canis IFA

A

Highly sensitive, poor specificity
Cross-reactivity w/ other E. Spp ie E chaffeensis, E ewingii
–not a problem ion the Northeast or California
No cross-reaction w/ A. Phagocytophilum
Very little cross reactivity w/ RMSF or A platys

19
Q

E canis dx - Canine Snap 3 and 4Dx Test

A

8min in house test
Positive titers: equivalent IFA titer of >1:500
Sensitivity of 95%, Specificity of 100%
Detects AB against E. Chaffeensis not E. Ewingii

20
Q

Challenges with Snap Test

A

Predictive value depends on sensitive and specificity but also prevalence
–Low prevalence areas = high false positive rates
Screening test so should confirm with IFA
Western blotting may be used to differentiate mixed IFX

21
Q

E. Canis dx PCR

A

More reliable than finding morulae
Usually positive by day 7 PI (CS by d9 PI) in experimental settings
Less reliable in natural IFXs
Real time PCR methods - may be more sensitive

22
Q

E canis ABX tx

A

In acute stage, rapid improvement
NOT ENROFLOX
Tetra, oxytet, doxy, minocycline, chloramphenicol, amicarbalide

23
Q

E canis Tx

A

May need to hospital E canis cases –> stabilize
Short term-prednisone in acute dz
–Vasculities
–Limit IFM, immune-mediated platelet and tissue destruction
Chronic cases
–Androgens or granulocyte colony stimulating factor to stim BM
Monitor serum globulin levels or IFA
–Should decrease over time

24
Q

E canis prevent

A

1) prophylactic ABX

2) strict tick control

25
Q

E canis prevent: prophylactic ABX

A

Tetracycline long term
Repository oxytet successful
Doxy

26
Q

E canis prevent: strict tick control

A

Dips/sprays - dichlorvos, chlorfenvinphos, dioxathion, propoxur, carbaryl
Flea/tick collars - reduce reinfestation, reliability unproven
Selamectin topically (Revolution) monthly too slow in kill
Combo of imidacloprid, permethrin = effective

27
Q

Anaplasma phagocytophilum

A 
Vectors (same as Lyme Dz)
--Ixodes scapularies 
--Ixodes pacificus 
Incubation period --> 1-3weeks 
Reservoir hosts = wide variety of small mammals, birds
28
Q

Anaplasma Pathogenesis

A 
After IFX, enters PMNs and multiplies 
Not known how causes dz 
10d post IFX --> strong immunity usually controls IFX 
Acute dz only (if at all)
--NO CHRONIC DZ
29
Q

Anaplasma CS

A

Middle aged dogs, presenting in spring, summer or early fall
MILD fever, lethargy, anorexia
Generalized pain /stiffness - jt pain rare
THROMBOCYTOPENIA BUT NO BLEEDING
Dogs with Anaplasma and lyme dz show more severe signs

30
Q

Anaplasma Dx

A
  • -MORULA IN PMNs (40% can be infected)
  • -~80% of cases have mild THROMBOCYTOPENIA, lymphopenia, eosinopenia
  • -More cases picked up on 4dx
  • -Standard test = IFA –> + by 5d PI
  • -Need paired sample 3weeks apart - 4 fold titer increase
  • -PCR not good
31
Q

Anaplasma K9 4dx - what to do with results?

A

Cross rxn w/ A platys, slight with E canis
–none with Lyme, RMSF
+ Souteast = A platys
+ west/Northeast = A phagocytophilum

32
Q

What if both E canis and Anaplasma are positive on the 4Dx?

A

Dual IFX
Anaplasma IFX w/ cross reaction w/ E canis
–likely to be an acute active infection and not convalescence
Unlikely to have E canis alone because virtually no cross reactivity between E canis antigen and anaplasma serum

33
Q

4Dx: if have E canis alone

A

Only going to react with positive to E canis

34
Q

4Dx: if have acute Anaplasma only

A

Could get reaction to both Anaplasma and E canis

35
Q

4Dx: if have convalescent Anaplasma

A

Probably only going to get reaction to Anaplasma

36
Q

Positive for Anaplasma - tx or don’t tx? Symptomatic

A

If symptomatic - w/ typical CBC changes
–Tx w/ doxy for 4 weeks
Remember: case likely to have a slightly positive E canis spot on the 4Dx

37
Q

Positive for Anaplasma - tx or don’t tx? Asymptomatic

A

Perform CBC - thrombocytopenia, eosinopenia
–Tx or ignore - repeat CBC in 3wks
–If E canis slightly positive (even close to acute IFX for Anaplasma), might want to treat
If no CBC changes, recovered from IFX –> don’t treat or run paired IFA
Look for other diseases

38
Q

Anaplasma IFA

A

Seroconversion occurs 2-5d AFTER modulate appear in the blood (5-9d PI)
–IFA becomes positive 7-14d PI
Need paired samples (3 weeks apart to show 4 fold increase) because 40% of morula and positive dogs will be seronegative
CR mild for E canis, other for anaplasma

39
Q

Anaplasma Treatment - yes

A

Most cases do not need tx
–most dogs get 3-4 week course of doxy anyway
Anaplasma = sensitive to enrofloxacin
unlike Ehrlichia

40
Q

Infectious cyclic thrombocytopenia - Etiology

A

Anaplasma platys - infects platelets
Transmitted by ticks
High incidence of combined IFX w/ E canis and A platys
A platys occurs mainly in SE (Florida)

41
Q

ICT: pathogenesis

A

IP 1-2wks
During initial IFX, get large # of platelets infected
Leads to drop in platelet count - parasite very difficult to find
Then platelet #s rise, cycle repeated
Cycles of high parasitemeia followed by thrombocytopenia recur Q1-2 weeks

42
Q

ICT Clinical Features

A

Dogs rarely become ill
Even with low platelet counts, don’t usually show signs - hemorrhage
Get severe signs if co-infected w/ E canis or Babesia

43
Q

ICT Dx

A

Morula in platelets
IFX - + just after first parasitemia
Remember 4Dx snap test picks up A platys

44
Q

ICT Tx

A

As per E canis BUT can use enrofloxacin (Baytril) if need be

SA Infectious Diseases (7 decks)

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