Rickettsia, Coxiella, Ehrlichia, Anaplasma Flashcards
Rickettsia general characteristics
Gram - bacteria
Obligate intracellular of vasc. endothelium
Stain with Giema
R. rickettsii is the causative agent of …
Rocky Mountain Spotted Fever
Rickettsia distribution
Throughout US (south central states), southern Canada, Central America, South America (New world)
R. rickettsii
Humans and dogs show clinical illness (petechiae)
Cats resistant to RMSF
R. felis
Not pathogenic to cats
Zoonotic
Rocky Mountain Spotted Fever
Most severe and reported rickettsial illness of humans in the US
Reportable, 90% in april- sep
Rocky Mountain Spotted Fever transmission
Ticks, fleas, mites and lice
20 Ixodid tick species → mostly Demacentor spp.
Transovarial and transstadial
Rickettsia exposure
1-3% ticks carry agent
6-20 h of attachment and feeding required
Dogs are _______ for the presence of RMSF
Sentinels
Rickettsia pathogenesis
On vascular endothelial and smooth muscle cells causing necrotizing vasculitis (escape from phagosome and cytosolic replication by binary fission) → rashes
Rickettsia diagnostics
Isolation (BSL 3 contaminent)
Immunofluorescent assay and ELISA
PCR assays (with tick with possible)
Rickettsia are sensitive to _________
tetracyclines
Coxiella burnetii is the causative agent for ________
Q fever
zoonotic, bioterrorism
Coxiella general characteristics
Small pleomorphic rods, intracellular
MZN (modified Ziehl Neelson) stain
Small cell variant (SCV) or vegetative large cell variant (LCV)
Coxiella transmission
Aerosol, ingestion
Limited transmission by ticks
Wind-borne over long distances
Coxiella survival
Survives in environment for months
Formalin, UV, classical or flash pasteurization, desiccation
0.5% Na hypochlorite
Coxiella pathogenesis
Invades vascular endothelium, respiratory and renal epithelia→ multiply in phagosomes and macros
Q fever
Febrile, occupational disease
Cattle, sheep, goats= reservoirs
Q fever latent infection
Placentitis with abortion or norm delivery → discharge of bacteria
In lactating mammary gland and uterus
Reactivated during parturition
C. burnetii diagnostics
Serology and molecular methods
BSL-3 labs permitted to culture
C. burnetti disinfection
Ethyl alcohol, chloroform, N-alkyl dimethyl benzyl and ammonium chloride inactivate within 30 mins
Ehrlichia and Neorickettsia general characteristics
Obligate intracellular, gram -
Found in granulocytes or monocytes as morulae
Causes acute or chronic disease (vascular disorders)
E. canis
Canine monocytic ehrlichiosis (CME)
Vector: brown dog tick (Rhipcephalus sanguineus)
E. ewingii
Canine granulocytic ehrlichiosis (CGE)
Vector: Lone star tick (amblyomma americanum)
Canine ehrlichiosis
Causes coagulation disorders: petechiae, epistaxis from vasculitis and thrombocytopenia, anemia (pancytopenia)
_____________ smear from hosts examined fro morulae for Ehrlichia
Buffy coat
Neorickettsia risticci
Cause of Potomac Horse fever (equine monocytic ehrlichiosis- EME)-
June to Sep
N. risticii pathogenesis
Infects equine monocytes, intestinal epithelium and colonic mast cells
N. risticii transmission
Flukes in water
Snails and flies intermediate hosts with flie
CS for N. risticii
Fever, anorexia, colic, depression, ileus, diarrhea and laminitis
Causes of eneterocolitis
Salmonellosis, clostridial colitis, antibiotic-induced colitis, parasites (strongyles)
Salmon poisoning in dogs
Caused by N. helminthoeca
Reservoir: eating raw fish with fluke*
In Northwestern USA
Salmon poisoning pathogenesis
Dog releases fluke eggs (fecal) → miracidia infects snail → cercaria infests salmon → dogs eats salmon
Salmon poisoning CS
Infects monocytes → fever, anorexia, depression, WL, swollen LNs, hemorragic enteritis
Anaplasma
Obligate intracellular
A. phagocytophilum* (neutros)
A. marginale and centrale of cattle
Anaplasma pathogenesis
Tickborne that parasitizes erythrocytes, phagocytes and platelets
Membrane-bound morulae in cells
A. phagocytophilum distribution
Upper midwest and coastal new england (ixodes scapularis)
SNAP 4Dx Plus test by IDEXX
Detects Abs produced by A. phagocytophilum, A. platys, B. burgdorferi, E. canis, E. ewingii
Detects heartworm Ag
Treatment for anaplasmosis
Doxycycline
