Rickettsia and Borrelia Flashcards
(24 cards)
review: the rickettsiales
minute obligate intracellular parasites of eukaryotic hosts (vertebrates, arthropods, other invertebrates)
The spotted fever rickettsias
Rickettsia rickettsii - tick vector
- united states: “Rocky Mountain Spotted Fever” (RMSF)
R. conorrii - TICK vector
- Europe: “Mediterranean Spotted Fever”
R. massiliae: TICK vector
- europe
R. felis - FLEA vector
- worldwide: “ Cat-flea typhus”
Rocky Mountain Spotted Fever
AKA “RMSF”
caused by Rickettsia rickettsii
results in acute or subclinical syndromes
- no chronic phase
Pathogenesis
- replicates in endothelial cells
- causes severe vasculitis
- Results in the “sickest” animals of all tick-borne diseases
seasonal - follows tick activity
- except in the far south and AZ
Tick life cycle
RMSF requires 5-20 hours of derma-center tick attachment to transit
clinical sings of RMSF
about half of dogs have known tick exposure
common signs:
- fever
- rash/petechiae
- myalgia (muscle pain)
- anorexia/vomiting
- abdominal pain
- headache (humans)
- depression
uncommon
- diarrhea
- conuctivitis
- lymphadenopathy
- hepatosplenomegaly
- vestibular disease
- coma and seizures
- edema
- PU/PD
- dyspnea/cough
- icterus
- arrythmias
- death
RMSF diagnosis
using antibodies
- correlate with clinical signs
- rising titer (acute and convalescent)
- exclusion of other causes
- response to treatment
PCR
- acute cases optimal
- many cases PCR negative
RMSF treatment
DOXY
- 5mg/kg PO q12 hr X 14 days
- 10mg/kg PO q 24 hr X14 days
ENROfloxacin
- 5-10mg/kg PO q 24 hr X 14 days
Prevention
- tick control
- gives sterilizing immunity:
eliminates pathogen before it can replicate (remember it needs 5-20 hours to transmit)
Rickettsia felis
an emerging dz in humans, dont care
vector is a cat FLEA
- humans get it when infected flea feces come in contact with broken skin
was first documented in N. and S. america, now is emerging in Sub-Saharan Africa, Southern Europe, Thailand, and Australia
Borrelia burgdorferi
a gram negative spirochete
transmited by ticks
- ixodes scapularis (deer tick)
distribution of lyme look familiar?
almost identical to anaplasma distribution
why? both pathogens are transmitted by the same tick vector - deer tick
lyme disease clinical signs
only half of owners of dogs diagnosed with lyme reported seeing a tick on the dogs
acute:
- fever
- lameness
chronic
- lameness
- glomerulonephropathy
- cardiac ?
- neurologic ?
lyme glomerulonephritis
current hypothesis is that it’s immune mediated
- glomerulonephritis
- tubular necrosis
- interstitial inflammation
Labrador retrieves (6.4 X) and golden retrievers (4.9 X) most at risk
lyme disease syndromes
about 30% of dogs with lyme nephropathy have been vaccinated
borreliosis diagnosis
documented clinical syndrome
- history of tick is helpful but not necessary
serology positive
- seronegative animals do not have lyme
- usually antibody positive when signs develop (excellent negative predictive value)
exclusion of other causes
response to therapy
what about PCR? - borreliosis
one example where PCR is NOT helpful
beagle study - all blood and joint taps were NEGATIVE even tho they were infected…
detecting borrelia in clinic
SNAP 4DX plus - serologic test (ELISA) - IDEXX
- ehrlichia canis/ E. ewingii
- anaplasma phagocycophilum/ A. platys (antibody)
- borrelia burgdorferi (C6 antibody)
(DOES differentiate vaccine from natural exposure)
(does NOT differentiate clinical from subclinical disease)
- heartworm (antigen)
C6 antibody
B. burgdorgeri makes the protein OspC (outer surface protein C), it’s necessary for transmission from tick to dog
- is present early in clinical infection
- SNAP tests detects antibody to this protein
More testing for tick-borne disease
AccuPlex4 - Antech diagnostics
combination test of 8 biomarkers for 4 infectious agents
- dirofilaria immitis (heartworm)
- ehrlichia canis
- anaplasma phaogyctophilum
- 5 B. burgdoferi markers
(can better detect chronic infection)
take home pt abotu diagnostics
borrelia antibody tests are NOT lyme disease tests
antibody presence DOES. NOT mean there’s active disease
Treating Lyme disease
doxy
- 10 mg/kg PO q12-24hr X 28 days
- amoxicillin 22 mg/kg PO q12 hr X 28 days
- vaccine? possible immune therapy benefits
If lyme nephritis
- ACE inhibitor
- low dose aspirin
- Prednisone?
- azathioprine ?
- mycophenolate ?
- cyclosporin ?
should you treat all seropositive dogs?
no signs of disease?
not recommended to treat if no clinical or pathologic abnormalities
what about the vaccines?
are not associated with nephritis
some vaccines have been shown to block infection and 1 year challenges
some vaccines probably work in some dogs, but immunity is not long-lived
vaccines (if used) should be combined with tick control
vaccination is very UNLIKELY to hurt dogs in endemic areas, and somewhat likely to help them
probably not needed in non-endemic areas
what about tick control?
many products out there
credelio (lotinaner) at 20 mg/kg begins to kill ticks on dogs in 4 hours and is 100% effective within 8 hours
Borrelia in cats
cats can be experimentally infected in B. burgdorferi via ixodes ticks
tick control is indicated in endemic areas
